6.9.3 Periodic RA and LA Updates

23.0603GPPGeneral Packet Radio Service (GPRS)Release 17Service descriptionStage 2TS

All GPRS-attached MSs, except A/Gb mode MSs in class‑B mode of operation engaged in CS communication, shall perform periodic RA updates. MSs that are IMSI-attached and not GPRS-attached shall perform periodic LA updates. Periodic RA updates are equivalent to intra SGSN routeing area updates as described in clause "Intra SGSN Routeing Area Update", with Update Type indicating periodic RA update. For MSs that are both IMSI-attached and GPRS-attached, the periodic updates depend on the mode of operation of the network:

– If the network operates in mode I, periodic RA updates shall be performed, and periodic LA updates shall not be performed. In this case, the MSC/VLR shall disable implicit detach for GPRS-attached MSs and instead rely on the SGSN to receive periodic RA updates. If periodic RA updates are not received in the SGSN and the SGSN detaches the MS, the SGSN shall notify the MSC/VLR by sending an IMSI Detach Indication message.

– If the network operates in mode II, both periodic RA updates and periodic LA updates shall be performed independently. RA updates are performed towards the SGSN, and LA updates are performed towards the MSC/VLR.

In A/Gb mode, the periodic RA update timer in the MS is stopped when an LLC PDU is sent since all sent LLC PDUs set the MM context state to READY. The periodic RA update timer is reset and started when the state returns to STANDBY.

In Iu mode, the periodic RA update timer in the MS is stopped when the MM context enters the PMM‑CONNECTED state. The periodic RA update timer is reset and started when the state returns to PMM‑IDLE state.

If the MS could not successfully complete the periodic RA update procedure after a retry scheme while the MS was in GERAN/UTRAN PS coverage, the MS shall wait a back-off time equal to the periodic LA update timer broadcast by the network before restarting the periodic RA update procedure.

NOTE: If ISR is activated, additional handling in MS and SGSN is described in TS 23.401 [89].