Content for  TS 23.273  Word version:  18.2.0

The procedures and signalling specified in clause 6.2 of TS 23.586 may be used to provision the Ranging/SL positioning service authorization and policy/parameter provisioning to UEs 1 to n, when in coverage.

Based on a trigger of service request (e.g. received from the application layer), which includes UE1/.../UEn, UE discovery is performed for Ranging/SL positioning as specified in clause 6.4 of TS 23.586:

• If UE1 is the target UE, UE1 discovers UEs 2 to n
• If UE1 is the Located UE, the target UE (i.e. one of the UEs 2 to n) discovers UE1 (and other Located UEs in the set of UEs 2 to n).

Secure groupcast and/or unicast links are established between UEs 1 to n as defined in clause 5.3 of TS 23.586 to enable UE1 to exchange Ranging and Sidelink Positioning Protocol (RSPP) messages over PC5-U reference point with each of UEs 2 to n and possibly enabling UEs 2 to n to exchange RSPP over PC5-U between each other.

UE1 and UEs 2 to n may communicate over PC5 for authorization of Ranging/SL positioning and receiving QoS parameters if needed. Each of UEs verifies that Ranging/SL positioning is permitted, including whether Ranging/SL positioning results may be transferred to an LCS Client or AF if this is used, according to any service authorization and policy/parameter provisioning received at step 1. QoS requirements for the Ranging/SL positioning may be also provided based on QoS requirements in the service request.

UE1 may obtain the Sidelink positioning capabilities of UEs 2 to n using the groupcast and/or unicast links established in step 3. Step 4 and 5 may be performed to transfer the information of UEs which are not served by the LMF.

Based on the Sidelink positioning capabilities of UE1/.../UEn, the target UE determines SL-MO-LR is to be performed. If UE1 is the Located UE (i.e. when the target UE is one of UE2/.../UEn and does not have NAS connection), the target UE initiates SL-MO-LR service request to UE1.

If UE1 is in CM-IDLE state, UE1 instigates a UE triggered Service Request in order to establish a signalling connection with the serving AMF of UE1.

UE1 sends a supplementary services SL-MO-LR request to the serving AMF in an UL NAS TRANSPORT message. The SL-MO-LR request indicates the other UEs 2 to n (using application layer ID and/or GPSI), indicates any assistance data needed, indicates whether location calculation assistance is needed, and indicates whether location results should be transferred to an LCS client or AF. The message shall include the identity of the LCS client or the AF and may include the address of the GMLC through which the LCS client or AF (via NEF) should be accessed. In addition, a Service Type indicates which MO-LR service of the LCS Client is requested by the UE may be included. For location calculation assistance from the LMF, the preferred type of Sidelink positioning/ranging location results (e.g. absolute locations, relative locations or distances and directions between pairs of UEs) and the required QoS are included. If UE1 is Located UE and one of UE2/.../UEn is the target UE that does not have NAS connection, the supplementary services SL-MO-LR request includes an indication that one of UE2/.../UEn is the target UE instead of UE1.

The serving AMF selects an LMF serving UE1 (e.g. an LMF that supports Sidelink positioning/ranging) and sends an Nlmf_Location_DetermineLocation service operation towards the LMF with the information from the SL-MO-LR Request. The service operation includes a LCS Correlation identifier.

The LMF sends a request to UE1 for the capabilities of UEs 1 to n.

UE 1 returns its capabilities to the LMF. UE1 may additionally return the capabilities of the UEs obtained at step 5 if requested by the LMF at step 10.

UE1 may send a request for specific assistance data to the LMF.

LMF sends the requested assistance data to UE1, and UE1 forwards the assistance data received from LMF to UE2/.../UEn. The assistance data may assist UEs 1 to n to obtain Sidelink location measurements at step 15 and/or may assist UE1 to calculate Sidelink positioning/ranging location results at step 16.

If the SL-MO-LR request at step 8 indicated location calculation assistance is needed and/or indicated transfer of Sidelink positioning/ranging location results to an LCS Client or AF, the LMF sends a request for location information to UE1 and may also send a request for location information to UE2/.../UEn if it is served by the LMF. If LMF determines to apply UE based SL Positioning, LMF includes in the request the indication of UE based SL Positioning. LMF may also provide the list of candidate Located UE(s), if absolute location is requested at step 8. If scheduled location time is received at step 14. LMF may include a scheduled location time.

UE1 instigates a Sidelink positioning/ranging procedure among UEs 1 to n in which UEs 1 to n obtain Sidelink location measurements and UEs 2 to n transfer their Sidelink location measurements to UE 1 and/or to the LMF (depending on the assistance requested). If scheduled location time is received at step 14, Sidelink positioning/ranging is performed at the scheduled location time.

If Target UE's absolute location information is required at step 8 and if absolute location of Located UE(s) is not available, the Target UE sends a request to the Located UE(s) to trigger 5GC-MO-LR procedure to let the Located UE(s) acquire their own absolute location. The QoS requirement received at step 8 is included in the request, which is used to derive the QoS for Located UE(s) positioning.

If LMF determines to use UE based calculation, at least one of UE1/.../UEn calculates Sidelink positioning/ranging location results based on the Sidelink location measurements obtained at step 15 and possibly using assistance data received at step 13. The Sidelink positioning/ranging location results can include absolute locations, relative locations or ranges and directions related to the UEs 1 to n.

If UE1 received a request for location information at step 14, UE1 sends a response to the LMF and includes the Sidelink location measurements obtained at step 15, the Sidelink positioning/ranging location results obtained at step 17 if step 17 was performed, or Located UE's absolute location obtained at step 16.

If Target UE's absolute location information is required at step 8 and if absolute location of Located UE(s) is not received at step 18, LMF can either retrieved the location of the Located UE(s) locally or triggers 5GC-MT-LR procedure to the GMLC to acquire the absolute location of the Located UE(s) using Application Layer ID or GPSI of the Located UE(s). LMF includes the QoS requirement received at step 8 in the request, which is used to derive the QoS for Located UE(s) positioning. If scheduled location time is used, LMF includes the scheduled location time in the request to GMLC.

The LMF calculates Sidelink positioning/ranging location results for UEs 1 to n from the Sidelink location measurements received at step 18 and absolute location of Located UE(s) at step 19. The Sidelink positioning/ranging location results can include absolute locations, relative locations or ranges and directions related to the UEs 1 to n, depending on the location request received in step 8.

The LMF returns an Nlmf_Location_DetermineLocation service operation response to the AMF and includes the Sidelink positioning/ranging location results received at step 18 or calculated at step 20.

If Sidelink positioning/ranging location results were received at step 21, the AMF performs steps 7-12 of clause 6.2 to send the Sidelink positioning/ranging location results to the GMLC and to an AF or LCS Client if this was requested at step 8. The Sidelink positioning/ranging location results include the identities for the respective UEs 1 to n received at step 8.

The LMF returns a supplementary services SL-MO-LR response to UE1 in a DL NAS TRANSPORT message and includes any Sidelink positioning/ranging location results calculated at step 20 if step 20 was performed. If UE1 is Located UE, and the target UE is one of the UEs 2 to n and does not have NAS connection, then UE1 may transfer the Sidelink positioning/ranging location results to the target UE.

The LCS Client or the AF (via NEF) sends an LCS service request to the (H)GMLC for Ranging/Sidelink Positioning location results for the n UEs which may each be identified by a GPSI or a SUPI. The request may include the required QoS, the required location results (e.g. absolute locations, relative locations or distances and/or directions related to the UEs), the SL reference UE(s) in case of relative locations, distance, or direction. The (H)GMLC or NEF authorizes the LCS Client or the AF for the usage of the LCS service. If the authorization fails, the remaining steps are skipped and the (H)GMLC or NEF responds to the LCS Client or the AF with the failure of the service authorization. In addition, an Application Layer ID shall be included for each of the n UEs to enable discovery of the UEs at step 12.

The (H)GMLC invokes a Nudm_SDM_Get service operation towards the UDM of each of the n UEs to get the privacy settings of the UE identified by its GPSI or SUPI. The UDM returns the UE Privacy setting of the UE. The (H)GMLC checks the UE LCS privacy profile.

The (H)GMLC invokes a Nudm_UECM_Get service operation towards the UDM of each of the n UEs (for which GPSI or SUPI is available), one at a time, using the GPSI or SUPI of each UE. The (H)GMLC selects the UE (e.g. which is treated as UE1 in following steps) that initiates the Ranging/SL Positioning and selects the corresponding serving AMF.

For a non-roaming case, this step is skipped. In the case of roaming, the (H)GMLC may receive an address of a (V)GMLC (together with the network address of the current serving AMF) from the UDM in step 3, otherwise, the (H)GMLC may use the NRF service in the (H)PLMN to select an available (V)GMLC in the (V)PLMN, based on the (V)PLMN identification contained in the AMF address received in step 3. The (H)GMLC then sends the location request to the (V)GMLC by invoking the Ngmlc_Location_ProvideLocation service operation towards the (V)GMLC. In the cases when the (H)GMLC did not receive the address of the (V)GMLC, or when the (V)GMLC address is the same as the (H)GMLC address, or when both PLMN operators agree, the (H)GMLC sends the location service request message to the serving AMF. In this case, step 4 is skipped. The (H)-GMLC also provides the LCS client type of AF, if received in step 1, or LCS client type of LCS client and other attributes to be sent to AMF in step 5.

In the case of roaming, the (V)GMLC first authorizes that the location request is allowed from this (H)GMLC, PLMN or from this country. If not, an error response is returned. The (H)GMLC or (V)GMLC invokes the Namf_Location_ProvidePositioningInfo service operation towards the AMF serving UE1 to request Sidelink positioning/ranging location results of the n UEs. The service operation includes the SUPI of UE1, Application layer IDs of the UEs, the client type and may include the required LCS QoS, the required location results (e.g. relative locations or ranges and directions related to the UEs) and other attributes as received or determined in step 1.

If UE1 is in CM-IDLE state, the AMF initiates a network triggered Service Request procedure to establish a signalling connection with UE1. If signalling connection establishment fails, steps 7-17 are skipped.

If the indicator of privacy check indicates an action is needed, then same operation as that of step 7-8 of clause 6.1.2 is carried out.

The serving AMF selects an LMF serving UE1 (e.g. an LMF that supports Ranging/Sidelink Positioning) and sends an Nlmf_Location_DetermineLocation service operation towards the LMF with the information received at step 5 e.g. required location results (e.g. relative locations or ranges and directions between pairs of UEs), SL reference UE(s) in case of relative locations, Application layer IDs of the UEs if received in step 5. The service operation includes a LCS Correlation identifier.

The LMF sends an SL-MT-LR request to the serving AMF as a supplementary services message, using the Namf_Communication_N1N2MessageTransfer service operation, and the session ID parameter is set to the LCS Correlation identifier. The SL-MT-LR request may include the application layer IDs of the other UEs 2 to n, the types of required location results (e.g. relative locations or distances and/or directions) and SL reference UE(s) in case of relative locations.

The serving AMF forwards the SL-MT-LR request and a Routing identifier equal to the LCS Correlation identifier to UE1 using a DL NAS TRANSPORT message.

UE1 attempts to discover the other UE 2 to n using their Application Layer IDs if not already discovered using procedure defined in clause 6.4 of TS 23.586.

UE1 obtains the sidelink positioning capabilities of the discovered UEs via the SLPP if not already obtained.

UE1 returns a supplementary services SL-MT-LR response to the serving AMF in an UL NAS TRANSPORT message and includes the Routing identifier received in step 11. The SL-MT-LR response indicates which of UEs 2 to n have been discovered and the sidelink positioning capabilities of the discovered UEs.

The serving AMF forwards the SL-MT-LR response to the LMF indicated by the Routing identifier received at step 14 and includes a LCS Correlation identifier equal to the Routing identifier.

Ranging/Sidelink Positioning of UE1 and the other discovered UEs occurs as for an SL-MO-LR as described for steps 10-19 of Figure 6.20.1-1 with the difference that Ranging/Sidelink Positioning location measurement data or results are always returned to the LMF and the LMF indicates to UE1 at step 13 or step 14 of Figure 6.20.1-1 whether the Ranging/Sidelink Positioning location results will be calculated by the LMF (at step 19) or by UE1 (at step 17). For some undiscovered UEs among the other UEs 2 to n, the LMF interacts with GMLC to initiate the 5GC-MT-LR procedure for UE2 to n to get their absolute locations, and calculates the relative locations or distances and/or directions related to the UEs.

The LMF returns the Sidelink positioning/ranging location results to the LCS Client or AF as in steps 13-15 and step 24 of clause 6.1.2. The results also include failure information of the UE(s) that was not discovered.