Content for  TS 23.273  Word version:  18.5.0

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6.1.4  5GC-MT-LR procedure involving Mobile Base Station Relay |R18|p. 56

Figure 6.1.4-1 illustrates the network positioning for the LCS clients when Mobile Base Station Relay(s) is involved.
In this scenario, it is assumed that the target UE may be identified using an SUPI or GPSI. The procedure follows the functionality in clause 5.9 and the 5G-MT-LR procedures in clauses 6.1.1 and 6.1.2. It is further assumed that:
  • The NG-RAN in Figure 6.1.4-1 is a donor-CU to the MBSR.
  • When the MBSR is integrated or fully migrated to a new gNB, the OAM triggers the LMF to perform TRP Information Exchange procedure. The LMF learns that a new integrated TRP at a gNB is mobile and its MBSR IAB UE ID (GPSI) via a TRP information exchange towards the gNB with the Cell ID of the TRP. The LMF may also performs NRPPa TRP information exchange procedure before the positioning procedure for a target UE, e.g. to determine the position capability of NG-RAN.
  • The LMF that performs the location estimation of the MBSR can be different than the LMF that performs the location estimation of the target UE (not shown in Figure 6.1.4-1).
Reproduction of 3GPP TS 23.273, Fig. 6.1.4-1: 5GC-MT-LR procedure involving Mobile Base Station Relay
Step 1.
[Optional] The location services client sends a request to the GMLC for a location for the target UE identified by an GPSI or an SUPI. The UE may or may not be served by a MBSR.
Step 2.
The GMLC invokes the Namf_Location_ProvidePositioningInfo service operation towards the AMF serving the target UE to request the current location of the target UE. The location procedure may be also triggered at the AMF for a 5GC-NI-LR as at step 1 in clause 6.10.1, or an event report sent by the UE for a deferred 5GC-MT-LR for periodic or triggered location as at step 25 in clause 6.3.1.
Step 3.
The 5GC-MT-LR procedure as specified in clause 6.1.1 step 5-8 or clause 6.1.2 step 6-12 are performed with the difference that the LMF selection also consider LMF capability supporting MBSR involvement. If the AMF is aware that the target UE is served by a MBSR, it would select the LMF that can support the MBSR handling.
Step 4.
LMF derives if any MBSR(s) is involved in the positioning of the target UE based on the cell-ID used for positioning measurements in the step 3. The AMF serving the target UE may indicate that the serving cell is an MBSR (if applicable). When the MBSR was integrated as a TRP (IAB-DU) with a gNB, the LMF may determine from in a TRP information exchange procedure that the cell-ID belongs to the MBSR and/or the UE-ID (GPSI) associated with MBSR. The LMF, when the OAM provides a new Cell Id to the LMF, performs a TRP information exchange as specified in TS 38.455 for the new Cell ID. When the MBSR is integrated or fully migrated in the NG-RAN, the Cell ID(s) of the MBSR is (are)provided to the LMF and, in the case of full migration, any stale Cell ID of fully migrated MBSR is removed from LMF by OAM. If the LMF selects any cell for UE positioning measurements, and the LMF determines it needs to perform a TRP information exchange with the cell, it shall perform TRP Information Exchange procedure as specified in TS 38.455.As the MBSR can be mobile the LMF may need to determine an updated location of the MBSR by either performing step 5-7 (option 1) or performing step 8-10 (option 2) if option 1 is not feasible. If several MBSRs were derived, then step 5-7 or step 8-10 are be performed for each MBSR.
Step 5.
[Conditional] The LMF initiates a NRPPa TRP Information Exchange procedure to request the updated location information of the TRP(s) associated with MBSR(s) by directing the TRP information exchange messages to the gNB associated with the Cell ID(s), for example, by setting the NRPPa TRP Information Type Item IE to "mobile TRP location info". Donor-CU further send a F1 TRP INFORMATION REQUEST message to any MBSR IAB-DU.
Step 6.
[Conditional] The MBSR IAB-UE initiates a 5GC-MO-LR procedure (as defined in clause 6.2) to get its location information. The MBSR IAB-UE's location info is used by the co-located MBSR IAB-DU to determine the updated location for its TRP.
Step 7.
[Conditional] The MBSR IAB-DU report its updated TRP location, e.g. TRP's geo-coordinate, velocity and the time for obtaining them, to the Donor-CU, which is further forwarded to LMF.
Step 8.
[Conditional] The LMF invokes the Ngmlc_Location_ProvideLocation_Request service operation to the GMLC by providing the identifier of MBSR IAB-UE and a scheduled location time. The LMF determines the identifier of MBSR IAB-UE based on the Cell ID of MBSR and the received the GPSI of the MBSR in a TRP information exchange when the MBSR was integrated as a TRP. LMF may receive the scheduled location time in step 3. Otherwise, LMF may generate the scheduled location time, e.g. based on response time.
Step 9.
[Conditional] The GMLC determines the AMF serving the MBSR and step 4-10 in clause 6.1.1 or steps 4-23 in clause 6.1.2 is performed. The privacy check in clause 5.4 is skipped for the MBSR based on the subscription data of the MBSR (IAB-UE). The scheduled location time received in step 8 is also provided to the MBSR IAB-UE when sending a location request to the MBSR.
Step 10.
[Conditional] The GMLC sends the location service response including the MBSR IAB-UE's location to the LMF.
Step 11.
[Conditional] The LMF performs one of the positioning procedures with the target UE described in clauses 6.11.1 and 6.11.2. To reduce the timing offset of the positioning measurements, the UE positioning may be scheduled with the same scheduled location time as the MBSR positioning in step 9. LMF sends the same time with the scheduled location time in step 8 to the target UE in clause 6.11.1. If Network Assisted procedure is used, the NG-RAN may provide the MBSR updated location and velocity information and the time obtained them to the LMF via NRPPa message as defined in TS 38.455.
Step 12.
The LMF uses the received location and velocity of the MBSR(s) when estimating the location of the target UE together with the measurements reports in step 3 or optionally the updated measurement reports in step 11.
Step 13.
The LMF returns the Nlmf_Location_DetermineLocation Response towards the AMF to return the current location of the target UE.
Step 14.
The AMF returns the Namf_Location_ProvidePositioningInfo Response towards the GMLC to return the current location of the target UE.
Step 15.
The GMLC sends the location service response to the location services client.

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