Post on 29-Nov-2015
description
We are Developing
How are you
GSM OverviewGSM Overview
Contents Chapter 1 Introduction
Chapter 2 Basic GSM Network Structure
Chapter 3 Radio Coverage
Chapter 4 Radio Transmission Problems
Chapter 5 Air interface
Chapter 6 Traffic Cases
Chapter 7 GSM Services
Banner Advertisement America 1929
Chapter 1 Introduction
Mobile Technology Evolution
Speech1G
GSM13 kbps
HSCSD576 kbps
Circuit Switched
GPRS115 kbps
Packet Switched
EDGE384 kbps
Time
Mobile Technology EvolutionMobile Technology Evolution
WCDMA(UMTS)2 Mbps
HSDPA36 Mbps
HSUPA576 Mbps
Circuit Switching Packet Switching
2G
275G
225G
25G
3G
35G
375G
1G
History of Mobile Communications
1980ndash1985
The first generation of modern cellular mobile networks put into service But it was all based on analog system(1G)
History of Mobile Communications
-Due to the projected growth in mobile telecommunications the European PTTs in 1982 decided to develop a Pan-European mobile system using digital technology
-This system is known as GSM a Global System for Mobile Communications
-The first commercial GSM network was launched in June 1992 in Germany International roaming was the important feature for subscribers
History of Mobile Communications
-However GSM is not just restricted to Europe Today GSM is available in over 130 countries around the world with more than 200 million subscribers
-Three different frequency bands are available for use by GSM systems GSM 900 1800 and 1900 MHz GSM 18001900 is intended for use in areas of high subscriber density
-Other digital mobile standards include D-AMPS in the US and PDC in Japan
History of Mobile Communications
-Universal Mobile Telecommunications System (UMTS) is one of the major new third-generation (3G) mobile systems in development
-UMTS will extend the capability of todayrsquos mobile (inc GSM) cordless and satellite technologies by providing increased capacity (up to 2 Mbs) and a greater range of services including multimedia
Analog to Digital
Analog to Digital (1G to 2G)
bullThe main restrictions of analog mobile systems are the limited capacity voice-only services and high operational costdifferent systems are incompatible in terms of equipment and operation eg NMT and TACS
bullWith digital systems such as GSM the available frequency spectrum is used more efficiently leading to increased capacity and reductions in associated costs for network operators equipment suppliers and subscribers
bullAnalog mobile systems were originally designed for voice However digital mobile systems can support voice data and a range of additional services such as a short message service and call forwarding (Call Divert)
bullAnalog mobile systems offered limited international roaming and a low level of security GSM on the other hand offers few restrictions on international roaming and provides advanced security using ciphering and authentication
Why Wireless
Why Wireless
source DestinationTransmission medium
Why Wireless
The kinds of transmission medium
1- Twisted-pair It is very low bandwidth and it is easily tapped either physically or by monitoring its electromagnetic radiation 2- Coaxial cable It is greater bandwidth than twisted-pair but it is very expensive
3- optical fibers It is very high bandwidth very high bit rate
Why Wireless
4 -Radio (wireless)
It is greatly depending on the particular frequency of the electromagnetic wave
Some of their advantages
a- They are very flexible
b- Portable system can be installed very quicklyc- There are often the most cost-effective solution
Types of communication
TX RX
TX+RX TX +RX
TX+RX TX +RX
Multiple-access for Digital Communication Systems
The frequency spectrum must be shared by all the users in the system
Three method for sharing spectrum
FDMA
Frequency-division multiple-access
TDMA
Time-division multiple-access
CDMA
Code-division multiple-access
Most modern systems use combinations
TDMAFDMA
CDMAFDMA
Multiple-Access
Three ways to separate signals
1 -Frequency
2 -Time
3 -Code
Frequency
Time
Code
FDMA
-Frequency-division multiple-access
-Each user is assigned one frequency
frequency
Channel 1 32 4
30 kHzguardband
FDMA
Frequency-Division Multiple-Access
ExamplesAMPSFrequency
Time
Code
TDMA
Time-division multiple-access
All users transmit at same frequency
Each user transmits at a different time
User 1
User 2
User 3
User 1
User 2
User 3guardtime
20 msectime slot
time
TDMA
Frequency
Time
Code
Time-Division Multiple-Access
CDMA
Frequency
Time
Code
Code-Division Multiple-AccessExamplesIS-95Bluetooth
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Contents Chapter 1 Introduction
Chapter 2 Basic GSM Network Structure
Chapter 3 Radio Coverage
Chapter 4 Radio Transmission Problems
Chapter 5 Air interface
Chapter 6 Traffic Cases
Chapter 7 GSM Services
Banner Advertisement America 1929
Chapter 1 Introduction
Mobile Technology Evolution
Speech1G
GSM13 kbps
HSCSD576 kbps
Circuit Switched
GPRS115 kbps
Packet Switched
EDGE384 kbps
Time
Mobile Technology EvolutionMobile Technology Evolution
WCDMA(UMTS)2 Mbps
HSDPA36 Mbps
HSUPA576 Mbps
Circuit Switching Packet Switching
2G
275G
225G
25G
3G
35G
375G
1G
History of Mobile Communications
1980ndash1985
The first generation of modern cellular mobile networks put into service But it was all based on analog system(1G)
History of Mobile Communications
-Due to the projected growth in mobile telecommunications the European PTTs in 1982 decided to develop a Pan-European mobile system using digital technology
-This system is known as GSM a Global System for Mobile Communications
-The first commercial GSM network was launched in June 1992 in Germany International roaming was the important feature for subscribers
History of Mobile Communications
-However GSM is not just restricted to Europe Today GSM is available in over 130 countries around the world with more than 200 million subscribers
-Three different frequency bands are available for use by GSM systems GSM 900 1800 and 1900 MHz GSM 18001900 is intended for use in areas of high subscriber density
-Other digital mobile standards include D-AMPS in the US and PDC in Japan
History of Mobile Communications
-Universal Mobile Telecommunications System (UMTS) is one of the major new third-generation (3G) mobile systems in development
-UMTS will extend the capability of todayrsquos mobile (inc GSM) cordless and satellite technologies by providing increased capacity (up to 2 Mbs) and a greater range of services including multimedia
Analog to Digital
Analog to Digital (1G to 2G)
bullThe main restrictions of analog mobile systems are the limited capacity voice-only services and high operational costdifferent systems are incompatible in terms of equipment and operation eg NMT and TACS
bullWith digital systems such as GSM the available frequency spectrum is used more efficiently leading to increased capacity and reductions in associated costs for network operators equipment suppliers and subscribers
bullAnalog mobile systems were originally designed for voice However digital mobile systems can support voice data and a range of additional services such as a short message service and call forwarding (Call Divert)
bullAnalog mobile systems offered limited international roaming and a low level of security GSM on the other hand offers few restrictions on international roaming and provides advanced security using ciphering and authentication
Why Wireless
Why Wireless
source DestinationTransmission medium
Why Wireless
The kinds of transmission medium
1- Twisted-pair It is very low bandwidth and it is easily tapped either physically or by monitoring its electromagnetic radiation 2- Coaxial cable It is greater bandwidth than twisted-pair but it is very expensive
3- optical fibers It is very high bandwidth very high bit rate
Why Wireless
4 -Radio (wireless)
It is greatly depending on the particular frequency of the electromagnetic wave
Some of their advantages
a- They are very flexible
b- Portable system can be installed very quicklyc- There are often the most cost-effective solution
Types of communication
TX RX
TX+RX TX +RX
TX+RX TX +RX
Multiple-access for Digital Communication Systems
The frequency spectrum must be shared by all the users in the system
Three method for sharing spectrum
FDMA
Frequency-division multiple-access
TDMA
Time-division multiple-access
CDMA
Code-division multiple-access
Most modern systems use combinations
TDMAFDMA
CDMAFDMA
Multiple-Access
Three ways to separate signals
1 -Frequency
2 -Time
3 -Code
Frequency
Time
Code
FDMA
-Frequency-division multiple-access
-Each user is assigned one frequency
frequency
Channel 1 32 4
30 kHzguardband
FDMA
Frequency-Division Multiple-Access
ExamplesAMPSFrequency
Time
Code
TDMA
Time-division multiple-access
All users transmit at same frequency
Each user transmits at a different time
User 1
User 2
User 3
User 1
User 2
User 3guardtime
20 msectime slot
time
TDMA
Frequency
Time
Code
Time-Division Multiple-Access
CDMA
Frequency
Time
Code
Code-Division Multiple-AccessExamplesIS-95Bluetooth
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Banner Advertisement America 1929
Chapter 1 Introduction
Mobile Technology Evolution
Speech1G
GSM13 kbps
HSCSD576 kbps
Circuit Switched
GPRS115 kbps
Packet Switched
EDGE384 kbps
Time
Mobile Technology EvolutionMobile Technology Evolution
WCDMA(UMTS)2 Mbps
HSDPA36 Mbps
HSUPA576 Mbps
Circuit Switching Packet Switching
2G
275G
225G
25G
3G
35G
375G
1G
History of Mobile Communications
1980ndash1985
The first generation of modern cellular mobile networks put into service But it was all based on analog system(1G)
History of Mobile Communications
-Due to the projected growth in mobile telecommunications the European PTTs in 1982 decided to develop a Pan-European mobile system using digital technology
-This system is known as GSM a Global System for Mobile Communications
-The first commercial GSM network was launched in June 1992 in Germany International roaming was the important feature for subscribers
History of Mobile Communications
-However GSM is not just restricted to Europe Today GSM is available in over 130 countries around the world with more than 200 million subscribers
-Three different frequency bands are available for use by GSM systems GSM 900 1800 and 1900 MHz GSM 18001900 is intended for use in areas of high subscriber density
-Other digital mobile standards include D-AMPS in the US and PDC in Japan
History of Mobile Communications
-Universal Mobile Telecommunications System (UMTS) is one of the major new third-generation (3G) mobile systems in development
-UMTS will extend the capability of todayrsquos mobile (inc GSM) cordless and satellite technologies by providing increased capacity (up to 2 Mbs) and a greater range of services including multimedia
Analog to Digital
Analog to Digital (1G to 2G)
bullThe main restrictions of analog mobile systems are the limited capacity voice-only services and high operational costdifferent systems are incompatible in terms of equipment and operation eg NMT and TACS
bullWith digital systems such as GSM the available frequency spectrum is used more efficiently leading to increased capacity and reductions in associated costs for network operators equipment suppliers and subscribers
bullAnalog mobile systems were originally designed for voice However digital mobile systems can support voice data and a range of additional services such as a short message service and call forwarding (Call Divert)
bullAnalog mobile systems offered limited international roaming and a low level of security GSM on the other hand offers few restrictions on international roaming and provides advanced security using ciphering and authentication
Why Wireless
Why Wireless
source DestinationTransmission medium
Why Wireless
The kinds of transmission medium
1- Twisted-pair It is very low bandwidth and it is easily tapped either physically or by monitoring its electromagnetic radiation 2- Coaxial cable It is greater bandwidth than twisted-pair but it is very expensive
3- optical fibers It is very high bandwidth very high bit rate
Why Wireless
4 -Radio (wireless)
It is greatly depending on the particular frequency of the electromagnetic wave
Some of their advantages
a- They are very flexible
b- Portable system can be installed very quicklyc- There are often the most cost-effective solution
Types of communication
TX RX
TX+RX TX +RX
TX+RX TX +RX
Multiple-access for Digital Communication Systems
The frequency spectrum must be shared by all the users in the system
Three method for sharing spectrum
FDMA
Frequency-division multiple-access
TDMA
Time-division multiple-access
CDMA
Code-division multiple-access
Most modern systems use combinations
TDMAFDMA
CDMAFDMA
Multiple-Access
Three ways to separate signals
1 -Frequency
2 -Time
3 -Code
Frequency
Time
Code
FDMA
-Frequency-division multiple-access
-Each user is assigned one frequency
frequency
Channel 1 32 4
30 kHzguardband
FDMA
Frequency-Division Multiple-Access
ExamplesAMPSFrequency
Time
Code
TDMA
Time-division multiple-access
All users transmit at same frequency
Each user transmits at a different time
User 1
User 2
User 3
User 1
User 2
User 3guardtime
20 msectime slot
time
TDMA
Frequency
Time
Code
Time-Division Multiple-Access
CDMA
Frequency
Time
Code
Code-Division Multiple-AccessExamplesIS-95Bluetooth
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Mobile Technology Evolution
Speech1G
GSM13 kbps
HSCSD576 kbps
Circuit Switched
GPRS115 kbps
Packet Switched
EDGE384 kbps
Time
Mobile Technology EvolutionMobile Technology Evolution
WCDMA(UMTS)2 Mbps
HSDPA36 Mbps
HSUPA576 Mbps
Circuit Switching Packet Switching
2G
275G
225G
25G
3G
35G
375G
1G
History of Mobile Communications
1980ndash1985
The first generation of modern cellular mobile networks put into service But it was all based on analog system(1G)
History of Mobile Communications
-Due to the projected growth in mobile telecommunications the European PTTs in 1982 decided to develop a Pan-European mobile system using digital technology
-This system is known as GSM a Global System for Mobile Communications
-The first commercial GSM network was launched in June 1992 in Germany International roaming was the important feature for subscribers
History of Mobile Communications
-However GSM is not just restricted to Europe Today GSM is available in over 130 countries around the world with more than 200 million subscribers
-Three different frequency bands are available for use by GSM systems GSM 900 1800 and 1900 MHz GSM 18001900 is intended for use in areas of high subscriber density
-Other digital mobile standards include D-AMPS in the US and PDC in Japan
History of Mobile Communications
-Universal Mobile Telecommunications System (UMTS) is one of the major new third-generation (3G) mobile systems in development
-UMTS will extend the capability of todayrsquos mobile (inc GSM) cordless and satellite technologies by providing increased capacity (up to 2 Mbs) and a greater range of services including multimedia
Analog to Digital
Analog to Digital (1G to 2G)
bullThe main restrictions of analog mobile systems are the limited capacity voice-only services and high operational costdifferent systems are incompatible in terms of equipment and operation eg NMT and TACS
bullWith digital systems such as GSM the available frequency spectrum is used more efficiently leading to increased capacity and reductions in associated costs for network operators equipment suppliers and subscribers
bullAnalog mobile systems were originally designed for voice However digital mobile systems can support voice data and a range of additional services such as a short message service and call forwarding (Call Divert)
bullAnalog mobile systems offered limited international roaming and a low level of security GSM on the other hand offers few restrictions on international roaming and provides advanced security using ciphering and authentication
Why Wireless
Why Wireless
source DestinationTransmission medium
Why Wireless
The kinds of transmission medium
1- Twisted-pair It is very low bandwidth and it is easily tapped either physically or by monitoring its electromagnetic radiation 2- Coaxial cable It is greater bandwidth than twisted-pair but it is very expensive
3- optical fibers It is very high bandwidth very high bit rate
Why Wireless
4 -Radio (wireless)
It is greatly depending on the particular frequency of the electromagnetic wave
Some of their advantages
a- They are very flexible
b- Portable system can be installed very quicklyc- There are often the most cost-effective solution
Types of communication
TX RX
TX+RX TX +RX
TX+RX TX +RX
Multiple-access for Digital Communication Systems
The frequency spectrum must be shared by all the users in the system
Three method for sharing spectrum
FDMA
Frequency-division multiple-access
TDMA
Time-division multiple-access
CDMA
Code-division multiple-access
Most modern systems use combinations
TDMAFDMA
CDMAFDMA
Multiple-Access
Three ways to separate signals
1 -Frequency
2 -Time
3 -Code
Frequency
Time
Code
FDMA
-Frequency-division multiple-access
-Each user is assigned one frequency
frequency
Channel 1 32 4
30 kHzguardband
FDMA
Frequency-Division Multiple-Access
ExamplesAMPSFrequency
Time
Code
TDMA
Time-division multiple-access
All users transmit at same frequency
Each user transmits at a different time
User 1
User 2
User 3
User 1
User 2
User 3guardtime
20 msectime slot
time
TDMA
Frequency
Time
Code
Time-Division Multiple-Access
CDMA
Frequency
Time
Code
Code-Division Multiple-AccessExamplesIS-95Bluetooth
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Speech1G
GSM13 kbps
HSCSD576 kbps
Circuit Switched
GPRS115 kbps
Packet Switched
EDGE384 kbps
Time
Mobile Technology EvolutionMobile Technology Evolution
WCDMA(UMTS)2 Mbps
HSDPA36 Mbps
HSUPA576 Mbps
Circuit Switching Packet Switching
2G
275G
225G
25G
3G
35G
375G
1G
History of Mobile Communications
1980ndash1985
The first generation of modern cellular mobile networks put into service But it was all based on analog system(1G)
History of Mobile Communications
-Due to the projected growth in mobile telecommunications the European PTTs in 1982 decided to develop a Pan-European mobile system using digital technology
-This system is known as GSM a Global System for Mobile Communications
-The first commercial GSM network was launched in June 1992 in Germany International roaming was the important feature for subscribers
History of Mobile Communications
-However GSM is not just restricted to Europe Today GSM is available in over 130 countries around the world with more than 200 million subscribers
-Three different frequency bands are available for use by GSM systems GSM 900 1800 and 1900 MHz GSM 18001900 is intended for use in areas of high subscriber density
-Other digital mobile standards include D-AMPS in the US and PDC in Japan
History of Mobile Communications
-Universal Mobile Telecommunications System (UMTS) is one of the major new third-generation (3G) mobile systems in development
-UMTS will extend the capability of todayrsquos mobile (inc GSM) cordless and satellite technologies by providing increased capacity (up to 2 Mbs) and a greater range of services including multimedia
Analog to Digital
Analog to Digital (1G to 2G)
bullThe main restrictions of analog mobile systems are the limited capacity voice-only services and high operational costdifferent systems are incompatible in terms of equipment and operation eg NMT and TACS
bullWith digital systems such as GSM the available frequency spectrum is used more efficiently leading to increased capacity and reductions in associated costs for network operators equipment suppliers and subscribers
bullAnalog mobile systems were originally designed for voice However digital mobile systems can support voice data and a range of additional services such as a short message service and call forwarding (Call Divert)
bullAnalog mobile systems offered limited international roaming and a low level of security GSM on the other hand offers few restrictions on international roaming and provides advanced security using ciphering and authentication
Why Wireless
Why Wireless
source DestinationTransmission medium
Why Wireless
The kinds of transmission medium
1- Twisted-pair It is very low bandwidth and it is easily tapped either physically or by monitoring its electromagnetic radiation 2- Coaxial cable It is greater bandwidth than twisted-pair but it is very expensive
3- optical fibers It is very high bandwidth very high bit rate
Why Wireless
4 -Radio (wireless)
It is greatly depending on the particular frequency of the electromagnetic wave
Some of their advantages
a- They are very flexible
b- Portable system can be installed very quicklyc- There are often the most cost-effective solution
Types of communication
TX RX
TX+RX TX +RX
TX+RX TX +RX
Multiple-access for Digital Communication Systems
The frequency spectrum must be shared by all the users in the system
Three method for sharing spectrum
FDMA
Frequency-division multiple-access
TDMA
Time-division multiple-access
CDMA
Code-division multiple-access
Most modern systems use combinations
TDMAFDMA
CDMAFDMA
Multiple-Access
Three ways to separate signals
1 -Frequency
2 -Time
3 -Code
Frequency
Time
Code
FDMA
-Frequency-division multiple-access
-Each user is assigned one frequency
frequency
Channel 1 32 4
30 kHzguardband
FDMA
Frequency-Division Multiple-Access
ExamplesAMPSFrequency
Time
Code
TDMA
Time-division multiple-access
All users transmit at same frequency
Each user transmits at a different time
User 1
User 2
User 3
User 1
User 2
User 3guardtime
20 msectime slot
time
TDMA
Frequency
Time
Code
Time-Division Multiple-Access
CDMA
Frequency
Time
Code
Code-Division Multiple-AccessExamplesIS-95Bluetooth
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
History of Mobile Communications
1980ndash1985
The first generation of modern cellular mobile networks put into service But it was all based on analog system(1G)
History of Mobile Communications
-Due to the projected growth in mobile telecommunications the European PTTs in 1982 decided to develop a Pan-European mobile system using digital technology
-This system is known as GSM a Global System for Mobile Communications
-The first commercial GSM network was launched in June 1992 in Germany International roaming was the important feature for subscribers
History of Mobile Communications
-However GSM is not just restricted to Europe Today GSM is available in over 130 countries around the world with more than 200 million subscribers
-Three different frequency bands are available for use by GSM systems GSM 900 1800 and 1900 MHz GSM 18001900 is intended for use in areas of high subscriber density
-Other digital mobile standards include D-AMPS in the US and PDC in Japan
History of Mobile Communications
-Universal Mobile Telecommunications System (UMTS) is one of the major new third-generation (3G) mobile systems in development
-UMTS will extend the capability of todayrsquos mobile (inc GSM) cordless and satellite technologies by providing increased capacity (up to 2 Mbs) and a greater range of services including multimedia
Analog to Digital
Analog to Digital (1G to 2G)
bullThe main restrictions of analog mobile systems are the limited capacity voice-only services and high operational costdifferent systems are incompatible in terms of equipment and operation eg NMT and TACS
bullWith digital systems such as GSM the available frequency spectrum is used more efficiently leading to increased capacity and reductions in associated costs for network operators equipment suppliers and subscribers
bullAnalog mobile systems were originally designed for voice However digital mobile systems can support voice data and a range of additional services such as a short message service and call forwarding (Call Divert)
bullAnalog mobile systems offered limited international roaming and a low level of security GSM on the other hand offers few restrictions on international roaming and provides advanced security using ciphering and authentication
Why Wireless
Why Wireless
source DestinationTransmission medium
Why Wireless
The kinds of transmission medium
1- Twisted-pair It is very low bandwidth and it is easily tapped either physically or by monitoring its electromagnetic radiation 2- Coaxial cable It is greater bandwidth than twisted-pair but it is very expensive
3- optical fibers It is very high bandwidth very high bit rate
Why Wireless
4 -Radio (wireless)
It is greatly depending on the particular frequency of the electromagnetic wave
Some of their advantages
a- They are very flexible
b- Portable system can be installed very quicklyc- There are often the most cost-effective solution
Types of communication
TX RX
TX+RX TX +RX
TX+RX TX +RX
Multiple-access for Digital Communication Systems
The frequency spectrum must be shared by all the users in the system
Three method for sharing spectrum
FDMA
Frequency-division multiple-access
TDMA
Time-division multiple-access
CDMA
Code-division multiple-access
Most modern systems use combinations
TDMAFDMA
CDMAFDMA
Multiple-Access
Three ways to separate signals
1 -Frequency
2 -Time
3 -Code
Frequency
Time
Code
FDMA
-Frequency-division multiple-access
-Each user is assigned one frequency
frequency
Channel 1 32 4
30 kHzguardband
FDMA
Frequency-Division Multiple-Access
ExamplesAMPSFrequency
Time
Code
TDMA
Time-division multiple-access
All users transmit at same frequency
Each user transmits at a different time
User 1
User 2
User 3
User 1
User 2
User 3guardtime
20 msectime slot
time
TDMA
Frequency
Time
Code
Time-Division Multiple-Access
CDMA
Frequency
Time
Code
Code-Division Multiple-AccessExamplesIS-95Bluetooth
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
History of Mobile Communications
-Due to the projected growth in mobile telecommunications the European PTTs in 1982 decided to develop a Pan-European mobile system using digital technology
-This system is known as GSM a Global System for Mobile Communications
-The first commercial GSM network was launched in June 1992 in Germany International roaming was the important feature for subscribers
History of Mobile Communications
-However GSM is not just restricted to Europe Today GSM is available in over 130 countries around the world with more than 200 million subscribers
-Three different frequency bands are available for use by GSM systems GSM 900 1800 and 1900 MHz GSM 18001900 is intended for use in areas of high subscriber density
-Other digital mobile standards include D-AMPS in the US and PDC in Japan
History of Mobile Communications
-Universal Mobile Telecommunications System (UMTS) is one of the major new third-generation (3G) mobile systems in development
-UMTS will extend the capability of todayrsquos mobile (inc GSM) cordless and satellite technologies by providing increased capacity (up to 2 Mbs) and a greater range of services including multimedia
Analog to Digital
Analog to Digital (1G to 2G)
bullThe main restrictions of analog mobile systems are the limited capacity voice-only services and high operational costdifferent systems are incompatible in terms of equipment and operation eg NMT and TACS
bullWith digital systems such as GSM the available frequency spectrum is used more efficiently leading to increased capacity and reductions in associated costs for network operators equipment suppliers and subscribers
bullAnalog mobile systems were originally designed for voice However digital mobile systems can support voice data and a range of additional services such as a short message service and call forwarding (Call Divert)
bullAnalog mobile systems offered limited international roaming and a low level of security GSM on the other hand offers few restrictions on international roaming and provides advanced security using ciphering and authentication
Why Wireless
Why Wireless
source DestinationTransmission medium
Why Wireless
The kinds of transmission medium
1- Twisted-pair It is very low bandwidth and it is easily tapped either physically or by monitoring its electromagnetic radiation 2- Coaxial cable It is greater bandwidth than twisted-pair but it is very expensive
3- optical fibers It is very high bandwidth very high bit rate
Why Wireless
4 -Radio (wireless)
It is greatly depending on the particular frequency of the electromagnetic wave
Some of their advantages
a- They are very flexible
b- Portable system can be installed very quicklyc- There are often the most cost-effective solution
Types of communication
TX RX
TX+RX TX +RX
TX+RX TX +RX
Multiple-access for Digital Communication Systems
The frequency spectrum must be shared by all the users in the system
Three method for sharing spectrum
FDMA
Frequency-division multiple-access
TDMA
Time-division multiple-access
CDMA
Code-division multiple-access
Most modern systems use combinations
TDMAFDMA
CDMAFDMA
Multiple-Access
Three ways to separate signals
1 -Frequency
2 -Time
3 -Code
Frequency
Time
Code
FDMA
-Frequency-division multiple-access
-Each user is assigned one frequency
frequency
Channel 1 32 4
30 kHzguardband
FDMA
Frequency-Division Multiple-Access
ExamplesAMPSFrequency
Time
Code
TDMA
Time-division multiple-access
All users transmit at same frequency
Each user transmits at a different time
User 1
User 2
User 3
User 1
User 2
User 3guardtime
20 msectime slot
time
TDMA
Frequency
Time
Code
Time-Division Multiple-Access
CDMA
Frequency
Time
Code
Code-Division Multiple-AccessExamplesIS-95Bluetooth
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
History of Mobile Communications
-However GSM is not just restricted to Europe Today GSM is available in over 130 countries around the world with more than 200 million subscribers
-Three different frequency bands are available for use by GSM systems GSM 900 1800 and 1900 MHz GSM 18001900 is intended for use in areas of high subscriber density
-Other digital mobile standards include D-AMPS in the US and PDC in Japan
History of Mobile Communications
-Universal Mobile Telecommunications System (UMTS) is one of the major new third-generation (3G) mobile systems in development
-UMTS will extend the capability of todayrsquos mobile (inc GSM) cordless and satellite technologies by providing increased capacity (up to 2 Mbs) and a greater range of services including multimedia
Analog to Digital
Analog to Digital (1G to 2G)
bullThe main restrictions of analog mobile systems are the limited capacity voice-only services and high operational costdifferent systems are incompatible in terms of equipment and operation eg NMT and TACS
bullWith digital systems such as GSM the available frequency spectrum is used more efficiently leading to increased capacity and reductions in associated costs for network operators equipment suppliers and subscribers
bullAnalog mobile systems were originally designed for voice However digital mobile systems can support voice data and a range of additional services such as a short message service and call forwarding (Call Divert)
bullAnalog mobile systems offered limited international roaming and a low level of security GSM on the other hand offers few restrictions on international roaming and provides advanced security using ciphering and authentication
Why Wireless
Why Wireless
source DestinationTransmission medium
Why Wireless
The kinds of transmission medium
1- Twisted-pair It is very low bandwidth and it is easily tapped either physically or by monitoring its electromagnetic radiation 2- Coaxial cable It is greater bandwidth than twisted-pair but it is very expensive
3- optical fibers It is very high bandwidth very high bit rate
Why Wireless
4 -Radio (wireless)
It is greatly depending on the particular frequency of the electromagnetic wave
Some of their advantages
a- They are very flexible
b- Portable system can be installed very quicklyc- There are often the most cost-effective solution
Types of communication
TX RX
TX+RX TX +RX
TX+RX TX +RX
Multiple-access for Digital Communication Systems
The frequency spectrum must be shared by all the users in the system
Three method for sharing spectrum
FDMA
Frequency-division multiple-access
TDMA
Time-division multiple-access
CDMA
Code-division multiple-access
Most modern systems use combinations
TDMAFDMA
CDMAFDMA
Multiple-Access
Three ways to separate signals
1 -Frequency
2 -Time
3 -Code
Frequency
Time
Code
FDMA
-Frequency-division multiple-access
-Each user is assigned one frequency
frequency
Channel 1 32 4
30 kHzguardband
FDMA
Frequency-Division Multiple-Access
ExamplesAMPSFrequency
Time
Code
TDMA
Time-division multiple-access
All users transmit at same frequency
Each user transmits at a different time
User 1
User 2
User 3
User 1
User 2
User 3guardtime
20 msectime slot
time
TDMA
Frequency
Time
Code
Time-Division Multiple-Access
CDMA
Frequency
Time
Code
Code-Division Multiple-AccessExamplesIS-95Bluetooth
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
History of Mobile Communications
-Universal Mobile Telecommunications System (UMTS) is one of the major new third-generation (3G) mobile systems in development
-UMTS will extend the capability of todayrsquos mobile (inc GSM) cordless and satellite technologies by providing increased capacity (up to 2 Mbs) and a greater range of services including multimedia
Analog to Digital
Analog to Digital (1G to 2G)
bullThe main restrictions of analog mobile systems are the limited capacity voice-only services and high operational costdifferent systems are incompatible in terms of equipment and operation eg NMT and TACS
bullWith digital systems such as GSM the available frequency spectrum is used more efficiently leading to increased capacity and reductions in associated costs for network operators equipment suppliers and subscribers
bullAnalog mobile systems were originally designed for voice However digital mobile systems can support voice data and a range of additional services such as a short message service and call forwarding (Call Divert)
bullAnalog mobile systems offered limited international roaming and a low level of security GSM on the other hand offers few restrictions on international roaming and provides advanced security using ciphering and authentication
Why Wireless
Why Wireless
source DestinationTransmission medium
Why Wireless
The kinds of transmission medium
1- Twisted-pair It is very low bandwidth and it is easily tapped either physically or by monitoring its electromagnetic radiation 2- Coaxial cable It is greater bandwidth than twisted-pair but it is very expensive
3- optical fibers It is very high bandwidth very high bit rate
Why Wireless
4 -Radio (wireless)
It is greatly depending on the particular frequency of the electromagnetic wave
Some of their advantages
a- They are very flexible
b- Portable system can be installed very quicklyc- There are often the most cost-effective solution
Types of communication
TX RX
TX+RX TX +RX
TX+RX TX +RX
Multiple-access for Digital Communication Systems
The frequency spectrum must be shared by all the users in the system
Three method for sharing spectrum
FDMA
Frequency-division multiple-access
TDMA
Time-division multiple-access
CDMA
Code-division multiple-access
Most modern systems use combinations
TDMAFDMA
CDMAFDMA
Multiple-Access
Three ways to separate signals
1 -Frequency
2 -Time
3 -Code
Frequency
Time
Code
FDMA
-Frequency-division multiple-access
-Each user is assigned one frequency
frequency
Channel 1 32 4
30 kHzguardband
FDMA
Frequency-Division Multiple-Access
ExamplesAMPSFrequency
Time
Code
TDMA
Time-division multiple-access
All users transmit at same frequency
Each user transmits at a different time
User 1
User 2
User 3
User 1
User 2
User 3guardtime
20 msectime slot
time
TDMA
Frequency
Time
Code
Time-Division Multiple-Access
CDMA
Frequency
Time
Code
Code-Division Multiple-AccessExamplesIS-95Bluetooth
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Analog to Digital
Analog to Digital (1G to 2G)
bullThe main restrictions of analog mobile systems are the limited capacity voice-only services and high operational costdifferent systems are incompatible in terms of equipment and operation eg NMT and TACS
bullWith digital systems such as GSM the available frequency spectrum is used more efficiently leading to increased capacity and reductions in associated costs for network operators equipment suppliers and subscribers
bullAnalog mobile systems were originally designed for voice However digital mobile systems can support voice data and a range of additional services such as a short message service and call forwarding (Call Divert)
bullAnalog mobile systems offered limited international roaming and a low level of security GSM on the other hand offers few restrictions on international roaming and provides advanced security using ciphering and authentication
Why Wireless
Why Wireless
source DestinationTransmission medium
Why Wireless
The kinds of transmission medium
1- Twisted-pair It is very low bandwidth and it is easily tapped either physically or by monitoring its electromagnetic radiation 2- Coaxial cable It is greater bandwidth than twisted-pair but it is very expensive
3- optical fibers It is very high bandwidth very high bit rate
Why Wireless
4 -Radio (wireless)
It is greatly depending on the particular frequency of the electromagnetic wave
Some of their advantages
a- They are very flexible
b- Portable system can be installed very quicklyc- There are often the most cost-effective solution
Types of communication
TX RX
TX+RX TX +RX
TX+RX TX +RX
Multiple-access for Digital Communication Systems
The frequency spectrum must be shared by all the users in the system
Three method for sharing spectrum
FDMA
Frequency-division multiple-access
TDMA
Time-division multiple-access
CDMA
Code-division multiple-access
Most modern systems use combinations
TDMAFDMA
CDMAFDMA
Multiple-Access
Three ways to separate signals
1 -Frequency
2 -Time
3 -Code
Frequency
Time
Code
FDMA
-Frequency-division multiple-access
-Each user is assigned one frequency
frequency
Channel 1 32 4
30 kHzguardband
FDMA
Frequency-Division Multiple-Access
ExamplesAMPSFrequency
Time
Code
TDMA
Time-division multiple-access
All users transmit at same frequency
Each user transmits at a different time
User 1
User 2
User 3
User 1
User 2
User 3guardtime
20 msectime slot
time
TDMA
Frequency
Time
Code
Time-Division Multiple-Access
CDMA
Frequency
Time
Code
Code-Division Multiple-AccessExamplesIS-95Bluetooth
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Analog to Digital (1G to 2G)
bullThe main restrictions of analog mobile systems are the limited capacity voice-only services and high operational costdifferent systems are incompatible in terms of equipment and operation eg NMT and TACS
bullWith digital systems such as GSM the available frequency spectrum is used more efficiently leading to increased capacity and reductions in associated costs for network operators equipment suppliers and subscribers
bullAnalog mobile systems were originally designed for voice However digital mobile systems can support voice data and a range of additional services such as a short message service and call forwarding (Call Divert)
bullAnalog mobile systems offered limited international roaming and a low level of security GSM on the other hand offers few restrictions on international roaming and provides advanced security using ciphering and authentication
Why Wireless
Why Wireless
source DestinationTransmission medium
Why Wireless
The kinds of transmission medium
1- Twisted-pair It is very low bandwidth and it is easily tapped either physically or by monitoring its electromagnetic radiation 2- Coaxial cable It is greater bandwidth than twisted-pair but it is very expensive
3- optical fibers It is very high bandwidth very high bit rate
Why Wireless
4 -Radio (wireless)
It is greatly depending on the particular frequency of the electromagnetic wave
Some of their advantages
a- They are very flexible
b- Portable system can be installed very quicklyc- There are often the most cost-effective solution
Types of communication
TX RX
TX+RX TX +RX
TX+RX TX +RX
Multiple-access for Digital Communication Systems
The frequency spectrum must be shared by all the users in the system
Three method for sharing spectrum
FDMA
Frequency-division multiple-access
TDMA
Time-division multiple-access
CDMA
Code-division multiple-access
Most modern systems use combinations
TDMAFDMA
CDMAFDMA
Multiple-Access
Three ways to separate signals
1 -Frequency
2 -Time
3 -Code
Frequency
Time
Code
FDMA
-Frequency-division multiple-access
-Each user is assigned one frequency
frequency
Channel 1 32 4
30 kHzguardband
FDMA
Frequency-Division Multiple-Access
ExamplesAMPSFrequency
Time
Code
TDMA
Time-division multiple-access
All users transmit at same frequency
Each user transmits at a different time
User 1
User 2
User 3
User 1
User 2
User 3guardtime
20 msectime slot
time
TDMA
Frequency
Time
Code
Time-Division Multiple-Access
CDMA
Frequency
Time
Code
Code-Division Multiple-AccessExamplesIS-95Bluetooth
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Why Wireless
Why Wireless
source DestinationTransmission medium
Why Wireless
The kinds of transmission medium
1- Twisted-pair It is very low bandwidth and it is easily tapped either physically or by monitoring its electromagnetic radiation 2- Coaxial cable It is greater bandwidth than twisted-pair but it is very expensive
3- optical fibers It is very high bandwidth very high bit rate
Why Wireless
4 -Radio (wireless)
It is greatly depending on the particular frequency of the electromagnetic wave
Some of their advantages
a- They are very flexible
b- Portable system can be installed very quicklyc- There are often the most cost-effective solution
Types of communication
TX RX
TX+RX TX +RX
TX+RX TX +RX
Multiple-access for Digital Communication Systems
The frequency spectrum must be shared by all the users in the system
Three method for sharing spectrum
FDMA
Frequency-division multiple-access
TDMA
Time-division multiple-access
CDMA
Code-division multiple-access
Most modern systems use combinations
TDMAFDMA
CDMAFDMA
Multiple-Access
Three ways to separate signals
1 -Frequency
2 -Time
3 -Code
Frequency
Time
Code
FDMA
-Frequency-division multiple-access
-Each user is assigned one frequency
frequency
Channel 1 32 4
30 kHzguardband
FDMA
Frequency-Division Multiple-Access
ExamplesAMPSFrequency
Time
Code
TDMA
Time-division multiple-access
All users transmit at same frequency
Each user transmits at a different time
User 1
User 2
User 3
User 1
User 2
User 3guardtime
20 msectime slot
time
TDMA
Frequency
Time
Code
Time-Division Multiple-Access
CDMA
Frequency
Time
Code
Code-Division Multiple-AccessExamplesIS-95Bluetooth
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Why Wireless
source DestinationTransmission medium
Why Wireless
The kinds of transmission medium
1- Twisted-pair It is very low bandwidth and it is easily tapped either physically or by monitoring its electromagnetic radiation 2- Coaxial cable It is greater bandwidth than twisted-pair but it is very expensive
3- optical fibers It is very high bandwidth very high bit rate
Why Wireless
4 -Radio (wireless)
It is greatly depending on the particular frequency of the electromagnetic wave
Some of their advantages
a- They are very flexible
b- Portable system can be installed very quicklyc- There are often the most cost-effective solution
Types of communication
TX RX
TX+RX TX +RX
TX+RX TX +RX
Multiple-access for Digital Communication Systems
The frequency spectrum must be shared by all the users in the system
Three method for sharing spectrum
FDMA
Frequency-division multiple-access
TDMA
Time-division multiple-access
CDMA
Code-division multiple-access
Most modern systems use combinations
TDMAFDMA
CDMAFDMA
Multiple-Access
Three ways to separate signals
1 -Frequency
2 -Time
3 -Code
Frequency
Time
Code
FDMA
-Frequency-division multiple-access
-Each user is assigned one frequency
frequency
Channel 1 32 4
30 kHzguardband
FDMA
Frequency-Division Multiple-Access
ExamplesAMPSFrequency
Time
Code
TDMA
Time-division multiple-access
All users transmit at same frequency
Each user transmits at a different time
User 1
User 2
User 3
User 1
User 2
User 3guardtime
20 msectime slot
time
TDMA
Frequency
Time
Code
Time-Division Multiple-Access
CDMA
Frequency
Time
Code
Code-Division Multiple-AccessExamplesIS-95Bluetooth
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Why Wireless
The kinds of transmission medium
1- Twisted-pair It is very low bandwidth and it is easily tapped either physically or by monitoring its electromagnetic radiation 2- Coaxial cable It is greater bandwidth than twisted-pair but it is very expensive
3- optical fibers It is very high bandwidth very high bit rate
Why Wireless
4 -Radio (wireless)
It is greatly depending on the particular frequency of the electromagnetic wave
Some of their advantages
a- They are very flexible
b- Portable system can be installed very quicklyc- There are often the most cost-effective solution
Types of communication
TX RX
TX+RX TX +RX
TX+RX TX +RX
Multiple-access for Digital Communication Systems
The frequency spectrum must be shared by all the users in the system
Three method for sharing spectrum
FDMA
Frequency-division multiple-access
TDMA
Time-division multiple-access
CDMA
Code-division multiple-access
Most modern systems use combinations
TDMAFDMA
CDMAFDMA
Multiple-Access
Three ways to separate signals
1 -Frequency
2 -Time
3 -Code
Frequency
Time
Code
FDMA
-Frequency-division multiple-access
-Each user is assigned one frequency
frequency
Channel 1 32 4
30 kHzguardband
FDMA
Frequency-Division Multiple-Access
ExamplesAMPSFrequency
Time
Code
TDMA
Time-division multiple-access
All users transmit at same frequency
Each user transmits at a different time
User 1
User 2
User 3
User 1
User 2
User 3guardtime
20 msectime slot
time
TDMA
Frequency
Time
Code
Time-Division Multiple-Access
CDMA
Frequency
Time
Code
Code-Division Multiple-AccessExamplesIS-95Bluetooth
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Why Wireless
4 -Radio (wireless)
It is greatly depending on the particular frequency of the electromagnetic wave
Some of their advantages
a- They are very flexible
b- Portable system can be installed very quicklyc- There are often the most cost-effective solution
Types of communication
TX RX
TX+RX TX +RX
TX+RX TX +RX
Multiple-access for Digital Communication Systems
The frequency spectrum must be shared by all the users in the system
Three method for sharing spectrum
FDMA
Frequency-division multiple-access
TDMA
Time-division multiple-access
CDMA
Code-division multiple-access
Most modern systems use combinations
TDMAFDMA
CDMAFDMA
Multiple-Access
Three ways to separate signals
1 -Frequency
2 -Time
3 -Code
Frequency
Time
Code
FDMA
-Frequency-division multiple-access
-Each user is assigned one frequency
frequency
Channel 1 32 4
30 kHzguardband
FDMA
Frequency-Division Multiple-Access
ExamplesAMPSFrequency
Time
Code
TDMA
Time-division multiple-access
All users transmit at same frequency
Each user transmits at a different time
User 1
User 2
User 3
User 1
User 2
User 3guardtime
20 msectime slot
time
TDMA
Frequency
Time
Code
Time-Division Multiple-Access
CDMA
Frequency
Time
Code
Code-Division Multiple-AccessExamplesIS-95Bluetooth
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Types of communication
TX RX
TX+RX TX +RX
TX+RX TX +RX
Multiple-access for Digital Communication Systems
The frequency spectrum must be shared by all the users in the system
Three method for sharing spectrum
FDMA
Frequency-division multiple-access
TDMA
Time-division multiple-access
CDMA
Code-division multiple-access
Most modern systems use combinations
TDMAFDMA
CDMAFDMA
Multiple-Access
Three ways to separate signals
1 -Frequency
2 -Time
3 -Code
Frequency
Time
Code
FDMA
-Frequency-division multiple-access
-Each user is assigned one frequency
frequency
Channel 1 32 4
30 kHzguardband
FDMA
Frequency-Division Multiple-Access
ExamplesAMPSFrequency
Time
Code
TDMA
Time-division multiple-access
All users transmit at same frequency
Each user transmits at a different time
User 1
User 2
User 3
User 1
User 2
User 3guardtime
20 msectime slot
time
TDMA
Frequency
Time
Code
Time-Division Multiple-Access
CDMA
Frequency
Time
Code
Code-Division Multiple-AccessExamplesIS-95Bluetooth
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Multiple-access for Digital Communication Systems
The frequency spectrum must be shared by all the users in the system
Three method for sharing spectrum
FDMA
Frequency-division multiple-access
TDMA
Time-division multiple-access
CDMA
Code-division multiple-access
Most modern systems use combinations
TDMAFDMA
CDMAFDMA
Multiple-Access
Three ways to separate signals
1 -Frequency
2 -Time
3 -Code
Frequency
Time
Code
FDMA
-Frequency-division multiple-access
-Each user is assigned one frequency
frequency
Channel 1 32 4
30 kHzguardband
FDMA
Frequency-Division Multiple-Access
ExamplesAMPSFrequency
Time
Code
TDMA
Time-division multiple-access
All users transmit at same frequency
Each user transmits at a different time
User 1
User 2
User 3
User 1
User 2
User 3guardtime
20 msectime slot
time
TDMA
Frequency
Time
Code
Time-Division Multiple-Access
CDMA
Frequency
Time
Code
Code-Division Multiple-AccessExamplesIS-95Bluetooth
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Multiple-Access
Three ways to separate signals
1 -Frequency
2 -Time
3 -Code
Frequency
Time
Code
FDMA
-Frequency-division multiple-access
-Each user is assigned one frequency
frequency
Channel 1 32 4
30 kHzguardband
FDMA
Frequency-Division Multiple-Access
ExamplesAMPSFrequency
Time
Code
TDMA
Time-division multiple-access
All users transmit at same frequency
Each user transmits at a different time
User 1
User 2
User 3
User 1
User 2
User 3guardtime
20 msectime slot
time
TDMA
Frequency
Time
Code
Time-Division Multiple-Access
CDMA
Frequency
Time
Code
Code-Division Multiple-AccessExamplesIS-95Bluetooth
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
FDMA
-Frequency-division multiple-access
-Each user is assigned one frequency
frequency
Channel 1 32 4
30 kHzguardband
FDMA
Frequency-Division Multiple-Access
ExamplesAMPSFrequency
Time
Code
TDMA
Time-division multiple-access
All users transmit at same frequency
Each user transmits at a different time
User 1
User 2
User 3
User 1
User 2
User 3guardtime
20 msectime slot
time
TDMA
Frequency
Time
Code
Time-Division Multiple-Access
CDMA
Frequency
Time
Code
Code-Division Multiple-AccessExamplesIS-95Bluetooth
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
FDMA
Frequency-Division Multiple-Access
ExamplesAMPSFrequency
Time
Code
TDMA
Time-division multiple-access
All users transmit at same frequency
Each user transmits at a different time
User 1
User 2
User 3
User 1
User 2
User 3guardtime
20 msectime slot
time
TDMA
Frequency
Time
Code
Time-Division Multiple-Access
CDMA
Frequency
Time
Code
Code-Division Multiple-AccessExamplesIS-95Bluetooth
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
TDMA
Time-division multiple-access
All users transmit at same frequency
Each user transmits at a different time
User 1
User 2
User 3
User 1
User 2
User 3guardtime
20 msectime slot
time
TDMA
Frequency
Time
Code
Time-Division Multiple-Access
CDMA
Frequency
Time
Code
Code-Division Multiple-AccessExamplesIS-95Bluetooth
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
TDMA
Frequency
Time
Code
Time-Division Multiple-Access
CDMA
Frequency
Time
Code
Code-Division Multiple-AccessExamplesIS-95Bluetooth
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
CDMA
Frequency
Time
Code
Code-Division Multiple-AccessExamplesIS-95Bluetooth
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Notes UL uplink (Mobile to BTS) helliphelliphelliphelliphellip DL Downlink (BTS to Mobile)
Overcoming Fading problems by using high sensitive receivers in the mobiles
When Making a call given a freq amp a time slot (discrete call)
Freq Hopping ( used by Military )
Doppler Shift used in speed detection (^f)
Power Measurement is made by the mobile to determine its location from the BTS
The size of a cell is limited to a maximum radius of 35 Km
High-Speed Uplink Packet Access (HSUPA) (375 G) is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 576 Mbits
High-Speed Uplink Packet Access (HSUPA) (375 G)
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Chapter 2 Basic GSM Network Structure
We hear Music But we donrsquot see the musicians
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
GSM Overview
Basic GSM Network Structure
Basic GSM Nodes
AUC Authentication CenterBGW Billing GateWayBSC Base Station ControllerBSS Base Station SubsystemBTS Base Transceiver StationDTI Data Transmission InterworkingEIR Equipment Identity RegisterGMSC Gateway MSCHLR Home Location RegisterISDN Integrated Services Digital NetworkMS Mobile StationMSC Mobile services Switching CenterPLMN Public Land Mobile NetworkPSTN Public Switched Telephony NetworkSMSC Short Message Service CenterSS Switching SubsystemTRC Transcoder Resources ControllerVLR Visitor Location Register
SSSS
D T I
BTSBTS
ISDN
PLMN
PSTN
ISDNISDN
PLMNPLMN
PSTN
SMSC
B G WH L R
E I R
GWMSCGMSC
MSCVLRMSCVLR
MS
Air If
BSCTRCBSCTRC
BSSBSS
AUC
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Administers its Base Station Controller(s) BSC(s)
Call setup routing amp supervision for mobile subscribers Contributes to the short messages transfer tofrom mobile
subscribers
Records charging and accounting data
GSM Overview
Basic GSM Network Structure
Mobile Services Switching Center (MSC)
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
HLR (home location register)The HLR is a centralized network database that stores and manages all mobile subscriptionsPermanent information
bull IMSI MSISDN
bull Services subscribed
bull Service restrictions (eg roaming restrictions)
bull Parameters for additional services
bull info about user equipment (IMEI)
bull Authentication data
Temporary information 1048790
Link to current location of the user
bull Current VLR address (if avail)
bull1048790Current MSC address (if avail)
bull1048790MSRN (if user outside PLMN)
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
VLR (visitor location register)
MSCVLR
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
GSM Overview
Basic GSM Network Structure
Equipment Identity Register (EIR)
Database that validates Mobile Equipments usage It contains White list
for normal handsets Gray list for faulty or non-type approved handsets amp
Black list for stolen handsets
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
GSM Overview
Basic GSM Network Structure
Short Message Service Center (SMSC)
Receives and stores short messages from mobile subscribers
Forwards short messages to mobile subscribers
If the delivery of short messages fails (due to mobile absent or full
memory condition) it starts a retry schedule to deliver the message
Generates charging data for the short messages delivered
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Manages the Radio Communication with the mobile stations over the air interface
Controls the locating algorithm and handovers between the BTSs Supervises the transport network resources and the operation amp maintenance of each BTS
GSM Overview
Basic GSM Network Structure
Base Station Controller (BSC)
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
FUNCTION OF BSC
bullPaging
bullChannel allocation
bullDynamic power control in MS and BTS
bullLocating the MS
bullHandover
bullFrequency Hopping
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
GSM Overview
Basic GSM Network Structure
Transcoder Resources Controller (TRC)
Provides the transcoding functionality for speech calls and rate adaptation for data calls
It can be integrated with the BSC or a standalone node It can provide the transcoding resources for up to 16 BSC
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
GSM Overview
Basic GSM Network Structure
Base Transceiver Station (BTS)
Consists of the radio transmitters receivers and the antenna system required to provide the coverage area for one cell
Converts the GSM radio signals into a format that can be recognized by the BSC
Records and passes to the BSC the periodic power measurement reports
Performs the network end function for the cipheringencryption process
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
The SIM Card contains
A processor and memory
that stores - The international mobile subscriber Identity IMSI
- The Authentication and ciphering keys
The Mobile Equipment is said to be a Mobile Station if the Subscriber Identity Module ( SIM Card ) is added to it
+GSM Overview
Basic GSM Network Structure
Mobile Station (MS)=
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Sim cardStores user addresses
IMSIMSISDNTIMSI rooming etc
Personalization
SIM stores user profile (subscribed services)
RAM available for SMS short numbers userrsquos directory etc
Protection codes PIN PUK
authentication and encryption features
subscriberrsquos secret authentication key (Ki)
Authentication algorithm (ldquosecretrdquo algorithm - A3 ndash not unique)
Cipher key generation algorithm (A8)
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
GSM Overview
Basic GSM Network Structure
CC Country CodeNDC Network Destination CodeSN Subscriber Number
VodaFone Egypt MSISDN
20
CC
10
NDC
1100477
SN
Mobile Station ISDN Number (MSISDN)
VodaFone UK MSISDN
44
CC
385
NDC
196099
SN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
GSM Overview
Basic GSM Network Structure
International Mobile Subscriber Identity (IMSI)
MCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
Vodafone UK IMSI
234
MCC
15
MNC
1234567890
MSIN
Vodafone Egypt IMSI
602
MCC
02
MNC
1234567890
MSIN
GSM Identities
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
GSM Overview
Basic GSM Network Structure
International Mobile Equipment Identity (IMEI)
IMEI
6 Digits
TAC
2 Digits
FAC
6 Digits
SN
TAC Type Approval Code The first two digits are the code for the country approvalSN Serial Number
Final Assembly Codes (FAC)
0102 AEG0740 Motorola1020 Nokia30 Ericsson404144 Siemens47 Optional International50 Bosch51 Sony51 Siemens51 Ericsson60 Alcatel70 Sagem75 Dancall80 Philips85 Panasonic
GSM Identities
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Temporary Mobile Subscriber Identity Number (TMSI)
The TMSI can be allocated to the mobile subscriber in order to be used instead of his IMSI during all radio communications The purpose is to keep subscriber information confidential on the air interface
The TMSI is relevant on the local MSCVLR level only and is changed at certain events or time intervals Each local operator can define its own TMSI structure
Basic GSM Network Structure
GSM Identities
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Mobile Station Roaming Number (MSRN)
When a mobile terminating call is to be set-up the HLR of the called subscriber requests the MSCVLR to allocate an MSRN to the called subscriber
This MSRN is returned via the HLR to the GMSC
The GMSC routes the call to the MSCVLR exchange where the called subscriber is currently registered
The routing is done using the MSRN When the routing is completed the MSRN is released
The interrogation call routing function (request for MSRN) is part of the MAP
All data exchanged between GMSC-HLR-MSCVLR for the purpose of interrogation is sent over S7 signaling
The MSRN is built up like an MSISDN
Basic GSM Network Structure
GSM Identities
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
GSM Overview
Basic GSM Network Structure
Security Features
Authentication to secure network against unauthorized access
Ciphering to protect subscriber data sent over the radio path against eavesdropping
Subscriber identity confidentiality
Equipment Identity Check to prevent fraudulent usage of mobile handsets
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Chapter 3 Radio Coverage
A visible pattern of sound waves
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Dead Spots
Problem of omni directional antennas
GSM Overview
Radio Coverage
Cell Geometry
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
R R
To solve the dead spot problem
bull The number of cells required to cover a given area
bull The cell transceiver power
Tradeoffs R
GSM Overview
Radio Coverage
Cell Geometrical Shape
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Omni-Directional AntennaSectorial Antenna
GSM Overview
Radio Coverage
Transceiver Antenna
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
The cells will take the form of overlapping circles
Due to the obstacles in the coverage area the actual shape of the cells would be Random
Sectorial Antenna
GSM Overview
Radio Coverage
Sectorial Antenna
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Overlaid amp Underlaid CellsNormal Cell Normal Cell
GSM Overview
Radio Coverage
Cell ClassificationMacrocell
Microcell
Slow moving subscribers
Fast moving subscribers
Picocell
In buildingcoverage
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Configure Cell Attributes
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Cell Basic Attributes
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Configure ARFCN
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Allocate ARFCN to TRX
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
To provide coverage for a large service area of a mobile network we have two Options
(A) Install one transceiver with high radio power at the center of the service area
Drawbacks
bull The mobile equipments used in this network should have high output power in order to be able to transmit signals across the coverage area
bull The usage of the radio resources would be limited
(B) Divide the service area into smaller areas (cells)
Advantages
bull Each cell as well as the mobile handsets will have relatively small power transceivers
bull The frequency spectrum might be ldquoreusedrdquo in two far separated cells This yields
Unlimited capacity of the system
Good interference characteristics
GSM Overview
Radio Coverage
GSM Coverage Plan
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
GSM Overview
Radio Coverage
Radio Access Methods
Frequency Division Multiple Access (FDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
GSM Overview
Radio Coverage
Radio Access Methods
Time Division Multiple Access (TDMA)
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
GSM Overview
Radio Coverage
Radio Access Methods
Hybrid TDMAFDMA
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
GSM Overview
Radio Coverage
Radio Access Methods
Code Division Multiple Access (CDMA)
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 900)
GSM 900 Frequency Allocation
F (MHz)915890
Uplink1 2 3 4 121 122 123 124
F (MHz)
Downlink
960935
1 2 3 4 121 122 123 124
8902
8904
8906
9352
9354
9356
200 KHz
1
1
121
121
Downlink 935 ndash 960 MHz
Uplink 890 ndash 915 MHz
ARFCN Absolute Radio Frequency Channel Number
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
GSM 1800 Frequency Allocation
F (MHz)17851710
Uplink1 2 3 4 371 372 373 374
F (MHz)
Downlink
18801805
1 2 3 4 371 372 373 374
17102
17104
17106
18052
18054
18056
200 KHz
Downlink 1805 ndash 1880 MHz
Uplink 1710 ndash 1785 MHz
GSM Overview
Radio Coverage
Spectrum Allocation (GSM 1800)
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
890 915
935 960
GSM 900With 124 ARFCN
25 MHz
45
MH
z
Uplink
Downlink
1710 1785
1805 1880
GSM 1800With 374 ARFCN
75 MHz
95
MH
z
Uplink
Downlink
GSM Overview
Radio Coverage
Comparison
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Total no of channels (frequencies) = 124
Every channel can be shared between a maximum of 8 subscribers
Maximum no of simultaneous calls = 8 X 124 = 992
Why do we need frequency reuse
The frequency reuse is performed by dividing the whole available frequencies between a group of neighboring cells which is called frequency reuse pattern or a ldquoClusterrdquo and then repeat this cluster over the whole network on 2 conditions
The group of frequencies allocated to a given cell must not be used in the adjacent cells
Enough distance between the cells where the same group of frequencies are reused
GSM Overview
Radio Coverage
Frequency Reuse
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
39 cluster in which the available frequencies are divided into 9 groups and distributed between 3 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
A3
A2
A1
B3
B2
B1
C3
C2
C1
GSM Overview
Radio Coverage
39 Cluster
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
4 12 Cluster
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
412 cluster in which the available frequencies are divided into 12 groups and distributed between 4 sites
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
A3
A2
A1
B3
B2
B1
C3
C2
C1
D3
D2
D1
GSM Overview
Radio Coverage
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
A3
A2
A1
C3
C2
C1
D3
D2
D1
B3
B2
B1
E3
E2
E1
F3
F2
F1
G3
G2
G1
7 21 cluster in which the available frequencies are divided into 21 groups and distributed between 7 sites
GSM Overview
Radio Coverage
7 21 Cluster
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Carrier to interference ratio
Itrsquos the difference in power level between the carrier in a given cell and the same carrier received from the nearest cell that reusesthe same frequency
Number of frequencies per site
Traffic ChannelsCI Ratio
39HighHighLow
412MediumMediumMedium
721LowLowHigh
GSM Overview
Radio Coverage
Which Cluster Size to use
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
R cell radius
K cluster size
D repeating distance
1
23
1
23
1
23
1
23
546
71
23
546
71
235
46
71
23
546
71
23
K = 12D
R
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12
546
71
23
98 10
11
12 K = 7
K = 3 D R K 3
Spatial Frequency Re-use in Cell Clusters
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Reuse Pattern(Cluster) -Cells are grouped into Clusters
-Available Band is distributed among the cells of the cluster
ldquo -Nrdquo is the number of cells in a cluster -Each frequency is reused after the same distance
ldquoDrdquo -Reuse Plan = gtgt (DR)sup2= 3N
Where R is the cell radius
5
23
4
7
1
65
N=7 Cell ClusterN=7 Cell Cluster
7 Cell Reuse Plan7 Cell Reuse Plan
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
23
4
7
1
65
D
Cellular System Concepts ldquoFrequency reuserdquo
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Co-channel Interference
bull Cells that have the same set of frequencies called co-channel cells and the interference between them is called co-channel interference
bull We cant remove co-channel interference by increasing the carrier transmitter power as it will increase the interference with the neighboring cells To solve co-channel interference we must separate the co-channel cells by a minimum distance to provide sufficient isolation due to propagation
bull In the case of each cell has the same size and transmitted power the co-channel interference ratio is independent of the transmitted power and depend on the radius of the cell (R) and the distance between the centers of the nearest co-channel cell (D) As the ratio DR increased the interference will be reduced as the distance between the co-channel cells will increase
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
Adjacent Channel Interference
bull It is interference resulting from signals which are adjacent in frequency to desired signal
bull It results from imperfect receiver filters which allow nearby frequencies to leak into the baseband
bull Adjacent frequencies must be avoided in the same cell and preferably in neighboring cells also
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
calculations
1 Up link BW = down link BW = (Total BW (MHZ) =50)2=25 MHZ2 No of frequencies = (uplink bw (MHZ) =25chspacing
(MHZ))=02=125 3Traffic channelscell= (no of frequencies=125cluster size=21) =6
4No of traffic channels= (traffic channelscell=6)8-2=465Trafficsubscriber= (Expected callhouruser=13600)(Average
calluser (second) =90) =00256 Using erlang b table B=2
Traffic channels=46 So trafficcell=3653
7 Subscribercell= (trafficcell=3653) (trafficsubscriber=0025) =14628 No of cells= (No of subscribers=300000)( subscribercell=1462)=206
9 No of BTSrsquos = (no of cells= 206)3=69
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
RESULTS
if we vary the cell size some outputs will change
1 no of cells will decrease 2 no of BTS will decrease
QuestionsQuestions
GSM Overview
QuestionsQuestions
GSM Overview