1.GSM Basic and Cellular Concepts
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Transcript of 1.GSM Basic and Cellular Concepts
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BSNL GSM
BY:
SHYAM SUNDER SAINIJTO (MSC)
CMTS Division, Udaipur
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Any time Anywhere
Mobility & Roaming
High capacity & subs. density Efficient use ofradio spectrum
Low cost
Flexibility
Innovative Services
MOBILE COMMUNICATION
OBJECTIVES
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History First mobile service started in 1946 in St.
Louis, Missouri, USA.
Manually operated service, restricted area ofservice, only few lucky subscribers.
Between 1950-60, it evolved to be
automatic with decreased cost.
Mobile telephony service appeared in its
useful form in 1960s.
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MOBILE COMMUNICATION
1946- 1960s 1980s 1990s 2000s
Appeared 1G 2G 3G
Analog Digital Digital
Terrestrial Terrestrial Terr. & Sat
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MOBILE COMMUNICATION
1 G -analog (cellular revolution)
- only mobile voice services
WIRELESS GENERATIONS
2 G - digital (breaking digital barrier)
- mostlyfor voice services & data deliverypossible
3 G - Voice & data ( breaking data barrier)
- Mainlyfor data services where voice services
will also be possible
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GSM Architecture
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B
T
S
MSC VLR
HLR
PSTN
ISDN
Data
Networks
Airinterface
OSS
B
T
S
B
T
S
MSC VLR
BSCBSC
A Interface
A-bis interface
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Abbreviation BSC - Base Station Controller
BTS - Base Transceiver Station
MSC-
Mobile Switching Center HLR - Home Location Register
EIR - Equipment Identity Register
AUC - Authentication Center
VLR - Visitor Location Register
OMC - Operation & Maintenance Center
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CELLULAR MOBILE CONCEPTS
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Propagation lossL in dBs
Transmit power PTand antenna gain GT
VoiceChannels
Orcontrol
channels
Lines to
MSC
Sitenoice
MS
Operating distance d
Planned cell radius R
Cell radio range - radius R max
Radio Cell Parameters
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GSM Network Structure
GSM Service Area: Total area served by the
combination ofall member countries where a mobilecan be served.
PLMN Service Area:It is one N/W area.
MSC Service Area:There can many MSC/VLR in onePLMN area.It is one Mobile Exch. Area.
GMSC: All I/C calls for PLMN N/W will be routedthrough GMSC. In a GSM/PLMN N/W all mobileterminated calls will be routed to a Gateway MSC.Call connections betweenPLMNs , or to fixed N/Wsmust be routed to a GMSC.The GMSC contains the
Inter workingfunctions to make these connections.
LocationArea
Cells
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LOCATIONAREA:There are several LA in a MSC/VLR
combinationA LA is a part ofthe MSC/VLR service area in
which a MS may move freelywithout updating location
information to the MSC/VLR exchange that control the LA.
Within a LA a paging message is broadcast in order to find
the called mobile subs. LA can be identified by system usingthe LAI.
CELL.A cell is an identity served by one BTS. The MS
distinguishes between cells using the BASE STATION
IDENTIFICATION CODE(BSIC) that the cell site broadcastover the air.
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GSMRelation between areas in GSM
Location AreaCell
Area served by a BTS
LocationAreaMSC ServiceAreaPLMN ServiceArea
GSM ServiceArea
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GSM
PLMN Service Area
V
MSC
MSC
MSC
MSC
VLR
VLR
VLR
I II
IVIII
I
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GSM
MSC Service Area
MSC
VLRLA1
LA2
LA3
LA6
LA4
LA5
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GSM
Cells
MSC
VLR
LA1
LA2
LA3
LA6LA4
LA5
C1C2 C3
C6C5
C4
C=CELL
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GSM
LA Coding
MCC
LAI
LACMNC
3 digit 3 digit 2Octets
MCC:Mobile country code, MNC: Mobile N/W Code,
LAC: Location Area code
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Location area consist of one or more than one cell which may
be served by one or more BSC s.
All the cells in a Location area are served by single VLR.
2. Location Area Identity (LAI ) -
Each location area in a GSM PLMN is identified by a Location
Area Identity ( LAI ).
Location Related Identities
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HLRSS 7
BSC
MSC 2
VLR 1
VLR 2
BSC
BSC
BSC
LA 1
LA 2
LA 3
BTS
BTS
BTS
BTS
BTS
BTS
Location Area
MSC 1
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LAI = MCC + MNC + LAC
MCC - Mobile Country Code.
MNC - Mobile Network Code.
LAC - Location Area Code .
Maximum length of LAC is 16 bits.
Thus there can be maximum of 65,536 Location Areas defined
in one GSM PLMN.
MCC MNC LAC
3 digits 2 digits 2 octets max
LAI
( 16 bits )
Location Related Identities
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ACLUSTER OF CELLS
4
5
6
7
2
3
11 2 3 4 5 6 7
GIVEN FREQ.
RESOURCE
CELLULAR MOBILE CONCEPTS
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14
2
1
3
5
6
7 2
6
3
4
5
7
DR
CELLULAR PRINCIPLE N=7
12 3 456 7
Frequency Reuse Pattern N=7
Given Freq Resource
CELLULAR MOBILE CONCEPTS
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GSM
CAPACITY CONSIDERATIONS
1
1
1
1
2
88 Access Channels
1--Signaling
7- Voice
With 2 % GoS
2.94 E
2.94E/25mE=120 Subs
120 Subs/Sector v 3 = 360 Subscribers
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Public Land Mobile Network INDIAhas adopted GSM standard for PLMN.
Digital Cellular System.
Operates at 900 MHz. International Roamingfacility.
Power class 0.8 to 20W.
Cell Radius upto 35 Kms.
Maximum mobility speed 250 Km/hr.
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Communication-
Mobile
TelephoneExchange
SubscriberLine(2W)
Inter-Exchange
Junction
Mobile SwitchingCentre (MSC)
BSC BTSMS
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GSM
Uplink & Downlink
Uplink means Reverse Path
Downlink means Forward Path
BT
S
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GSM
Specifications - I
Frequency Bands -
Mobile to Cell (UP-LINK) - 890 to 915 MHz
Cell to Mobile (DOWN -LINK) - 935 to 960 MHz
Bandwidth - 25 MHz
Carrier Separation - 200 KHz
Access Method - TDMA/FDMA
Modulation - GMSK
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GSM
Specifications - II
Number ofChannels - 124
Voice Channel Coding - ( 13 Kbps)
FULL RATE - 13Kb/s ; HALF RATE - 6.5 Kb/s
Bit Rate - 270.833 Kbps
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GSM - MULTIPLE ACCESS GSM uses both FDMA & TDMA
Freq
Mhz.890.2
0
890.4
1
890.6
2
890.8
3
891.0
4 5
915
124
FDMAAccess along Frequency axis Each RF carrier 200khz apart Total 124 RF Channels available.
One or more carrier assigned to each base station
In most cases 124 RF Channels are used
...