The external location services client sends a request to the GMLC for a location for the target UE identified by an GPSI or an SUPI. The request may include the required QoS, Supported GAD shapes and client type. If location is required for more than one UE, the steps following below may be repeated and in that case the GMLC shall verify whether the number of Target UEs in the LCS request is equal to or less than the Maximum Target UE Number of the LCS client. If Maximum Target UE Number is exceeded, the GMLC shall reject the LCS request, the step 2-10 are skipped, and then GMLC respond to the client with proper error cause in the step 11.
The GMLC invokes a Nudm_UECM_Get service operation towards the home UDM of the target UE to be located with the GPSI or SUPI of this UE.
The UDM returns the network addresses of the current serving AMF.
The GMLC invokes the Namf_Location_ProvidePositioningInfo service operation towards the AMF to request the current location of the UE. The service operation includes the SUPI, and client type and may include the required QoS and Supported GAD shapes.
If the UE is in CM IDLE state, the AMF initiates a network triggered Service Request procedure as defined in clause 188.8.131.52 of TS 23.502
to establish a signalling connection with the UE.
The AMF selects an LMF based on the available information as defined in clause 5.1
or based on AMF local configuration. The LMF selection takes the 5G-AN currently serving the UE into account. The selection may use a NRF query.
The AMF invokes the Nlmf_Location_DetermineLocation
service operation towards the LMF to request the current location of the UE. The service operation includes a LCS Correlation identifier, the serving cell identity of the Primary Cell in the Master RAN node and the Primary Cell in the Secondary RAN node when available based on Dual Connectivity scenarios, and the client type and may include an indication if UE supports LPP, the required QoS and Supported GAD shapes. If any of the procedures in clause 6.11.1
or clause 6.11.2
are used the service operation includes the AMF identity.
The LMF performs one or more of the positioning procedures described in clauses 6.11.1
, 6.11.2 and 6.11.3. During this step the LMF may use the Namf_Communication_N1N2MessageTransfer
service operation to request the transfer of a Positioning related N1 message to the UE or the transfer of a Network Positioning message to the serving NG-RAN node (gNB or NG-eNB) for the UE.
The LMF returns the Nlmf_Location_DetermineLocation Response towards the AMF to return the current location of the UE. The service operation includes the LCS Correlation identifier, the location estimate, its age and accuracy and may include information about the positioning method.
The AMF returns the Namf_Location_ProvidePositioningInfo Response towards the GMLC/LRF to return the current location of the UE. The service operation includes the location estimate, its age and accuracy and may include information about the positioning method.
The GMLC sends the location service response to the external location services client.