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Speech decoding
Channel decoding
De-interleaving
Burst Formatting
De-ciphering
DemodulationModulation
Ciphering
Burst Formatting
Interleaving
Channel Coding
Speech coding
Radio Interface
Speech Speech
13 Kbps
22.8 Kbps
22.8 Kbps
33.6 Kbps
33.6 Kbps
270.83 Kbps
CM
MM
RR
LAPDm
MS
RR
LAP Dm
Um
LAPD
BTSM
LAPD
Abis
RR
BTSM SCCP
MTP3
BS SAP
BTS BSC
MTP2
SCCP
MTP3
BS SAP
MTP2
CM
MM
MSC
A
Trafficchannels
(TCH)
Signalingchannel
TCH/F: Full-rate Traffic Channel
TCH/H: Half-rate Traffic Channel
FCCH: Frequency correction
SCH: Synchronization
BCCH: Broadcast control
PCH: Paging
AGCH: Access grant
RACH: Random accessSDCCH: Stand-alone dedicated control
GSM Registration (simplified)• When an MS needs registration (first turned on, found the current cell has a
different ID)1. MS sends Channel Request to BSC2. BSC replies with Activation Response3. MS sends Activation ACK4. BSC assigns a channel to process registration5. MS sends Location Update Request to MSC6. MSC replies with Authentication Request7. MS replies with Authentication Response8. MSC checks the authentication9. MSC assigns TMSI to MS10. MS sends ACK for TMSI11. MSC updates VLR and HLR12. BSC informs the MS to release the channel for registration
Location Registry
Location Registry
• Registration Message Flow– Inter-LA movement• In the same MSC
– Inter-MSC movement• In the same GSM Operator
– Inter-VLR movement
Registration Message Flow-- Inter-LA Movement
1
2
3
4
HLR
MSC2
LA2LA1
MSC1
VLR2VLR1
17
Mobile Switching
Center
VLR
old BSS
1
3
24
5 6
78
GSM: handoff with common MSC
new BSS
1. old BSS informs MSC of impending handoff, provides list of 1+ new BSSs
2. MSC sets up path (allocates resources) to new BSS
3. new BSS allocates radio channel for use by mobile
4. new BSS signals MSC, old BSS: ready 5. old BSS tells mobile: perform handoff to
new BSS6. mobile, new BSS signal to activate new
channel7. mobile signals via new BSS to MSC: handoff
complete. MSC reroutes call8 MSC-old-BSS resources released
Call Setup
MS BSS MSC/VLR HLR PSTN
Channel REQuest
IMMediate ASSignComplete layer 3 Info,
AUThentication REQuest
TMSI REALlocation CoMmanD
SETUP
Mobile-originated call, mobile to land call flow (part 1 of 2)
AUThentication RESponse
Cipher Mode CompleteCipher Mode CMD
Cipher Mode CMDCipher Mode Complete
TMSI REALlocation COMplete
MS BSS MSC/VLR HLR PSTNCALL PROCeeding
Mobile-originated call, mobile to land call flow (part 2 of 2)
Assignment Request
ASSignment CoMmanD
Assignment CompleteAssignment Complete
Initial Address Message (IAM)
Address Complete message (ACM)Alerting
Answer Signal/answer Message(ANM)connect
Connect Acknowledge
PriorMSC
PriorVLR HLR
ServingVLR
ServingMSC
ServingBase
Call setup to a roaming subscriber
Receive callsetup request
LOCATION REQUEST INVOKE
ROUTE REQUEST INVOKE
ROUTE REQUEST INVOKE
ROUTE REQUEST RESULT
ROUTE REQUEST RESULT
LOCATION REQUEST RESULT
Call setup request
(temporary phone number) Page command
PAGE
Delete MIN
conversation VMPS call setup
GMSC
MSC/VLR
BSC
HLR
BTS BTS BTS
MSISDN
MSISDN
MSRN
IMSI
MSISDN-->IMSI-->MSC/VLR Service Area
IMSI<-->MSRN
6.
1.3.
5.
4.
7.
8.
8. 9.
2.
PSTN5.
Call Delivery
MS BSS MSC/VLR HLR PSTN
Mobile-terminated call, land to mobile call flow (part 1 of 2)
Send routing info.Provide roaming numberRoaming number