5.8 Sidelink

38.3313GPPNRProtocol specificationRadio Resource Control (RRC)Release 17TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

5.8.1 General

NR sidelink communication consists of unicast, groupcast and broadcast. For unicast, the PC5-RRC connection is a logical connection between a pair of a Source Layer-2 ID and a Destination Layer-2 ID in the AS. The PC5-RRC signalling, as specified in clause 5.8.9, can be initiated after its corresponding PC5 unicast link establishment (TS 23.287 [55]). The PC5-RRC connection and the corresponding sidelink SRBs and sidelink DRB(s) are released when the PC5 unicast link is released as indicated by upper layers.

For each PC5-RRC connection of unicast, one sidelink SRB (i.e. SL-SRB0) is used to transmit the PC5-S message(s) before the PC5-S security has been established. One sidelink SRB (i.e. SL-SRB1) is used to transmit the PC5-S messages to establish the PC5-S security. One sidelink SRB (i.e. SL-SRB2) is used to transmit the PC5-S messages after the PC5-S security has been established, which is protected. One sidelink SRB (i.e. SL-SRB3) is used to transmit the PC5-RRC signalling, which is protected and only sent after the PC5-S security has been established. One sidelink SRB (i.e. SL-SRB4) is used to transmit/receive the NR sidelink discovery messages.

For unicast of NR sidelink communication, AS security comprises of integrity protection of PC5 signalling (SL-SRB1, SL-SRB2 and SL-SRB3) and user data (SL-DRBs), and it further comprises of ciphering of PC5 signaling (SL-SRB1 only for the Direct Link Security Mode Complete message as specified in TS 24.587 [57] for V2X service or TS 24.554 [72] for Proximity-services, SL-SRB2 and SL-SRB3) and user data (SL-DRBs). The ciphering and integrity protection algorithms and parameters for a PC5 unicast link are exchanged by PC5-S messages in the upper layers as specified in TS 33.536 [60], and apply to the corresponding PC5-RRC connection in the AS. Once AS security is activated for a PC5 unicast link in the upper layers as specified in TS 33.536 [60], all messages on SL-SRB2 and SL-SRB3 and/or user data on SL-DRBs of the corresponding PC5-RRC connection are integrity protected and/or ciphered by the PDCP.

For unicast of NR sidelink communication, if the change of the key is indicated by the upper layers as specified in TS 24.587 [57], UE re-establishes the PDCP entity of the SL-SRB1, SL-SRB2, SL-SRB3 and SL-DRBs on the corresponding PC5-RRC connection.

NOTE 1: In case the configurations for NR sidelink communication are acquired via the E-UTRA, the configurations for NR sidelink communication in SIB12 and sl-ConfigDedicatedNR within RRCReconfiguration used in clause 5.8 are provided by the configurations in SystemInformationBlockType28 and sl-ConfigDedicatedForNR within RRCConnectionReconfiguration as specified in TS 36.331 [10], respectively.

NOTE 2: In this release, there is one-to-one correspondence between the PC5-RRC connection and the PC5 unicast link as specified in TS 38.300[2].

NOTE 3: All SL-DRBs related to the same PC5-RRC connection have the same activation/deactivation setting for ciphering and the same activation/deactivation setting for integrity protection as specified in TS 33.536 [60].

NOTE 4: When integrity check failure concerning SL-SRB1 for a specific destination is detected, the UE sends an indication to the upper layers [57].

NOTE 5: The selection of NULL algorithms means that the PC5 messages are considered protected for the purposes of being allowed to be sent or received.

5.8.2 Conditions for NR sidelink communication/discovery operation

The UE shall perform NR sidelink communication operation only if the conditions defined in this clause are met:

1> if the UE’s serving cell is suitable (RRC_IDLE or RRC_INACTIVE or RRC_CONNECTED); and if either the selected cell on the frequency used for NR sidelink communication/discovery operation belongs to the registered or equivalent PLMN as specified in TS 24.587 [57] or the UE is out of coverage on the frequency used for NR sidelink communication/discovery operation as defined in TS 38.304 [20] and TS 36.304 [27]; or

1> if the UE’s serving cell (RRC_IDLE or RRC_CONNECTED) fulfils the conditions to support NR sidelink communication/discovery in limited service state as specified in TS 23.287 [55]; and if either the serving cell is on the frequency used for NR sidelink communication/discovery operation or the UE is out of coverage on the frequency used for NR sidelink communication/discovery operation as defined in TS 38.304 [20] and TS 36.304 [27]; or

1> if the UE has no serving cell (RRC_IDLE);

5.8.3 Sidelink UE information for NR sidelink communication/discovery

5.8.3.1 General

Figure 5.8.3.1-1: Sidelink UE information for NR sidelink communication/discovery

The purpose of this procedure is to inform the network that the UE:

– is interested or no longer interested to receive or transmit NR sidelink communication/discovery,

– is requesting assignment or release of transmission resource for NR sidelink communication/discovery,

– is reporting QoS parameters and QoS profile(s) related to NR sidelink communication,

– is reporting that a sidelink radio link failure or sidelink RRC reconfiguration failure has been detected,

– is reporting the sidelink UE capability information of the associated peer UE for unicast communication,

– is reporting the RLC mode information of the sidelink data radio bearer(s) received from the associated peer UE for unicast communication,

– is reporting the accepted sidelink DRX configuration received from the associated peer UE for NR sidelink unicast reception,

– is reporting the sidelink DRX assistance information received from the associated peer UE for NR sidelink unicast transmission, when the UE is configured with sl-ScheduledConfig,

– is reporting, for NR sidelink groupcast transmission, the sidelink DRX on/off indication for the associated Destination Layer-2 ID,

– is reporting, for NR sidelink groupcast or broadcast reception, the Destination Layer-2 ID and QoS profile(s) associated with its interested services to which sidelink DRX is applied,

– is reporting DRX configuration reject information from its associated peer UE for NR sidelink unicast transmission, when the UE is configured with sl-ScheduledConfig,

– is reporting parameters related to U2N relay operation.

5.8.3.2 Initiation

A UE capable of NR sidelink communication or NR sidelink discovery or NR sidelink U2N relay operation that is in RRC_CONNECTED may initiate the procedure to indicate it is (interested in) receiving or transmitting NR sidelink communication or NR sidelink discovery or NR sidelink U2N relay operation in several cases including upon successful connection establishment or resuming, upon change of interest, upon changing QoS profiles, upon receiving UECapabilityInformationSidelink from the associated peer UE, upon RLC mode information updated from the associated peer UE or upon change to a PCell providing SIB12 including sl-ConfigCommonNR. A UE capable of NR sidelink communication may initiate the procedure to request assignment of dedicated sidelink DRB configuration and transmission resources for NR sidelink communication transmission. A UE capable of NR sidelink communication may initiate the procedure to report to the network that a sidelink radio link failure or sidelink RRC reconfiguration failure has been declared. A UE capable of NR sidelink discovery may initiate the procedure to request assignment of dedicated resources for NR sidelink discovery transmission or NR sidelink discovery reception. A UE capable of U2N relay operation may initiate the procedure to report/update parameters for acting as U2N Relay UE or U2N Remote UE (including L2 Remote UE’s source L2 ID).

A UE capable of NR sidelink operation that is in RRC_CONNECTED may initiate the procedure to report the sidelink DRX configuration received from the associated peer UE for NR sidelink unicast reception, upon accepting the sidelink DRX configuration from the associated peer UE. A UE capable of NR sidelink communication that is in RRC_CONNECTED and is performing sidelink unicast transmission with resource allocation mode 1 may initiate the procedure to report the sidelink DRX assistance information or the sidelink DRX configuration reject information received from the associated peer UE, upon receiving either of them from the associated peer UE. A UE capable of NR sidelink communication that is performing sidelink groupcast transmission may initiate the procedure to report the sidelink DRX on/off indication for the associated Destination Layer-2 ID.

A UE capable of NR sidelink operation that is in RRC_CONNECTED may initiate the procedure to report the Destination Layer-2 ID and QoS profile associated with its interested services that sidelink DRX is applied, for NR sidelink groupcast or broadcast reception.

Upon initiating this procedure, the UE shall:

1> if SIB12 including sl-ConfigCommonNR is provided by the PCell:

2> ensure having a valid version of SIB12 for the PCell;

2> if configured by upper layers to receive NR sidelink communication on the frequency included in sl-FreqInfoList in SIB12 of the PCell:

3> if the UE did not transmit a SidelinkUEInformationNR message since last entering RRC_CONNECTED state; or

3> if since the last time the UE transmitted a SidelinkUEInformationNR message the UE connected to a PCell not providing SIB12 including sl-ConfigCommonNR; or

3> if the last transmission of the SidelinkUEInformationNR message did not include sl-RxInterestedFreqList; or if the frequency configured by upper layers to receive NR sidelink communication on has changed since the last transmission of the SidelinkUEInformationNR message:

4> initiate transmission of the SidelinkUEInformationNR message to indicate the NR sidelink communication reception frequency of interest in accordance with 5.8.3.3;

2> else:

3> if the last transmission of the SidelinkUEInformationNR message included sl-RxInterestedFreqList:

4> initiate transmission of the SidelinkUEInformationNR message to indicate it is no longer interested in NR sidelink communication reception in accordance with 5.8.3.3;

2> if configured by upper layers to transmit non-relay NR sidelink communication on the frequency included in sl-FreqInfoList in SIB12 of the PCell:

3> if the UE did not transmit a SidelinkUEInformationNR message since last entering RRC_CONNECTED state; or

3> if since the last time the UE transmitted a SidelinkUEInformationNR message the UE connected to a PCell not providing SIB12 including sl-ConfigCommonNR; or

3> if the last transmission of the SidelinkUEInformationNR message did not include sl-TxResourceReqList; or if the information carried by the sl-TxResourceReqList has changed since the last transmission of the SidelinkUEInformationNR message:

4> initiate transmission of the SidelinkUEInformationNR message to indicate the NR sidelink communication transmission resources required by the UE in accordance with 5.8.3.3;

2> else:

3> if the last transmission of the SidelinkUEInformationNR message included sl-TxResourceReqList:

4> initiate transmission of the SidelinkUEInformationNR message to indicate it no longer requires NR sidelink communication transmission resources in accordance with 5.8.3.3.

2> if configured by upper layer to receive NR sidelink non-relay discovery messages on the frequency included in sl-FreqInfoList in SIB12 of the PCell including sl-NonRelayDiscovery:

3> if the UE did not transmit a SidelinkUEInformationNR message since last entering RRC_CONNECTED state; or

3> if the last transmission of the SidelinkUEInformationNR message did not include sl-RxInterestedFreqListDisc; or if the frequency configured by upper layers to receive NR sidelink L2 U2N relay discovery messages or NR sidelink L3 U2N relay discovery messages on has changed since the last transmission of the SidelinkUEInformationNR message:

4> initiate transmission of the SidelinkUEInformationNR message to indicate the NR sidelink discovery reception frequency of interest in accordance with 5.8.3.3;

2> else:

3> if the last transmission of the SidelinkUEInformationNR message included sl-RxInterestedFreqListDisc:

4> initiate transmission of the SidelinkUEInformationNR message to indicate it is no longer interested in NR sidelink discovery messages reception in accordance with 5.8.3.3;

2> if configured by upper layer to receive NR sidelink L2 U2N relay discovery messages on the frequency included in sl-FreqInfoList in SIB12 of the PCell including sl-L2U2N-Relay; or if configured by upper layer to receive NR sidelink L3 U2N relay discovery messages on the frequency included in sl-FreqInfoList in SIB12 of the PCell including sl-L3U2N-RelayDiscovery:

3> if the UE did not transmit a SidelinkUEInformationNR message since last entering RRC_CONNECTED state; or

3> if since the last time the UE transmitted a SidelinkUEInformationNR message the UE connected to a PCell not providing SIB12 including sl-ConfigCommonNR or connected to a PCell providing SIB12 but not including sl-L2U2N-Relay in case of L2 U2N relay operation or connected to a PCell providing SIB12 but not including sl-L3U2N-RelayDiscovery in case of L3 U2N relay operation; or

3> if the last transmission of the SidelinkUEInformationNR message did not include sl-RxInterestedFreqListDisc; or if the frequency configured by upper layers to receive NR sidelink discovery messages on has changed since the last transmission of the SidelinkUEInformationNR message:

4> if the UE is capable of U2N Relay UE, and if SIB12 includes sl-RelayUE-ConfigCommon, and if the U2N Relay UE threshold conditions as specified in 5.8.14.2 are met; or

4> if the UE is selecting a U2N Relay UE / has a selected U2N Relay UE, and if SIB12 includes sl-RemoteUE-ConfigCommon, and if the U2N Remote UE threshold conditions as specified in 5.8.15.2 are met:

5> initiate transmission of the SidelinkUEInformationNR message to indicate the NR relay sidelink discovery reception frequency of interest in accordance with 5.8.3.3;

2> else:

3> if the last transmission of the SidelinkUEInformationNR message included sl-RxInterestedFreqListDisc:

4> initiate transmission of the SidelinkUEInformationNR message to indicate it is no longer interested in NR relay sidelink discovery messages reception in accordance with 5.8.3.3;

2> if configured by upper layer to transmit NR sidelink non-relay discovery messages on the frequency included in sl-FreqInfoList in SIB12 of the PCell including sl-NonRelayDiscovery:

3> if the UE did not transmit a SidelinkUEInformationNR message since last entering RRC_CONNECTED state; or

3> if the last transmission of the SidelinkUEInformationNR message did not include sl-TxResourceReqListDisc; or if the information carried by the sl-TxResourceReqListDisc has changed since the last transmission of the SidelinkUEInformationNR message:

4> initiate transmission of the SidelinkUEInformationNR message to indicate the NR sidelink non-relay discovery messages resources required by the UE in accordance with 5.8.3.3;

2> else:

3> if the last transmission of the SidelinkUEInformationNR message included sl-TxResourceReqListDisc:

4> initiate transmission of the SidelinkUEInformationNR message to indicate it no longer requires NR sidelink non-relay discovery messages resources in accordance with 5.8.3.3;

2> if configured by upper layer to transmit NR sidelink L2 U2N relay discovery messages on the frequency included in sl-FreqInfoList in SIB12 of the PCell including sl-L2U2N-Relay; or if configured by upper layer to transmit NR sidelink L3 U2N relay discovery messages on the frequency included in sl-FreqInfoList in SIB12 of the PCell including sl-L3U2N-RelayDiscovery:

3> if the UE did not transmit a SidelinkUEInformationNR message since last entering RRC_CONNECTED state; or

3> if since the last time the UE transmitted a SidelinkUEInformationNR message the UE connected to a PCell not providing SIB12 including sl-ConfigCommonNR or connected to a PCell providing SIB12 but not including sl-L2U2N-Relay in case L2 U2N relay operation or connected to a PCell providing SIB12 but not including sl-L3U2N-RelayDiscovery in case of L3 U2N relay operation; or

4> if the UE is capable of U2N Relay UE, and if SIB12 includes sl-RelayUE-ConfigCommon, and if the U2N Relay UE threshold conditions as specified in 5.8.14.2 are met; or

5> initiate transmission of the SidelinkUEInformationNR message to indicate the NR sidelink relay discovery messages resources required by the UE in accordance with 5.8.3.3;

2> else:

3> if the last transmission of the SidelinkUEInformationNR message included sl-TxResourceReqListDisc:

4> initiate transmission of the SidelinkUEInformationNR message to indicate it no longer requires NR sidelink relay discovery messages resources in accordance with 5.8.3.3;

2> if configured by upper layer to transmit NR sidelink L2 U2N relay communication on the frequency included in sl-FreqInfoList in SIB12 of the PCell including sl-L2U2N-Relay or if configured by upper layer to transmit NR sidelink L3 U2N relay communication on the frequency included in sl-FreqInfoList in SIB12 of the PCell including sl-L3U2N-RelayDiscovery:

3> if the UE did not transmit a SidelinkUEInformationNR message since last entering RRC_CONNECTED state; or

3> if since the last time the UE transmitted a SidelinkUEInformationNR message the UE connected to a PCell not providing SIB12 including sl-ConfigCommonNR or connected to a PCell providing SIB12 but not including sl-L2U2N-Relay in case L2 U2N relay operation or connected to a PCell providing SIB12 but not including sl-L3U2N-RelayDiscovery in case of L3 U2N relay operation; or

3> if the last transmission of the SidelinkUEInformationNR message did not include sl-TxResourceReqL2U2N-Relay; or if the information carried by the sl-TxResourceReqL2U2N-Relay has changed since the last transmission of the SidelinkUEInformationNR message; or if the last transmission of the SidelinkUEInformationNR message did not include sl-TxResourceReqL3U2N-Relay; or if the information carried by the sl-TxResourceReqL3U2N-Relay has changed since the last transmission of the SidelinkUEInformationNR message:

4> if the UE is capable of U2N Relay UE, and if SIB12 includes sl-RelayUE-ConfigCommon, and if the U2N Relay UE threshold conditions as specified in 5.8.14.2 are met; or

5> initiate transmission of the SidelinkUEInformationNR message to indicate the NR sidelink relay communication transmission resources required by the UE in accordance with 5.8.3.3;

2> else:

3> if the last transmission of the SidelinkUEInformationNR message included sl-TxResourceReqL2U2N-Relay or sl-TxResourceReqL3U2N-Relay:

4> initiate transmission of the SidelinkUEInformationNR message to indicate it no longer requires NR sidelink relay communication transmission resources in accordance with 5.8.3.3;

2> if configured by upper layers to perform NR sidelink reception on the frequency included in sl-FreqInfoList in SIB12 of the PCell and if sl-DRX-ConfigCommonGC-BC is included in SIB12-IEs:

3> if the UE received a sidelink DRX configuration in the RRCReconfigurationSidelink message for NR sidelink unicast reception from the associated peer UE and the UE accepted the sidelink DRX configuration:

4> if the UE did not transmit a SidelinkUEInformationNR message since last entering RRC_CONNECTED state; or

4> if since the last time the UE transmitted a SidelinkUEInformationNR message the UE connected to a PCell not providing SIB12 including sl-DRX-ConfigCommonGC-BC; or

4> if the last transmission of the SidelinkUEInformationNR message did not include sl-RxDRX-ReportList; or if the information carried by sl-RxDRX-ReportList has changed since the last transmission of the SidelinkUEInformationNR message:

5> initiate transmission of the SidelinkUEInformationNR message to report the sidelink DRX configuration in accordance with 5.8.3.3;

3> else:

4> if the last transmission of the SidelinkUEInformationNR message included sl-RxDRX-ReportList:

5> initiate transmission of the SidelinkUEInformationNR message to indicate the sidelink DRX configuration is no longer used in accordance with 5.8.3.3;

3> if the UE is performing NR sidelink groupcast or broadcast reception and is interested in a service that sidelink DRX is applied:

4> if the UE did not transmit a SidelinkUEInformationNR message since last entering RRC_CONNECTED state; or

4> if since the last time the UE transmitted a SidelinkUEInformationNR message the UE connected to a PCell not providing SIB12 including sl-DRX-ConfigCommonGC-BC; or

4> if the last transmission of the SidelinkUEInformationNR message did not include sl-RxInterestedGC-BC-DestList; or if the information carried by sl-RxInterestedGC-BC-DestList has changed since the last transmission of the SidelinkUEInformationNR message:

5> initiate transmission of the SidelinkUEInformationNR message to report the Destination Layer-2 ID and QoS profile associated with the service in accordance with 5.8.3.3;

3> else:

4> if the last transmission of the SidelinkUEInformationNR message included sl-RxInterestedGC-BC-DestList:

5> initiate transmission of the SidelinkUEInformationNR message to indicate it is no longer interested in the service that sidelink DRX is applied in accordance with 5.8.3.3;

2> if configured by upper layers to perform NR sidelink transmission on the frequency included in sl-FreqInfoList in SIB12 of the PCell and if sl-DRX-ConfigCommonGC-BC is included in SIB12-IEs and if the UE is configured with sl-ScheduledConfig:

3> if the UE received a sidelink DRX assistance information or a sidelink DRX configuration reject information from the associated peer UE for NR sidelink unicast transmission:

4> initiate transmission of the SidelinkUEInformationNR message to report the sidelink DRX assistance information or the sidelink DRX configuration reject information in accordance with 5.8.3.3;

3> if the UE is performing NR sidelink groupcast transmission:

4> initiate transmission of the SidelinkUEInformationNR message to report sidelink DRX on/off indication for the corresponding destination in accordance with 5.8.3.3;

5.8.3.3 Actions related to transmission of SidelinkUEInformationNR message

The UE shall set the contents of the SidelinkUEInformationNR message as follows:

1> if the UE initiates the procedure to indicate it is (no more) interested to receive NR sidelink communication or to request (configuration/ release) of NR sidelink communication transmission resources or to report to the network that a sidelink radio link failure or sidelink RRC reconfiguration failure has been declared or to report to the network the sidelink DRX configuration for NR sidelink unicast reception or to report to the network the sidelink DRX assistance information or the sidelink DRX configuration reject information for NR sidelink unicast transmission or to report to the network the Destination Layer-2 ID and QoS profile associated with its interested services that sidelink DRX is applied for NR sidelink groupcast or broadcast reception or to report to the network the Destination Layer-2 ID and the sidelink DRX on/off indication for the corresponding destination for NR sidelink groupcast transmission or to indicate it is (no more) interested to receive NR sidelink discovery messages or to request (configuration/ release) of NR sidelink discovery messages transmission resources or to request (configuration/ release) of NR sidelink U2N relay communication transmission resources (i.e. UE includes all concerned information, irrespective of what triggered the procedure):

2> if SIB12 including sl-ConfigCommonNR is provided by the PCell:

3> if configured by upper layers to receive NR sidelink communication:

4> include sl-RxInterestedFreqList and set it to the frequency for NR sidelink communication reception;

3> if configured by upper layers to transmit non-relay NR sidelink communication:

4> include sl-TxResourceReqList and set its fields (if needed) as follows for each destination for which it requests network to assign NR sidelink communication resource:

5> set sl-DestinationIdentity to the destination identity configured by upper layer for NR sidelink communication transmission;

5> set sl-CastType to the cast type of the associated destination identity configured by the upper layer for the NR sidelink communication transmission;

5> set sl-RLC-ModeIndication to include the RLC mode(s) and optionally QoS profile(s) of the sidelink QoS flow(s) of the associated RLC mode(s), if the associated bi-directional sidelink DRB has been established due to the configuration by RRCReconfigurationSidelink;

5> set sl-QoS-InfoList to include QoS profile(s) of the sidelink QoS flow(s) of the associated destination configured by the upper layer for the NR sidelink communication transmission;

5> set sl-InterestedFreqList to indicate the frequency of the associated destination for NR sidelink communication transmission;

5> set sl-TypeTxSyncList to the current synchronization reference type used on the associated sl-InterestedFreqList for NR sidelink communication transmission.

5> set sl-CapabilityInformationSidelink to include UECapabilityInformationSidelink message, if any, received from the associated peer UE.

4> if a sidelink radio link failure or a sidelink RRC reconfiguration failure has been declared, according to clauses 5.8.9.3 and 5.8.9.1.8, respectively;

5> include sl-FailureList and set its fields as follows for each destination for which it reports the NR sidelink communication failure:

6> set sl-DestinationIdentity to the destination identity configured by upper layer for NR sidelink communication transmission;

6> if the sidelink RLF is detected as specified in clause 5.8.9.3:

7> set sl-Failure as rlf for the associated destination for the NR sidelink communication transmission;

6> else if RRCReconfigurationFailureSidelink is received:

7> set sl-Failure as configFailure for the associated destination for the NR sidelink communication transmission;

3> if SIB12 including sl-NonRelayDiscovery and if configured by upper layers to receive NR sidelink non-relay discovery messages, or if SIB12 including sl-L2U2N-Relay and if configured by upper layers to receive NR sidelink L2 U2N relay discovery messages, or if SIB12 including sl-L3U2N-RelayDiscovery and if configured by upper layers to receive NR sidelink L3 U2N relay discovery messages:

4> include sl-RxInterestedFreqListDisc and set it to the frequency for NR sidelink discovery messages reception;

4> if the UE is capable of L2 U2N remote UE:

5> include sl-SourceIdentityRemoteUE and set it to the source identity configured by upper layer for NR sidelink L2 U2N relay communication transmission;

3> if SIB12 including sl-NonRelayDiscovery and if configured by upper layers to transmit NR sidelink non-relay discovery messages, or if SIB12 including sl-L2U2N-Relay and if configured by upper layers to transmit NR sidelink L2 U2N relay discovery messages, or if SIB12 including sl-L3U2N-RelayDiscovery and if configured by upper layers to transmit NR sidelink L3 U2N relay discovery messages:

4> include sl-TxResourceReqListDisc and set its fields (if needed) as follows for each destination for which it requests network to assign NR sidelink discovery messages resource:

5> set sl-DestinationIdentityDisc to the destination identity configured by upper layer for NR sidelink discoverymessages transmission;

5> if the UE is acting as L2 U2N Relay UE:

6> set sl-SourceIdentityRelayUE to the source identity configured by upper layer for NR sidelink L2 U2N relay discovery messages transmission;

5> set sl-CastTypeDisc to the cast type of the associated destination identity configured by the upper layer for the NR sidelink discovery messages transmission;

5> set sl-TxInterestedFreqListDisc to indicate the frequency of the associated destination for NR sidelink discovery messages transmission;

5> set sl-TypeTxSyncListDisc to the current synchronization reference type used on the associated sl-InterestedFreqList for NR sidelink discovery messages transmission;

5> set sl-DiscoveryType to the current discovery type of the associated destination identity configured by the upper layer for NR sidelink discovery messages transmission;

3> if SIB12 including sl-L2U2N-Relay and if configured by upper layers to transmit NR sidelink L2 U2N relay communication and the UE is acting as L2 U2N Relay UE:

4> include sl-TxResourceReqL2U2N-Relay in sl-TxResourceReqListCommRelay and set its fields (if needed) as follows for each destination for which it requests network to assign NR sidelink L2 U2N relay communication resource:

5> set sl-DestinationIdentityL2U2N to the destination identity configured by upper layer for NR sidelink L2 U2N relay communication transmission;

5> set sl-TxInterestedFreqListL2U2N to indicate the frequency of the associated destination for NR sidelink L2 U2N relay communication transmission;

5> set sl-TypeTxSyncListL2U2N to the current synchronization reference type used on the associated sl-InterestedFreqListL2U2N for NR sidelink L2 U2N relay communication transmission;

5> set sl-LocalID-Request to request local ID for L2 U2N Remote UE;

5> set sl-PagingIdentityRemoteUE to the paging UE ID received from peer L2 U2N Remote UE, if it is not released as in 5.8.9.8.3;

5> set sl-CapabilityInformationSidelink to include UECapabilityInformationSidelink message, if any, received from peer UE.

4> include ue-Type and set it to relayUE;

3> if SIB12 including sl-L2U2N-Relay and if configured by upper layers to transmit NR sidelink L2 U2N relay communication and the UE has a selected L2 U2N Relay UE:

4> include sl-TxResourceReqL2U2N-Relay in sl-TxResourceReqListCommRelay and set its fields (if needed) as follows to request network to assign NR sidelink L2 U2N relay communication resource:

5> set sl-TxInterestedFreqListL2U2N to indicate the frequency of the associated destination for NR sidelink L2 U2N relay communication transmission;

5> set sl-TypeTxSyncListL2U2N to the current synchronization reference type used on the associated sl-InterestedFreqListL2U2N for NR sidelink L2 U2N relay communication transmission;

5> set sl-CapabilityInformationSidelink to include UECapabilityInformationSidelink message, if any, received from peer UE.

4> include ue-Type and set it to remoteUE;

3> if SIB12 including sl-L3U2N-RelayDiscovery and if configured by upper layers to transmit NR sidelink L3 U2N relay communication:

4> include sl-TxResourceReqL3U2N-Relay in sl-TxResourceReqListCommRelay and set its fields (if needed) as follows for each destination for which it requests network to assign NR sidelink L3 U2N relay communication resource:

5> set sl-DestinationIdentity to the destination identity configured by upper layer for NR sidelink L3 U2N relay communication transmission;

5> set sl-CastType to the cast type of the associated destination identity configured by the upper layer for the NR sidelink L3 U2N relay communication transmission;

5> set sl-QoS-InfoList to include QoS profile(s) of the sidelink QoS flow(s) of the associated destination configured by the upper layer for the NR sidelink L3 U2N relay communication transmission;

5> set sl-TxInterestedFreqList to indicate the frequency of the associated destination for NR sidelink L3 U2N relay communication transmission;

5> set sl-TypeTxSyncList to the current synchronization reference type used on the associated sl-InterestedFreqList for NR sidelink L3 U2N relay communication transmission.

5> set sl-CapabilityInformationSidelink to include UECapabilityInformationSidelink message, if any, received from peer UE.

4> include ue-Type and set it to relayUE if the UE is acting as NR sidelink L3 U2N Relay UE or to remoteUE otherwise;

3> if sl-DRX-ConfigCommonGC-BC is included in SIB12-IEs:

4> if configured by upper layers to perform NR sidelink reception:

5> include sl-RxDRX-ReportList and set its fields (if needed) as follows for each destination for which it reports to network:

6> set sl-DRX-ConfigFromTx to include the accepted sidelink DRX configuration of the associated destination for NR sidelink unicast communication, if received from the associated peer UE;

5> include sl-RxInterestedGC-BC-DestList and set its fields (if needed) as follows for each Destination Layer-2 ID for which it reports to network:

6> set sl-RxInterestedQoS-InfoList to include the QoS profile of its interested service(s) that sidelink DRX is applied for the associated destination for NR sidelink groupcast or broadcast reception;

NOTE: It is up to UE implementation to set the QoS profile in sl-RxInterestedQoS-InfoList for NR sidelink discovery reception.

6> set sl-DestinationIdentity to the associated destination identity configured by upper layer for NR sidelink groupcast or broadcast reception;

4> if configured by upper layers to perform NR sidelink transmission and configured with sl-ScheduledConfig:

5> include sl-TxResourceReqList and/or sl-TxResourceReqListCommRelay and set its fields (if needed) as follows for each destination for which it reports to network:

6> set sl-DRX-InfoFromRxList to include the sidelink DRX assistance information of the associated destination, if any, received from the associated peer UE;

6> if the RRCReconfigurationCompleteSidelink message includes the sl-DRX-ConfigReject:

7> set sl-Failure as drxReject-v1710 for the associated destination for the NR sidelink communication transmission;

6> set sl-DRX-Indication to include the sidelink DRX on/off indication for the associated destination for NR sidelink groupcast transmission;

1> if the UE initiates the procedure while connected to an E-UTRA PCell:

2> submit the SidelinkUEInformationNR to lower layers via SRB1, embedded in E-UTRA RRC message ULInformationTransferIRAT as specified in TS 36.331 [10], clause 5.6.28;

1> else:

2> submit the SidelinkUEInformationNR message to lower layers for transmission.

5.8.4 Void

5.8.5 Sidelink synchronisation information transmission for NR sidelink communication/discovery

5.8.5.1 General

Figure 5.8.5.1-1: Synchronisation information transmission for NR sidelink communication/discovery, in (partial) coverage

Figure 5.8.5.1-2: Synchronisation information transmission for NR sidelink communication/discovery, out of coverage

The purpose of this procedure is to provide synchronisation information to a UE. This procedure also applies to NR sidelink discovery.

5.8.5.2 Initiation

A UE capable of NR sidelink communication/discovery and SLSS/PSBCH transmission shall, when transmitting NR sidelink communication/discovery, and if the conditions for NR sidelink communication/discovery operation are met and when the following conditions are met:

1> if in coverage on the frequency used for NR sidelink communication/discovery, as defined in TS 38.304 [20]; and has selected GNSS or the cell as synchronization reference as defined in 5.8.6.3; or

1> if out of coverage on the frequency used for NR sidelink communication/discovery, and the frequency used to transmit NR sidelink communication/discovery is included in sl-FreqInfoToAddModList in sl-ConfigDedicatedNR within RRCReconfiguration message or included in sl-FreqInfoList within SIB12; and has selected GNSS or the cell as synchronization reference as defined in 5.8.6.3:

2> if in RRC_CONNECTED; and if networkControlledSyncTx is configured and set to on; or

2> if networkControlledSyncTx is not configured; and for the concerned frequency syncTxThreshIC is configured; and the RSRP measurement of the reference cell, selected as defined in 5.8.6.3, for NR sidelink communication/discovery transmission is below the value of syncTxThreshIC:

3> transmit sidelink SSB on the frequency used for NR sidelink communication/discovery in accordance with 5.8.5.3 and TS 38.211 [16], including the transmission of SLSS as specified in 5.8.5.3 and transmission of MasterInformationBlockSidelink as specified in 5.8.9.4.3;

1> else:

2> for the frequency used for NR sidelink communication/discovery, if syncTxThreshOoC is included in SidelinkPreconfigNR; and the UE is not directly synchronized to GNSS, and the UE has no selected SyncRef UE or the PSBCH-RSRP measurement result of the selected SyncRef UE is below the value of syncTxThreshOoC; or

2> for the frequency used for NR sidelink communication/discovery, if the UE selects GNSS as the synchronization reference source:

3> transmit sidelink SSB on the frequency used for NR sidelink communication/discovery in accordance with TS 38.211 [16] , including the transmission of SLSS as specified in 5.8.5.3 and transmission of MasterInformationBlockSidelink as specified in 5.8.9.4.3;

5.8.5.3 Transmission of SLSS

The UE shall select the SLSSID and the slot in which to transmit SLSS as follows:

1> if triggered by NR sidelink communication/discovery and in coverage on the frequency used for NR sidelink communication/discovery, as defined in TS 38.304 [20]; or

1> if triggered by NR sidelink communication/discovery, and out of coverage on the frequency used for NR sidelink communication/discovery, and the concerned frequency is included in sl-FreqInfoToAddModList in sl-ConfigDedicatedNR within RRCReconfiguration message or included in sl-FreqInfoList within SIB12:

2> if the UE has selected GNSS as synchronization reference in accordance with 5.8.6.2:

3> select SLSSID 0;

3> use sl-SSB-TimeAllocation1 included in the entry of configured sl-SyncConfigList corresponding to the concerned frequency, that includes txParameters and gnss-Sync;

3> select the slot(s) indicated by sl-SSB-TimeAllocation1;

2> if the UE has selected a cell as synchronization reference in accordance with 5.8.6.2:

3> select the SLSSID included in the entry of configured sl-SyncConfigList corresponding to the concerned frequency, that includes txParameters and does not include gnss-Sync;

3> select the slot(s) indicated by sl-SSB-TimeAllocation1;

1> else if triggered by NR sidelink communication/discovery and the UE has GNSS as the synchronization reference:

2> select SLSSID 0;

2> if sl-SSB-TimeAllocation3 is configured for the frequency used in SidelinkPreconfigNR:

3> select the slot(s) indicated by sl-SSB-TimeAllocation3;

2> else:

3> select the slot(s) indicated by sl-SSB-TimeAllocation1;

1> else:

2> select the synchronisation reference UE (i.e. SyncRef UE) as defined in 5.8.6;

2> if the UE has a selected SyncRef UE and inCoverage in the MasterInformationBlockSidelink message received from this UE is set to true; or

2> if the UE has a selected SyncRef UE and inCoverage in the MasterInformationBlockSidelink message received from this UE is set to false while the SLSS from this UE is part of the set defined for out of coverage, see TS 38.211 [16]:

3> select the same SLSSID as the SLSSID of the selected SyncRef UE;

3> select the slot in which to transmit the SLSS according to the sl-SSB-TimeAllocation1 or sl-SSB-TimeAllocation2 included in the preconfigured sidelink parameters corresponding to the concerned frequency, such that the timing is different from the SLSS of the selected SyncRef UE;

2> else if the UE has a selected SyncRef UE and the SLSS from this UE was transmitted on the slot(s) indicated sl-SSB-TimeAllocation3, which is configured for the frequency used in SidelinkPreconfigNR:

3> select SLSSID 337;

3> select the slot(s) indicated by sl-SSB-TimeAllocation2;

2> else if the UE has a selected SyncRef UE:

3> select the SLSSID from the set defined for out of coverage having an index that is 336 more than the index of the SLSSID of the selected SyncRef UE, see TS 38.211 [16];

3> select the slot in which to transmit the SLSS according to sl-SSB-TimeAllocation1 or sl-SSB-TimeAllocation2 included in the preconfigured sidelink parameters corresponding to the concerned frequency, such that the timing is different from the SLSS of the selected SyncRef UE;

2> else (i.e. no SyncRef UE selected):

3> if the UE has not randomly selected an SLSSID:

4> randomly select, using a uniform distribution, an SLSSID from the set of sequences defined for out of coverage except SLSSID 336 and 337, see TS 38.211 [16];

4> select the slot in which to transmit the SLSS according to the sl-SSB-TimeAllocation1 or sl-SSB-TimeAllocation2 (arbitrary selection between these) included in the preconfigured sidelink parameters in SidelinkPreconfigNR corresponding to the concerned frequency;

5.8.5a Sidelink synchronisation information transmission for V2X sidelink communication

5.8.5a.1 General

Figure 5.8.5a.1-1: Synchronisation information transmission for V2X sidelink communication, in (partial) coverage

Figure 5.8.5a.1-2: Synchronisation information transmission for V2X sidelink communication, out of coverage

The purpose of this procedure is to provide synchronisation information to a UE.

5.8.5a.2 Initiation

A UE capable of V2X sidelink communication initiates the transmission of SLSS and MasterInformationBlock-SL-V2X according to the conditions and the procedures specified for V2X sidelink communication in clause 5.10.7 of TS 36.331 [10].

NOTE 1: When applying the procedure in this clause, SIB13 and SIB14 correspond to SystemInformationBlockType21 and SystemInformationBlockType26 specified in TS 36.331 [10] respectively

5.8.6 Sidelink synchronisation reference

5.8.6.1 General

The purpose of this procedure is to select a synchronisation reference and used when transmitting NR sidelink communication/discovery. This procedure also applies to NR sidelink discovery.

5.8.6.2 Selection and reselection of synchronisation reference

The UE shall:

1> if the frequency used for NR sidelink communication/discovery is included in sl-FreqInfoToAddModList in sl-ConfigDedicatedNR within RRCReconfiguration message or included in sl-ConfigCommonNR within SIB12, and sl-SyncPriority is configured for the concerned frequency and set to gnbEnb:

2> select a cell as the synchronization reference source as defined in 5.8.6.3:

1> else if the frequency used for NR sidelink communication is included in sl-FreqInfoToAddModList in sl-ConfigDedicatedNR within RRCReconfiguration message or included in sl-ConfigCommonNR within SIB12, and sl-SyncPriority for the concerned frequency is not configured or is set to gnss, and GNSS is reliable in accordance with TS 38.101-1 [15] and TS 38.133 [14]:

2> select GNSS as the synchronization reference source;

1> else if the frequency used for NR sidelink communication/discovery is included in SL-PreconfigurationNR, and sl-SyncPriority in SidelinkPreconfigNR is set to gnss and GNSS is reliable in accordance with TS 38.101-1 [15] and TS 38.133 [14]:

2> select GNSS as the synchronization reference source;

1> else:

2> perform a full search (i.e. covering all subframes and all possible SLSSIDs) to detect candidate SLSS, in accordance with TS 38.133 [14]

2> when evaluating the one or more detected SLSSIDs, apply layer 3 filtering as specified in 5.5.3.2 using the preconfigured sl-filterCoefficient, before using the PSBCH-RSRP measurement results;

2> if the UE has selected a SyncRef UE:

3> if the PSBCH-RSRP of the strongest candidate SyncRef UE exceeds the minimum requirement TS 38.133 [14] by sl-SyncRefMinHyst and the strongest candidate SyncRef UE belongs to the same priority group as the current SyncRef UE and the PSBCH-RSRP of the strongest candidate SyncRef UE exceeds the PSBCH-RSRP of the current SyncRef UE by syncRefDiffHyst; or

3> if the PSBCH-RSRP of the candidate SyncRef UE exceeds the minimum requirement TS 38.133 [14] by sl-SyncRefMinHyst and the candidate SyncRef UE belongs to a higher priority group than the current SyncRef UE; or

3> if GNSS becomes reliable in accordance with TS 38.101-1 [15] and TS 38.133 [14], and GNSS belongs to a higher priority group than the current SyncRef UE; or

3> if a cell is detected and gNB/eNB (if sl-NbAsSync is set to true) belongs to a higher priority group than the current SyncRef UE; or

3> if the PSBCH-RSRP of the current SyncRef UE is less than the minimum requirement defined in TS 38.133 [14]:

4> consider no SyncRef UE to be selected;

2> if the UE has selected GNSS as the synchronization reference for NR sidelink communication/discovery:

3> if the PSBCH-RSRP of the candidate SyncRef UE exceeds the minimum requirement defined in TS 38.133 [14] by sl-SyncRefMinHyst and the candidate SyncRef UE belongs to a higher priority group than GNSS; or

3> if GNSS becomes not reliable in accordance with TS 38.101-1 [15] and TS 38.133 [14]:

4> consider GNSS not to be selected;

2> if the UE has selected cell as the synchronization reference for NR sidelink communication/discovery:

3> if the selected cell is not detected:

4> consider the cell not to be selected;

2> if the UE has not selected any synchronization reference:

3> if the UE detects one or more SLSSIDs for which the PSBCH-RSRP exceeds the minimum requirement defined in TS 38.133 [14] by sl-SyncRefMinHyst and for which the UE received the corresponding MasterInformationBlockSidelink message (candidate SyncRef UEs), or if the UE detects GNSS that is reliable in accordance with TS 38.101-1 [15] and TS 38.133 [14], or if the UE detects a cell, select a synchronization reference according to the following priority group order:

4> if sl-SyncPriority corresponding to the concerned frequency is set to gnbEnb:

5> UEs of which SLSSID is part of the set defined for in coverage, and inCoverage, included in the MasterInformationBlockSidelink message received from this UE, is set to true, starting with the UE with the highest PSBCH-RSRP result (priority group 1);

5> UE of which SLSSID is part of the set defined for in coverage, and inCoverage, included in the MasterInformationBlockSidelink message received from this UE, is set to false, starting with the UE with the highest PSBCH-RSRP result (priority group 2);

5> GNSS that is reliable in accordance with TS 38.101-1 [15] and TS 38.133 [14] (priority group 3);

5> UEs of which SLSSID is 0, and inCoverage, included in the MasterInformationBlockSidelink message received from this UE, is set to true, or of which SLSSID is 0 and SLSS is transmitted on slot(s) indicated by sl-SSB-TimeAllocation3, starting with the UE with the highest PSBCH-RSRP result (priority group 4);

5> UEs of which SLSSID is 0 and SLSS is not transmitted on slot(s) indicated by sl-SSB-TimeAllocation3, and inCoverage, included in the MasterInformationBlockSidelink message received from this UE, is set to false, starting with the UE with the highest PSBCH-RSRP result (priority group 5);

5> UEs of which SLSSID is 337 and inCoverage, included in the MasterInformationBlockSidelink message received from this UE, is set to false, starting with the UE with the highest PSBCH-RSRP result (priority group 5);

5> Other UEs, starting with the UE with the highest PSBCH-RSRP result (priority group 6);

4> if sl-SyncPriority corresponding to the concerned frequency is set to gnss, and sl-NbAsSync is set to true:

5> UEs of which SLSSID is 0, and inCoverage, included in the MasterInformationBlockSidelink message received from this UE, is set to true, or of which SLSSID is 0 and SLSS is transmitted on slot(s) indicated by sl-SSB-TimeAllocation3, starting with the UE with the highest PSBCH-RSRP result (priority group 1);

5> the cell detected by the UE as defined in 5.8.6.3 (priority group 3);

5> Other UEs, starting with the UE with the highest S-RSRP result (priority group 6);

4> if sl-SyncPriority corresponding to the concerned frequency is set to gnss, and sl-NbAsSync is set to false:

5> Other UEs, starting with the UE with the highest PSBCH-RSRP result (priority group 3);

NOTE: How the UE achieves subframe boundary alignment between V2X sidelink communication and NR sidelink communication/discovery (if both are performed by the UE) is as specified in TS 38.213, clause 16.7.

5.8.6.3 Sidelink communication transmission reference cell selection

A UE capable of NR sidelink communication/discovery that is configured by upper layers to transmit NR sidelink communication/discovery shall:

1> for the frequency used to transmit NR sidelink communication/discovery, select a cell to be used as reference for synchronization in accordance with the following:

2> if the frequency concerns the primary frequency:

3> use the PCell or the serving cell as reference;

2> else if the frequency concerns a secondary frequency:

3> use the concerned SCell as reference;

2> else if the UE is in coverage of the concerned frequency:

3> use the DL frequency paired with the one used to transmit NR sidelink communication/discovery as reference;

2> else (i.e., out of coverage on the concerned frequency):

3> use the PCell or the serving cell as reference, if needed;

5.8.7 Sidelink communication reception

A UE capable of NR sidelink communication that is configured by upper layers to receive NR sidelink communication shall:

1> if the conditions for NR sidelink communication operation as defined in 5.8.2 are met:

2> if the frequency used for NR sidelink communication is included in sl-FreqInfoToAddModList in RRCReconfiguration message or sl-FreqInfoList included in SIB12:

3> if the UE is configured with sl-RxPool included in RRCReconfiguration message with reconfigurationWithSync (i.e. handover):

4> configure lower layers to monitor sidelink control information and the corresponding data using the pool of resources indicated by sl-RxPool;

3> else if the cell chosen for NR sidelink communication provides SIB12:

4> configure lower layers to monitor sidelink control information and the corresponding data using the pool of resources indicated by sl-RxPool in SIB12;

2> else:

3> configure lower layers to monitor sidelink control information and the corresponding data using the pool of resources that were preconfigured by sl-RxPool in SL-PreconfigurationNR, as defined in clause 9.3;

5.8.8 Sidelink communication transmission

A UE capable of NR sidelink communication that is configured by upper layers to transmit NR sidelink communication and has related data to be transmitted shall:

1> if the conditions for NR sidelink communication operation as defined in 5.8.2 are met:

2> if the frequency used for NR sidelink communication is included in sl-FreqInfoToAddModList in sl-ConfigDedicatedNR within RRCReconfiguration message or included in sl-ConfigCommonNR within SIB12:

3> if the UE is in RRC_CONNECTED and uses the frequency included in sl-ConfigDedicatedNR within RRCReconfiguration message:

4> if the UE is configured with sl-ScheduledConfig:

5> if T310 for MCG or T311 is running; and if sl-TxPoolExceptional is included in sl-FreqInfoList for the concerned frequency in SIB12 or included in sl-ConfigDedicatedNR in RRCReconfiguration; or

5> if T301 is running and the cell on which the UE initiated RRC connection re-establishment provides SIB12 including sl-TxPoolExceptional for the concerned frequency; or

5> if T304 for MCG is running and the UE is configured with sl-TxPoolExceptional included in sl-ConfigDedicatedNR for the concerned frequency in RRCReconfiguration:

6> configure lower layers to perform the sidelink resource allocation mode 2 based on random selection using the pool of resources indicated by sl-TxPoolExceptional as defined in TS 38.321 [3];

5> else:

6> configure lower layers to perform the sidelink resource allocation mode 1 for NR sidelink communication;

5> if T311 is running, configure the lower layers to release the resources indicated by rrc-ConfiguredSidelinkGrant (if any);

4> if the UE is configured with sl-UE-SelectedConfig:

5> if a result of full/partial sensing, if selected and is allowed by sl-AllowedResourceSelectionConfig, on the resources configured in sl-TxPoolSelectedNormal for the concerned frequency included in sl-ConfigDedicatedNR within RRCReconfiguration is not available in accordance with TS 38.214 [19];

6> if sl-TxPoolExceptional for the concerned frequency is included in RRCReconfiguration; or

6> if the PCell provides SIB12 including sl-TxPoolExceptional in sl-FreqInfoList for the concerned frequency:

7> configure lower layers to perform the sidelink resource allocation mode 2 based on random selection using the pool of resources indicated by sl-TxPoolExceptional as defined in TS 38.321 [3];

5> else, if the sl-TxPoolSelectedNormal for the concerned frequency is included in the sl-ConfigDedicatedNR within RRCReconfiguration:

6> configure lower layers to perform the sidelink resource allocation mode 2 based on resource selection operation according to sl-AllowedResourceSelectionConfig (as defined in TS 38.321 [3] and TS 38.214 [19]) using the pools of resources indicated by sl-TxPoolSelectedNormal for the concerned frequency;

3> else:

4> if the cell chosen for NR sidelink communication transmission provides SIB12:

5> if SIB12 includes sl-TxPoolSelectedNormal for the concerned frequency, and a result of full/partial sensing, if selected and is allowed by sl-AllowedResourceSelectionConfig, on the resources configured in the sl-TxPoolSelectedNormal is available in accordance with TS 38.214 [19] or random selection, if allowed by sl-AllowedResourceSelectionConfig, is selected:

6> configure lower layers to perform the sidelink resource allocation mode 2 based on resource selection operation according to sl-AllowedResourceSelectionConfig using the pools of resources indicated by sl-TxPoolSelectedNormal for the concerned frequency as defined in TS 38.321 [3];

5> else if SIB12 includes sl-TxPoolExceptional for the concerned frequency:

6> from the moment the UE initiates RRC connection establishment or RRC connection resume, until receiving an RRCReconfiguration including sl-ConfigDedicatedNR, or receiving an RRCRelease or an RRCReject; or

6> if a result of full/partial sensing, if selected and is allowed by sl-AllowedResourceSelectionConfig, on the resources configured in sl-TxPoolSelectedNormal for the concerned frequency in SIB12 is not available in accordance with TS 38.214 [19]:

7> configure lower layers to perform the sidelink resource allocation mode 2 based on random selection (as defined in TS 38.321 [3]) using the pool of resources indicated by sl-TxPoolExceptional for the concerned frequency;

2> else:

3> configure lower layers to perform the sidelink resource allocation mode 2 based on sensing (as defined in TS 38.321 [3] and TS 38.213 [13]) using the pools of resources indicated by sl-TxPoolSelectedNormal in SidelinkPreconfigNR for the concerned frequency.

NOTE 1: The UE continues to use resources configured in rrc-ConfiguredSidelinkGrant (while T310 is running) until it is released (i.e. until T310 has expired). The UE does not use sidelink configured grant type 2 resources while T310 is running.

NOTE 2: In case of RRC reconfiguration with sync, the UE uses resources configured in rrc-ConfiguredSidelinkGrant (while T304 on the MCG is running) if provided by the target cell.

NOTE 3: It is up to UE implementation to determine, in accordance with TS 38.321[3], which resource pool to use if multiple resource pools are configured, and which resource allocation scheme is used in the AS based on UE capability (for a UE in RRC_IDLE/RRC_INACTIVE) and the allowed resource schemes sl-allowedResourceSelectionConfig in the resource pool configuration.

If configured to perform sidelink resource allocation mode 2, the UE capable of NR sidelink communication that is configured by upper layers to transmit NR sidelink communication shall perform resource selection operation according to sl-AllowedResourceSelectionConfig on all pools of resources which may be used for transmission of the sidelink control information and the corresponding data. The pools of resources are indicated by SidelinkPreconfigNR, sl-TxPoolSelectedNormal in sl-ConfigDedicatedNR, or sl-TxPoolSelectedNormal in SIB12 for the concerned frequency, as configured above.

5.8.9 Sidelink RRC procedure

5.8.9.1 Sidelink RRC reconfiguration

5.8.9.1.1 General

Figure 5.8.9.1.1-1: Sidelink RRC reconfiguration, successful

Figure 5.8.9.1.1-2: Sidelink RRC reconfiguration, failure

The purpose of this procedure is to modify a PC5-RRC connection, e.g. to establish/modify/release sidelink DRBs or PC5 Relay RLC channels, to (re-)configure NR sidelink measurement and reporting, to (re-)configure sidelink CSI reference signal resources, to (re)configure CSI reporting latency bound, to (re)configure sidelink DRX, and to (re-)configure the latency bound of SL Inter-UE coordination report.

The UE may initiate the sidelink RRC reconfiguration procedure and perform the operation in clause 5.8.9.1.2 on the corresponding PC5-RRC connection in following cases:

– the release of sidelink DRBs associated with the peer UE, as specified in clause 5.8.9.1a.1;

– the establishment of sidelink DRBs associated with the peer UE, as specified in clause 5.8.9.1a.2;

– the modification for the parameters included in SLRB-Config of sidelink DRBs associated with the peer UE, as specified in clause 5.8.9.1a.2;

– the release of PC5 Relay RLC channels for L2 U2N Relay UE and Remote UE, as specified in clause 5.8.9.7.1;

– the establishment of PC5 Relay RLC channels for L2 U2N Relay UE and Remote UE, as specified in clause 5.8.9.7.2;

– the modification for the parameters included in SL-RLC-ChannelConfigPC5 of PC5 Relay RLC channels for L2 U2N Relay UE and Remote UE, as specified in clause 5.8.9.7.2;

– the (re-)configuration of the peer UE to perform NR sidelink measurement and report.

– the (re-)configuration of the sidelink CSI reference signal resources and CSI reporting latency bound;

– the (re-)configuration of the peer UE to perform sidelink DRX;

– the (re-)configuration of the latency bound of SL Inter-UE coordination report.

In RRC_CONNECTED, the UE applies the NR sidelink communications parameters provided in RRCReconfiguration (if any). In RRC_IDLE or RRC_INACTIVE, the UE applies the NR sidelink communications parameters provided in system information (if any). For other cases, UEs apply the NR sidelink communications parameters provided in SidelinkPreconfigNR (if any). When UE performs state transition between above three cases, the UE applies the NR sidelink communications parameters provided in the new state, after acquisition of the new configurations. Before acquisition of the new configurations, UE continues applying the NR sidelink communications parameters provided in the old state.

5.8.9.1.2 Actions related to transmission of RRCReconfigurationSidelink message

The UE shall set the contents of RRCReconfigurationSidelink message as follows:

1> for each sidelink DRB that is to be released, according to clause 5.8.9.1a.1.1, due to configuration by sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR or by upper layers:

2> set the entry included in the slrb-ConfigToReleaseList corresponding to the sidelink DRB;

1> for each sidelink DRB that is to be established or modified, according to clause 5.8.9.1a.2.1, due to receiving sl-ConfigDedicatedNR, SIB12 or SidelinkPreconfigNR:

2> set the SLRB-Config included in the slrb-ConfigToAddModList, according to the received sl-RadioBearerConfig and sl-RLC-BearerConfig corresponding to the sidelink DRB;

1> set the sl-MeasConfig as follows:

2> If the frequency used for NR sidelink communication is included in sl-FreqInfoToAddModList in sl-ConfigDedicatedNR within RRCReconfiguration message or included in sl-ConfigCommonNR within SIB12:

3> if UE is in RRC_CONNECTED:

4> set the sl-MeasConfig according to stored NR sidelink measurement configuration information for this destination;

3> if UE is in RRC_IDLE or RRC_INACTIVE:

4> set the sl-MeasConfig according to stored NR sidelink measurement configuration received from SIB12;

2> else:

3> set the sl-MeasConfig according to the sl-MeasPreconfig in SidelinkPreconfigNR;

1> set the sl-LatencyBoundIUC-Report;

1> start timer T400 for the destination;

1> set the sl-CSI-RS-Config;

1> set the sl-LatencyBoundCSI-Report;

1> set the sl-ResetConfig;

NOTE 1: Whether/how to set the parameters included in sl-CSI-RS-Config, sl-LatencyBoundCSI-Report and sl-ResetConfig is up to UE implementation.

1> set the sl-DRX-ConfigUC-PC5 as follows:

3> if UE is in RRC_CONNECTED and if sl-ScheduledConfig is included in sl-ConfigDedicatedNR within RRCReconfiguration:

4> set the sl-DRX-ConfigUC-PC5 according to stored NR sidelink DRX configuration information for this destination.

NOTE 2: If UE is in RRC_IDLE or in RRC_INACTIVE or out of coverage, or in RRC_CONNECTED and sl-UE-SelectedConfig is included in sl-ConfigDedicatedNR within RRCReconfiguration, it is up to UE implementation to set the sl-DRX-ConfigUC-PC5.

1> for each PC5 Relay RLC channel that is to be released due to configuration by sl-ConfigDedicatedNR:

2> set the SL-RLC-ChannelID corresponding to the PC5 Relay RLC channel in the sl-RLC-ChannelToReleaseListPC5;

1> for each PC5 Relay RLC channel that is to be established or modified due to receiving sl-ConfigDedicatedNR:

2> set the SL-RLC-ChannelConfigPC5 included in the sl-RLC-ChannelToAddModListPC5, according to the received sl-RLC-ChannelConfig corresponding to the PC5 Relay RLC channel;

The UE shall submit the RRCReconfigurationSidelink message to lower layers for transmission.

5.8.9.1.3 Reception of an RRCReconfigurationSidelink by the UE

The UE shall perform the following actions upon reception of the RRCReconfigurationSidelink:

1> if the RRCReconfigurationSidelink includes the sl-ResetConfig:

2> perform the sidelink reset configuration procedure as specified in 5.8.9.1.10;

1> if the RRCReconfigurationSidelink includes the slrb-ConfigToReleaseList:

2> for each entry value included in the slrb-ConfigToReleaseList that is part of the current UE sidelink configuration;

3> perform the sidelink DRB release procedure, according to clause 5.8.9.1a.1;

1> if the RRCReconfigurationSidelink includes the slrb-ConfigToAddModList:

2> for each slrb-PC5-ConfigIndex value included in the slrb-ConfigToAddModList that is not part of the current UE sidelink configuration:

3> if sl-MappedQoS-FlowsToAddList is included:

4> apply the SL-PQFI included in sl-MappedQoS-FlowsToAddList;

3> perform the sidelink DRB addition procedure, according to clause 5.8.9.1a.2;

2> for each slrb-PC5-ConfigIndex value included in the slrb-ConfigToAddModList that is part of the current UE sidelink configuration:

3> if sl-MappedQoS-FlowsToAddList is included:

4> add the SL-PQFI included in sl-MappedQoS-FlowsToAddList to the corresponding sidelink DRB;

3> if sl-MappedQoS-FlowsToReleaseList is included:

4> remove the SL-PQFI included in sl-MappedQoS-FlowsToReleaseList from the corresponding sidelink DRB;

3> if the sidelink DRB release conditions as described in clause 5.8.9.1a.1.1 are met:

4> perform the sidelink DRB release procedure according to clause 5.8.9.1a.1.2;

3> else if the sidelink DRB modification conditions as described in clause 5.8.9.1a.2.1 are met:

4> perform the sidelink DRB modification procedure according to clause 5.8.9.1a.2.2;

1> if the RRCReconfigurationSidelink message includes the sl-MeasConfig:

2> perform the sidelink measurement configuration procedure as specified in 5.8.10;

1> if the RRCReconfigurationSidelink message includes the sl-CSI-RS-Config:

2> apply the sidelink CSI-RS configuration;

1> if the RRCReconfigurationSidelink message includes the sl-LatencyBoundCSI-Report:

2> apply the configured sidelink CSI report latency bound;

1> if the RRCReconfigurationSidelink includes the sl-RLC-ChannelToReleaseListPC5:

2> for each SL-RLC-ChannelID value included in the sl-RLC-ChannelToReleaseListPC5 that is part of the current UE sidelink configuration;

3> perform the PC5 Relay RLC channel release procedure, according to clause 5.8.9.7.1;

1> if the RRCReconfigurationSidelink includes the sl-RLC-ChannelToAddModListPC5:

2> for each sl-RLC-ChannelID-PC5 value included in the sl-RLC-ChannelToAddModListPC5 that is not part of the current UE sidelink configuration:

3> perform the PC5 RLC channel addition procedure, according to clause 5.8.9.7.2;

2> for each sl-RLC-ChannelID-PC5 value included in the sl-RLC-ChannelToAddModListPC5 that is part of the current UE sidelink configuration:

3> perform the PC5 Relay RLC channel modification procedure according to clause 5.8.9.7.2;

1> if the RRCReconfigurationSidelink message includes the sl-DRX-ConfigUC-PC5, and

1> if the UE accepts the sl-DRX-ConfigUC-PC5:

2> configure lower layers to perform sidelink DRX operation according to sl-DRX-ConfigUC-PC5 for the associated destination as defined in TS 38.321 [3];

1> if the RRCReconfigurationSidelink message includes the sl-LatencyBoundIUC-Report:

2> apply the configured sidelink IUC report latency bound;

1> if the UE is unable to comply with (part of) the configuration included in the RRCReconfigurationSidelink (i.e. sidelink RRC reconfiguration failure):

2> continue using the configuration used prior to the reception of the RRCReconfigurationSidelink message;

2> set the content of the RRCReconfigurationFailureSidelink message;

3> submit the RRCReconfigurationFailureSidelink message to lower layers for transmission;

1> else:

2> set the content of the RRCReconfigurationCompleteSidelink message;

3> if the UE rejects the sidelink DRX configuration sl-DRX-ConfigUC-PC5 received from the peer UE:

4> include the sl-DRX-ConfigReject in the RRCReconfigurationCompleteSidelink message;

4> consider no sidelink DRX to be applied for the corresponding sidelink unicast communication;

3> submit the RRCReconfigurationCompleteSidelink message to lower layers for transmission;

NOTE 1: When the same logical channel is configured with different RLC mode by another UE, the UE handles the case as sidelink RRC reconfiguration failure.

NOTE 2: It is up to the UE whether or not to indicate the rejection to the peer UE for a received sidelink DRX configuration.

5.8.9.1.4 Void

5.8.9.1.5 Void

5.8.9.1.6 Void

5.8.9.1.7 Void

5.8.9.1.8 Reception of an RRCReconfigurationFailureSidelink by the UE

The UE shall perform the following actions upon reception of the RRCReconfigurationFailureSidelink:

1> stop timer T400 for the destination, if running;

1> continue using the configuration used prior to corresponding RRCReconfigurationSidelink message;

1> if UE is in RRC_CONNECTED:

2> perform the sidelink UE information for NR sidelink communication procedure, as specified in 5.8.3.3 or clause 5.10.15 in TS 36.331 [10];

5.8.9.1.9 Reception of an RRCReconfigurationCompleteSidelink by the UE

The UE shall perform the following actions upon reception of the RRCReconfigurationCompleteSidelink:

1> stop timer T400 for the destination, if running;

1> consider the configurations in the corresponding RRCReconfigurationSidelink message to be applied.

2> if the RRCReconfigurationCompleteSidelink message includes the sl-DRX-ConfigReject:

3> consider no sidelink DRX to be applied for the corresponding sidelink unicast communication.

5.8.9.1.10 Sidelink reset configuration

The UE shall:

1> release/clear current sidelink radio configuration of this destination received in the RRCReconfigurationSidelink;

1> release the sidelink DRBs of this destination, in according to clause 5.8.9.1a.1;

1> reset the sidelink specific MAC of this destination.

NOTE 1: Sidelink radio configuration is not just the resource configuration but may include other configurations included in the RRCReconfigurationSidelink message except the sidelink DRBs of this destination.

NOTE 2: After the sidelink DRB release procedure, UE may perform the sidelink DRB addition according to the current sidelink configuration of this destination, received in sl-ConfigDedicatedNR, SIB12 and SidelinkPreconfigNR, according to clause 5.8.9.1a.2.

5.8.9.1a Sidelink radio bearer management

5.8.9.1a.1 Sidelink DRB release

5.8.9.1a.1.1 Sidelink DRB release conditions

For NR sidelink communication, a sidelink DRB release is initiated in the following cases:

1> for groupcast, broadcast and unicast, if slrb-Uu-ConfigIndex (if any) of the sidelink DRB is included in sl-RadioBearerToReleaseList in sl-ConfigDedicatedNR; or

1> for groupcast and broadcast, if no sidelink QoS flow with data indicated by upper layers is mapped to the sidelink DRB for transmission, which is (re)configured by receiving SIB12 or SidelinkPreconfigNR; or

1> for groupcast, broadcast and unicast, if SL-RLC-BearerConfigIndex (if any) of the sidelink DRB is included in sl-RLC-BearerToReleaseList in sl-ConfigDedicatedNR; or

1> for unicast, if no sidelink QoS flow with data indicated by upper layers is mapped to the sidelink DRB for transmission, which is (re)configured by receiving SIB12 or SidelinkPreconfigNR, and if no sidelink QoS flow mapped to the sidelink DRB, which is (re)configured by receiving RRCReconfigurationSidelink, has data; or

1> for unicast, if SLRB-PC5-ConfigIndex (if any) of the sidelink DRB is included in slrb-ConfigToReleaseList in RRCReconfigurationSidelink or if sl-ResetConfig is included in RRCReconfigurationSidelink; or

1> for unicast, when the corresponding PC5-RRC connection is released due to sidelink RLF being detected, according to clause 5.8.9.3; or

1> for unicast, when the corresponding PC5-RRC connection is released due to upper layer request according to clause 5.8.9.5.

5.8.9.1a.1.2 Sidelink DRB release operations

For each sidelink DRB, whose sidelink DRB release conditions are met as in clause 5.8.9.1a.1.1, the UE capable of NR sidelink communication that is configured by upper layers to perform NR sidelink communication shall:

1> for groupcast and broadcast; or

1> for unicast, if the sidelink DRB release was triggered after the reception of the RRCReconfigurationSidelink message; or

1> for unicast, after receiving the RRCReconfigurationCompleteSidelink message, if the sidelink DRB release was triggered due to the configuration received within the sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR or indicated by upper layers:

2> release the PDCP entity for NR sidelink communication associated with the sidelink DRB;

2> if SDAP entity for NR sidelink communication associated with this sidelink DRB is configured:

3> indicate the release of the sidelink DRB to the SDAP entity associated with this sidelink DRB (TS 37.324 [24], clause 5.3.3);

2> release SDAP entities for NR sidelink communication, if any, that have no associated sidelink DRB as specified in TS 37.324 [24] clause 5.1.2;

1> for groupcast and broadcast; or

1> for unicast, after receiving the RRCReconfigurationCompleteSidelink message, if the sidelink DRB release was triggered due to the configuration received within the sl-ConfigDedicatedNR:

2> for each sl-RLC-BearerConfigIndex included in the received sl-RLC-BearerToReleaseList that is part of the current UE sidelink configuration:

3> release the RLC entity and the corresponding logical channel for NR sidelink communication, associated with the sl-RLC-BearerConfigIndex.

1> for unicast, if the sidelink DRB release was triggered due to the reception of the RRCReconfigurationSidelink message; or

1> for unicast, after receiving the RRCReconfigurationCompleteSidelink message, if the sidelink DRB release was triggered due to the configuration received within the SIB12, SidelinkPreconfigNR or indicated by upper layers:

2> release the RLC entity and the corresponding logical channel for NR sidelink communication associated with the sidelink DRB;

2> perform the sidelink UE information procedure in clause 5.8.3 for unicast if needed.

1> if the sidelink radio link failure is detected for a specific destination:

2> release the PDCP entity, RLC entity and the logical channel of the sidelink DRB for the specific destination.

5.8.9.1a.2 Sidelink DRB addition/modification

5.8.9.1a.2.1 Sidelink DRB addition/modification conditions

For NR sidelink communication, a sidelink DRB addition is initiated only in the following cases:

1> if any sidelink QoS flow is (re)configured by sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR and is to be mapped to one sidelink DRB, which is not established; or

1> if any sidelink QoS flow is (re)configured by RRCReconfigurationSidelink and is to be mapped to a sidelink DRB, which is not established;

For NR sidelink communication, a sidelink DRB modification is initiated only in the following cases:

1> if any of the sidelink DRB related parameters is changed by sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR or RRCReconfigurationSidelink for one sidelink DRB, which is established;

5.8.9.1a.2.2 Sidelink DRB addition/modification operations

For the sidelink DRB, whose sidelink DRB addition conditions are met as in clause 5.8.9.1a.2.1, the UE capable of NR sidelink communication that is configured by upper layers to perform NR sidelink communication shall:

1> for groupcast and broadcast; or

1> for unicast, if the sidelink DRB addition was triggered due to the reception of the RRCReconfigurationSidelink message; or

1> for unicast, after receiving the RRCReconfigurationCompleteSidelink message, if the sidelink DRB addition was triggered due to the configuration received within the sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR or indicated by upper layers:

2> if an SDAP entity for NR sidelink communication associated with the destination and the cast type of the sidelink DRB does not exist:

3> establish an SDAP entity for NR sidelink communication as specified in TS 37.324 [24] clause 5.1.1;

2> (re)configure the SDAP entity in accordance with the sl-SDAP-ConfigPC5 received in the RRCReconfigurationSidelink or sl-SDAP-Config received in sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR, associated with the sidelink DRB;

2> establish a PDCP entity for NR sidelink communication and configure it in accordance with the sl-PDCP-ConfigPC5 received in the RRCReconfigurationSidelink or sl-PDCP-Config received in sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR, associated with the sidelink DRB;

2> establish a RLC entity for NR sidelink communication and configure it in accordance with the sl-RLC-ConfigPC5 received in the RRCReconfigurationSidelink or sl-RLC-Config received in sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR, associated with sidelink DRB;

2> if this procedure was due to the reception of a RRCReconfigurationSidelink message:

3> configure the MAC entity with a logical channel in accordance with the sl-MAC-LogicalChannelConfigPC5 received in the RRCReconfigurationSidelink associated with the sidelink DRB, and perform the sidelink UE information procedure in clause 5.8.3 for unicast if need;

2> else:

3> configure the MAC entity with a logical channel associated with the sidelink DRB, by assigning a new logical channel identity, in accordance with the sl-MAC-LogicalChannelConfig received in the sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR.

NOTE 1: When a sidelink DRB addition is due to the configuration by RRCReconfigurationSidelink, it is up to UE implementation to select the sidelink DRB configuration as necessary transmitting parameters for the sidelink DRB, from the received sl-ConfigDedicatedNR (if in RRC_CONNECTED), SIB12 (if in RRC_IDLE/INACTIVE), SidelinkPreconfigNR (if out of coverage) with the same RLC mode as the one configured in RRCReconfigurationSidelink.

For the sidelink DRB, whose sidelink DRB modification conditions are met as in clause 5.8.9.1a.2.1, the UE capable of NR sidelink communication that is configured by upper layers to perform NR sidelink communication shall:

1> for groupcast and broadcast; or

1> for unicast, if the sidelink DRB modification was triggered due to the reception of the RRCReconfigurationSidelink message; or

1> for unicast, after receiving the RRCReconfigurationCompleteSidelink message, if the sidelink DRB modification was triggered due to the configuration received within the sl-ConfigDedicatedNR, SIB12 or SidelinkPreconfigNR:

2> reconfigure the SDAP entity of the sidelink DRB, in accordance with the sl-SDAP-ConfigPC5 received in the RRCReconfigurationSidelink or sl-SDAP-Config received in sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR, if included;

2> reconfigure the PDCP entity of the sidelink DRB, in accordance with the sl-PDCP-ConfigPC5 received in the RRCReconfigurationSidelink or sl-PDCP-Config received in sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR, if included;

2> reconfigure the RLC entity of the sidelink DRB, in accordance with the sl-RLC-ConfigPC5 received in the RRCReconfigurationSidelink or sl-RLC-Config received in sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR, if included;

2> reconfigure the logical channel of the sidelink DRB, in accordance with the sl-MAC-LogicalChannelConfigPC5 received in the RRCReconfigurationSidelink or sl-MAC-LogicalChannelConfig received in sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR, if included.

5.8.9.1a.3 Sidelink SRB release

The UE shall:

1> if a PC5-RRC connection release for a specific destination is requested by upper layers or AS layer; or

1> if the sidelink radio link failure is detected for a specific destination:

2> release the PDCP entity, RLC entity and the logical channel of the sidelink SRB for PC5-RRC message of the specific destination;

2> consider the PC5-RRC connection is released for the destination.

1> if PC5-S transmission for a specific destination is terminated in upper layers:

2> release the PDCP entity, RLC entity and the logical channel of the sidelink SRB(s) for PC5-S message of the specific destination;

1> if discovery transmission for a specific destination is terminated in upper layers:

2> release the PDCP entity, RLC entity and the logical channel of the sidelink SRB4 for discovery message of the specific destination;

5.8.9.1a.4 Sidelink SRB addition

The UE shall:

1> if transmission of PC5-S message for a specific destination is requested by upper layers for sidelink SRB:

2> establish PDCP entity, RLC entity and the logical channel of a sidelink SRB for PC5-S message, as specified in clause 9.1.1.4;

1> if transmission of discovery message for a specific destination is requested by upper layers for sidelink SRB:

2> establish PDCP entity, RLC entity and the logical channel of a sidelink SRB4 for discovery message, as specified in clause 9.1.1.4;

1> if a PC5-RRC connection establishment for a specific destination is indicated by upper layers:

2> establish PDCP entity, RLC entity and the logical channel of a sidelink SRB for PC5-RRC message of the specific destination, as specified in clause 9.1.1.4;

2> consider the PC5-RRC connection is established for the destination.

5.8.9.2 Sidelink UE capability transfer

5.8.9.2.1 General

This clause describes how the UE compiles and transfers its sidelink UE capability information for unicast to the initiating UE.

Figure 5.8.9.2.1-1: Sidelink UE capability transfer

5.8.9.2.2 Initiation

The UE may initiate the sidelink UE capability transfer procedure upon indication from upper layer when it needs (additional) UE radio access capability information.

5.8.9.2.3 Actions related to transmission of the UECapabilityEnquirySidelink by the UE

The initiating UE shall set the contents of UECapabilityEnquirySidelink message as follows:

1> include in UE radio access capabilities for sidelink within ue-CapabilityInformationSidelink, if needed;

NOTE 1: It is up to initiating UE to decide whether ue-CapabilityInformationSidelink should be included.

1> set frequencyBandListFilterSidelink to include frequency bands for which the peer UE is requested to provide supported bands and band combinations;

NOTE 2: The initiating UE is not allowed to send the UECapabilityEnquirySidelink message without including the field frequencyBandListFilterSidelink.

1> submit the UECapabilityEnquirySidelink message to lower layers for transmission.

5.8.9.2.4 Actions related to reception of the UECapabilityEnquirySidelink by the UE

The peer UE shall set the contents of UECapabilityInformationSidelink message as follows:

1> include UE radio access capabilities for sidelink within ue-CapabilityInformationSidelink;

1> compile a list of "candidate band combinations" only consisting of bands included in frequencyBandListFilterSidelink, and prioritized in the order of frequencyBandListFilterSidelink (i.e. first include band combinations containing the first-listed band, then include remaining band combinations containing the second-listed band, and so on).

1> include into supportedBandCombinationListSidelinkNR as many band combinations as possible from the list of "candidate band combinations", starting from the first entry;

1> include the received frequencyBandListFilterSidelink in the field appliedFreqBandListFilter of the requested UE capability;

1> submit the UECapabilityInformationSidelink message to lower layers for transmission.

NOTE: If the UE cannot include all band combinations due to message size or list size constraints, it is up to UE implementation which band combinations it prioritizes.

5.8.9.3 Sidelink radio link failure related actions

The UE shall:

1> upon indication from sidelink RLC entity that the maximum number of retransmissions for a specific destination has been reached; or

1> upon T400 expiry for a specific destination; or

1> upon indication from MAC entity that the maximum number of consecutive HARQ DTX for a specific destination has been reached; or

1> upon integrity check failure indication from sidelink PDCP entity concerning SL-SRB2 or SL-SRB3 for a specific destination:

2> consider sidelink radio link failure to be detected for this destination;

2> release the DRBs of this destination, according to clause 5.8.9.1a.1;

2> release the SRBs of this destination, according to clause 5.8.9.1a.3;

2> release the PC5 Relay RLC channels of this destination if configured, in according to clause 5.8.9.7.1;

2> discard the NR sidelink communication related configuration of this destination;

2> reset the sidelink specific MAC of this destination;

2> consider the PC5-RRC connection is released for the destination;

2> indicate the release of the PC5-RRC connection to the upper layers for this destination (i.e. PC5 is unavailable);

2> if UE is in RRC_CONNECTED:

3> if the UE is acting as L2 U2N Remote UE:

4> initiate the RRC connection re-establishment procedure as specified in 5.3.7.

3> else:

4> perform the sidelink UE information for NR sidelink communication procedure, as specified in 5.8.3.3;

NOTE: It is up to UE implementation on whether and how to indicate to upper layers to maintain the keep-alive procedure [55].

5.8.9.4 Sidelink common control information

5.8.9.4.1 General

The sidelink common control information is carried by MasterInformationBlockSidelink. The sidelink common control information may change at any transmission, i.e. neither a modification period nor a change notification mechanism is used. This procedure also applies to NR sidelink discovery.

A UE configured to receive or transmit NR sidelink communication/discovery shall:

1> if the UE has a selected SyncRef UE, as specified in 5.8.6:

2> ensure having a valid version of the MasterInformationBlockSidelink message of that SyncRef UE;

5.8.9.4.2 Actions related to reception of MasterInformationBlockSidelink message

Upon receiving MasterInformationBlockSidelink, the UE shall:

1> apply the values included in the received MasterInformationBlockSidelink message.

5.8.9.4.3 Transmission of MasterInformationBlockSidelink message

The UE shall set the contents of the MasterInformationBlockSidelink message as follows:

1> if in coverage on the frequency used for the NR sidelink communication as defined in TS 38.304 [20].

2> set inCoverage to true;

2> if tdd-UL-DL-ConfigurationCommon is included in the received SIB1:

3> set sl-TDD-Config to the value representing the same meaning as that is included in tdd-UL-DL-ConfigurationCommon, as described in TS 38.213, clause 16.1 [13];

2> else:

3> set sl-TDD-Config to the value as specified in TS 38.213 [13], clause 16.1;

2> if syncInfoReserved is included in an entry of configured sl-SyncConfigList corresponding to the concerned frequency from the received SIB12:

3> set reservedBits to the value of syncInfoReserved in the received SIB12;

2> else:

3> set all bits in reservedBits to 0;

1> else if out of coverage on the frequency used for NR sidelink communication as defined in TS 38.304 [20]; and the concerned frequency is included in sl-FreqInfoToAddModList in RRCReconfiguration or in sl-FreqInfoList within SIB12:

2> set inCoverage to true;

2> set reservedBits to the value of the corresponding field included in the preconfigured sidelink parameters (i.e. sl-PreconfigGeneral in SidelinkPreconfigNR defined in 9.3);

2> set sl-TDD-Config to the value representing the same meaning as that is included in the corresponding field included in the preconfigured sidelink parameters (i.e. sl-PreconfigGeneral in SL-PreconfigurationNR defined in 9.3) as described in TS 38.213, clause 16.1 [13];

1> else if out of coverage on the frequency used for NR sidelink communication as defined in TS 38.304 [20]; and the UE selects GNSS as the synchronization reference and sl-SSB-TimeAllocation3 is not configured for the frequency used in SidelinkPreconfigNR:

2> set inCoverage to true;

2> set reservedBits to the value of the corresponding field included in the preconfigured sidelink parameters (i.e. sl-PreconfigGeneral in SidelinkPreconfigNR defined in 9.3);

1> else if the UE has a selected SyncRef UE (as defined in 5.8.6):

2> set inCoverage to false;

2> set sl-TDD-Config and reservedBits to the value of the corresponding field included in the received MasterInformationBlockSidelink;

1> else:

2> set inCoverage to false;

2> set reservedBits to the value of the corresponding field included in the preconfigured sidelink parameters (i.e. sl-PreconfigGeneral in SidelinkPreconfigNR defined in 9.3);

1> set directFrameNumber and slotIndex according to the slot used to transmit the SLSS, as specified in 5.8.5.3;

1> submit the MasterInformationBlockSidelink to lower layers for transmission upon which the procedure ends;

5.8.9.5 Actions related to PC5-RRC connection release requested by upper layers

The UE initiates the procedure when upper layers request the release of the PC5-RRC connection as specified in TS 24.587 [57] or TS 24.554 [72]. The UE shall not initiate the procedure for power saving purposes.

The UE shall:

1> if the PC5-RRC connection release for the specific destination is requested by upper layers:

2> discard the NR sidelink communication related configuration of this destination;

2> release the DRBs of this destination if configured, in according to clause 5.8.9.1a.1;

2> release the SRBs of this destination, in according to clause 5.8.9.1a.3;

2> release the PC5 Relay RLC channels if configured, in according to clause 5.8.9.7.1;

2> reset the sidelink specific MAC of this destination.

2> consider the PC5-RRC connection is released for the destination;

5.8.9.6 Sidelink UE assistance information

5.8.9.6.1 General

Figure 5.8.9.6.1-1: Sidelink UE assistance information

The purpose of this procedure is for a UE to inform its peer UE of the sidelink DRX assistance information used to determine the sidelink DRX configuration for unicast communication.

For sidelink unicast, a UE may include its desired sidelink DRX configurations in the UEAssistanceInformationSidelink as the sidelink DRX assistance information which is transmitted to its peer UE.

NOTE: It is up to UE implementation to determine its desired sidelink DRX configurations for unicast communication.

5.8.9.6.2 Initiation

For sidelink unicast, if both a RX UE and its peer TX UE for a direction of sidelink communication are capable of sidelink DRX, the RX UE that is interested in sending the sidelink DRX assistance information may send the UEAssistanceInformationSidelink as the sidelink DRX assistance information to its peer UE when the sidelink DRX assistance information has not been sent previously or when the previously transmitted sidelink DRX assistance information has changed.

5.8.9.6.3 Actions related to reception of UEAssistanceInformationSidelink message

For sidelink unicast, when a UE is in RRC_CONNECTED and is performing sidelink operation with resource allocation mode 1, it may report the sidelink DRX assistance information received within the UEAssistanceInformationSidelink from its peer UE to the network as specified in 5.8.3. For sidelink unicast, when a UE is in RRC_CONNECTED and is performing sidelink operation with resource allocation mode 2 or is in RRC_IDLE or RRC_INACTIVE or out of coverage, regardless of whether the UE has obtained the sidelink DRX assistance information from the UEAssistanceInformationSidelink transmitted from its peer UE or not, it may determine the sidelink DRX configuration SL-DRX-ConfigUC for its peer UE.

NOTE: When UE determines the sidelink DRX configuration for its peer UE, it may take the sidelink DRX assistance information received from its peer UE into account.

5.8.9.7 PC5 Relay RLC channel management for L2 U2N relay

5.8.9.7.1 PC5 Relay RLC channel release

The UE shall:

1> if the PC5 Relay RLC channel release was triggered after the reception of the RRCReconfigurationSidelink message; or

1> after receiving the RRCReconfigurationCompleteSidelink message, if the PC5 Relay RLC channel release was triggered due to the configuration received within the sl-ConfigDedicatedNR:

2> for each sl-RLC-ChannelID in sl-RLC-ChannelToReleaseList received in sl-ConfigDedicatedNR within RRCReconfiguration or for each sl-RLC-ChannelID-PC5 included in the received sl-RLC-ChannelToReleaseListPC5 that is part of the current UE sidelink configuration:

3> release the RLC entity and the corresponding logical channel associated with the sl-RLC-ChannelID or sl-RLC-ChannelID-PC5;

1> if the PC5 Relay RLC channel release was triggered for a specific destination by upper layers as specified in 5.8.9.5:

2> release the RLC entity and the corresponding logical channel associated with the sl-RLC-ChannelID or sl-RLC-ChannelID-PC5 of the specific destination;

5.8.9.7.2 PC5 Relay RLC channel addition/modification

Upon PC5-RRC connection establishment between the L2 U2N Relay UE and L2 U2N Remote UE, the L2 U2N Relay UE shall:

1> establish a SRAP entity as specified in TS 38.351 [66], if no SRAP entity has been established;

1> apply RLC specified configuration of SL-RLC0 as specified in clause 9.1.1.4:

1> apply RLC default configuration of SL-RLC1 as defined in clause 9.2.4 if the L2 U2N Relay UE is in RRC_IDLE/INACTIVE state;

The UE shall:

1> if the PC5 Relay RLC channel addition/modification was triggered due to the reception of the RRCReconfigurationSidelink message; or

1> after receiving the RRCReconfigurationCompleteSidelink message, if the PC5 Relay RLC channel addition/modification was triggered due to the configuration received within the sl-ConfigDedicatedNR:

2> if the current configuration contains a PC5 Relay RLC channel with the received sl-RLC-ChannelID or sl-RLC-ChannelID-PC5:

3> reconfigure the sidelink RLC entity in accordance with the received sl-RLC-Config or sl-RLC-ConfigPC5;

3> reconfigure the sidelink MAC entity with a logical channel in accordance with the received sl-MAC-LogicalChannelConfig or sl-MAC-LogicalChannelConfigPC5;

2> else (a PC5 Relay RLC channel with the received sl-RLC-ChannelID or sl-RLC-ChannelID-PC5 was not configured before):

3> establish a sidelink RLC entity in accordance with the received sl-RLC-Config or sl-RLC-ConfigPC5;

3> configure the sidelink MAC entity with a logical channel in accordance with the received sl-MAC-LogicalChannelConfig or sl-MAC-LogicalChannelConfigPC5.

5.8.9.8 Remote UE information

5.8.9.8.1 General

Figure 5.8.9.8.1-1: Remote UE information

This procedure is used by the L2 U2N Remote UE in RRC_IDLE/RRC_INACTIVE to inform about the required SIB(s) and provide Paging related information to the connected L2 U2N Relay UE.

NOTE: MIB is not required by a L2 U2N Remote UE.

5.8.9.8.2 Actions related to transmission of RemoteUEInformationSidelink message

When entering RRC_IDLE or RRC_INACTIVE, or upon change in any of the information in the RemoteUEInformationSidelink while in RRC_IDLE or RRC_INACTIVE, the L2 U2N Remote UE shall:

1> if the UE has not stored a valid version of a SIB, in accordance with clause 5.2.2.2.1, of one or several required SIB(s) in accordance with clause 5.2.2.1 and the requested SIB has not been indicated in RemoteUEInformationSidelink message to the L2 U2N Relay UE before:

2> include sl-RequestedSIB-List in the RemoteUEInformationSidelink to indicate the requested SIB(s);

1> if the UE has not sent sl-PagingInfo-RemoteUE in the RemoteUEInformationSidelink message to the L2 U2N Relay UE before, set sl-PagingInfo-RemoteUE as follows:

2> if the L2 U2N Remote UE is in RRC_IDLE:

3> include ng-5G-S-TMSI in the sl-PagingIdentityRemoteUE;

3> if the UE specific DRX cycle is configured by upper layer, set sl-PagingCycleRemoteUE to the value of UE specific Uu DRX cycle configured by upper layer;

2> else if the L2 U2N Remote UE is in RRC_INACTIVE:

3> include ng-5G-S-TMSI and fullI-RNTI in the sl-PagingIdentityRemoteUE;

3> if the UE specific DRX cycle is configured by upper layer,

4> set sl-PagingCycleRemoteUE to the minimum value of UE specific Uu DRX cycles (configured by upper layer and configured by RRC);

3> else:

4> set sl-PagingCycleRemoteUE to the value of UE specific DRX cycle configured by RRC;

1> submit the RemoteUEInformationSidelink message to lower layers for transmission;

When entering RRC_CONNECTED, if L2 U2N remote UE had sent sl-RequestedSIB-List and/or sl-PagingInfo-RemoteUE, the L2 U2N Remote UE shall:

1> set the sl-RequestedSIB-List to the value release if requested before;

1> set the sl-PagingInfo-RemoteUE to the value release if sent before;

1> submit the RemoteUEInformationSidelink message to lower layers for transmission;

5.8.9.8.3 Reception of RemoteUEInformationSidelink message by the L2 U2N Relay UE

The L2 U2N Relay UE shall:

1> if the RemoteUEInformationSidelink includes the sl-PagingInfo-RemoteUE:

2> if the UE is in RRC_CONNECTED on an active BWP with common search space configured including pagingSearchSpace; or

2> if the UE is in RRC_IDLE or RRC_INACTIVE:

3> if the sl-PagingInfo-RemoteUE is set to setup:

4> monitor the Paging message at the L2 U2N Remote UE’s paging occasion calculated according to sl-PagingIdentityRemoteUE and sl-PagingCycleRemoteUE included in sl-PagingInfo-RemoteUE;

3> else (the sl-PagingInfo-RemoteUE is set to release):

4> stop monitoring the Paging message at the L2 U2N Remote UE’s paging occasion;

4> release the received paging information in sl-PagingInfo-RemoteUE;

2> else (the UE is in RRC_CONNECTED on an active BWP without pagingSearchSpace configured):

3> if the sl-PagingInfo-RemoteUE is set to setup:

4> include the received sl-PagingIdentityRemoteUE in SidelinkUEInformationNR message and perform Sidelink UE information transmission in accordance with 5.8.3;

3> else (the sl-PagingInfo-RemoteUE is set to release):

4> initiate transmission of the SidelinkUEInformationNR message to release the sl-PagingIdentityRemoteUE in SidelinkUEInformationNR message in accordance with 5.8.3;

4> release the received paging information in sl-PagingInfo-RemoteUE;

1> if the RemoteUEInformationSidelink includes the sl-RequestedSIB-List:

2> if the sl-RequestedSIB-List is set to setup:

3> if the L2 U2N Relay UE has not stored a valid version of SIB(s) indicated in sl-RequestedSIB-List:

4> perform acquisition of the system information indicated in sl-RequestedSIB-List in accordance with 5.2.2;

3> else:

4> perform the Uu message transfer procedure in accordance with 5.8.9.9;

2> if the sl-RequestedSIB-List is set to release:

3> release received SIB request in sl-RequestedSIB-List.

5.8.9.9 Uu message transfer in sidelink

5.8.9.9.1 General

Figure 5.8.9.9.1-1: Uu message transfer in sidelink

The purpose of this procedure is to transfer Paging message and System Information from the L2 U2N Relay UE to the L2 U2N Remote UE in RRC_IDLE/RRC_INACTIVE.

5.8.9.9.2 Actions related to transmission of UuMessageTransferSidelink message

The L2 U2N Relay UE initiates the Uu message transfer procedure when at least one of the following conditions is met:

1> upon receiving Paging message related to the connected L2 U2N Remote UE from network (including Paging message within RRCReconfiguration message);

1> upon acquisition of the SIB(s) requested by the connected L2 U2N Remote UE (as indicated in sl-RequestedSIB-List in the RemoteUEInformationSidelink) or upon receiving the updated SIB(s) from network which has been requested by the connected L2 U2N Remote UE;

1> upon unsolicited SIB1 forwarding to the connected L2 U2N Remote UE or upon receiving the updated SIB1 from network;

For each associated L2 U2N Remote UE, the L2 U2N Relay UE shall set the contents of UuMessageTransferSidelink message as follows:

1> include sl-PagingDelivery if the Paging message received from network containing the ue-Identity of the L2 U2N Remote UE;

1> include sl-SIB1-Delivery if any of the conditions for initiating Uu message transfer procedure related to SIB1 are met;

1> include sl-SystemInformationDelivery if any of the conditions for initiating Uu message transfer procedure related to System Information are met;

1> submit the UuMessageTransferSidelink message to lower layers for transmission.

NOTE: The L2 U2N Relay UE may perform unsolicited forwarding of SIB1 to the L2 U2N Remote UE based on UE implementation.

5.8.9.9.3 Reception of the UuMessageTransferSidelink

Upon receiving the UuMessageTransferSidelink message, the L2 U2N Remote UE shall:

1> if sl-PagingDelivery is included:

2> perform the paging reception procedure as specified in clause 5.3.2.3;

1> if sl-SystemInformationDelivery and/or sl-SIB1-Delivery is included:

2> perform the actions specified in clause 5.2.2.4.

5.8.9.10 Notification Message

5.8.9.10.1 General

Figure 5.8.9.8.1-1: Notification message in sidelink

This procedure is used by a U2N Relay UE to send notification to the connected U2N Remote UE.

5.8.9.10.2 Initiation

The U2N Relay UE may initiate the procedure when one of the following conditions is met:

1> upon Uu RLF as specified in 5.3.10;

1> upon reception of an RRCReconfiguration including the reconfigurationWithSync;

1> upon cell reselection;

1> upon L2 U2N Relay UE’s RRC connection failure including RRC connection reject as specified in 5.3.3.5 and 5.3.13.10, and T300 expiry as specified in 5.3.3.7, and RRC resume failure as specified in 5.3.13.5;

5.8.9.10.3 Actions related to transmission of NotificationMessageSidelink message

The U2N Relay UE shall set the indication type as follows:

1> if the UE initiates transmission of the NotificationMessageSidelink message due to Uu RLF:

2> set the indicationType as relayUE-Uu-RLF;

1> else if the UE initiates transmission of the NotificationMessageSidelink message due to reconfiguration with sync:

2> set the indicationType as relayUE-HO;

1> else if the UE initiates transmission of the NotificationMessageSidelink message due to cell reselection:

2> set the indicationType as relayUE-CellReselection;

1> if the UE initiates transmission of the NotificationMessageSidelink message due to Uu RRC connection establishment/Resume failure:

2> set the indicationType as relayUE-Uu-RRC-Failure;

1> submit the NotificationMessageSidelink message to lower layers for transmission.

5.8.9.10.4 Actions related to reception of NotificationMessageSidelink message

Upon receiving the NotificationMessageSidelink, the U2N Remote UE shall:

1> if the indicationType is included:

2> if the UE is L2 U2N Remote UE in RRC_CONNECTED:

3> if T301 is not running, initiate the RRC connection re-establishment procedure as specified in 5.3.7;

2> else (the UE is L3 U2N Remote UE, or L2 U2N Remote UE in RRC_IDLE or RRC_INACTIVE):

3> if the PC5-RRC connection with the U2N Relay UE is determined to be released:

4> indicate upper layers to trigger PC5 unicast link release;

3> else (i.e., maintain the PC5 RRC connection):

4> if the UE is L2 U2N Remote UE and the indicationType is relayUE-HO or relayUE-CellReselection:

5> consider cell re-selection occurs;

NOTE: For L3 U2N Remote UE, or L2 U2N Remote UE in RRC_IDLE or RRC_INACTIVE, it is up to Remote UE implementation whether to release or keep the PC5 unicast link.

5.8.10 Sidelink measurement

5.8.10.1 Introduction

The UE may configure the associated peer UE to perform NR sidelink measurement and report on the corresponding PC5-RRC connection in accordance with the NR sidelink measurement configuration for unicast by RRCReconfigurationSidelink message.

The NR sidelink measurement configuration includes the following parameters for a PC5-RRC connection:

1. NR sidelink measurement objects: Object(s) on which the associated peer UE shall perform the NR sidelink measurements.

– For NR sidelink measurement, a NR sidelink measurement object indicates the NR sidelink frequency of reference signals to be measured.

2. NR sidelink reporting configurations: NR sidelink measurement reporting configuration(s) where there can be one or multiple NR sidelink reporting configurations per NR sidelink measurement object. Each NR sidelink reporting configuration consists of the following:

– Reporting criterion: The criterion that triggers the UE to send a NR sidelink measurement report. This can either be periodical or a single event description.

– RS type: The RS that the UE uses for NR sidelink measurement results. In this release, only DMRS is supported for NR sidelink measurement.

– Reporting format: The quantities that the UE includes in the measurement report. In this release, only RSRP measurement is supported.

3. NR sidelink measurement identities: A list of NR sidelink measurement identities where each NR sidelink measurement identity links one NR sidelink measurement object with one NR sidelink reporting configuration. By configuring multiple NR sidelink measurement identities, it is possible to link more than one NR sidelink measurement object to the same NR sidelink reporting configuration, as well as to link more than one NR sidelink reporting configuration to the same NR sidelink measurement object. The NR sidelink measurement identity is also included in the NR sidelink measurement report that triggered the reporting, serving as a reference to the network.

4. NR sidelink quantity configurations: The NR sidelink quantity configuration defines the NR sidelink measurement filtering configuration used for all event evaluation and related reporting, and for periodical reporting of that NR sidelink measurement. In each configuration, different filter coefficients can be configured for different NR sidelink measurement quantities.

Both UEs of the PC5-RRC connection maintains a NR sidelink measurement object list, a NR sidelink reporting configuration list, and a NR sidelink measurement identities list according to signalling and procedures in this specification.

5.8.10.2 Sidelink measurement configuration

5.8.10.2.1 General

The UE shall:

1> if the received sl-MeasConfig includes the sl-MeasObjectToRemoveList in the RRCReconfigurationSidelink:

2> perform the sidelink measurement object removal procedure as specified in 5.8.10.2.4;

1> if the received sl-MeasConfig includes the sl-MeasObjectToAddModList in the RRCReconfigurationSidelink:

2> perform the sidelink measurement object addition/modification procedure as specified in 5.8.10.2.5;

1> if the received sl-MeasConfig includes the sl-ReportConfigToRemoveList in the RRCReconfigurationSidelink:

2> perform the sidelink reporting configuration removal procedure as specified in 5.8.10.2.6;

1> if the received sl-MeasConfig includes the sl-ReportConfigToAddModList in the RRCReconfigurationSidelink:

2> perform the sidelink reporting configuration addition/modification procedure as specified in 5.8.10.2.7;

1> if the received sl-MeasConfig includes the sl-QuantityConfig in the RRCReconfigurationSidelink:

2> perform the sidelink quantity configuration procedure as specified in 5.8.10.2.8;

1> if the received sl-MeasConfig includes the sl-MeasIdToRemoveList in the RRCReconfigurationSidelink:

2> perform the sidelink measurement identity removal procedure as specified in 5.8.10.2.2;

1> if the received sl-MeasConfig includes the sl-MeasIdToAddModList in the RRCReconfigurationSidelink:

2> perform the sidelink measurement identity addition/modification procedure as specified in 5.8.10.2.3;

5.8.10.2.2 Sidelink measurement identity removal

The UE shall:

1> for each sl-MeasId included in the received sl-MeasIdToRemoveList that is part of the current UE configuration in VarMeasConfigSL:

2> remove the entry with the matching sl-MeasId from the sl-MeasIdList within the VarMeasConfigSL;

2> remove the NR sidelink measurement reporting entry for this sl-MeasId from the VarMeasReportListSL, if included;

2> stop the periodical reporting timer and reset the associated information (e.g. sl-TimeToTrigger) for this sl-MeasId.

NOTE: The UE does not consider the message as erroneous if the sl-MeasIdToRemoveList includes any sl-MeasId value that is not part of the current UE configuration.

5.8.10.2.3 Sidelink measurement identity addition/modification

The UE shall:

1> for each sl-MeasId included in the received sl-MeasIdToAddModList:

2> if an entry with the matching sl-MeasId exists in the sl-MeasIdList within the VarMeasConfigSL:

3> replace the entry with the value received for this sl-MeasId;

2> else:

3> add a new entry for this sl-MeasId within the VarMeasConfigSL;

2> remove the measurement reporting entry for this sl-MeasId from the VarMeasReportListSL, if included;

2> stop the periodical reporting timer and reset the associated information (e.g. sl-TimeToTrigger) for this sl-MeasId;

5.8.10.2.4 Sidelink measurement object removal

The UE shall:

1> for each sl-MeasObjectId included in the received sl-MeasObjectToRemoveList that is part of sl-MeasObjectList in VarMeasConfigSL:

2> remove the entry with the matching sl-MeasObjectId from the sl-MeasObjectList within the VarMeasConfigSL;

2> remove all sl-MeasId associated with this sl-MeasObjectId from the sl-MeasIdList within the VarMeasConfigSL, if any;

2> if a sl-MeasId is removed from the sl-MeasIdList:

3> remove the measurement reporting entry for this sl-MeasId from the VarMeasReportListSL, if included;

3> stop the periodical reporting timer and reset the associated information (e.g. sl-TimeToTrigger) for this sl-MeasId.

NOTE: The UE does not consider the message as erroneous if the sl-MeasObjectToRemoveList includes any sl-MeasObjectId value that is not part of the current UE configuration.

5.8.10.2.5 Sidelink measurement object addition/modification

The UE shall:

1> for each sl-MeasObjectId included in the received sl-MeasObjectToAddModList:

2> if an entry with the matching sl-MeasObjectId exists in the sl-MeasObjectList within the VarMeasConfigSL, for this entry:

3> for each sl-MeasId associated with this sl-MeasObjectId included in the sl-MeasIdList within the VarMeasConfigSL, if any:

4> remove the measurement reporting entry for this sl-MeasId from the VarMeasReportListSL, if included;

4> stop the periodical reporting timer and reset the associated information (e.g. sl-TimeToTrigger) for this sl-MeasId;

3> reconfigure the entry with the value received for this sl-MeasObject;

2> else:

3> add a new entry for the received sl-MeasObject to the sl-MeasObjectList within VarMeasConfigSL.

5.8.10.2.6 Sidelink reporting configuration removal

The UE shall:

1> for each sl-ReportConfigId included in the received sl-ReportConfigToRemoveList that is part of the current UE configuration in VarMeasConfigSL:

2> remove the entry with the matching sl-ReportConfigId from the sl-ReportConfigList within the VarMeasConfigSL;

2> remove all sl-MeasId associated with the sl-ReportConfigId from the sl-MeasIdList within the VarMeasConfigSL, if any;

2> if a sl-MeasId is removed from the sl-MeasIdList:

3> remove the measurement reporting entry for this sl-MeasId from the VarMeasReportListSL, if included;

3> stop the periodical reporting timer and reset the associated information (e.g. sl-TimeToTrigger) for this sl-MeasId.

NOTE: The UE does not consider the message as erroneous if the sl-ReportConfigToRemoveList includes any sl-ReportConfigId value that is not part of the current UE configuration.

5.8.10.2.7 Sidelink reporting configuration addition/modification

The UE shall:

1> for each sl-ReportConfigId included in the received sl-ReportConfigToAddModList:

2> if an entry with the matching sl-ReportConfigId exists in the sl-ReportConfigList within the VarMeasConfigSL, for this entry:

3> reconfigure the entry with the value received for this sl-ReportConfig;

3> for each sl-MeasId associated with this sl-ReportConfigId included in the sl-MeasIdList within the VarMeasConfigSL, if any:

4> remove the measurement reporting entry for this sl-MeasId from the VarMeasReportListSL, if included;

4> stop the periodical reporting timer and reset the associated information (e.g. sl-TimeToTrigger) for this sl-MeasId;

2> else:

3> add a new entry for the received sl-ReportConfig to the sl-ReportConfigList within the VarMeasConfigSL.

5.8.10.2.8 Sidelink quantity configuration

The UE shall:

1> for each received sl-QuantityConfig:

2> set the corresponding parameter(s) in sl-QuantityConfig within VarMeasConfigSL to the value of the received sl-QuantityConfig parameter(s);

1> for each sl-MeasId included in the sl-MeasIdList within VarMeasConfigSL:

2> remove the measurement reporting entry for this sl-MeasId from the VarMeasReportListSL, if included;

2> stop the periodical reporting timer and reset the associated information (e.g. sl-TimeToTrigger) for this sl-MeasId.

5.8.10.3 Performing NR sidelink measurements

5.8.10.3.1 General

A UE shall derive NR sidelink measurement results by measuring one or multiple DMRS associated per PC5-RRC connection as configured by the peer UE associated, as described in 5.8.10.3.2. For all NR sidelink measurement results the UE applies the layer 3 filtering as specified in clause 5.5.3.2, before using the measured results for evaluation of reporting criteria and measurement reporting. In this release, only NR sidelink RSRP can be configured as trigger quantity and reporting quantity.

The UE shall:

1> for each sl-MeasId included in the sl-MeasIdList within VarMeasConfigSL:

2> if the sl-MeasObject is associated to NR sidelink and the sl-RS-Type is set to dmrs:

3> derive the layer 3 filtered NR sidelink measurement result based on DMRS for the trigger quantity and each measurement quantity indicated in sl-ReportQuantity using parameters from the associated sl-MeasObject, as described in 5.8.10.3.2.

2> perform the evaluation of reporting criteria as specified in 5.8.10.4.

5.8.10.3.2 Derivation of NR sidelink measurement results

The UE may be configured by the peer UE associated to derive NR sidelink RSRP measurement results per PC5-RRC connection associated to the NR sidelink measurement objects based on parameters configured in the sl-MeasObject and in the sl-ReportConfig.

The UE shall:

1> for each NR sidelink measurement quantity to be derived based on NR sidelink DMRS:

2> derive the corresponding measurement of NR sidelink frequency indicated quantity based on DMRS as described in TS 38.215 [9] in the concerned sl-MeasObject;

2> apply layer 3 filtering as described in 5.5.3.2;

5.8.10.4 Sidelink measurement report triggering

5.8.10.4.1 General

The UE shall:

1> for each sl-MeasId included in the sl-MeasIdList within VarMeasConfigSL:

2> if the sl-ReportType is set to sl-EventTriggered and if the entry condition applicable for this event, i.e. the event corresponding with the sl-EventId of the corresponding sl-ReportConfig within VarMeasConfigSL, is fulfilled for NR sidelink frequency for all NR sidelink measurements after layer 3 filtering taken during sl-TimeToTrigger defined for this event within the VarMeasConfigSL, while the VarMeasReportListSL does not include a NR sidelink measurement reporting entry for this sl-MeasId (a first NR sidelink frequency triggers the event):

3> include a NR sidelink measurement reporting entry within the VarMeasReportListSL for this sl-MeasId;

3> set the sl-NumberOfReportsSent defined within the VarMeasReportListSL for this sl-MeasId to 0;

3> include the concerned NR sidelink frequency in the sl-FrequencyTriggeredList defined within the VarMeasReportListSL for this sl-MeasId;

3> initiate the NR sidelink measurement reporting procedure, as specified in 5.8.10.5;

2> else if the sl-ReportType is set to sl-EventTriggered and if the entry condition applicable for this event, i.e. the event corresponding with the sl-EventId of the corresponding sl-ReportConfig within VarMeasConfigSL, is fulfilled for NR sidelink frequency not included in the sl-FrequencyTriggeredList for all NR sidelink measurements after layer 3 filtering taken during sl-TimeToTrigger defined for this event within the VarMeasConfigSL (a subsequent NR sidelink frequency triggers the event):

3> set the sl-NumberOfReportsSent defined within the VarMeasReportListSL for this sl-MeasId to 0;

3> include the concerned NR sidelink frequency in the sl-FrequencyTriggeredList defined within the VarMeasReportListSL for this sl-MeasId;

3> initiate the NR sidelink measurement reporting procedure, as specified in 5.8.10.5;

2> else if the sl-ReportType is set to sl-EventTriggered and if the leaving condition applicable for this event is fulfilled for NR sidelink frequency included in the sl-FrequencyTriggeredList defined within the VarMeasReportListSL for this sl-MeasId for all NR sidelink measurements after layer 3 filtering taken during sl-TimeToTrigger defined within the VarMeasConfigSL for this event:

3> remove the concerned NR sidelink frequency in the sl-FrequencyTriggeredList defined within the VarMeasReportListSL for this sl-MeasId;

3> if sl-ReportOnLeave is set to true for the corresponding reporting configuration:

4> initiate the NR sidelink measurement reporting procedure, as specified in 5.8.10.5;

3> if the sl-FrequencyTriggeredList defined within the VarMeasReportListSL for this sl-MeasId is empty:

4> remove the NR sidelink measurement reporting entry within the VarMeasReportListSL for this sl-MeasId;

4> stop the periodical reporting timer for this sl-MeasId, if running;

2> if sl-ReportType is set to sl-Periodical and if a (first) NR sidelink measurement result is available:

3> include a NR sidelink measurement reporting entry within the VarMeasReportListSL for this sl-MeasId;

3> set the sl-NumberOfReportsSent defined within the VarMeasReportListSL for this sl-MeasId to 0;

3> initiate the NR sidelink measurement reporting procedure, as specified in 5.8.10.5, immediately after the quantity to be reported becomes available for the NR sidelink frequency:

2> upon expiry of the periodical reporting timer for this sl-MeasId:

3> initiate the NR sidelink measurement reporting procedure, as specified in 5.8.10.5.

5.8.10.4.2 Event S1 (Serving becomes better than threshold)

The UE shall:

1> consider the entering condition for this event to be satisfied when condition S1-1, as specified below, is fulfilled;

1> consider the leaving condition for this event to be satisfied when condition S1-2, as specified below, is fulfilled;

1> for this NR sidelink measurement, consider the NR sidelink frequency corresponding to the associated sl-MeasObject associated with this event.

Inequality S1-1 (Entering condition)

Ms – Hys > Thresh

Inequality S1-2 (Leaving condition)

Ms + Hys < Thresh

The variables in the formula are defined as follows:

Ms is the NR sidelink measurement result of the NR sidelink frequency, not taking into account any offsets.

Hys is the hysteresis parameter for this event (i.e. sl-Hysteresis as defined within sl-ReportConfig for this event).

Thresh is the threshold parameter for this event (i.e. s1-Threshold as defined within sl-ReportConfig for this event).

Ms is expressed in dBm in case of RSRP.

Hys is expressed in dB.

Thresh is expressed in the same unit as Ms.

5.8.10.4.3 Event S2 (Serving becomes worse than threshold)

The UE shall:

1> consider the entering condition for this event to be satisfied when condition S2-1, as specified below, is fulfilled;

1> consider the leaving condition for this event to be satisfied when condition S2-2, as specified below, is fulfilled;

1> for this NR sidelink measurement, consider the NR sidelink frequency indicated by the sl-MeasObject associated to this event.

Inequality S2-1 (Entering condition)

Ms + Hys < Thresh

Inequality S2-2 (Leaving condition)

Ms – Hys > Thresh

The variables in the formula are defined as follows:

Ms is the NR sidelink measurement result of the NR sidelink frequency, not taking into account any offsets.

Hys is the hysteresis parameter for this event (i.e. sl-Hysteresis as defined within sl-ReportConfig for this event).

Thresh is the threshold parameter for this event (i.e. s2-Threshold as defined within sl-ReportConfig for this event).

Ms is expressed in dBm in case of RSRP.

Hys is expressed in dB.

Thresh is expressed in the same unit as Ms.

5.8.10.5 Sidelink measurement reporting

5.8.10.5.1 General

Figure 5.8.10.5.1-1: NR sidelink measurement reporting

The purpose of this procedure is to transfer measurement results from the UE to the peer UE associated.

For the sl-MeasId for which the NR sidelink measurement reporting procedure was triggered, the UE shall set the sl-MeasResults within the MeasurementReportSidelink message as follows:

1> set the sl-MeasId to the measurement identity that triggered the NR sidelink measurement reporting;

1> if the sl-ReportConfig associated with the sl-MeasId that triggered the NR sidelink measurement reporting is set to sl-EventTriggered or sl-Periodical:

2> set sl-ResultDMRS within sl-MeasResult to include the NR sidelink DMRS based quantity indicated in the sl-ReportQuantity within the concerned sl-ReportConfig;

1> increment the sl-NumberOfReportsSent as defined within the VarMeasReportListSSL for this sl-MeasId by 1;

1> stop the periodical reporting timer, if running;

1> if the sl-NumberOfReportsSent as defined within the VarMeasReportListSL for this sl-MeasId is less than the sl-ReportAmount as defined within the corresponding sl-ReportConfig for this sl-MeasId:

2> start the periodical reporting timer with the value of sl-ReportInterval as defined within the corresponding sl-ReportConfig for this sl-MeasId;

1> else:

2> if the sl-ReportType is set to sl-Periodical:

3> remove the entry within the VarMeasReportListSL for this sl-MeasId;

3> remove this sl-MeasId from the sl-MeasIdList within VarMeasConfigSL;

1> submit the MeasurementReportSidelink message to lower layers for transmission, upon which the procedure ends.

5.8.11 Zone identity calculation

The UE shall determine an identity of the zone (i.e. Zone_id) in which it is located using the following formulae, if sl-ZoneConfig is configured:

x₁= Floor (x / L) Mod 64;

y₁= Floor (y / L) Mod 64;

Zone_id = y₁ * 64 + x₁.

The parameters in the formulae are defined as follows:

L is the value of sl-ZoneLength included in sl-ZoneConfig;

x is the geodesic distance in longitude between UE’s current location and geographical coordinates (0, 0) according to WGS84 model [58] and it is expressed in meters;

y is the geodesic distance in latitude between UE’s current location and geographical coordinates (0, 0) according to WGS84 model [58] and it is expressed in meters.

NOTE: How the calculated zone_id is used is specified in TS 38.321 [3].

5.8.12 DFN derivation from GNSS

When the UE selects GNSS as the synchronization reference source, the DFN, the subframe number within a frame and slot number within a frame used for NR sidelink communication/discovery are derived from the current UTC time, by the following formulae:

DFN= Floor (0.1*(Tcurrent –Tref–OffsetDFN)) mod 1024

SubframeNumber= Floor (Tcurrent –Tref–OffsetDFN) mod 10

SlotNumber= Floor ((Tcurrent –Tref–OffsetDFN)*2^μ) mod (10*2^μ)

Where:

Tcurrent is the current UTC time obtained from GNSS. This value is expressed in milliseconds;

Tref is the reference UTC time 00:00:00 on Gregorian calendar date 1 January, 1900 (midnight between Thursday, December 31, 1899 and Friday, January 1, 1900). This value is expressed in milliseconds;

OffsetDFN is the value sl-OffsetDFN if configured, otherwise it is zero. This value is expressed in milliseconds.

μ=0/1/2/3 corresponding to the 15/30/60/120 kHz of SCS for SL, respectively.

NOTE 1: In case of leap second change event, how UE obtains the scheduled time of leap second change to adjust Tcurrent correspondingly is left to UE implementation. How UE handles to avoid the sudden discontinuity of DFN is left to UE implementation.

NOTE 2: Void.

5.8.13 NR sidelink discovery

5.8.13.1 General

The purpose of this procedure is to perform NR sidelink discovery as specified in TS 23.304 [65].

5.8.13.2 NR sidelink discovery monitoring

A UE capable of NR sidelink discovery that is configured by upper layers to monitor NR sidelink discovery messages shall:

1> if the frequency used for NR sidelink discovery is included in sl-FreqInfoToAddModList in RRCReconfiguration message and sl-DiscConfig is included in RRCReconfiguration; or if the frequency used for NR sidelink discovery is included in sl-FreqInfoList included in SIB12 and sl-DiscConfigCommon is included in SIB12:

2> if the UE is configured with sl-DiscRxPool for NR sidelink discovery reception included in RRCReconfiguration message with reconfigurationWithSync (i.e. handover):

3> configure lower layers to monitor sidelink control information and the corresponding data using the resource pool indicated by sl-DiscRxPool for NR sidelink discovery reception in RRCReconfiguration;

2> else if the UE is configured with sl-RxPool for NR sidelink discovery reception included in RRCReconfiguration message with reconfigurationWithSync (i.e. handover):

3> configure lower layers to monitor sidelink control information and the corresponding data using the resource pool indicated by sl-RxPool for NR sidelink discovery reception in RRCReconfiguration;

2> else if the cell chosen for NR sidelink discovery reception provides SIB12:

3> if sl-DiscRxPool for NR sidelink is included in SIB12:

4> configure lower layers to monitor sidelink control information and the corresponding data using the resource pool indicated by sl-DiscRxPool for NR sidelink discovery reception in SIB12;

3> else if sl-RxPool for NR sidelink is included in SIB12:

4> configure lower layers to monitor sidelink control information and the corresponding data using the resource pool indicated by sl-RxPool for NR sidelink discovery reception in SIB12;

1> else:

2> if out of coverage on the concerned frequency for NR sidelink discovery:

3> if sl-DiscRxPool was preconfigured:

4> configure lower layers to monitor sidelink control information and the corresponding data using the resource pool that was preconfigured by sl-DiscRxPool for NR sidelink discovery reception in SL-PreconfigurationNR, as defined in clause 9.3;

3> else:

4> configure lower layers to monitor sidelink control information and the corresponding data using the resource pool that was preconfigured by sl-RxPool for NR sidelink discovery reception in SL-PreconfigurationNR, as defined in clause 9.3;

NOTE: If sl-DiscRxPool and sl-RxPool are both include in SIB12 or preconfigured, it is up to UE implementation whether to monitor sidelink control information and the corresponding data using the resource pool indicated by sl-RxPool for NR sidelink discovery reception.

5.8.13.3 NR sidelink discovery transmission

A UE capable of NR sidelink discovery that is configured by upper layer to transmit NR sidelink discovery message shall:

1> if the frequency used for NR sidelink discovery is included in sl-FreqInfoToAddModList in sl-ConfigDedicatedNR within RRCReconfiguration message and sl-DiscConfig is included in RRCReconfiguration; or if the frequency used for NR sidelink discovery is included in sl-FreqInfoList within SIB12 and sl-DiscConfigCommon is included in SIB12:

2> if the UE is in RRC_CONNECTED and uses the frequency included in sl-ConfigDedicatedNR within RRCReconfiguration message:

3> if the UE is acting as NR sidelink U2N Relay UE, and if the NR sidelink U2N Relay UE threshold conditions as specified in 5.8.14.2 are met based on sl-RelayUE-Config; or

3> if the UE is selecting NR sidelink U2N Relay UE / has a selected NR sidelink U2N Relay UE/ configured with measurement object associated to L2 U2N Relay UEs, and if the NR sidelink U2N Remote UE threshold conditions as specified in 5.8.15.2 are met based on sl-RemoteUE-Config; or

3> if the UE is performing NR sidelink non-relay discovery:

4> if the UE is configured with sl-ScheduledConfig:

5> if T301 is running and the cell on which the UE initiated RRC connection re-establishment provides SIB12 including sl-TxPoolExceptional for the concerned frequency; or

5> if T304 for MCG is running and the UE is configured with sl-TxPoolExceptional included in sl-ConfigDedicatedNR for the concerned frequency in RRCReconfiguration:

6> configure lower layers to perform the sidelink resource allocation mode 2 based on random selection using the resource pool indicated by sl-TxPoolExceptional as defined in TS 38.321 [3];

5> else:

6> configure lower layers to perform the sidelink resource allocation mode 1 using the resource pool indicated by sl-DiscTxPoolScheduling or sl-TxPoolScheduling for NR sidelink discovery transmission on the concerned frequency in RRCReconfiguration;

5> if T311 is running, configure the lower layers to release the resources indicated by rrc-ConfiguredSidelinkGrant (if any);

4> if the UE is configured with sl-UE-SelectedConfig:

5> if the sl-DiscTxPoolSelected for NR sidelink discovery transmission on the concerned frequency is included in the sl-ConfigDedicatedNR within RRCReconfiguration, and if a result of full/partial sensing, if selected and is allowed by sl-AllowedResourceSelectionConfig, on the resources configured in sl-DiscTxPoolSelected for NR sidelink discovery transmission on the concerned frequency included in sl-ConfigDedicatedNR within RRCReconfiguration is not available in accordance with TS 38.214 [19]; or

5> if the sl-DiscTxPoolSelected for NR sidelink discovery transmission on the concerned frequency is not included in the sl-ConfigDedicatedNR within RRCReconfiguration, and a result of full/partial sensing, if selected and is allowed by sl-AllowedResourceSelectionConfig, on the resources configured in sl-TxPoolSelectedNormal for NR sidelink discovery transmission on the concerned frequency included in sl-ConfigDedicatedNR within RRCReconfiguration is not available in accordance with TS 38.214 [19];

6> if sl-TxPoolExceptional for the concerned frequency is included in RRCReconfiguration; or

6> if the PCell provides SIB12 including sl-TxPoolExceptional in sl-FreqInfoList for the concerned frequency:

7> configure lower layers to perform the sidelink resource allocation mode 2 based on random selection using the resource pool indicated by sl-TxPoolExceptional as defined in TS 38.321 [3];

5> else, if the sl-DiscTxPoolSelected for NR sidelink discovery transmission on the concerned frequency is included in the sl-ConfigDedicatedNR within RRCReconfiguration:

5> else, if the sl-TxPoolSelectedNormal for NR sidelink discovery transmission on the concerned frequency is included in the sl-ConfigDedicatedNR within RRCReconfiguration:

6> configure lower layers to perform the sidelink resource allocation mode 2 based on resource selection operation according to sl-AllowedResourceSelectionConfig (as defined in TS 38.321 [3] and TS 38.214 [19]) using the pools of resources indicated by sl-TxPoolSelectedNormal for NR sidelink discovery transmission on the concerned frequency in RRCReconfiguration;

2> else if the cell chosen for NR sidelink discovery transmission provides SIB12:

3> if the UE is acting as NR sidelink U2N Relay UE and if the NR sidelink U2N Relay UE threshold conditions as specified in 5.8.14.2 are met based on sl-RelayUE-ConfigCommon in SIB12; or

3> if the UE is selecting NR sidelink U2N Relay UE / has a selected NR sidelink U2N Relay UE and if the NR sidelink U2N Remote UE threshold conditions as specified in 5.8.15.2 are met based on sl-RemoteUE-ConfigCommon in SIB12; or

3> if the UE is performing NR sidelink non-relay discovery:

4> if SIB12 includes sl-DiscTxPoolSelected for NR sidelink discovery transmission on the concerned frequency, and a result of full/partial sensing, if selected and is allowed by sl-AllowedResourceSelectionConfig, on the resources configured in the sl-DiscTxPoolSelected for NR sidelink discovery transmission is available in accordance with TS 38.214 [19] or random selection, if allowed by sl-AllowedResourceSelectionConfig, is selected:

5> configure lower layers to perform the sidelink resource allocation mode 2 based on resource selection operation according to sl-AllowedResourceSelectionConfig using the pools of resources indicated by sl-DiscTxPoolSelected for NR sidelink discovery transmission on the concerned frequency in SIB12 as defined in TS 38.321 [3];

4> else if SIB12 includes sl-TxPoolSelectedNormal for NR sidelink discovery transmission on the concerned frequency, and a result of full/partial sensing, if selected and is allowed by sl-AllowedResourceSelectionConfig, on the resources configured in the sl-TxPoolSelectedNormal for NR sidelink discovery transmission is available in accordance with TS 38.214 [19] or random selection, if allowed by sl-AllowedResourceSelectionConfig, is selected:

5> configure lower layers to perform the sidelink resource allocation mode 2 based on resource selection operation according to sl-AllowedResourceSelectionConfig using the pools of resources indicated by sl-TxPoolSelectedNormal for NR sidelink discovery transmission on the concerned frequency in SIB12 as defined in TS 38.321 [3];

4> else if SIB12 includes sl-TxPoolExceptional for the concerned frequency:

5> from the moment the UE initiates RRC connection establishment or RRC connection resume, until receiving an RRCReconfiguration including sl-ConfigDedicatedNR, or receiving an RRCRelease or an RRCReject; or

5> if a result of full/partial sensing, if selected and is allowed by sl-AllowedResourceSelectionConfig, on the resources configured in sl-DiscTxPoolSelected for NR sidelink discovery transmission on the concerned frequency in SIB12 is not available in accordance with TS 38.214 [19]; or

5> if sl-DiscTxPoolSelected for NR sidelink discovery transmission on the concerned frequency is not included in SIB12 and if a result of full/partial sensing, if selected and is allowed by sl-AllowedResourceSelectionConfig, on the resources configured in sl-TxPoolSelectedNormal for NR sidelink discovery transmission on the concerned frequency in SIB12 is not available in accordance with TS 38.214 [19]:

6> configure lower layers to perform the sidelink resource allocation mode 2 based on random selection (as defined in TS 38.321 [3]) using one of the pools of resources indicated by sl-TxPoolExceptional for the concerned frequency;

1> else if out of coverage on the concerned frequency for NR sidelink discovery:

2> if the UE is acting as L3 U2N Relay UE and if the NR sidelink U2N Relay UE threshold conditions as specified in 5.8.14.2 are met based on sl-RelayUE-ConfigCommon in SidelinkPreconfigNR; or

2> if the UE is selecting NR sidelink U2N Relay UE / has a selected NR sidelink U2N Relay UE and if the NR sidelink U2N Remote UE threshold conditions as specified in 5.8.15.2 are met based on sl-RemoteUE-ConfigCommon in SidelinkPreconfigNR; or

2> if the UE is performing NR sidelink non-relay discovery:

3> configure lower layers to perform the sidelink resource allocation mode 2 based on resource selection operation according to sl-AllowedResourceSelectionConfig (as defined in TS 38.321 [3] and TS 38.213 [13]) using the pools of resources indicated in sl-DiscTxPoolSelected or sl-TxPoolSelectedNormal for NR sidelink discovery transmission on the concerned frequency in SidelinkPreconfigNR.

NOTE: It is up to UE implementation to determine, in accordance with TS 38.321[3], which resource pool to use if multiple resource pools are configured, and which resource allocation scheme is used in the AS based on UE capability (for a UE in RRC_IDLE/RRC_INACTIVE) and the allowed resource schemes sl-allowedResourceSelectionConfig in the resource pool configuration.

5.8.14 NR sidelink U2N Relay UE operation

5.8.14.1 General

This procedure is used by a UE supporting NR sidelink U2N Relay UE operation configured by upper layers to receive/ transmit NR sidelink discovery messages to evaluate AS layer conditions.

5.8.14.2 NR sidelink U2N Relay UE threshold conditions

A UE capable of NR sidelink U2N Relay UE operation shall:

1> if the threshold conditions specified in this clause were previously not met:

2> if threshHighRelay is not configured; or the RSRP measurement of the PCell, or the cell on which the UE camps, is below threshHighRelay by hystMaxRelay if configured; and

2> if threshLowRelay is not configured; or the RSRP measurement of the PCell, or the cell on which the UE camps, is above threshLowRelay by hystMinRelay if configured:

3> consider the threshold conditions to be met (entry);

1> else:

2> if the RSRP measurement of the PCell, or the cell on which the UE camps, is above threshHighRelay if configured; or

2> if the RSRP measurement of the PCell, or the cell on which the UE camps, is below threshLowRelay if configured;

3> consider the threshold conditions not to be met (leave);

5.8.15 NR sidelink U2N Remote UE operation

5.8.15.1 General

This procedure is used by a UE supporting NR sidelink U2N Remote UE operation configured by upper layers to receive/ transmit NR sidelink discovery message to evaluate AS layer conditions.

5.8.15.2 NR Sidelink U2N Remote UE threshold conditions

A UE capable of NR sidelink U2N Remote UE operation shall:

1> if the threshold conditions specified in this clause were previously not met:

2> if threshHighRemote is not configured; or the RSRP measurement of the PCell, or the cell on which the UE camps, is below threshHighRemote by hystMaxRemote if configured, or

2> if the UE has no serving cell:

3> consider the threshold conditions to be met (entry);

1> else:

2> if the RSRP measurement of the PCell, or the cell on which the UE camps, is above threshHighRemote if configured:

3> consider the threshold conditions not to be met (leave);

The L2 U2N Remote UE considers the cell indicated by sl-ServingCellInfo in the SL-AccessInfo-L2U2N-r17 received from the connected L2 U2N Relay UE as the camping cell.

5.8.15.3 Selection and reselection of NR sidelink U2N Relay UE

A UE capable of NR sidelink U2N Remote UE operation that is configured by upper layers to search for a NR sidelink U2N Relay UE shall:

1> if the UE has no serving cell; or

1> if the RSRP measurement of the cell on which the UE camps (for L2 and L3 U2N Remote UE in RRC_IDLE or RRC_INACTIVE)/ the PCell (for L3 U2N Remote UE in RRC_CONNECTED) is below threshHighRemote within sl-remoteUE-Config:

2> if the UE does not have a selected NR sidelink U2N Relay UE; or

2> if the UE has a selected NR sidelink U2N Relay UE, and SL-RSRP of the currently selected NR sidelink U2N Relay UE is available and is below sl-RSRP-Thresh; or

2> if the UE has a selected NR sidelink U2N Relay UE, and SL-RSRP of the currently selected NR sidelink U2N Relay UE is not available, and SD-RSRP of the currently selected U2N Relay UE is below sl-RSRP-Thresh; or

NOTE 1: U2N Remote UE uses SL-RSRP measurements for relay reselection trigger evaluation when there is data transmission from U2N Relay UE to U2N Remote UE, and it is left to UE implementation whether to use SL-RSRP or SD-RSRP for relay reselection trigger evaluation in case of no data transmission from U2N Relay UE to U2N Remote UE. If SD-RSRP is used, the discovery procedure will be performed between the U2N Remote UE and the selected U2N Relay UE.

2> if the UE has a selected NR sidelink U2N Relay UE, and upper layers indicate not to use the currently selected NR sidelink U2N Relay UE; or

2> if the UE has a selected NR sidelink U2N Relay UE, and upper layers request the release of the PC5-RRC connection or when AS layer releases the PC5-RRC connection with the currently selected U2N Relay UE as specified in clause 5.8.9.5; or

2> if the UE has a selected NR sidelink U2N Relay UE, and sidelink radio link failure is detected on the PC5-RRC connection with the current U2N Relay UE as specified in clause 5.8.9.3:

3> perform NR sidelink discovery procedure as specified in clause 5.8.13 in order to search for candidate NR sidelink U2N Relay UEs;

4> when evaluating the one or more detected NR sidelink U2N Relay UEs, apply layer 3 filtering as specified in 5.5.3.2 across measurements that concern the same U2N Relay UE ID and using the sl-FilterCoefficientRSRP in SystemInformationBlockType12 (if in RRC_IDLE/INACTIVE), the sl-FilterCoefficientRSRP in sl-ConfigDedicatedNR (if in RRC_CONNECTED) or the preconfigured sl-FilterCoefficientRSRP as defined in 9.3 (out of coverage), before using the SD-RSRP measurement results;

4> consider a candidate NR sidelink U2N Relay UE for which SD-RSRP exceeds sl-RSRP-Thresh by sl-HystMin has met the AS criteria;

4> consider one of the available suitable NR sidelink U2N relay UE(s) can be selected;

NOTE 2: A candidate NR sidelink U2N Relay UE which meets all AS layer criteria defined in 5.8.15.3 and higher layer criteria defined in TS 23.304 [65] can be regarded as suitable NR sidelink U2N Relay UE by the NR sidelink U2N Remote UE. If multiple suitable NR sidelink U2N Relay UEs are available, it is up to Remote UE implementation to choose one NR sidelink U2N Relay UE. The details of the interaction with upper layers are up to UE implementation.

NOTE 3: For L2 U2N Remote UEs in RRC_IDLE/INACTIVE and L3 U2N Remote UEs, the cell (re)selection procedure and relay (re)selection procedure run independently. If both suitable cells and suitable NR sidelink U2N Relay UEs are available, it is up to NR sidelink U2N Remote UE implementation to select either a cell or a NR sidelink U2N Relay UE. Furthermore, L3 U2N Remote UE’s selection on both cell and NR sidelink U2N Relay UE is also based on UE implementation.

3> if the UE did not detect any candidate NR sidelink U2N Relay UE for which SD-RSRP exceeds sl-RSRP-Thresh by sl-HystMin:

4> consider no NR sidelink U2N Relay UE to be selected.