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). 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 for V2X service or TS 24.554 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, 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, 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 or TS 24.554, UE re-establishes the PDCP entity of the SL-SRB1, SL-SRB2, SL-SRB3 and SL-DRBs on the corresponding PC5-RRC connection.
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 or TS 24.554 or the UE is out of coverage on the frequency used for NR sidelink communication/discovery operation as defined in TS 38.304 and TS 36.304; or
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; 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 and TS 36.304; or
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, when the UE is configured with sl-ScheduledConfig,
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.
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 profile(s), 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 configured with sl-ScheduledConfig and is performing sidelink unicast transmission 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 configured with sl-ScheduledConfig and 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(s) associated with its interested service(s) that sidelink DRX is applied, for NR sidelink groupcast or broadcast reception.
Upon initiating this procedure, the UE shall:
if since the last time the UE transmitted a SidelinkUEInformationNR message the UE connected to a PCell not providing SIB12 including sl-ConfigCommonNR; or
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:
initiate transmission of the SidelinkUEInformationNR message to indicate the NR sidelink communication reception frequency of interest in accordance with clause 5.8.3.3;
initiate transmission of the SidelinkUEInformationNR message to indicate it is no longer interested in NR sidelink communication reception in accordance with clause 5.8.3.3;
if since the last time the UE transmitted a SidelinkUEInformationNR message the UE connected to a PCell not providing SIB12 including sl-ConfigCommonNR; or
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:
initiate transmission of the SidelinkUEInformationNR message to indicate the NR sidelink communication transmission resources required by the UE in accordance with clause 5.8.3.3;
initiate transmission of the SidelinkUEInformationNR message to indicate it no longer requires NR sidelink communication transmission resources in accordance with clause 5.8.3.3.
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:
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-NonRelayDiscovery; or
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 non-relay discovery messages on has changed since the last transmission of the SidelinkUEInformationNR message:
initiate transmission of the SidelinkUEInformationNR message to indicate the NR sidelink discovery reception frequency of interest in accordance with clause 5.8.3.3;
initiate transmission of the SidelinkUEInformationNR message to indicate it is no longer interested in NR sidelink non-relay discovery messages reception in accordance with 5.8.3.3;
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:
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
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:
if the UE is selecting a U2N Relay UE / has a selected U2N Relay UE / configured with measurement object associated to L2 U2N Relay UEs, and if SIB12 includes sl-RemoteUE-ConfigCommon:
initiate transmission of the SidelinkUEInformationNR message to indicate the NR relay sidelink discovery reception frequency of interest in accordance with clause 5.8.3.3;
initiate transmission of the SidelinkUEInformationNR message to indicate it is no longer interested in NR relay sidelink discovery messages reception in accordance with clause 5.8.3.3;
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:
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-NonRelayDiscovery; or
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:
initiate transmission of the SidelinkUEInformationNR message to indicate the NR sidelink non-relay discovery messages resources required by the UE in accordance with clause 5.8.3.3;
initiate transmission of the SidelinkUEInformationNR message to indicate it no longer requires NR sidelink non-relay discovery messages resources in accordance with clause 5.8.3.3;
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:
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
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:
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 clause 5.8.14.2 are met; or
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 clause 5.8.15.2 are met:
initiate transmission of the SidelinkUEInformationNR message to indicate the NR sidelink relay discovery messages resources required by the UE in accordance with clause 5.8.3.3;
initiate transmission of the SidelinkUEInformationNR message to indicate it no longer requires NR sidelink relay discovery messages resources in accordance with clause 5.8.3.3;
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:
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
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; or
if configured by upper layers not to transmit either NR sidelink L2 U2N relay communication or NR sidelink L3 U2N relay communication, and if the last transmission of the SidelinkUEInformationNR message includes both sl-TxResourceReqL2U2N-Relay and sl-TxResourceReqL3U2N-Relay:
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 clause 5.8.14.2 are met; or
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 clause 5.8.15.2 are met:
initiate transmission of the SidelinkUEInformationNR message to indicate the NR sidelink relay communication transmission resources required by the UE in accordance with clause 5.8.3.3;
initiate transmission of the SidelinkUEInformationNR message to indicate it no longer requires NR sidelink relay communication transmission resources in accordance with clause 5.8.3.3;
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:
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:
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
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:
initiate transmission of the SidelinkUEInformationNR message to indicate the sidelink DRX configuration is no longer used in accordance with clause 5.8.3.3;
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
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:
initiate transmission of the SidelinkUEInformationNR message to report the Destination Layer-2 ID and QoS profile(s) associated with the service(s) in accordance with clause 5.8.3.3;
initiate transmission of the SidelinkUEInformationNR message to indicate it is no longer interested in the service that sidelink DRX is applied in accordance with clause 5.8.3.3;
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:
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:
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
if the last transmission of the SidelinkUEInformationNR message did not include sl-DRX-InfoFromRxList or sl-FailureList; or if the information carried by sl-DRX-InfoFromRxList or sl-FailureList has changed since the last transmission of the SidelinkUEInformationNR message:
initiate transmission of the SidelinkUEInformationNR message to report the sidelink DRX assistance information or the sidelink DRX configuration reject information in accordance with clause 5.8.3.3;
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
if the last transmission of the SidelinkUEInformationNR message did not include sl-DRX-Indication; or if the information carried by sl-DRX-Indication has changed since the last transmission of the SidelinkUEInformationNR message:
initiate transmission of the SidelinkUEInformationNR message to report sidelink DRX on/off indication for the corresponding destination in accordance with clause 5.8.3.3;
if the UE initiates the procedure 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
if the UE initiates the procedure to report to the network the sidelink DRX assistance information or the sidelink DRX configuration reject information for NR sidelink unicast transmission; or
if the UE initiates the procedure to report to the network the Destination Layer-2 ID and QoS profile(s) associated with its interested service(s) that sidelink DRX is applied for NR sidelink groupcast or broadcast reception; or
if the UE initiates the procedure 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
if the UE initiates the procedure 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):
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:
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;
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;
set sl-TypeTxSyncList to the current synchronization reference type used on the associated sl-InterestedFreqList for NR sidelink communication transmission.
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;
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:
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:
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:
set sl-TypeTxSyncListDisc to the current synchronization reference type used on the associated sl-InterestedFreqList for NR sidelink discovery messages transmission;
set sl-DiscoveryType to the current discovery type of the associated destination identity configured by the upper layer for NR sidelink discovery messages transmission;
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:
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:
set sl-TypeTxSyncListL2U2N to the current synchronization reference type used on the associated sl-InterestedFreqListL2U2N for NR sidelink L2 U2N relay communication transmission;
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:
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:
set sl-TypeTxSyncListL2U2N to the current synchronization reference type used on the associated sl-InterestedFreqListL2U2N for NR sidelink L2 U2N relay communication transmission;
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:
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;
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;
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;
set sl-TypeTxSyncList to the current synchronization reference type used on the associated sl-InterestedFreqList for NR sidelink L3 U2N relay communication transmission.
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;
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;
include sl-TxResourceReqList and/or sl-TxResourceReqListCommRelay and set its fields (if needed) as follows for each destination for which it reports to network:
set sl-DRX-InfoFromRxList to include the sidelink DRX assistance information of the associated destination, if any, received from the associated peer UE;
submit the SidelinkUEInformationNR to lower layers via SRB1, embedded in E-UTRA RRC message ULInformationTransferIRAT as specified in clause 5.6.28 of TS 36.331;
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:
if in coverage on the frequency used for NR sidelink communication/discovery, as defined in TS 38.304; and has selected GNSS or the cell as synchronization reference as defined in clause 5.8.6.3; or
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 clause 5.8.6.3:
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 clause 5.8.6.3, for NR sidelink communication/discovery transmission is below the value of syncTxThreshIC:
transmit sidelink SSB on the frequency used for NR sidelink communication/discovery in accordance with clause 5.8.5.3 and TS 38.211, including the transmission of SLSS as specified in clause 5.8.5.3 and transmission of MasterInformationBlockSidelink as specified in clause 5.8.9.4.3;
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
transmit sidelink SSB on the frequency used for NR sidelink communication/discovery in accordance with TS 38.211 , including the transmission of SLSS as specified in clause 5.8.5.3 and transmission of MasterInformationBlockSidelink as specified in clause 5.8.9.4.3;
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; or
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:
use sl-SSB-TimeAllocation1 included in the entry of configured sl-SyncConfigList corresponding to the concerned frequency, that includes txParameters and gnss-Sync;
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;
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:
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;
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:
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;
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;
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;
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;
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.
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.
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:
else 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 for the concerned frequency is not configured or is set to gnss, and GNSS is reliable in accordance with TS 38.101-1 and TS 38.133:
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 and TS 38.133:
when evaluating the one or more detected SLSSIDs, apply layer 3 filtering as specified in clause 5.5.3.2 using the preconfigured sl-filterCoefficient, before using the PSBCH-RSRP measurement results;
if the PSBCH-RSRP of the strongest candidate SyncRef UE exceeds the minimum requirement TS 38.133 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
if the PSBCH-RSRP of the candidate SyncRef UE exceeds the minimum requirement TS 38.133 by sl-SyncRefMinHyst and the candidate SyncRef UE belongs to a higher priority group than the current SyncRef UE; or
if the PSBCH-RSRP of the candidate SyncRef UE exceeds the minimum requirement defined in TS 38.133 by sl-SyncRefMinHyst and the candidate SyncRef UE belongs to a higher priority group than GNSS; or
if the PSBCH-RSRP of the candidate SyncRef UE exceeds the minimum requirement defined in TS 38.133 by sl-SyncRefMinHyst and the candidate SyncRef UE belongs to a higher priority group than gNB/eNB; or
if the UE detects one or more SLSSIDs for which the PSBCH-RSRP exceeds the minimum requirement defined in TS 38.133 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 and TS 38.133, or if the UE detects a cell, select a synchronization reference according to the following priority group order:
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);
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);
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);
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);
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);
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);
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 PSBCHS-RSRP result (priority group 2);
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 2);
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 4);
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 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);
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 PSBCHS-RSRP result (priority group 2);
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 2);
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:
if the frequency used for NR sidelink communication is included in sl-FreqInfoToAddModList in RRCReconfiguration message or sl-FreqInfoList included in SIB12:
configure lower layers to monitor sidelink control information and the corresponding data using the pool(s) of resources indicated by sl-RxPool in SIB12;
configure lower layers to monitor sidelink control information and the corresponding data using the pool(s) of resources that were preconfigured by sl-RxPool in SL-PreconfigurationNR, as defined in clause 9.3.
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:
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:
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
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
if T304 for MCG is running and the UE is configured with sl-TxPoolExceptional included in sl-ConfigDedicatedNR for the concerned frequency in RRCReconfiguration:
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;
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;
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;
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 and TS 38.214) using the pools of resources indicated by sl-TxPoolSelectedNormal for the concerned frequency;
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 or random selection, if allowed by sl-AllowedResourceSelectionConfig, is selected:
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;
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
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:
configure lower layers to perform the sidelink resource allocation mode 2 based on random selection (as defined in TS 38.321) using the pool of resources indicated by sl-TxPoolExceptional for the concerned frequency;
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 and TS 38.214) using the pools of resources indicated by sl-TxPoolSelectedNormal in SidelinkPreconfigNR for the concerned frequency.
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.