AMF provides the subscriber's location information to the GMLC using the event exposure mechanism. The GMLC subscribes to a one-time location event report from the AMF through the UDM by invoking the event exposure service of the UDM. Subsequently, the UDM initiates the event exposure subscription API towards the AMF.

After sending a response to the UDM, if the subscription request is for an immediate location, the AMF provides the last known user location to the GMLC and deletes the subscription locally, as it is a one-time report. If the subscription request is for the current location, the AMF, based on the UE state, either invokes NG-RAN location reporting procedures towards the gNB or performs paging to fetch the current location of the UE and sends the location report to the GMLC accordingly. If the system fails to fetch the current location, the AMF sends the last known user location to the GMLC.

This feature supports the reporting of UE location for non-emergency subscribers. Following are the key points for this feature to work:

• If the feature is not enabled through configuration or unsupported combinations are used, AMF rejects the request with a 403, UNSPECIFIED error.

• AMF supports SUPI, GPSI, and PEI as UE identifiers, with SUPI being preferred option. AMF supports only one GPSI per UE.

• Although SUPI, PEI, and GPSI are considered conditional IEs according to the specifications, the AMF treats at least one of them as mandatory for its functionality. Therefore, the AMF requires at least one of these IEs to be present.

• AMF starts a timer for 50 seconds when location reporting control is sent to gNB. In case of no response from gNB and if session exists, AMF sends the last known location to GMLC.

• If AMF receives a new subscription request from the same peer NF (same NF ID) while an older subscription is still active, AMF deletes the older subscription and proceed with processing of new request.

Following are the limitations of this feature:

• The event exposure functionality is available exclusively for location report triggers under the following conditions:

  • UE Type: Single UE

  • Report Type: One-time report

  • Location Filter: Cell-ID only

• AMF does not support UE location reporting in roaming scenarios.

• AMF does not support modify and delete operations for subscribed events.

GMLC profile configuration includes:

• Operator Policy Network Element Profile Configuration

• NF Client Profile Configuration for Mutual Transport Layer Security (mTLS)

• GMLC Profile Configuration

• Failure Handling Profile Configuration

Note	AMF sends out the event notifications without a GMLC profile also, but it does not support FHT/MTLS functionality in the absence of GMLC profile configuration.

Following is an example of show command to view the active event subscritption.

[amf] amf# show subscriber supi 123456789012345

      "EventSubscriptionData": [
        {
          "EventList": [
            {
              "Type": "LOCATION_REPORT",
              "LocationFilterList": [
                "CELL_ID"
              ],
              "RefId": 100
            }
          ],
          "EventNotifyUri": "http://10.1.14.150:9110/namf-evts/v1/eventNotificationUrl",
          "NotifyCorrelationId": "ngmlc-evt-supi-XXXX-XXXXX",
          "Options": {
            "Trigger": "ONE_TIME"
          },
          "SubscriptionId": "amfevt-1717581907694157698-imsi-123456789012345",
          "NfType": "UDM"
        }
      ]

This section describes operations, administration, and maintenance support for this feature.