5.3.11 UE Reachability procedures

23.4013GPPGeneral Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) accessRelease 18TS

5.3.11.1 General

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

– UE Reachability Notification Request procedure; and

– UE Activity Notification procedure.

5.3.11.2 UE Reachability Notification Request procedure

The UE Reachability Notification Request procedure is illustrated in Figure 5.3.11.2-1.

Figure 5.3.11.2-1: UE Reachability Notification Request Procedure

1) If a service-related entity requests the HSS to provide an indication regarding UE reachability on EPS, the HSS stores the service-related entity and sets the URRP-MME parameter to indicate that such request is received. If the value of URRP-MME parameter has changed from "not set" to "set", the HSS sends a UE-REACHABILITY-NOTIFICATION-REQUEST (URRP-MME) to the MME. If the MME has an MM context for that user, the MME sets URRP-MME 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.

5.3.11.3 UE Activity Notification procedure

The UE Activity Notification procedure is illustrated in Figure 5.3.11.3-1.

Figure 5.3.11.3-1: UE Activity Procedure

1) The MME receives an indication regarding UE reachability, e.g. an Attach Request message from the UE or MME receive an indication from S‑GW that UE has handed over to non-3GPP coverage.

2) If the MME contains an MM context of the UE and if URRP-MME for that UE is configured to report once that the UE is reachable, the MME shall send a UE-Activity-Notification (IMSI, UE-Reachable) message to the HSS and clears the corresponding URRP-MME 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-MME set, it triggers appropriate notifications to the entities that have subscribed to the HSS for this notification and clears the URRP-MME for that UE.