5.3.4.4 UE mobility event notification

5G System supports the functionality of tracking and reporting UE mobility events.

The AMF provides the UE mobility related event reporting to NF that has been authorized to subscribe to the UE mobility event reporting service. Any NF service consumer such as SMF, NEF, LMF, TSCTSF or NWDAF that wants to be reported on the UE location is able to subscribe to the UE mobility event notification service to the AMF with the following parameters:

• Event reporting type that specifies what to be reported on UE mobility (e.g. UE location, UE mobility on Area of Interest).
• Event filters indicating the:
• Area Of Interest that specifies a location area within 3GPP system. The Area Of Interest is represented by a list of Tracking Areas, list of cells or list of (R)AN node identifiers. In the case of LADN, the event consumer (e.g. SMF) provides the "LADN DNN" or "LADN DNN and S-NSSAI" to refer the LADN service area as the Area Of Interest. In the case of PRA, the event consumer (e.g. SMF or PCF) may provide an identifier for Area Of Interest to refer predefined area as the Area Of Interest. In the case of Partial Network Slice Support and Support for Network Slices with Network Slice Area of Service not matching deployed Tracking Areas as described in clauses 5.15.17 and 5.15.18, the event consumer (e.g. SMF) provides the S-NSSAI to refer the slice restriction area (area restriction applies for the S-NSSAI) as the Area Of Interest.
• The Area Of Interest may include a "RAN timing synchronization status change event" indicator, indicating that the presence in Area of Interest can be determined based on the most recent N2 connection.
• The Area Of Interest may include an "Adjust AoI based on RA" indicator, indicating that the Area of Interest may be adjusted depending on UE's RA.
• The Area Of Interest may include the "Notify the consumer considering UE identity" indicator, containing a list of UE identities or Internal Group ID and informing the AMF to notify the NF consumer about Area of Interest events only if an event is for the UE belonging to the provided list UEs. The indicator may be included when the request is targeted to Any UE.
• The Area Of Interest may include the "Notify the consumer considering DNN/S-NSSAI" indicator, containing one or more DNN(s)/S-NSSAI(s) and informing the AMF to notify the NF consumer about Area of Interest events only if an event is for the UE having a PDU sessions established for the specified DNN(s)/S-NSSAI(s).
• S-NSSAI and optionally the NSI ID(s).
• Event Reporting Information: event reporting mode, number of reports, maximum duration of reporting, event reporting condition (e.g. when the target UE moved into a specified Area Of Interest, immediate reporting flag, reporting threshold reached).
• Notification Endpoint of NF service consumer to be notified.
• The target of event reporting that indicates a (list of) specific UE(s), a group of UE(s) or any UE (i.e. all UEs served by the AMF). Further details on the information provided by the NF service consumer are provided in clause 4.15 of TS 23.502 [3].

If an NF service consumer subscribes to the UE mobility event notification service provided by AMF for reporting of UE presence in Area Of Interest, the AMF tracks UE's location considering UE's CM state and using NG-RAN procedures (if RRC_INACTIVE state applies to NG-RAN) in order to determine the UE presence in the Area Of Interest, as described in clause 4.15.4.2 of TS 23.502 [3]. Upon detecting the change of the UE presence in the Area Of Interest, the AMF notifies the UE presence in the Area Of Interest and the new UE location to the subscribed NF service consumer.

If the Area Of Interest in the subscription to the UE mobility event notification includes "RAN timing synchronization status change event" indicator as described in Table 5.2.2.3.1-1 of TS 23.502 [3] and the registration request from the UE includes a UE 5GMM Core Network Capability with an indication for "support for network reconnection due to RAN timing synchronization status change " as described in clause 5.4.4a, the AMF reports the UE presence in Area of Interest based on the most recent N2 connection as described in Annex D of TS 23.502 [3].

If the Area Of Interest in the subscription to the UE mobility event notification includes "Adjust AoI based on RA" indicator as described in Table 5.2.2.3.1-1 in TS 23.502 [3], the AMF reports the UE presence in Area of Interest based on the most recent N2 connection as described in Annex D in TS 23.502 [3].

When the AMF is changed, the subscription of mobility event for a UE or group of UEs is transferred from the old AMF. Subscriptions targeted to Any UE shall not be moved to another AMF due to UE mobility. The new AMF may decide not to notify the SMF with the current status related to the subscription of mobility event if the new AMF determines that, based on MM Context of the UE, the event is reported by the old AMF.

In the network deployment where a UE may leave or enter the Area Of Interest without any notification to the 5GC in CM-CONNECTED state (i.e. in the case that RRC_INACTIVE state applies to the NG-RAN), the AMF may initiate the NG-RAN location reporting as described in clause 5.4.7 or N2 Notification as described in clause 4.8.3 of TS 23.502 [3] to track the UE presence in the Area Of Interest.

The AMF may provide UE mobility event reporting to PCF, using Policy Control Request Triggers defined in TS 23.503 [45].