6.15 UE Reachability procedures

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

There are two procedures necessary for any service related entity that would need to be notified on the reachability of the UE at NAS level:

– UE Reachability Notification Request procedure, and

– UE Activity Notification procedure.

The UE Reachability Notification Request procedure is illustrated in Figure 6.15‑1.

Figure 6.15-1: UE Reachability Notification Request Procedure

1) If a service-related entity requests the HSS to provide an indication regarding UE reachability, the HSS stores the request in the URRP-SGSN parameter. If the value of URRP-SGSN parameter has changed from "not set" to "set", the HSS sends a UE-REACHABILITY-NOTIFICATION-REQUEST (URRP-SGSN) to the SGSN. If the SGSN has an MM context for that user, the SGSN stores URRP-SGSN to indicate the need to report to the HSS information regarding changes in UE reachability, e.g. when the next NAS activity with that UE is detected.

The UE Activity Notification procedure is illustrated in Figure 6.15‑2.

Figure 6.15-2: UE Activity Procedure

1) The SGSN receives an indication regarding UE reachability, e.g. an Routeing Area Update Request message from the UE.

2) If the SGSN contains an MM context of the UE and if URRP-SGSN for that UE is configured to report once that the UE is reachable, the SGSN shall send a UE-Activity-Notification (IMSI, UE-Reachable) message to the HSS and clears the corresponding URRP-SGSN for that UE.

3) When the HSS receives the UE-Activity-Notification (IMSI, UE-Reachable) message or the Update Location message for an UE that has URRP-SGSN set, it triggers appropriate notifications to the entities that have subscribed to the HSS for this notification.