Telecom Tutorials by Samir Amberkar

Voice Call [Under GSM >> Signaling]    §

Step 1: Reaching till MSC/VLR. It is same as for Location Update except the access reason would be Voice call and the L3 request would be "CM Service Request"

MS1

BTS1

BSC1

MSC1

VLR1

RACH - RR - Channel Request CCM - Channel Required DCM - Channel Activate DCM - Channel Activate Ack CCM - Immediate Assignent AGCH, RR - Immediate Assignment SDCCH, CC - CM Service Req1 RLM (CM Service Req) BSSMAP - Complete Layer 3 Info SCCP connection confirmed MAP - Process Access Request

1: For Layer 2 setup, MS sends SABM frame containing CM Service Req. BTS acknowledges with UA frame containing received CM Service Req.

We will continue "Voice Call" in next article.

References: GSM Networks book by Heine, GSM book by Mouly and Pautet, Signaling diagrams from 24.007/24.008 (R99).

© Copyright Samir Amberkar 2010

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