Content for  TS 23.586  Word version:  18.4.0

This feature is used to estimate the location of a Target UE with the assistance of the network by using the location of one or more Located UEs and the distance and/or direction between the Target UE and the Located UE(s). UE assisted mode, UE based mode or Network based positioning can be used to estimate the location of the Located UE as specified in TS 23.273. When 5GC is involved for Sidelink Positioning, there can be Network based Operation for Sidelink Positioning (see clauses 5.5.2, 5.5.3) and Network-assisted Operation for SL Positioning (see clauses 5.5.4, 5.5.5). The Network based SL Positioning and Network-assisted SL Positioning each has two cases:

• When the Target UE can establish a NAS signalling connection (see clauses 5.5.2, 5.5.4); or
• When the Target UE cannot establish a NAS signalling connection (see clauses 5.5.3, 5.5.5).

In this Release, for Network based SL Positioning and Network-assisted SL Positioning, positioning of a Target UE having no NAS signalling connection is not supported. In this Release, UE Positioning using SL Positioning involving 5GC is only supported when Target UE and Located UE are registered in the same PLMN i.e. no support for inter PLMN UE Positioning using SL Positioning when the Target UE and Located UE are registered in different PLMNs. Roaming is supported when Target UE and Located UE are registered in the same PLMN, e.g. Target UE is registered in a VPLMN and Located UE is registered in its HPLMN.

A UE with a NAS connection is in RM-REGISTERED state. The UE can enter CM-Connected state by performing UE triggered Service Request for 5GC-MO-LR or SL-MO-LR, performing Network triggered Service Request for 5GC-NI-LR, 5GC-MT-LR or SL-MT-LR. As the Target UE can establish a NAS signalling connection with the AMF, the functionality specified in TS 23.273 for location services can be reused including e.g. 5GC-MO-LR, 5GC-MT-LR, 5GC-NI-LR, SL-MT-LR and SL-MO-LR with the additional functionality captured in this clause.

• The Location Service is triggered via the AMF serving the Target UE. The location request comes either from an AF/external client via the GMLC, a 5G NF, or the Target UE.
• The LTE positioning protocol (LPP) as specified in TS 37.355 is used between the Target UE and the LMF. When LCS procedures are used to estimate the location of the Located UE, LPP is used between Located UE and LMF.
• The LMF determines if UE Positioning using SL positioning will be applied, when the 5GC-MO-LR, 5GC-MT-LR or SL-MT-LR service is triggered. When LMF determines that UE Positioning using SL positioning is used, LMF may trigger the Target UE to perform the discovery of Located UE(s).
• The Target UE can determine if UE Positioning using SL positioning will be applied, when it is determined, the Target UE triggers the SL-MO-LR as described in clause 6.20.1 of TS 23.273.
• The Target UE discovers Located UE(s) for UE Positioning using SL positioning. Optionally, to assist the Target UE the LMF may provide to the Target UE a list of candidate Located UE(s) with the Application Layer ID(s). In this case the LMF maintains the candidate list of Located UE(s) including e.g. the capability, the Application Layer ID and location information of the Located UE(s). If the Target UE selects the Located UE(s), the Target UE reports the UE identity i.e. Application Layer ID of the selected Located UE(s) to LMF, otherwise it reports the UE identity of all discovered Located UE(s) to the LMF.
• The Target UE and Located UE(s) perform Ranging/SL positioning. The Target UE includes the UE identity i.e. Application Layer ID of the Located UE(s) to the LMF together with the Ranging measurement data or estimation result. The LMF may interact with GMLC to get the location of Located UE.
• The LMF uses the location of Located UE(s) together with the Ranging/SL positioning measurement data or estimation results reported by Target UE and optionally also by Located UEs to estimate the location of the Target UE.
• LMF may either determine the absolute location of the Target UE in geographic coordinate or local coordinate expressed by a coordinate ID. For the latter case, Coordinate ID may be provided by LCS client or AF and used for Located UE selection by the Target UE. Coordinate ID should be considered for Located UE selection if Coordinate ID is received from LMF to determine the Target UE location in local coordinates.
• In case the location of Located UE(s) is not known, the LMF interacts with GMLC a required QoS to get the location of Located UE. The Ranging/SL positioning and the positioning of the Located UE(s) can be scheduled with the same time using the scheduled location time, as specified in TS 23.273, to improve the Target UE positioning accuracy.
• The LMF provides the UE location estimate to the Target UE over LPP, or to the AMF, and AMF forwards the UE location to the GMLC, or to the 5GC NF according to legacy functionality.

When Target UE cannot establish the NAS connection with AMF due to the Target UE being out of coverage and at least one of the discovered Located UEs can establish NAS connection for 5GC-MO-LR, the following principles are applied:

• The Target UE performs the Located UE's discovery and selection.
• The Target UE and Located UE(s) perform Ranging/SL positioning.
• The Target UE selects at least one of the Located UEs that can use SL-MO-LR service for SL Positioning.
• The Target UE may transmit its ranging measurement data/results to the Located UE(s).
• Each Located UE that can establish the NAS connection may report the Ranging/SL positioning measurement data or result and the routing identifier from Target UE to the LMF via the serving AMF of the Located UE. This may include ranging measurement data/results received from the Target UE. The endpoints for LPP messages are the LMF and the Located UE(s).
• The LMF may use the received information (i.e. Ranging/SL positioning measurement or estimation result with the same routing identifier) and the location of Located UE(s) to calculate the location of the Target UE, and provide the resulting location via the Located UE to the Target UE.
• If a LMF is aware of multiple Located UEs associated with the same Target UE based on the same routing identifier, it may perform the calculation using all information from these Located UEs.
• If the LMF has the Target UE context, the LMF may provide the resulting location via the GMLC to the LCS Client or AF as specified in clause 6.3 of TS 23.273. If the UE context was deleted, then this functionality cannot be performed.

In this Release, Network-based SL positioning for UE without NAS connection is not supported.

For Network-assisted SL Positioning for UE with NAS connection, the procedure is similar to that of the Network based SL Positioning for UE with NAS connection (in clause 5.5.2), with the following exceptions:

• Target UE performs result calculation.
• The LMF may provide assistance information, e.g. absolute location of the Located UE, in the SLPP message to the Target UEto assist the Sidelink Positioning result calculation.

For Network-assisted SL Positioning for UE without NAS connection, the procedure is similar to that of the Network based SL Positioning for UE without NAS connection (in clause 5.5.3), with the following exceptions:

• The LMF may decide to choose a SL Positioning Server UE, e.g. Located UE, for result calculation, as described in clause 5.3.1.
• The LMF may provide assistance information to the SL Positioning Server UE to assist the Sidelink Positioning result calculation.

In this Release, Network-assisted SL positioning for UE without NAS connection is not supported.

Ranging/SL Positioning service can be exposed to the authorized SL Positioning Client UE, 5GC NF or AF to obtain the relative position or distance/direction result between two or more UEs capable of Ranging/SL Positioning. Ranging/SL Positioning service also can be used by the authorized SL Positioning Client UE, 5GC NF, AF or the LCS client to obtain the absolute position of Target UE if the 5GC NF, AF or the LCS client determines that Ranging/SL Positioning is applicable. The Ranging/SL Positioning service request includes the identifiers of the two or more UEs. When the service exposure is via PC5, the identifiers can be Ranging/SL Positioning Application Layer IDs. 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 as defined in clause 4.4). The service request may further include periodic or trigger event parameters, e.g. the time interval between successive location reports and the total number of reports, the trigger events, the duration of event reporting, the minimum and maximum time intervals between successive event reports, the maximum event sampling interval, whether location estimates shall be included in event reports, and whether only one location report is required or more than one. Trigger events can be;

• the relative position/distance between at least one pair of UEs of the indicated UEs is less than the threshold;
• the relative position/distance between at least one pair of UEs of the indicated UEs exceeds the threshold;
• the relative positions/distances between all UEs are less than the threshold; or
• the relative positions/distances between all UEs exceed the threshold.

The 5GS Ranging/SL Positioning service may be exposed to the AF either via direct interaction with the GMLC or via the NEF for an AF in untrusted domain. Thus, the ranging AF may contact GMLC directly or via NEF to provide a ranging or Sidelink positioning operation request. The service exposure in clause 5.5 of TS 23.273 is reused with enhancements. The request may include the attributes as described in clause 5.6.1. The result is returned by the GMLC to the AF directly or via NEF if needed. The detailed procedure is specified in clause 6.7.2. The Ranging/SL Positioning result calculation is performed by LMF or UEs. When absolute positioning for one Target UE is requested, procedure as described in clause 5.5 is carried out. The Ranging/SL Positioning service request may be initiated by a 5GC NF. In this case, the 5GC NF interacts with the GMLC directly.

QoS of Ranging/SL Positioning includes two aspects:

• Ranging/SL Positioning QoS, which refers to the quality requirement of the Ranging/SL Positioning result
• RSPP transport QoS, which refers to the quality requirement of the PC5-U communication for transmitting RSPP traffic.

Ranging/SL Positioning QoS requirement may be provided in the Ranging/SL Positioning service request generated at the application layer, and is provided from the application layer to the Ranging/SL Positioning layer. Ranging/SL Positioning QoS requirement may be included in the Ranging/SL Positioning Service request from SL Positioning Client UE. The Ranging/SL Positioning layer maps the Ranging/SL Positioning QoS requirement to the Ranging/SL Positioning QoS parameters and provides the Ranging/SL Positioning QoS parameters to the AS layer. If there is no received Ranging/SL Positioning QoS requirement from the application layer, the Ranging/SL Positioning layer determines the Ranging/SL Positioning QoS parameters based on the Ranging/SL positioning Policy/parameters as configured in the clause of 5.1. Ranging/SL Positioning QoS information contains attributes defined in clause 4.1b of TS 23.273 with the following additions:

• The accuracy attribute also includes
  • the relative horizontal accuracy, and the relative vertical accuracy for relative positioning;
  • the distance accuracy and direction accuracy for Ranging.
• Range, which indicates the applicability of the QoS attributes in the Ranging/SL Positioning operation over PC5.
• Priority level.
• Delay Budget.

Ranging/SL Positioning QoS information is used for determination of Ranging/SL Positioning method. The Ranging/SL Positioning methods are defined in TS 38.355.

The V2X/ProSe layer handles the RSPP traffic as the V2X/ProSe application data packets for the QoS treatment. QoS handling mechanism of V2X as defined in clause 5.4 of TS 23.287 or QoS handling mechanism of 5G ProSe as defined in clause 5.6.1 of TS 23.304 is reused. PQI values as defined in TS 23.287 and TS 23.304 may be reused for RSPP transport QoS.