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GSM System GSM System OverviewOverview
& & Radio NetworkRadio Network
PlanningPlanningIn-house TrainingIn-house Training
15-17 March 05
By Radio Access Network Department
To provide preliminary / in-house training to new engineers on GSM system survey
To share knowledge on radio network planning, design and dimensioing concept
OBJECTIVESOBJECTIVES
To introduce the usage of tools, parameters and features
To present current strategies / practices for radio network planning in DiGi
Day 1
GSM System overview
BSS System
Frequency Planning
TRAINING TRAINING SCOPESCOPEDay 2
Cell Planning
Link Budget Planning
Tools Usage
Common Projects
Day 3
Dimensioing Principles
Features
Parameters and CDD
9.30am – 12.45pm9.30am – 12.45pm
2.00pm – 6.00pm2.00pm – 6.00pm
9.30am – 12.45pm9.30am – 12.45pm
2.00pm – 6.00pm2.00pm – 6.00pm
9.30am – 12.45pm9.30am – 12.45pm
2.30pm – 6.00pm2.30pm – 6.00pm
Turn on SILENT MODE for your mobile phone
LEAVE room to take phone calls
If you wish to use your laptop during training, type the keypad SOFTLY
Be PUNCTUAL
TRY NOT TO keep leaving the room to attend to other matters
GROUND RULESGROUND RULES
AgendaAgenda
Morning Session
• Introduction to GSM
• System Architecture
• Channel Concept
• Idle Mode Behavior
• Locating
• Traffic Cases
• Handover Concepts
Noon Session
• Ericsson BSS System
• Siemens BSS System
• Other BSS system
• Frequency Planning
• Frequency Hopping
• Dual-Band / EGSM
DAY 1
Evolution of Mobile TechnologyEvolution of Mobile Technology
Stands for Global System for Mobile communication.
Is actually a digital wireless telecommunications standard widely used throughout the world, transmitting voice and data operating on 900 and 1800 frequency bands (800 and 1900 MHz frequency bands in the US)
What is mobile technology?Wireless communication that provides mobility.Most common and widely used today is the GSM standard.
What is GSM?
Year Standard Mobile System Technology Market1981 NMT 450 Nordic Mobile
TelephonyAnalogue Europe, Middle East
1983 AMPS Advanced MobilePhone System
Analogue North and SouthAmerica
1985 TACS Total AccessCommunicationSystem
Analogue Europe and China
1986 NMT 900 Nordic MobileTelephony
Analogue Europe, Middle East
1991/2 GSM Global System forMobile Communications
Digital Worldwide
1991 D-AMPS Digital-AMPS Digital North and SouthAmerica
1994 PDC Personal DigitalCellular
Digital Japan
1995 PCS 1900 PersonalCommunicationServices
Digital North America
Evolution of Mobile Evolution of Mobile StandardsStandards
Digital Digital CommunicationsCommunications
Analogue signal
Digital signal
A continuous signal that is infinitely and continuously variable in amplitude and /or frequency.
A discreet or discontinuously signal using only 2 values, “0” or “1”.
Why go to digital ?Digital is less prone to interference and able to rebuild to the original signal
Analog Signal
FilteringDigital Signal
PAM-signal
Quantization/Coding
Sampling
Acoustics
Digital signals can repair themselves!
New pulse trainPulse train distortedby noise
Re-generated pulse train
…X kms…
GSM System GSM System ArchitectureArchitecture
BTS
BTS
BSC/TRA
GSM System Architecture
Base Station System
HLR EIR
MSC/VLR
AUC
GMSC
PSTN
BTS
Mobile Phone
BSC
MSC/VLR
GGSNSGSN
Switching System
OperationTerminal
OMC
Mobile Phone
SIMcard
HLR
BTS
Mobile Phone
SIMcard
GSM System Architecture
BTS
Transmission
Core Network
BTS
Mobile Phone
Radio
EIR
MSC/VLR
BSC/TRA
GGSN
GMSC
AUC
BSC
PSTN
MSC/VLR
SGSN
OperationTerminal
OMC
HLR
BTS
Mobile Phone
SIMcard
GSM System Architecture
BTS
BTS
Mobile Phone
EIR
MSC/VLR
BSC/TRA
GGSN
GMSC
AUC
BSC
PSTN
MSC/VLR
SGSN
OperationTerminal
OMC
UmA-bis
A
Gb
A Base Transceiver Station controls the radio interface to the MS. The BTS comprises the radio equipment such as transceivers and antennas. Each BTS operates at 1 or several pairs of frequencies. There is an Uplink (MS to BTS) & Downlink (BTS to MS) frequency. At least 1 transmitter and 1 receiver is needed.
A Base Station ControllerBase Station Controller is the central point of the BSS. It controls all radio related functions of a GSM network. The BSC controls all radio related functions of a GSM network. It is a high capacity switch the provides function such as
- MS connection
- MS handover
- Radio Network Management
- Remote control of the BTSs
BTS & BSCBTS & BSC
Abbreviations & Functions
Abbreviations & Functions
A Mobile Services Switching Center (MSC) performs the telephony switching functions for the mobile network. It controls calls to and from other telephony and data systems.
A Gateway MSC (GMSC) interrogates HLR in order to route a call to a Mobile Station(MS).
A Home Location Register is a centralized network database that stores and manages all mobile subscription belonging to a specific operator (PLMN - Public Land Mobile Network). Information stored includes:– Subscriber identity
– Subscriber supplementary services
– Subscriber location information
MSC, GMSC & HLRMSC, GMSC & HLR
Abbreviations & Functions
A Visitor Location Register temporary stores information of all subscribers in an MSC area. There is a VLR for each MSC. When a subscriber move into a new MSC area, the VLR request a copy of a subscribed information from the HLR.
A Authentication Center is to authenticate subscribers attempting to use the network. The AUC is a database connected to the HLR
A Equipment Identity Register is a database of mobile equipment identity, which prevent calls from stolen or unauthorized MS.
VLR, AUC & EIRVLR, AUC & EIR
Abbreviations & Functions
SGSN & GGSNSGSN & GGSN
A Serving GPRS Support Node handles packet data traffic of users in one geographical area
A Gateway GPRS Support Node connects to outside data networks.
Packet data traffic runs on a new backbone IP network and is separate from the existing GSM core network that is used mainly for speech.
Abbreviations & Functions
OMC & NMCOMC & NMC
A Operation and Maintenance Centre is a computerized monitoring center which is connected to other network components such as MSCs and BSCs via X.25 data network links. In the OMC, staff are presented with information about the status of the network and can monitor and control a variety of system parameters. There may be one or several OMCs within a network depending on the network size.
A Network Management Centre is a centralized control of a network. Only one NMC is required for a network and this controls the subordinate OMCs. The advantage of this hierarchical approach is that staff at the NMC can concentrate on long term system-wide issues, whereas local personnel at each OMC can concentrate on short term, regional issues.
A SITESITE is the physical location of which a base station is placed. Includes all equipment put up by the operator (mast, antennas,cabin, base station rack etc.)
A CELLCELL is each uniquely identified GSM capacity source in a BTS, defined by its own coverage footprint (or coverage cell)
A TransceiverTransceiver or TRX/TRU is a single transmitter/receiver unit that able to provide one single GSM frequency to the cell’s coverage footprint.
Site, Cell, & TRXSite, Cell, & TRX
Abbreviations & Functions
Abbreviations & Functions
OthersOthers
A MS = Mobile StationMobile Station is used by a mobile subscriber to communicate with the mobile network. The range or coverage area of an MS depends on the output power of the MS.
A SIM = Subscriber Identity ModuleSubscriber Identity Module is a “smart card” that store subscriber’s information.
A PLMN = Public Land Mobile Network. In any one country there may be serveral, one for each operator’s network
A PSTN = Public Switched Telephone Network. The worldwide set of interconnected switched voice telephone networks that deliver fixed telephone services to the general public and are usually accessed by telephones/key telephone systems
Channel Channel ConceptsConcepts
TDMA Frame
TS TS TS TSTS TS TS TS
0 1 2 43 5 76
ff11
1 TDMA frame
1 physical channel
Each timeslot on a TDMA frame is called a physical channel
Therefore there are 8 physical channels per carrier frequency
Physical channels can be used to transmit speech, data or signaling information
A physical channel may carry different messages, depending on the information that is to be sent
These messages are called logical channel
Frames & Bursts
Logical Channel
FCCHFCCHFCCHFCCH FCCHFCCHSCHSCH FCCHFCCHBCCHBCCH FCCHFCCHPCHPCH FCCHFCCHAGCHAGCH FCCHFCCHRACHRACH FCCHFCCHSDCCHSDCCH FCCHFCCHSACCHSACCH FCCHFCCHFACCHFACCH FCCHFCCHHRHR FCCHFCCHFR & FR & EFREFR
BCHBCH CCCHCCCH DCCHDCCH
Each burst is 156.25 bit times long (~0.577ms) and carried in 1 TS
TCHTCH PDCHPDCH
Control ChannelsControl Channels Traffic ChannelsTraffic Channels
Logical ChannelsLogical Channels
Frequency Correction Channel (FCCH) - DLBTS - Transmits carrier frequency
MS - Identify BCCH carrier by the carrier frequency
Synchronization Channel (SCH) - DLBTS - Transmits information about the TDMA frame
structure in a cell (e.g frame number) and the BTS identity (BSIC)
MS - Synchronizes with the frame structure and decodes the BSIC
Broadcast Control Channel (BCCH) - DLBTS - Transmits LAI, max output power allowed in the
cell, and identity of BCCH carriers of neighbouring cells
MS - Receives LAI information. Set MS output power based on information received on the BCCH. The MS store the list off neighbouring cells’ BCCH to assist in measurements for handover decision.
Broadcast Channel (BCH)
Paging Channel (PCH) - DLBTS - Transmits a paging message to indicate incoming
call or SMS. Paging message contains the identity of MS subscriber
MS – listen to paging channel at certain intervals and respond by using for a RACH
Random Access Channel (RACH) - ULBTS - Receive request from MS for a signaling channel
(e.g. to setup call)
MS – Respond to paging and request for a signaling channel
Access Grant Channel (AGCH) - DLBTS - Assign a signaling channel(SDCCH) to MSMS - Receive signaling channel (SDCCH) assignment.
Common Control Channel (CCCH)
If a MS subscriber wish to make of receive a call, CCCH must be read
Standalone Dedicated Control Channel (SDCCH) – UL & DLBTS - Perform call set up. Assign a TCH.MS - MS receive TCH assignment information.SDCCH is also used for sending SMS and location updating
Standalone Dedicated Slow Associated Control Channel (SACCH) – UL & DL
BTS - Tell MS the transmitting power to use and give instruction on
Timing Advance (TA)MS - Send measurements reports contain the info of own and
neighbouring BTS’s signal strength
Standalone Fast Associated Control Channel (FACCH) – UL & DL
BTS - Transmit handover informationMS - Transmit handover information
Dedicated Control Channel (DCCH)
When the MS and BSS is ready to begin call set-up, MS & BSS will use DCCH
Enhanced Full Rate (FR)Occupies one physical channel but with improved
speech quality
Full Rate (FR)Occupies one physical channel, and transmit full rate
speech (13kbits/s)
Half Rate (HR)Two Half Rate speech (6.5kbits/s) can share one
physical channel, but with poorer speech quality compared to a Full Rate TCH
Traffic Channel (TCH)
Traffic Channel (TCH) is a channel that carry voice traffic.
Packet Data Channel (PDCH)
Packet Data Channel (PDCH) is a channel that carry GPRS/EGPRS traffic.
B-PDCHA Packet Data Channel (PDCH) used for the transfer
of GPRS CS-1 to CS-2
G-PDCHA Packet Data Channel (PDCH) used for the transfer
of GPRS CS-1 to CS-4
E-PDCHA Packet Data Channel (PDCH) used for the transfer
of EGPRS and GPRS CS-1 to CS-4
Ericsson DefinitionEricsson Definition
Channel Allocation
0 1 2 43 5 76
TRX 0
0 1 2 43 5 76
TRX 1
0 1 2 43 5 76
TRX 2
BCCH SDCCH TCH TCH PDCH PDCH PDCH PDCH
TCH SDCCH TCH TCH TCH TCH TCH TCH
TCH TCH TCH TCH TCH TCHTCH TCH
15 mins Break15 mins Break
Idle Mode Idle Mode BehaviourBehaviour
What is idle mode?
A powered on circuit-switched mobile station (MS) that does not have a dedicated channel allocated is defined as being in idle mode.
While in idle mode it is important that the mobile is both able to access and be reached by the system
The idle mode behaviour is managed by the MS. It can be controlled by parameters which the MS receives from the base station on the Broadcast Control Channel (BCCH)
Idle mode Behaviour
PLMN SelectionPLMN SelectionSelection upon MS Power-On, or recovery from lack of coverage once registered to a PLMN, the MS will be capable of making/receiving calls will normally operate on the Home PLMN, unless no coverage available special settings required for National Roaming
Cell SelectionCell SelectionThe algorithm tries to find the most suitable cell of the selected PLMN may enter “limited service state” if unable to register to a PLMN –> Emergency Calls only when coverage lost, MS will return to the PLMN selection state…Two Steps: 1) Stored BA List
2) Normal Cell Selection a. the cell belongs to the selected PLMN b. the cell is not barred c. the registered LA is not incl. in “forbidden LAs” d. the cell selection criterion is fulfilled
Idle mode Behaviour
Cell ReselectionCell ReselectionContinuously measures the BCCH of current Serving Cell, and 6 strongest neighbour cells also attempts to decode the BSIC parameter for each of the 6 neighbouring cells the selected cell instructs the MS which NCC is allowed to be monitored takes measurements when listening to its own paging group most of the time, the MS is in sleep mode
Location UpdateLocation UpdateThe network must always be updated where the subscriber is!There are 3 types of location updating:
a. Normalb. Periodicc. IMSI Attach/Detach
Idle mode Behaviour
PLMN PLMN SelectionSelection
Cell SelectionCell Selection
Cell Cell ReselectionReselection
Location Location UpdatingUpdating
Idle mode BehaviourCell SelectionCell Selection
The MS will find the most suitable cell of the home PLMN according to various requirement.
A cell is considered suitable if:
a) It belong to the home PLMN.
b) It is not barred.
c) The cell selection criterion is fulfilled (i.e. C1)
C1 = (received Rx Level – ACCMIN) – max (CCHPWR – P, 0)
where, ACCMIN is min access requirement for a MS to access a PLMN. CCHPWR is max MS transmitted power allowed to use. P is the max power output of the MS according to its class.
Hence, C1 = Rx Level - ACCMIN
Idle mode Behaviour
Cell ReselectionCell Reselection
C2 = C1 + CRO – TO * H (PT-T) for PT not equal to 31C2 = C1 – CRO for PT equal to 31
Where,
CRO is cell reselection offset (0=0dB, 1=2dB … 63=126dB)TO is temporary offset (0=0dB, 1=10dB … 6=60dB)PT is Penalty Time (0=20s, 1=40s …30=600s)
In DiGi, we use PT = 31, hence, 2nd formula is selected.
LocatingLocating
What is Locating?
The locating algorithm works out the basis for handover decisions.It is the algorithm for cell selection for active mobile after immediate assignment
It is implemented in the BSC and has 2 major objectives: a) Quality & continuity of calls b) ‘Cell size’ control in order to minimize total interference in the network
* The algorithm works continuously, completing a calculation cycle in general every 480ms. (1 SACCH period)
What is Locating?
Locating Algorithm
INPUTINPUTThe input to the algorithm is signal strength and quality measurements from the MS and from the base station currently serving the connection.
OUTPUTOUTPUTThe output is a list of cells that the algorithm judges to be possible candidates for handover.
The cells in the list are ranked and sorted in descending order of preference for handover.
Locating AlgorithmA locating individual is A locating individual is created;created;Transfer of penalty list to new Transfer of penalty list to new cellcell
Initiations
Filtering
Urgency Condition
Basic Ranking
Aux. Radio Network
Functions Evaluation
Organizing the list
Sending the list
Allocation reply
penalty list
measurement results
After a handover, a new locating individual is created and takes over the handling of the connection
A penalty list will be transfer from old to the new locating individual.
Locating AlgorithmA locating individual is A locating individual is created;created;Transfer of penalty list to new Transfer of penalty list to new cellcell
Initiations
Filtering
Urgency Condition
Basic Ranking
Aux. Radio Network
Functions Evaluation
Organizing the list
Sending the list
Allocation reply
penalty list
measurement results Measure for SS, Quality & Measure for SS, Quality &
TATA
Locating AlgorithmSACCH Measurement PeriodSACCH Measurement Period
The SS, Quality & TA measurements are made and reported once for each SACCH period (i.e. 480ms).
DTX (Discontinuous Transmission)
When DTX is employed on a TCH, not all TDMA frames may be transmitted.However, there are some TDMA subset frames always be transmitted and these frames can be employed to assess SS & Quality level measurement.
Full set is a measurement base on all TDMA frames during the SACCH period.Sub set is measurement based on those TDMA frames when DTX is active.
Measurement ReportsThe measurement reports are sent from the BTS to the BSC every SACCHperiod (480 ms) starting when the MS is assigned an SDCCH. The measurement reports are stored and filtered in the BSC.
Note that the MS can measure SS up to 32 neighbours but can only report the 6 strongest in a report.
Measurement Report
The MS transmits the downlink measurement to the BTS.The BTS adds the serving cell uplink measurement and transmits further to the BSC.
Example of MS downlink measurement report as observed in TEMS
Downlink SS (full set)Downlink SS (sub set)Downlink Quality (full set)Downlink Quality (sub set)
Downlink SS (6 strongest neighbours)
Locating AlgorithmA locating individual is A locating individual is created;created;Transfer of penalty list to new Transfer of penalty list to new cellcell
Initiations
Filtering
Urgency Condition
Basic Ranking
Aux. Radio Network
Functions Evaluation
Organizing the list
Sending the list
Allocation reply
penalty list
measurement results Measure for SS, Quality & Measure for SS, Quality &
TATA
BQ handover, TA handoverBQ handover, TA handover
2 criteria are used for urgency detection:
a) Bad Quality (BQ) own here while you’re here
b) Excessive Timing Advance (TA)
Locating AlgorithmA locating individual is A locating individual is created;created;Transfer of penalty list to new Transfer of penalty list to new cellcell
Initiations
Filtering
Urgency Condition
Basic Ranking
Aux. Radio Network
Functions Evaluation
Organizing the list
Sending the list
Allocation reply
penalty list
measurement results Measure for SS, Quality & Measure for SS, Quality &
TATA
BQ handover, TA handoverBQ handover, TA handover
Signal strength rankingSignal strength ranking
A neighbour must pass a minimum SS check in order to be ranked.
a) Correction of BTS output power
b) Evaluation of the minimum signal strength condition
c) Subtraction of signal strength penalties (e.g. LOC_penalty, HCS_penalty)
Locating AlgorithmA locating individual is A locating individual is created;created;Transfer of penalty list to new Transfer of penalty list to new cellcell
Initiations
Filtering
Urgency Condition
Basic Ranking
Aux. Radio Network
Functions Evaluation
Organizing the list
Sending the list
Allocation reply
penalty list
measurement results Measure for SS, Quality & Measure for SS, Quality &
TATA
BQ handover, TA handoverBQ handover, TA handover
Signal strength rankingSignal strength ranking
HCS, Intra-cell HCS, Intra-cell handover, CLS, etc.handover, CLS, etc.
6 auxiliary radio network functions are incorporated in thelocating algorithm:
a) Assignment to Another Cellb) Hierarchical Cell Structures (HCS)c) Overlaid/Underlaid Subcellsd) Intra-cell Handovere) Cell Load Sharing (CLS)f) Extended Range
Locating AlgorithmA locating individual is A locating individual is created;created;Transfer of penalty list to new Transfer of penalty list to new cellcell
Initiations
Filtering
Urgency Condition
Basic Ranking
Aux. Radio Network
Functions Evaluation
Organizing the list
Sending the list
Allocation reply
penalty list
measurement results Measure for SS, Quality & Measure for SS, Quality &
TATA
BQ handover, TA handoverBQ handover, TA handover
Signal strength rankingSignal strength ranking
HCS, Intra-cell HCS, Intra-cell handover, CLS, etc.handover, CLS, etc.
Ordering the Candidate Ordering the Candidate ListList
Locating AlgorithmA locating individual is A locating individual is created;created;Transfer of penalty list to new Transfer of penalty list to new cellcell
Initiations
Filtering
Urgency Condition
Basic Ranking
Aux. Radio Network
Functions Evaluation
Organizing the list
Sending the list
Allocation reply
penalty list
measurement results Measure for SS, Quality & Measure for SS, Quality &
TATA
BQ handover, TA handoverBQ handover, TA handover
Signal strength rankingSignal strength ranking
HCS, Intra-cell HCS, Intra-cell handover, CLS, etc.handover, CLS, etc.
Ordering the Candidate Ordering the Candidate ListList
Sent for Channel Sent for Channel AllocationAllocation
If Success, transfer to new If Success, transfer to new locating individual, else locating individual, else connection remainsconnection remains
Locating Algorithm
Sending The List
The first cell in the candidate list is the “best” candidate.
At congestion the next cell in the candidate list is tried.
Allocation Reply
At success a penalty list is transferred from the locating individual to the new one. If the handover reason was due to urgency a penalty for the abandoned cell must be included.
The old locating individual is then deleted.
At inter-BSC handover it is not possible to send the penalty list.However, it is possible to indicate if the cause of handover wasdue to BQ or TA.
The penalties of the new cell will then be used
Traffic CasesTraffic Cases
Power on… (1)The MS search the subscribed or available network by sending an IMSI attach message to the network
Searchin
g
Searching
DiGi 016
012
016
013
013
016
016
012
The MS logon to the strongest signal
If the subscribed network is available, Authentication Center (AUC) will decide whether or not to give permission for the subscriber.
If authenticated, mobile phone will register to the network.
The VLR determines whether there is a record for the subscriber already present. If not, the VLR contacts the subscriber’s HLR for a copy of the subscription information.
The VLR update the MS status to IDLE and acknowledgement is sent to the MS
AuthenticationRegiste
ring
Power on… (2)
HLR/AUC
BSC
MSC/VLRIDLE Mode
During IMSI attach, the VLR may determine that the current LAI of the MS is different from the LAI stored in the MS’s subscription information. If so, the VLR updates the LAI of the MS.
Location Update…
LA 1LA 1
LA 2LA 2
send location updating message via SDCCH
The MS knows that the new cell LAI by listening to the BCCH in the new cell. If an MS changes cells within the same LA, the network is not updated
What is What is Periodic Periodic RegistratioRegistration?n?
If Mobile phone can’t search for a subscribed network, it will enter “limited service state”.
• Only allows Emergency Calls (112)
Operator A
Operator B
Operator A
Operator C
Operator C
Operator C
Emergency Calls
only
Emergency Calls only
DiGi
Power on… (3)
Making call… (1)
BSC
request for
access usingrequesting…
grant access
you got access
MSC/VLRPlease give him
a voice call
channel…
Please give him a voice
call channel…granting voice call channel..
calling 06-6513056
Telekom
Malaysia
I want to make a voice call…
I want to make a voice call…
check subscription
GMSC
HLR/AUC
1. RACH1. RACH
2. AGCH2. AGCH
3. SDCCH3. SDCCH
4. TCH4. TCH
Receiving call…
BSC KL
BSC JB
BSC Penang
Query the HLR:Where is the subscriber?
Page the subscriber
route the call here!
Telekom
Malaysia
calling 016-2200200
HLR/AUC
GMSC
MSC/VLR
MSC/VLR
MSC/VLRrespond to page
He’s in KL!
BSC PJ
1. PCH1. PCH
2. RACH2. RACH
3. AGCH3. AGCH
Assign SDCCHrespond to call
4. SDCCH4. SDCCH
5. TCH5. TCH
Example: A connection from a Norwegian subscriber visiting Thailand, calling a Malaysian subscriber who is on a visit to the Philippines:
Mobile A
Mobile B +6016***
HLRA
MSC/VLRA
+6016**Request for authentication data
Authentication data
1
2 3
MSC/VLRB
MSC/VLR
HLRB
Where is +6016**?+6016** is in MSC/VLR xx5
47
6
Norway
Malaysia
Thailand
Philippines
International phone network
+6016**
A physical connection that has to remain connected throughout the call
Handover Handover ConceptConcept
Handover Concept
• As the MS moves out of range (coverage) of “old” cell.
• The MS is assigned to “new” RF channel in adjacent cell based on signal strength.
• “Old” channel will then be available for “reuse” by another subscriber.
Reason of handoverReason of handover- signal strength- signal quality- timing advance- load balancing features setting- forced handover (maintenance)
Handover Concept
Intra-cell HandoverIntra-cell Handover
• It is a special type of handover.• Performed when the BSC considers the quality of current connection too low, but no indication from the measurements that another cell would be better• BSC identify another channel in the same cell which may offer better quality and MS is ordered to retune to itThe BSC will attempt to handover first to a
channel on another frequency
As we travel around…
Station B
Station A
Station C
Station B, you are stronger
than me! Please take over!
Ok..Ok..
Station C, you are stronger
than me! Please take over!
Ok..Ok..
As we travel around…(3)
Station B
Station A
Station B, you are stronger
than me! Please take over!
Ok..Ok..
Oopss…sorry, no one to pass the
call…
Call Dropped!!
No COVERAGE!!
Hello…can’t hear you…you breaking up…
hELLo!?!
As we travel around…(4)
Station B
Station A
Station C
Station B, you are stronger than me! Please take over!
Ok..Ok..
Station C, you are stronger than me! Please take over!
Station C, can you hear me?
What? Are you talking to me?
Not clear…
Call Drop!!
Bad Quality – INTERFERENCE!!
As we travel around…(2)
Station B
Station A
Station C
Station B, you are stronger than me! Please take over!
Ok..Ok..
Station C, you are stronger than me! Please take over!
Oh no! My channels
are all full!
Call Drop!!
No Capacity – CONGESTION!!
Power off…The MS sends an IMSI detach message to the network at power off, and the VLR will marks the IMSI as detached. No acknowledgement is sent to the MS.
If IMSI detach message is sent when radio link quality is poor, the message might not be decoded. In this case, the MS is still considered as attached. If periodic registration is use, the system will soon determine that the MS is detached and the VLR will performs an implicit detach.
MS purging is used to inform the HLR that the VLR is about to remove a subscriber record from the VLR. The HLR will marked the MS as unreachable. This saves unneccessary network signalling and database lookup.
DiGi 016
HLR/AUC
BSC
MSC/VLR
IMSI detach
END END of of
Morning SessionMorning Session
… … to be continued to be continued at 2.00pmat 2.00pm
BackupBackup
Common TerminologyCommon Terminology
•SIM Subscriber Identity Module
A smart card is used to store subscriber’s information. Advantages of security and portability to subscriber
•PSTN Public Switched Telephone Network
A standard landline or fixed network phone system
•SMS Short Message Service
A service that enables the user to send and receive text messages to and from mobile device
• IN Intelligent NetworkTelecommunications network architecture that provides flexibility for facilitating the introduction of new capabilities and services, including those under customer control.
•MMS Multimedia Messaging ServiceAn evolution of SMS which that allows mobile subscribers to exchange multimedia messages with other mobile subscribers. MMS support the transmission of additional media types such as text, picture, audio, video and also a combination of mention media types
•WAP Wireless Application Protocol
A standardised way that a mobile phone talks to a server installed in the mobile phone network.
•GPRS General Packet Radio Service
Standardised as part of GSM Phase 2+, GPRS represents the first implementation of packet switching within GSM, which is a circuit switched technology. GPRS offers theoretical data speeds of up to 115kbit/s using multislot techniques. GPRS is an essential precursor for 3G as it introduces the packet switched core required for UMTS
•EDGE Enhanced Data for GSM Evolution
A 3G technology that delivers broadband-like data speeds to mobile devices. It allows consumers to connect to the Internet and send and receive data, including digital images, web pages and photographs, three times faster than possible with an ordinary GSM/GPRS network
•3G 3rd Generation (Mobile Network)3G is characterized by high-speed, high-bandwidth services that support a variety ofapplications, including wireline quality voice and high-resolution video, wirelessly.
Common TerminologyCommon Terminology
ITU-T Standard Management SystemITU-T Standard Management System
Network ElementNetwork Element
Element ManagementElement Management
Network ManagementNetwork Management
Service Service ManagementManagement
BusinessBusinessManagementManagement