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LTE - RRC/S1 release

LTE - end-to-end RRC/S1 release [Under LTE]
» E-UTRA and E-UTRAN overall description - 36.300, Rel 8 «
» E-UTRAN access - 23.401, Rel 8 «
» S1AP - 36.413, Rel 8 «
» GTPv2-C - 29.274, Rel 8 «
» RRC - 36.331, Rel 8 «

In earlier articles on UE states (TAU, Service Request, Detach), we looked at various procedures from UE point of view. Let us now look at these procedures from EPC point of view.

RRC release result into release of all radio bearers, but EPS bearers remain active. The decision about RRC release is taken by eNB (e.g. user inactivity, O&M decision) or by MME (NAS decision like detach, attach failure). The procedure is known as "S1 release" procedure (23.401:5.3.5).

LTE-s1-release-708167.png

GTP Access Release procedure release user plane S1-U tunnel only from eNB side; the tunnel from SGW side remain part of UE contexts (at SGW and MME). Note that GTP tunnel between SGW and PGW is also not being released. This mean that user data coming from PDN need not stop at PGW; it comes to SGW and gets buffered, at which point SGW triggers "network service request" procedure.

In next article, we will look at Service Request procedures.

Copyright © Samir Amberkar 2010-12§

LTE - quick bits on mobility « LTE Index » LTE - end-to-end Service Request