Content for  TS 29.118  Word version:  18.0.0

If timer Ts6-1 is not running, the MME shall start the location update for non-EPS services procedure when it receives from the UE:

• an attach request indicating combined EPS/IMSI attach;
• a combined tracking area update request indicating Combined TA/LA updating with IMSI attach;
• a combined tracking area update request and the MME detects that the LAI has changed;
• a combined tracking area update request and the state of the SGs association is SGs-NULL; or
• a combined tracking area update request and the MME serving the UE has changed.

If timer Ts6-1 is not running, the MME may start the location update for non-EPS services procedure when it receives from the UE:

• a combined tracking area update request or a periodic tracking area update , if the MM context variable "VLR-Reliable" for the UE is set to "false" (see subclause 5.7.3).

If multiple PLMNs are available for the CS domain, the MME shall select a PLMN for CS domain as specified in TS 23.272. If the MME cannot select any PLMN for CS domain for the UE, the MME informs the UE that the CS domain is not available. The MME shall determine the new location area identification as follows:

• if the MME received a combined attach request or combined tracking area update request from the UE with an indication for "SMS only", or the network only supports "SMS only" or the network only has a few VLRs that support SGs interface, the MME may allocate a default location area identification specifically configured for that case;
• else the MME derives the location area identification from the current tracking area identity where the UE is located. For this the MME may take any access restrictions provided by the HSS into account, if the network is using separate location areas for GERAN and UTRAN cells.

The MME shall derive the VLR name from the location area identification which was determined. For networks supporting the feature 'Intra Domain Connection of RAN Nodes to Multiple CN Nodes', the VLR name is derived as described in TS 23.236.The MME shall include the location area identification in the new location area identifier information element in the SGsAP-LOCATION-UPDATE-REQUEST message. In networks supporting the feature 'Intra Domain Connection of RAN Nodes to Multiple CN Nodes' (TS 23.236), if the TMSI based NRI container is not received from the UE, and the MME determines that the serving VLR of the UE is changed, the MME shall include in the Old location area identifier a specific LAI value which is not broadcasted in the network and not associated with any VLR. In networks supporting the feature "Intra Domain Connection of RAN Nodes to Multiple CN Nodes" as defined in TS 23.236, the MME shall support load re-distribution of UEs to another VLR than the current one. When the MME receives a periodic tracking area update request or a combined tracking area update request, the MME shall check whether for this UE there is a SGs association to a VLR for which load re-distribution has been initiated in the MME by O&M. If this is the case and

• if a combined tracking area update request is received, the MME shall derive the new VLR name as described in TS 23.236 and then send the SGsAP-LOCATION-UPDATE-REQUEST message to the new selected VLR; or
• if a periodic tracking area update request is received, dependent on network configuration and operator policy, the MME shall take one of the following actions:
  • perform a network initiated detach with detach type "IMSI detach" immediately after the completion of the periodic tracking area update procedure; or
  • derive the new VLR name as described in TS 23.236 and then send the SGsAP-LOCATION-UPDATE-REQUEST message to the new selected VLR.

If the VLR is configured for gateway core network (GWCN), the MME shall select a CS domain operator as specified in TS 23.272 and proceed as follows:

• If the preferred RAT of the selected CS domain operator is GERAN and the UE does not support GERAN network sharing (see subclause 10.5.5.12 of TS 24.008), the MME shall include the selected CS domain operator in the selected CS domain operator information element, and the common PLMN in the new location area identifier information element in the SGsAP-LOCATION-UPDATE-REQUEST message; or
• If only common PLMN ID and no multiple PLMN IDs are provided in CS domain for selection by the UE (see subclause 4.2.3.1 of TS 23.251), the MME shall include the selected CS domain operator in the selected CS domain operator information element, and the common PLMN in the new location area identifier information element in the SGsAP-LOCATION-UPDATE-REQUEST message.

If multiple PLMN IDs are provided in CS domain for selection by the UE and the UE supports GERAN network sharing (see subclause 10.5.5.12 of TS 24.008), the MME shall include the selected PLMN for CS domain in the new location area identifier information element as specified in TS 23.251. The SGsAP-LOCATION-UPDATE-REQUEST message includes the type of location update performed by the UE in the EPS location update type information element. If the UE has performed a combined attach or a combined tracking area update indicating "combined TA/LA updating with IMSI attach", the MME indicates "IMSI attach", otherwise the MME indicates "Normal location update". The MME shall include the TMSI status in the SGsAP-LOCATION-UPDATE-REQUEST message if the UE indicates in the ATTACH REQUEST or the TRACKING AREA UPDATE REQUEST message that it has no valid TMSI available. The MME shall also include the old location area identifier in the SGsAP-LOCATION-UPDATE-REQUEST message if the UE included the old location area identification in the ATTACH REQUEST or TRACKING AREA UPDATE REQUEST message. The MME shall include the TMSI based NRI container in the SGsAP-LOCATION-UPDATE-REQUEST message if received from the UE. If the MME supports the "Automatic Device Detection" (see TS 22.101) or the "Trace for Management Based Activation/Deactivation" (see TS 32.422), the MME shall include the IMEISV in the SGsAP-LOCATION-UPDATE-REQUEST message. The MME shall add the UE's current TAI and E-CGI to the SGsAP-LOCATION-UPDATE-REQUEST message. When the MME sends the SGsAP-LOCATION-UPDATE-REQUEST, the MME shall start timer Ts6-1. If timer Ts6-1 is running and the MME receives from the UE:

• an attach request indicating combined EPS/IMSI attach; or
• a combined tracking area update with or without IMSI attach.

Then:

• if the LAI determined by the MME is the same as in the outstanding request, the MME shall not process this new request and shall wait for the VLR response to the ongoing procedure;
• if the LAI determined by the MME is different but the VLR name is the same as for previous LAI, any response from the VLR to the outstanding request is ignored, the MME shall stop and reset timer Ts6-1 and the MME shall start the location update for non-EPS services procedure; or
• if the LAI determined by the MME is different and the VLR name is different as for previous LAI, any response from the previously addressed VLR to the outstanding request is ignored, the MME shall stop and reset timer Ts6-1, and the MME shall start the location update for non-EPS services procedure.

When the MME receives from the UE a tracking area update request and the MME serving the UE has changed, the MME shall stop and reset timer Ts6-1.

If the MME supports restoration for CS services via an alternative VLR as defined in TS 23.007 and, upon reception of a combined tracking area update request or a periodic tracking area update request from the UE, the MME determines that the VLR serving the UE is no longer in service, the MME may:

• if a combined tracking area update request is received, select an alternative VLR that is in service for the UE and immediately perform the location update for non-EPS services procedure towards the selected VLR as described in subclause 5.2; or
• if a periodic tracking area update request is received, dependent on network configuration and operator policy,
  • perform a network initiated detach with detach type "IMSI detach" immediately after the completion of the periodic tracking area update procedure and then select an alternative VLR that is in service for the UE during the subsequent combined tracking area update procedure, before performing the location update for non-EPS services procedure towards the selected VLR as described in subclause 5.2; or
  • select an alternative VLR that is in service for the UE and immediately perform the location update for non-EPS services procedure towards the selected VLR as described in subclause 5.2.

If the MME supports restoration for CS services via an alternative VLR as defined in TS 23.007 and, upon reception of an UPLINK NAS TRANSPORT message (see TS 24.301) from the UE, the MME determines that the VLR serving the UE is no longer in service, the MME may:

• request the UE to re-attach for non-EPS services as specified in TS 24.301 and then select an alternative VLR that is in service for the UE during the subsequent combined tracking area update procedure, before performing the location update for non-EPS services procedure towards the selected VLR as described in subclause 5.2.