Figure 6.1.1-1 illustrates the general network positioning for the LCS clients external to the PLMN for the regulatory location service for non-roaming scenario. In this scenario, it is assumed that the target UE is identified using an SUPI or GPSI.
This procedure is applicable to a request from an LCS client for a current location of the target UE, and it is assumed that the LCS client is authorised to use the location service and no privacy verification is required.
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 and Supported GAD shapes. 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 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.
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, UE Positioning Capability if available 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 shall determine a geographical location and optionally a location in local coordinates.
The LMF returns the Nlmf_Location_DetermineLocation Response towards the AMF to return the current location of the UE and UE Positioning Capability if the UE Positioning Capability is received in step 8 including an indication that the capabilities are non-variable and not received from AMF in step 7. The service operation includes the LCS Correlation identifier, the location estimate, its age and accuracy and may include information about the positioning method and the timestamp of the location estimate.
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 and the timestamp of the location estimate. The AMF stores the UE Positioning Capability in UE context when received from LMF.