The "Ranging/Sidelink Positioning authorised" information and the RSPP transport QoS parameters shall be provided to the NG-RAN node for scheduled resource allocation mode resource management. The "Ranging/Sidelink Positioning authorised" information indicates whether the UE is authorized to perform Ranging/Sidelink Positioning over PC5. The RSPP transport QoS parameters include parameters defined in clause 5.7.3, which are generated by the PCF and are provided to the AMF when receiving the Ranging/Sidelink Positioning Capability in Npcf_UEPolicyControl_Create Request from the AMF or when receiving the updated subscription data from UDR. During registration, the UE includes the Ranging/Sidelink Positioning Capability as defined in clause 4.3.1 as part of the "5GMM capability" in the Registration Request message. AMF determines whether the UE is authorised to perform Ranging and Sidelink Positioning based on UE's Ranging/Sidelink Positioning Capability and the Ranging/Sidelink Positioning Service Authorisation included in the subscription data received from UDM. The AMF stores the Ranging/Sidelink Positioning Capability in the UE context. If the UE is authorised to perform Ranging based services and Sidelink Positioning, the "Ranging/Sidelink Positioning authorised" information and the RSPP transport QoS parameters shall be provided from the AMF to the NG-RAN node in a NGAP message during Registration procedure, Service Request procedure and N2 Handover procedure, and from source NG-RAN node to target NG-RAN node over Xn during Xn Handover procedure as defined in clause 6.3.

Both Model A and Model B discovery as defined in clause 6.3.2 of TS 23.304 are supported for the 5G ProSe capable UEs discovery (including commercial and public safety use cases). During Ranging/SL Positioning UE direct discovery, the discovery message indicates this discovery message is for "Ranging/Sidelink Positioning"; During Ranging/SL Positioning Group Member Discovery, the Application Layer Group ID indicates a Ranging/Sidelink Positioning group that the UE belongs to. Procedures for V2X communication over PC5 reference point as defined in TS 23.287 are supported for the V2X capable UEs discovery. When unicast mode V2X communication procedure as defined in clause 6.3.3 of TS 23.287 is used, the Service Type in Layer-2 link establishment procedure indicates "Ranging/Sidelink Positioning"; when broadcast mode or groupcast mode V2X communication procedure as defined in clause 6.3.1 or clause 6.3.2 of TS 23.287 is used, Service Type indicates "Ranging/Sidelink Positioning". The role(s) of the discovered UE (e.g. Target UE, SL Reference UE, SL Positioning Server UE, Located UE) is (are) included in discovery message (for 5G ProSe capable UE) and unicast link establishment messages (for V2X capable UE) as RSPP specific meta data, which contents are defined in clause 6.11 of TS 38.355. More details on this and other information conveyed during discovery can be found in clause 6.4. The procedures for Ranging/Sidelink Positioning UE Discovery & Selection are defined in clause 6.4.

When Sidelink Positioning is applied for Target UE in a SL-MO-LR, SL-MT-LR, 5GC-MO-LR or 5GC-MT-LR procedure, Located UE(s) may be discovered and selected:

• When LMF determines to apply Sidelink Positioning for Target UE, LMF triggers the Target UE to perform discovery of the Located UE.
• When the Target UE determines to apply Sidelink Positioning, the Target UE triggers the discovery of the Located UE.

The LMF may be pre-configured with the list of candidate Located UEs including e.g. the capability, stationary information and location information of the Located UE(s), e.g. RSU or the operator deployed Located UE. The LMF may provide to the Target UE a list of candidate Located UE(s). The discovery of Located UEs follows the same principles as specified in clause 5.2.1. The UE can indicate its role "Located UE" in its list of supported roles during discovery, if it is authorized to be a Located UE in a given PLMN as per the Authorization and Provisioning for Ranging/SL positioning service as specified in clause 5.1. A Target UE may discover and select one or more Located UEs to be used in the Ranging/SL positioning procedures as specified in clauses 5.3 to 5.5. Multiple candidate Located UEs may be discovered, in that case, the Located UE(s) is selected from the candidate Located UE list. The Located UE(s) is selected based on:

• Candidate list of Located UE(s), if available.
• Capabilities of the candidate Located UE(s), e.g. the supported Sidelink Positioning methods.
• The required positioning QoS of Target UE, positioning QoS supported by the candidate Located UE(s).
• Whether the serving PLMN of candidate Located UE(s) is same with serving PLMN of Target UE.
• UE's information, candidate Located UE's location.

When LMF determines SL positioning for target UE and trigger the discovery of the Located UE, LMF can decide that LMF or target UE selects Located UEs. If the decision is LMF selecting Located UEs, Target UE sends the multiple discovered candidate Located UEs to the LMF for the selection. After the LMF determines the selected Located UE(s), the LMF sends the selected Located UE(s) to the Target UE. In this release of the specification, for UE Positioning assisted by Sidelink Positioning and involving 5GC, the Target UE shall discover and select Located UEs that are in the same serving PLMN of the Target UE as described in clause 5.5.1. LMF needs to provide located UE for discovery when AF request ranging between two UEs. Additionally, LMF may be provisioned with Located UEs that may be sent to target UE as candidate list of located UEs.

SL Positioning Server UE Discovery & Selection is performed by the Target UE, when it meets one or more of the following criteria:

• The Target UE and the discovered SL Reference UEs are currently not served by a network supporting Ranging/SL Positioning (e.g. because they are out-of-coverage or the serving network does not support Ranging/SL Positioning). SL Reference UE and Target UE may indicate whether its serving network supports Ranging/SL Positioning or not to each other. The indication of serving network not supporting Ranging/SL Positioning is also used to notify each other when UE has no NAS connection available.
• The Target UE is not capable of performing SL Positioning Server UE functionalities or related positioning methods.
• The SL Reference UEs are not capable of performing SL Positioning Server UE functionalities or related positioning methods.

The discovery of SL Positioning Server UE follows the same principles as specified in clause 5.2.1. The UE can indicate its role "SL Positioning Server UE" in its list of supported roles during discovery, if it is authorized to be a SL Positioning Server UE in a given PLMN as per the Authorization and Provisioning for Ranging/SL positioning service as specified in clause 5.1. The Target UE shall discover and select a SL Positioning Server UEs that are in the same or different serving PLMN of the Target UE and the SL Reference UE(s).

When Ranging/Sidelink Positioning is applied for Target UE in a SL-MO-LR, SL-MT-LR, 5GC-MO-LR or 5GC-MT-LR procedure, SL Reference UE may be discovered and selected:

• When LMF determines to apply Ranging/Sidelink Positioning for Target UE, LMF triggers the Target UE to perform discovery of the SL Reference UE.
• When the Target UE determines to apply Ranging/Sidelink Positioning, the Target UE triggers the discovery of the SL Reference UE.

The discovery of SL Reference UEs follows the same principles as specified in clause 5.2.1. The UE can indicate its role "SL Reference UE" in its list of supported roles during discovery, if it is authorized for Ranging/SL positioning service as specified in clause 5.1. A Target UE may discover and select one or more SL Reference UEs to be used in the Ranging/SL positioning procedures as specified in clauses 5.3 to 5.5. When multiple candidate SL Reference UEs are discovered, the SL Reference UE(s) is selected based on:

• Capabilities of the candidate SL Reference UE(s), e.g. the supported Sidelink Positioning methods.
• The required positioning QoS.

Any UE supporting Ranging/SL Positioning, e.g. Target UE, SL Reference UE, Sidelink Positioning Server UE, Located UE, shall have a Ranging/SL Positioning layer, which is above the AS layer and handles service requests received from application layer to control the Ranging/SL Positioning operation. The Ranging/SL Positioning layer provides the support of authorization and provisioning as described in clause 5.1, the UE discovery and selection as described in clause 5.2, the Ranging/SL Positioning Protocol (RSPP), including protocols between UEs and the protocols between UE and LMF for Ranging/SL Positioning. Ranging/SL Positioning layer supports the Ranging/SL Positioning service sessions for one time or periodic ranging, ranging for distance or direction measurement or both. The Ranging/SL Positioning layer provides the ranging parameters to AS layer, including one time or periodic ranging, ranging for distance or direction measurement or both. The RSPP is exchanged over SR5 over PC5-U reference point between UEs (i.e. Target UE, SL Reference UE, Located UE and SL Positioning Server UE) to manage the Ranging/SL Positioning service sessions between UEs or among a group of UEs and between UE and LMF to manage the Ranging/SL Positioning service sessions between UE and LMF. Multiple UEs may be involved in a single Ranging/Sidelink Positioning session. When the Ranging/SL Positioning service session is among a group of UEs, the RSPP may provide group related identifier information for the PC5 transport layer handling. The transport of the RSPP over PC5-U is specified in clause 5.3.2. The transport of the RSPP between UE and LMF is specified in clause 5.3.3. A LMF shall be involved when the Target UE is in the network coverage and the serving network is capable to support ranging functionalities. The details of Network based Ranging/SL Positioning operation, and Network assisted SL Positioning are described in detail in clause 5.5. When Network assisted Ranging/SL Positioning is used, the use of RSPP is necessary for Ranging/SL Positioning control. A SL Positioning Server UE can be discovered and selected for result calculation, method determination, assistant data distribution and SL Reference UE selection in case of out-of-coverage or for UE-only Operation if the serving network does not support Ranging/SL Positioning. If the LMF capable for Ranging/SL Positioning is reachable by Target UE and/or SL Reference UE, the LMF can still decide that a SL Positioning Server UE, Target UE or SL Reference UE executes the result calculation. A SL Positioning Server UE can be co-located with a Target UE or SL Reference UE.

RSPP, including SLPP messages defined in TS 38.355 and Supplementary Service messages defined in TS 24.080, is used between UE and LMF.