5.6.11 UE presence in Area of Interest reporting usage by SMF

When a PDU Session is established or modified, or when the user plane path has been changed (e.g. UPF re-allocation/addition/removal), SMF may determine an Area of Interest, e.g. based on UPF Service Area, subscription by PCF for reporting UE presence in Presence Reporting Area, etc.

For 3GPP access, the Area of Interest corresponds:

• either to Presence Information that may correspond to:
• a list of Tracking Areas; or
• a list of Presence Reporting Area ID(s) and optionally the elements comprising TAs and/or NG-RAN nodes and/or cells identifiers corresponding to the PRA ID(s); or
• a LADN DNN; or
• a LADN DNN and a S-NSSAI; or
• a S-NSSAI.

For Non-3GPP access, the Area of Interest corresponds to:

• N3GPP TAI (see clause 5.3.2.3).

For UE location change into or out of an "area of interest", the SMF subscribes to "UE mobility event notification" service provided by AMF for reporting of UE presence in Area of Interest as described in clause 5.3.4.4. The AMF may send the UE location to the SMF along with the notification, e.g. for UPF selection. Upon reception of a notification from AMF, the SMF determines how to deal with the PDU Session, e.g. reallocate UPF.

In the case of LADN, the SMF provides the LADN DNN to the AMF to subscribe to "UE mobility event notification" for reporting UE presence in LADN service area. Upon reception of a notification from the AMF, the SMF determines how to deal with the PDU Session as described in clause 5.6.5.

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 SMF provides the S-NSSAI to the AMF to "UE mobility event notification" for reporting UE presence in slice restriction area. Upon reception of a notification from the AMF, the SMF determines how to deal with the PDU Session as described in clauses 5.15.17 and 5.15.18.

For use cases related to policy control and charging decisions, the PCF may subscribe to event reporting from the SMF or the AMF, for UE presence in a Presence Reporting Area.

A Presence Reporting Area can be:

• A "UE-dedicated Presence Reporting Area", defined in the subscriber profile and composed of a short list of TAs and/or NG-RAN nodes and/or cells identifiers in a PLMN; or derived from the Area of Interest provided by the Application Function to the PCF (see clause 5.6.7) and composed of a short list of TAs and/or NG-RAN nodes and/or cells identifiers in a PLMN; or
• A "Core Network predefined Presence Reporting Area", predefined in the AMF and composed of a short list of TAs and/or NG-RAN nodes and/or cells identifiers in a PLMN.

In the case of Change of UE Presence in Presence Reporting Area, for core network predefined Presence Reporting Area, the AMF determines the "area of interest" corresponding to the Presence Reporting Area Identifier(s), provided by the PCF or the SMF, as a list of TAIs and/or cell identifiers and/or NG-RAN node identifiers based on local configuration. For UE-dedicated Presence Reporting Areas, the subscription for UE location change notification for an "area of interest" shall contain the PRA Identifier(s) and the list(s) of TAs, or NG-RAN Node identifier and/or cell identifiers composing the Presence Reporting Area(s). For Core Network predefined Presence Reporting Areas, the subscription for UE location change notification for an "area of interest" shall contain the PRA identifier(s).

NOTE 1: If the Presence Reporting Area (PRA) and RAN Notification Area (RNA) are partially overlapping, the PCF will not get notified for the change of PRA when UE enters or leaves the PRA but remains in the RNA in CM-CONNECTED with RRC_INACTIVE state, because AMF is not informed.

Each Core Network predefined Presence Reporting Area can be configured with a priority level in the AMF. In order to prevent overload, the AMF may set the reporting for one or more of the received Presence Reporting Area(s) to inactive under consideration of the priority configured for each of Core Network predefined Presence Reporting Area(s), while storing the reporting request for this Presence Reporting Area in the UE context.

NOTE 2: Change of UE presence in Presence Reporting Area reporting does not apply to home routed roaming.

The AMF may be configured with a PRA identifier which refers to a Set of Core Network predefined Presence Reporting Areas. If the PCF subscribes to change of UE location for an area of interest for a Set of Presence reporting areas and provides a PRA identifier then the SMF may subscribe for event reporting for this Set of Presence Reporting Areas by only indicating this PRA Identifier in the area of interest. When the Presence Reporting Area(s) to be reported belong to a set of Core Network predefined Presence Reporting Areas in which the AMF is requested to report on change of UE presence, the AMF shall additionally add to the report the PRA Identifier of the Set of Core Network predefined Presence Reporting Areas.

Upon change of AMF, the PRA identifier(s) and if provided, the list(s) of Presence Reporting Area elements are transferred for all PDU sessions as part of MM Context information to the target AMF during the mobility procedure. If one or more Presence Reporting Area(s) was set to inactive, the target AMF may decide to reactivate one or more of the inactive Presence Reporting Area(s). The target AMF indicates per PDU session to the corresponding SMF/PCF the PRA identifier(s) and whether the UE is inside or outside the Presence Reporting Area(s) as well as the inactive Presence Reporting Area(s), if any.

NOTE 3: The target AMF cannot set the Presence Reporting Area(s) received from the source serving node to inactive.

The subscription may be maintained during the life of PDU Session, regardless of the UP activation state of PDU Session (i.e. whether UP connection of the PDU Session is activated or not).

SMF may determine a new area of interest and send a new subscription to the AMF with the new area of interest.

SMF un-subscribes to "UE mobility event notification" service when PDU Session is released.