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GSM Call Routing
1. The called MS is powered off
GMSCMS BSS MSC VLR HLR GMSC
(
(
MSISDN
+91 9885 xxxxxx
Initial and Final
1 Address Message
2 Send Routing Info
3 Routing Info Ack
Subscriber Absent The Calling
Mobile hears the
announcement of
mobile is powered
off
AP Vodafone AP Airtel
MSISDN
+91 9885 xxxxxx
CFN
4 IFAM
MS BSS MSC VLR HLR GMSC PSTN
2. The called MS activates the CFU to a PSTN No.
Initial and Final
1 Address Message
2 Send Routing Info
3 Routing Info Ack
MSISDN
+91 9885 xxxxxx
MSISDN
+91 9885 xxxxxx
+91 40 66235307
3. The called MS has been barred all incoming call.
MS BSS MSC VLR HLR GMSC
Initial and Final
1 Address Message
2 Send Routing Info
3 Routing Info Ack
GMSC
MSISDN
+91 9885 xxxxxx
MSISDN
+91 9885 xxxxxx
Call Barred
4. The Called MS are not known at HLR
MS BSS MSC VLR HLR GMSC
Initial and Final
1 Address Message
2 Send Routing Info
3 Routing Info Ack
GMSC
MSISDN
+91 9885 xxxxxx
MSISDN
+91 9885 xxxxxx
Unknown Subscriber
Call Routing
Scenarios
2 REQ. FOR SERVICE
1 CHANNEL REQUEST
DCCH ASSIGN
SIGNALING LINK
ESTABLISHED
6 COMPLETE CALL
CALL PROCEEDING
3 AUTHENTICATION
SET Cipher MODE
4 SET-UP
5 EQUIP. ID REQ.
MS BSS MSC VLR HLR PSTN
Mobile Originated Sequence
Signaling Link request
Signaling Link Granted
Call setup is in Process
Setup Voice Call
Dailed digits …+91 40 66235307
Channel request
<
MS BSS MSC VLR HLR PSTN
7 ASSIG. COMMAND
ASSIG. COMPLETE
Switch from Signaling
Mode to Voice
8.Initial and Final Address
Message (IFAM)
Alerting
MS hears ring
tone from land
phone
Address Complete(ACM)
9 Answer (ANS)Connect
Ring tone
stops
10 Connect Acknowldge
BILLING STARTSSpeech Started
Called Subscriber Answered
Switch Informs
Call Answered
Acknowledge Call
Answered received
Hi RK
Ring Alert
Passed to Mobile
Switch routes the call to PSTN
PSTN indicates to Switch
Called Subscriber Informed Via Ring
+91 40 66235307
Mobile Originated Sequence
<
MSISDN
+91 9885 xxxxxx
IMSI
404 13 xxxxxxxxxx
MSRN
LAI & TMSI)TMSI)TMSI)
PCH>
MSRN MSRN
MSRN
Initial and Final
1 Address Message
2 Send Routing Info
3 Routing Info Ack
Initial and Final
Address Message
4 Send Info For I/C
Call Setup
5 Page
Paging Request
MS BSS MSC VLR HLR GMSC GMSC
MSISDN
+91 9885 xxxxxx
091 9885 xxxxxx (roaming number)
091 9885 xxxxxx (roaming number)
LAI – 404 13 location Area Code
Mobile Terminated Sequence
AP Vodafone AP Airtel
MS BSS MSC VLR HLR GMSC GMSC
Billing
starts
7 Connect
Connect ACK ANS
Ringing stops
at Other
Mobile
Subscriber
picks up
Hello...
6 Assignment
Command
Assignment
Complete
Alert
Ringtone Alert Acknowledge
Ring Tone at
the Other
Mobile
Address Complete
Speech Started
Mobile Subscriber Answered
Mobile Terminated Sequence
AP Vodafone AP Airtel
Call Setup Request
Call Setup Confirmed

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Call flow

  • 2. 1. The called MS is powered off GMSCMS BSS MSC VLR HLR GMSC ( ( MSISDN +91 9885 xxxxxx Initial and Final 1 Address Message 2 Send Routing Info 3 Routing Info Ack Subscriber Absent The Calling Mobile hears the announcement of mobile is powered off AP Vodafone AP Airtel MSISDN +91 9885 xxxxxx
  • 3. CFN 4 IFAM MS BSS MSC VLR HLR GMSC PSTN 2. The called MS activates the CFU to a PSTN No. Initial and Final 1 Address Message 2 Send Routing Info 3 Routing Info Ack MSISDN +91 9885 xxxxxx MSISDN +91 9885 xxxxxx +91 40 66235307
  • 4. 3. The called MS has been barred all incoming call. MS BSS MSC VLR HLR GMSC Initial and Final 1 Address Message 2 Send Routing Info 3 Routing Info Ack GMSC MSISDN +91 9885 xxxxxx MSISDN +91 9885 xxxxxx Call Barred
  • 5. 4. The Called MS are not known at HLR MS BSS MSC VLR HLR GMSC Initial and Final 1 Address Message 2 Send Routing Info 3 Routing Info Ack GMSC MSISDN +91 9885 xxxxxx MSISDN +91 9885 xxxxxx Unknown Subscriber
  • 7. 2 REQ. FOR SERVICE 1 CHANNEL REQUEST DCCH ASSIGN SIGNALING LINK ESTABLISHED 6 COMPLETE CALL CALL PROCEEDING 3 AUTHENTICATION SET Cipher MODE 4 SET-UP 5 EQUIP. ID REQ. MS BSS MSC VLR HLR PSTN Mobile Originated Sequence Signaling Link request Signaling Link Granted Call setup is in Process Setup Voice Call Dailed digits …+91 40 66235307 Channel request
  • 8. < MS BSS MSC VLR HLR PSTN 7 ASSIG. COMMAND ASSIG. COMPLETE Switch from Signaling Mode to Voice 8.Initial and Final Address Message (IFAM) Alerting MS hears ring tone from land phone Address Complete(ACM) 9 Answer (ANS)Connect Ring tone stops 10 Connect Acknowldge BILLING STARTSSpeech Started Called Subscriber Answered Switch Informs Call Answered Acknowledge Call Answered received Hi RK Ring Alert Passed to Mobile Switch routes the call to PSTN PSTN indicates to Switch Called Subscriber Informed Via Ring +91 40 66235307 Mobile Originated Sequence
  • 9. < MSISDN +91 9885 xxxxxx IMSI 404 13 xxxxxxxxxx MSRN LAI & TMSI)TMSI)TMSI) PCH> MSRN MSRN MSRN Initial and Final 1 Address Message 2 Send Routing Info 3 Routing Info Ack Initial and Final Address Message 4 Send Info For I/C Call Setup 5 Page Paging Request MS BSS MSC VLR HLR GMSC GMSC MSISDN +91 9885 xxxxxx 091 9885 xxxxxx (roaming number) 091 9885 xxxxxx (roaming number) LAI – 404 13 location Area Code Mobile Terminated Sequence AP Vodafone AP Airtel
  • 10. MS BSS MSC VLR HLR GMSC GMSC Billing starts 7 Connect Connect ACK ANS Ringing stops at Other Mobile Subscriber picks up Hello... 6 Assignment Command Assignment Complete Alert Ringtone Alert Acknowledge Ring Tone at the Other Mobile Address Complete Speech Started Mobile Subscriber Answered Mobile Terminated Sequence AP Vodafone AP Airtel Call Setup Request Call Setup Confirmed