Section: 4.15.13.4 Specific procedure for the 5GC assistance to member UE selection based on the UE's current location, historical location and direction and UE separation distance
Content: Figure 4.15.13.4-1: 5GC assistance to Member UE selection based on the UE's current and historical location, direction and separation distance 1. AF requests 5GS assistance to support the Member UE selection by considering the UE's historical location, UE's current location, direction and UE separation distance. AF includes the UE lists and the following criteria as part of the member UE selection request: - UE historical location: The Target AoI where the UEs have been roving over the historical nomadic period before moving into the FL coverage area. - UE current location: The current AoI which is the coverage area of the FL training server where the selected UEs located in to participate in the FL operation. - UE Direction: Select the UE with the different direction in the FL coverage Area. - UE separation distance: Select UEs that are geographically separated, fulfilling the separation distance no smaller than the certain predefined separation distance. When providing a target area for e.g. FL operation, the AF may provide sub-areas, and provide a maximum number of UEs that should take part in FL from each sub-area. 2. NEF translates the GPSIs to SUPIs and maps the filtering criteria into the corresponding UE filtering information. 3-4. The NEF invokes Namf_EventExposure_Subscribe service operation with the UE list, the current AoI and event ID = Location report. AMF will provide a list of UEs that are within the current AoI to the NEF using the Namf_EventExposure_Notify service operation. The NEF obtains the list of possible member UEs from AMF within the current AoI. 5. In order to identify the appropriate NWDAF which can provide analytics output to derive the visited AOI info and get the UE direction for the possible target member UEs above, the NEF initiates NWDAF discovery request (Analytics ID = UE mobility/Relative Proximity, AOI = Target AOI) with UE list received from step 4. 6-7. The NEF invokes NWDAF Analytics Info request (UE list received from step 4, Analytics ID = UE mobility, Relative Proximity, Filters include "Visited AoI = Target AOI", "target period = historical nomadic period" and "proximity attributes"). In a response, NWDAF provides a list of UEs that were ever roving within the target AOI, at the minimum, over the historical nomadic period. Additionally, NWDAF provides a list of UEs location in the order of which the UE passes through. Thus, the NEF gets the corresponding statistics of UE mobility, the UE's direction and distance between UEs in the group/list. 8-9. Based on the information provided by the AMF and NWDAF, the NEF can determine the FL candidate UEs which are now within the FL coverage area but were roving within the target AOI over the historical nomadic period and UE with the different direction and separated from each other fulfilling the minimum distance threshold as requested by AF. The NEF notifies AF for such UE candidate list. 10. The NEF also needs to consider the list of UEs which are now within the FL coverage area, but may move out of the FL coverage area. Therefore, for each UE in the candidate list in steps 8-9, the NEF invokes the Namf_EventExposure_Notify service with UE ID = SUPI, Event ID=UE moving in/out of AOI in order to keep tracking the movement of the UE(s). 11-12. If step 10 identifies any UE which is moving out of the FL coverage area, the NEF may further notify the AF of the given UE which is moving out the coverage.