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UMTS (Signaling briefly) - 9

Signaling briefly [Under UMTS]

To get a better feel of protocol layers, let us have a brief look at signaling: An example of voice call is taken.

NAS signaling initiated due to certain user action or otherwise (e.g. user initiated voice call or cell reselection done by phy layer). NAS layer (CC/MM for voice call) request RRC setup.
CN mean rest of Core network (like HLR, GMSC etc.)

RRC connection setup

RRC/Initial Direct Transfer message
[NAS message]
RANAP/Initial UE message
[NAS message]

NAS authentication procedure and ciphering & integrity key generation procedures
HLR/AuC signaling

RANAP/Security Mode Command
Access (stratum) level configuration and application of ciphering and integrity protection
RANAP/Security Mode Complete

NAS procedures continue in CN and between UE and CN (e.g. CC/SETUP request, RA\LA update in CN for voice call and location update respectively) with the help of RANAP and RRC (UL/DL) Direct Transfer messages over Iu and Uu interfaces respectively.
GMSC/MGW signaling

At some point, NAS would require AS to setup user plane bearers. This is triggered by network.
RAB Assignment Request
Iu bearers will be configured. For CS services, ALCAP will have to setup CS bearer.
Access (stratum) level Radio bearer(s) setup procedures
RAB Assignment Response

NAS procedures continue in CN and between UE and CN. Radio bearers will be used for user data transfer.
GMSC/MGW signaling

References: UMTS by Sanchez and Thioune, and WCDMA for UMTS by Holma and Toskala.

Copyright © Samir Amberkar 2010§

Protocol layers - PS « UMTS Index » Iu interfaces