5 High level functionality and features

23.5863GPPArchitectural Enhancements to support Ranging based services and Sidelink PositioningRelease 18TS

Editor’s note: This clause defines high level functionality and features.

5.1 Authorization and Provisioning for Ranging/SL positioning service

In 5GS, the parameters for Ranging/SL positioning service may be made available to the UE in following ways:

– provisioned in the ME; or

– configured in the UICC; or

– provisioned in the ME and configured in the UICC; or

– provided or updated by the Ranging/SL positioning Application Server via PCF and/or PC1 reference point; or

– provided or updated by the PCF to the UE.

The UE shall apply any given parameter in the following priority order:

– provided or updated by the PCF (regardless whether the parameter is determined by the PCF itself or provided by the Ranging/SL positioning Application Server to the PCF), if available, otherwise;

– provided or updated by the Ranging/SL positioning Application Server via SR1 reference point, if available, otherwise;

– configured in the UICC, if available, otherwise;

– provisioned in the ME, if available.

The parameters provided or updated by the Ranging/SL positioning Application Server via SR1 reference point may need to be complemented with configuration data from other sources listed above.

NOTE: The Ranging/SL positioning Application Server can provision the same Ranging/SL positioning parameters via 5GC or directly to the UE via SR1 reference point, and can revoke (e.g. delete) the Ranging/SL positioning parameters via 5GC in order for the provisioning via SR1 reference point to take effect.

The basic principles of service authorization and provisioning for Ranging/SL positioning service are as follows:

– The PCF in the HPLMN may configure a list of PLMNs where the UE is authorized to use Ranging/SL positioning.

– The UE is authorized to use Ranging/SL positioning only in the PLMN(s) indicated by the PCF, and the equivalent PLMNs thereof.

– The PCF in the HPLMN merges authorization information from home and other PLMNs and provides the UE with the final authorization information.

– The PCF in the VPLMN or HPLMN may revoke the authorization (via H-PCF when roaming) at any time by using the UE Configuration Update procedure for transparent UE Policy delivery procedure defined in clause 4.2.4.3 of TS 23.502 [3].

– The Ranging/SL positioning Policy/parameters provisioning to UE is controlled by the PCF and may be triggered by UE. The PCF provisions one or more of the following Policy/parameters:

– When the UE is served by NG-RAN, the PLMNs in which the UE is authorized to perform Ranging/SL positioning service over PC5 reference point for acquiring relative distance, relative direction, high accuracy relative distance and high accuracy relative direction.

– When the UE is not served by NG-RAN, indicates whether the UE is authorized to perform Ranging/SL positioning service over PC5 reference point for acquiring relative distance, relative direction, high accuracy relative distance and high accuracy relative direction.

– The mapping between Ranging/SL positioning services (e.g. ProSe identifiers, V2X service types) and Ranging/SL positioning QoS parameters.

– The authorized Ranging/SL positioning role per PLMN, e.g. target UE, reference UE, assistant UE, and located UE.

– When the UE is not served by NG-RAN, indicates the authorized Ranging/SL positioning role, e.g. target UE, reference UE, assistant UE, and located UE.

Editor’s note: FFS if authorized roles for Assistant UE is needed.

5.2 Ranging/Sidelink Positioning UE Discovery & Selection

5.2.1 General

Both Model A and Model B discovery as defined in clause 6.3.2 of TS 23.304 [7] are supported for the 5G ProSe capable UEs discovery (including commercial and public safety use cases).

Procedures for V2X communication over PC5 reference point as defined in TS 23.287 [6] are supported for the V2X capable UEs discovery.

Editor’s note: Whether and how to support Restricted ProSe Discovery defined in TS 23.304 [7] for the 5G ProSe capable UE is FFS.

Editor’s note: Information element in discovery message and whether 5G DDNMF is involved are FFS.

5.2.2 Located UE Discovery & Selection

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.

Editor’s note: Privacy aspects of sharing the location of a Located UE (e.g. to any Target UE) and exposing information about such privacy aspects during discovery (e.g. to facilitate Located UE selection by a Target UE) needs to be aligned with SA WG3.

A Target UE may discover and select one or more Located UEs (and other Reference UEs) to be used in the Ranging/SL positioning procedures as specified in clauses 5.3 through 5.5. In this release of the specification, for network assisted ranging and SL positioning, the Target UE shall discover and select Located UEs that are in the same serving PLMN of the Target UE.

Editor’s note: other selection criteria are FFS.

Editor’s note: Whether LMF will select Located UEs for Ranging/SL positioning procedure will be decided by RAN.

Editor’s note: It is FFS if the LMF can provide candidate list of Located UE to participate in the network assisted SL positioning for the target UE, e.g.to perform targeted discovery.

Editor’s note: It is FFS whether an indication of whether a Located UE is static/mobile needs to be provided during discovery in line with SA1 requirements in TS 22.261, e.g. to facilitate Located UE selection in various coverage scenarios.

NOTE: The role of being “Located UE” is dynamic and can change over time, in particular if the Located UE is moving. Hence, the discovery results need to be refreshed if there is a (significant) delay between discovery and initiating of a ranging procedure with a discovered Located UE. How often this is done is up to UE implementation.

Editor’s note: The criteria to determine if the location of a UE is sufficiently stable and accurate in order for the UE to announce itself as a “Located UE” needs to be aligned with RAN WGs.

5.3 Ranging/SL Positioning control

5.3.1 General

Any UE supporting Ranging/SL Positioning, e.g. Target UE, Reference UE, Sidelink Positioning Server 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) defined in TS 38.xxx [x], 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.

Editor’s note: The specification number for RSPP (SLPP for RAN) will be added based on RAN WG input.

Editor’s note: The protocol used between UE and LMF will be decided by RAN and could be an extension of LPP, a new protocol or both.

The RSPP is exchanged over SR5 over PC5-U reference point between UEs (i.e. Target UE, Reference UE, Assistant UE, Located UE and SL Positioning Server UE) to manage the Ranging/SL Positioning service sessions between UEs or among a group of UEs. 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 RSPP supports the following functions:

– exchange the Ranging/Sidelink Positioning capability;

– exchange the Ranging/Sidelink Positioning assistant data;

– exchange Ranging/Sidelink positioning measurement data/result.

NOTE 1: Group management is out-of-scope of this specification.

NOTE 2: RSPP signalling negotiation determines whether measurement results or Ranging/Sidelink Positioning results are exchanged over the SR5.

A LMF shall be involved when at least one of the Target UE and the Reference UE are in the network coverage and the serving network is capable to support ranging functionalities. The details of Network assisted Ranging/SL Positioning operation is 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 Reference UE, the LMF can still decide that Target UE or Reference UE executes the result calculation. A SL Positioning Server UE can be co-located with a Target UE or Reference UE.

Editor’s note: Functionalities of the SL Positioning Server UE will be determined by RAN WGs.

5.3.2 Transport of RSPP over PC5

5.3.2.1 General

Depending on type of the UE (e.g. V2X capable or 5G ProSe capable), V2X Communication procedures as defined in TS 23.287 [6] or 5G ProSe Direct Communication procedures as defined in TS 23.304 [7] are used for the RSPP transport between UEs over PC5:

– For V2X capable UEs, policies and parameters defined in TS 23.287 [6] clause 5.1.2.1 are used to determine the corresponding transport configurations for the RSPP signalling. The V2X service type shall take the value(s) defined for "Ranging/SL Positioning Protocol" in corresponding format in different regions, e.g. ITS-AID, PSID, or AID as described in TS 23.287 [6] clause 3.1.

– For 5G ProSe capable UEs, policies and parameters defined in TS 23.304 [7] clause 5.1.3.1 applies. To determine the parameters, the ProSe services (i.e. ProSe identifiers) shall take the value(s) defined for "Ranging/SL Positioning Protocol" in corresponding format described in TS 23.304 [7] clause 3.1.

NOTE: For a UE that is both V2X capable and 5G ProSe capable, separate RSPP sessions will be used, i.e. no V2X and 5G ProSe cross communication is supported.

Depends on the policy and parameter configuration on the UE, the RSPP may be transported using different communication mode over PC5 (i.e. broadcast mode, groupcast mode or unicast mode), with associated QoS configurations. Procedures defined in clause 6.3 of TS 23.287 [6] and clause 5.3 of TS 23.304 [7] are used to support the corresponding communicated modes.

Same RSPP messages are used for V2X capable UEs and 5G ProSe capable UEs. The RSPP message is carried using "Non-IP" PDCP SDU type for V2X capable UEs as defined in clause 6.1.1 of TS 23.287 [6], and "Unstructured" PDCP SDU type for 5G ProSe capable UEs as defined in clause 6.1.2.2 of TS 23.304 [7].

Editor’s note: The transport of RSPP over PC5 reference point will be further aligned with RAN WG decisions.

5.3.2.2 Identifiers used for RSPP transport over PC5

As defined in clause 5.6.1 of TS 23.287 [6] and clause 5.8.2 of TS 23.304 [7], multiple identifiers need to be determined for the PC5 operations, depending on the communicate mode used.

For broadcast mode, the destination Layer-2 ID and source Layer-2 ID(s) are chosen based on UE configuration, as defined in clause 5.6.1.2 of TS 23.287 [6] and clause 5.8.2.2 of TS 23.304 [7].

For groupcast mode, the RSPP may provide the group identifier information. The UE converts the provided group identifier information to a destination Layer-2 ID. If the RSPP does not provide the group information, the UE determines the destination Layer-2 ID based on configuration of the mapping between V2X Service type or ProSe Identifier and Layer-2 ID. Details of the identifier determination are described in clause 5.6.1.3 of TS 23.287 [6] and clause 5.8.2.3 of TS 23.304 [7].

For unicast mode, the UE needs to establish a unicast link to the peer UE. To support the operation as defined in clause 5.6.1.4 of TS 23.287 [6] and 5.8.2.4 of TS 23.304 [7], the RSPP needs to provide the Application Layer IDs of the UE and the peer UE, and to be used in the PC5 unicast link establishment procedure. When the Application Layer ID changes, the Layer-2 IDs used for the unicast link shall also be changed.

NOTE: The Application Layer ID to be used is determined by RSPP layer signalling.

Based on privacy configurations, the UE may periodically change its source Layer 2 ID, as defined in TS 23.287 [6] and TS 23.304 [7].

5.4 Void

5.5 Network assisted Sidelink Positioning

5.5.1 General

Editor’s note: The final name of the term "Network assisted Sidelink Positioning" is FFS.

This feature is used to estimate the location of a 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 UE and the Located UE(s).

The Network assisted SL Positioning feature has two cases:

– When the UE can establish a NAS signalling connection, or

– When the UE cannot establish a NAS signalling connection

For Ranging, UE assisted mode, UE based mode or standalone mode can be used to estimate the distance and/or direction between the UE and the Located UE(s). These modes are defined in TS 23.273 [8].

UE assisted mode, UE based mode or Network assisted positioning can be used to estimate the location of the Located UE as specified in TS 23.273 [8].

In this release, Network Assisted SL Positioning is only supported when Target UE and Located UE are registered in the same PLMN i.e., no support for inter PLMN Network Assisted 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.

5.5.2 Network assisted SL Positioning of UE with NAS connection

A UE with a NAS signalling connection is in CM-Connected state. The UE enters CM-Connected state by performing UE triggered Service Request for 5GC-MO-LR or performing Network triggered Service Request for 5GC-NI-LR or 5GC-MT-LR. As the Target UE can establish a NAS signalling connection with the AMF, the functionality specified in TS 23.273 [8] for location services can be reused including e.g. 5GC-MO-LR, 5GC-MT-LR and 5GC-NI-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 [9] 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.

Editor’s note: RAN WGs will determine whether and what enhancements and the subset functionalities of LPP are needed to support Network assisted SL positioning including an 5GC-MT-LR, 5GC-MO-LR and 5GC-NI-LR.

– Either the Target UE or LMF determines if network assisted SL positioning will be applied. When LMF determines that network assisted SL positioning is used, LMF may trigger the Target UE to perform the discovery of Located UE(s).

– The Target UE discovers Located UE(s) for network assisted SL positioning. Optionally, to assist the Target UE the LMF may provide to the Target UE a list of candidate Located UE(s). In this case the LMF maintains the candidate list of Located UE(s) including e.g. the capability and location information of the Located UE(s).

– The Target UE and Located UE(s) perform ranging/SL positioning. The Target UE includes the UE identity 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.

Editor’s note: It is FFS what UE identity of the Located UE that the Target UE provides to the LMF. Depending on which UE identity, the LMF or the GMLC may need to resolve this by query another NF. The security impact will be coordinated with SA3.

– 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.

– In case the Located UE is a non-stationary UE, the LMF interacts with GMLC to get the location of Located UE, and the ranging/SL positioning and the positioning of the Located UE(s) can be scheduled with the same time, as specified in TS 23.273 [8], to improve the Target UE positioning accuracy.

NOTE: The LMF may need to compensate the time difference of the positioning of Target UE and Located UE with additional information.

– The LMF provides the UE location estimate to the Target UE over LPP or the AMF forwards the UE location to the GMLC, or to the 5GC NF according to legacy functionality.

5.5.3 Network assisted SL positioning without NAS connection

When Target UE cannot establish the NAS connection with AMF due to the Target UE being out of coverage, for 5GC-MO-LR or pending 5GC-MT-LR (e.g. deferred 5GC-MT-LR), the following principles are applied:

– The Target UE performs the Located UE’s discovery and selection.

– The Target UE may transmit its ranging measurements/results to the Located UE(s).

– Located UE(s) may report the ranging/SL positioning measurement result to the LMF. This may include ranging measurements/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 to calculate the location of the Target UE, and provide the resulting location via the Located UE to the Target UE or via 5G NF to the LCS client or the Application Server.

Editor’s note: It is FFS if an enhanced 5GC-MO-LR message is sent by the Located UE.

Editor’s note: Security aspects require confirmation from SA WG3.

Editor’s note: It is FFS when AMF does not maintain target UE’s context or GMLC cannot get target UE AMF address because of deregistration, whether and how location report from Located UE on behalf of Target UE is supported.

Editor’s note: How LMF associates the ranging/SL positioning measurement or estimation result from different Located UEs is FFS.

Editor’s note: It is FFS whether the pending 5GC-MT-LR also includes the 5GC-MT-LR.

5.6 Ranging/SL Positioning service exposure

5.6.1 General

Ranging/SL Positioning service can be exposed to the authorized SL Positioning Client UE, 5GC NF or AF to obtain the relative distance/direction result between two UEs capable of Ranging/SL positioning.

Ranging/SL Positioning service also can be exposed to the authorized 5GC NF, AF or the LCS client to obtain the absolute position of Target UE using the procedure as specified in TS 23.273 [8]. When absolute positioning is requested, LMF and Target UE may decide whether SL positioning or Uu positioning needs to be performed.

Editor’s note: The attributes included in the Ranging/SL Positioning service requests are FFS.

5.6.2 Service exposure to SL Positioning Client UE

5.6.2.1 General

The Ranging/SL Positioning service may be exposed to an authorized SL Positioning Client UE. The Client UE can initiate the Ranging/SL Positioning service through PC5 or through the 5GC network, e.g. based on PC5 or Uu availability.

5.6.2.2 Ranging/SL Positioning service exposure though PC5

For Ranging/SL Positioning service exposure to a UE through PC5 in the following way:

– SL Positioning Client UE discovers one of Reference UE and Target UE;

– SL Positioning Client UE invokes the Ranging/SL Positioning service request to the discovered Reference UE/Target UE for obtaining the Ranging and SL positioning result between Reference UE and Target UE. This request includes the user info of SL Positioning Client UE, Reference UE and Target UE.

– The UE providing the exposure service triggers the authorization of SL Positioning Client UE for the Ranging/SL Positioning service invocation, performs the Ranging/SL positioning control between Reference UE and Target UE (as defined in clause 6.X), and returns the Ranging/SL positioning result to SL Positioning Client UE.

Editor’s note: Privacy handling on Ranging /SL Positioning service exposure through PC5 will be aligned with SA3.

Editor’s note: It is FFS which layer to handle the PC5 message of Ranging and sidelink positioning service request/response.

5.6.2.3 Ranging/SL Positioning service exposure though 5GC network

For Ranging/SL Positioning service exposure to a UE through network, the user plane-based procedure, or control plane-based procedure is used.

When using the user plane-based procedure:

– The SL Positioning Client UE is provisioned with the Onboarding Enrolment Information during the registration procedure. The Onboarding Enrolment Information is specified in TS 33.122 [11].

– The SL Positioning client UE invokes the Application exposure API over the application layer as specified clause 5.x for an AF.

– The authorization of the SL positioning client UE for Ranging and sidelink positioning service invocation performed and checking that the Reference UE’s and Target UE’s privacy criteria are met, follows the same the procedures as for the AF in clause 5.X.

When using the control plane-based procedure:

– The SL Positioning Client UE invokes the Ranging/SL Positioning service exposure via the 5GC-MO-LR procedure with Sidelink Positioning for relative positioning as defined in clause 6.2.x of TS 23.273 [8].

– The Client UE sends the 5GC-MO-LR request to AMF and this triggers the AMF to send the Ranging/SL positioning request to the GMLC for the Ranging/SL Positioning service with including the SL positioning client UE ID.

– The AMF sends the Ranging/SL positioning result to the SL positioning client UE when it receives the result from the GMLC.

Editor’s note: The procedure for Privacy handling on Ranging /SL Positioning service exposure through the 5GC network by 5GC-MO-LR will be aligned with SA3. This includes the authorization of the SL positioning client UE for Ranging and sidelink positioning service invocation of two other UEs.

NOTE: In this release, for the control plane-based procedure, the SL positioning client UE and the UE who provides the exposure service are registered in the same PLMN.

5.6.3 Service Exposure to the AF

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 to the 5GS.

The service exposure in clause 5.5 of TS 23.273 [8] is reused with enhancements. The request may indicate with corresponding events if the server requires relative distance/direction of target UEs, absolute positioning of target UEs, or both. The request shall include one or multiple target UEs and optionally it may include additional information such as the SL reference UE for relative distance/direction, the required positioning QoS, etc. For relative distance/direction, at least two UE’s identities are included as attribute in the location service requests and accuracy and latency for distance and/or direction measurements are included in Requested QoS information. The result is returned by the 5GC to the AF via NEF, if needed. The detailed procedure is specified in clause 6.1.X.

In addition, the LCS architecture specified in TS 23.273 [8] is re-used and the 5GC-MT-LR and 5GC-MO-LR procedures there specified are taken as baseline. LMF is the responsible 5GC NF to forward the Ranging/Sidelink Positioning request to the UE, and one Ranging/SL Positioning capable LMF is selected by the AMF for a Ranging/Sidelink Positioning session. The AMF serves either the Target UE or the SL Reference UE or both. In case the selected LMF does not have the context information for all involved UEs, a similar context transfer as specified in TS 23.273 [8] can be performed.

The Ranging/SL Positioning result calculation is performed by LMF or UEs. When absolute positioning is requested, LMF and target UE may decide whether SL positioning or Uu positioning needs to be performed. LMF may combine Ranging/Sidelink Positioning results and Uu positioning results before exposing the results to the AF.

5.6.4 Service exposure to 5GC NF

The 5GS Ranging/SL Positioning service request may be initiated by a 5GC NF. In this case, the 5GC NF initially interacts with GMLC and the LCS architecture specified in TS 23.273 [8] may also be re-used as described in clause 5.6.2.

Editor’s note: Further details of service exposure to 5GC NF are FFS.

5.7 QoS Handling

5.7.1 General

QoS of Ranging/SL Positioning includes 2 aspects:

– Ranging/SL Positioning QoS, which refers to the quality of the Ranging/SL Positioning result

– RSPP transport QoS, which refers to the quality of the PC5-U communication for transmitting RSPP traffic.

5.7.2 Handling of Ranging/SL Positioning QoS

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 information contains attributes defined in clause 4.1b of TS 23.273 [8] with the following additions:

– The accuracy attribute also includes the accuracy of horizontal/vertical distance and the accuracy of horizontal/vertical direction;

– Range, which indicates the applicability of the QoS attributes in the Ranging/SL Positioning operation over PC5.

Editor’s note: Other QoS attributes are FFS, and will be aligned with RAN WGs.

5.7.3 Handling of RSPP transport QoS

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 TS 23.287 [6] or QoS handling mechanism of 5G ProSe as defined in TS 23.304 [7] is reused.

Editor’s note: PQI values for RSPP transport is FFS.

5.8 Subscription to Ranging/SL Positioning

The subscription information in the UDM contains information to give the user permission to use 5G Ranging/SL Positioning.

At any time, the operator can amend or remove the UE subscription rights from subscription information in the UDM, or to revoke the user’s permission to use Ranging/SL Positioning.

The following subscription information is defined for Ranging/SL Positioning:

– subscription for UE acting as Target UE.

– subscription for UE acting as SL Reference UE.

– subscription for UE acting as Located UE.

– subscription for UE acting as Assistant UE.

Editor’s note: FFS if subscription for acting as Assistant UE is needed.

– Ranging/SL positioning QoS parameters.

– the list of the PLMNs authorized for Ranging/SL Positioning services, including:

– the list of the PLMNs where the UE is authorised for perform Ranging/SL positioning service over PC5 reference point.

– the list of the PLMNs where the UE is authorised for Ranging/SL positioning service with Direct Discovery Model A, i.e. to announce or monitor or both.

– the list of the PLMNs where the UE is authorised for Ranging/SL positioning service with Direct Discovery Model B, i.e. to perform Discoverer operation or Discoveree operation or both.

5.9 Charging

Editor’s note: The charging solutions for the support of Ranging based services and Sidelink Positioning is expected to be defined by SA5, and SA2 will make the alignment based on the outcome of the SA5 work.

5.10 Security

Editor’s note: The security impacts for the support of Ranging based services and Sidelink Positioning, e.g. privacy protection and service access authorization, will be defined based on SA3 feedback.