Content for TS 38.321 Word version: 18.3.0

1… 4… 5… 5.1.2… 5.2… 5.4… 5.4.4… 5.5… 5.9… 5.18… 5.18.18… 5.19… 5.22… 5.22.1.4… 5.22.2… 5.23… 6… 6.1.3… 6.1.3.8… 6.1.3.11… 6.1.3.17… 6.1.3.21… 6.1.3.26… 6.1.3.31… 6.1.3.37… 6.1.3.42… 6.1.3.49… 6.1.3.53… 6.1.3.59… 6.1.3.64… 6.1.3.70… 6.1.3.74… 6.1.3.79… 6.1.4… 6.2… 7…

5.22.1.4 Multiplexing and assembly 5.22.1.4.0 General 5.22.1.4.1 Logical channel prioritization 5.22.1.4.1.1 General 5.22.1.4.1.2 Selection of logical channels and SL-PRS 5.22.1.4.1.3 Allocation of sidelink resources 5.22.1.4.2 Multiplexing of MAC Control Elements and MAC SDUs 5.22.1.5 Scheduling Request 5.22.1.6 Buffer Status Reporting 5.22.1.7 CSI Reporting 5.22.1.9 IUC-Request transmission 5.22.1.10 IUC-Information Reporting 5.22.1.10.1 General 5.22.1.10.2 Reception of IUC-Information Reporting 5.22.1.11 TX carrier (re-)selection 5.22.1.12 SL-PRS Resource Request
...

5.22.1.4 Multiplexing and assembly p. 178

5.22.1.4.0 General p. 178

For PDU(s) associated with one SCI, MAC shall consider only logical channels with the same Source Layer-2 ID-Destination Layer-2 ID pair for one of unicast, groupcast and broadcast which is associated with the pair. Multiple transmissions for different Sidelink processes are allowed to be independently performed in different PSSCH durations.

5.22.1.4.1 Logical channel prioritization p. 178

5.22.1.4.1.1 General p. 178

The sidelink Logical Channel Prioritization procedure is applied whenever a new transmission is performed.

RRC controls the scheduling of sidelink data by signalling for each logical channel:

sl-Priority where an increasing priority value indicates a lower priority level;
sl-PrioritisedBitRate which sets the sidelink Prioritized Bit Rate (sPBR);
sl-BucketSizeDuration which sets the sidelink Bucket Size Duration (sBSD).

RRC additionally controls the LCP procedure by configuring mapping restrictions for each logical channel:

sl-configuredGrantType1Allowed which sets whether a configured grant Type 1 can be used for sidelink transmission;
sl-AllowedCG-List which sets the allowed configured grant(s) for sidelink transmission;
sl-HARQ-FeedbackEnabled which sets whether the logical channel is allowed to be multiplexed with logical channel(s) with sl-HARQ-FeedbackEnabled set to enabled or disabled.

The following UE variable is used for the Logical channel prioritization procedure:

SBj which is maintained for each logical channel j.

The MAC entity shall initialize SBj of the logical channel to zero when the logical channel is established.

For each logical channel j, the MAC entity shall:

1 >

increment SBj by the product sPBR × T before every instance of the LCP procedure, where T is the time elapsed since SBj was last incremented;

1 >

if the value of SBj is greater than the sidelink bucket size (i.e. sPBR × sBSD):

2 >

set SBj to the sidelink bucket size.

5.22.1.4.1.2 Selection of logical channels and SL-PRS p. 179

The MAC entity shall for each SCI corresponding to a new transmission:

1 >

if sl-BWP-DiscPoolConfig, sl-BWP-DiscPoolConfigCommon, sl-BWP-PoolConfigA2X or sl-BWP-PoolConfigCommonA2X is configured according to TS 38.331; and

1 >

if COT sharing information has not been received from lower layers as specified in TS 37.213; and

1 >

if the new transmission is not associated to a sidelink grant on SL-PRS Dedicated resource pool:

2 >

if the new transmission is associated to a sidelink grant in sl-DiscTxPoolSelected or sl-DiscTxPoolScheduling configured in sl-BWP-DiscPoolConfig or sl-BWP-DiscPoolConfigCommon:

3 >

select a Destination associated with NR sidelink discovery as specified in TS 23.304, that is in the SL Active time for the SL transmission occasion if SL DRX is applied for the destination, and among the logical channels that satisfy all the following conditions for the SL grant associated to the SCI:

4 >

SL data for NR sidelink discovery is available for transmission; and

4 >

SBj > 0, in case there is any logical channel having SBj > 0; and

4 >

sl-configuredGrantType1Allowed, if configured, is set to true in case the SL grant is a Configured Grant Type 1; and

4 >

sl-AllowedCG-List, if configured, includes the configured grant index associated to the SL grant.

2 >

else if the new transmission is associated to a sidelink grant in sl-TxPoolSelectedNormal configured in sl-BWP-PoolConfigA2X or sl-BWP-PoolConfigCommonA2X:

3 >

select a Destination associated to one of unicast, groupcast and broadcast (excluding the Destination(s) associated with NR sidelink discovery as specified in TS 23.304 or A2X communication), that is in the SL Active time for the SL transmission occasion if SL DRX is applied for the destination, and having at least one of the MAC CE and the logical channel and pending SL-PRS transmission(s) with the highest priority, among the logical channels that satisfy all the following conditions and MAC CE(s), if any, and SL-PRS(s), if any for the SL grant associated to the SCI:

4 >

SL data for A2X communication is available for transmission; and

4 >

SBj > 0, in case there is any logical channel having SBj > 0.

2 >

else:

3 >

select a Destination associated to one of unicast, groupcast and broadcast (excluding the Destination(s) associated with NR sidelink discovery as specified in TS 23.304), that is in the SL Active time for the SL transmission occasion if SL DRX is applied for the destination, and having at least one of the MAC CE and the logical channel and pending SL-PRS transmission(s) with the highest priority, among the logical channels that satisfy all the following conditions and MAC CE(s), if any, and SL-PRS(s), if any for the SL grant associated to the SCI:

4 >

SL data for NR sidelink communication is available for transmission; and

4 >

SBj > 0, in case there is any logical channel having SBj > 0; and

4 >

sl-configuredGrantType1Allowed, if configured, is set to true in case the SL grant is a Configured Grant Type 1; and

4 >

sl-AllowedCG-List, if configured, includes the configured grant index associated to the SL grant; and

4 >

sl-HARQ-FeedbackEnabled is set to disabled, if PSFCH is not configured for the SL grant associated to the SCI.

1 >

else:

2 >

if COT sharing information has been received from lower layers as specified in TS 37.213:

3 >

if resources used for initial transmission for the SL grant associated to the SCI are within the COT duration and MAC entity decides to use shared COT with type-2 LBT:

4 >

select a Destination associated to one of unicast, groupcast and broadcast that satisfy the following destination condition and CAPC condition, and having at least one of the MAC CE and the logical channel with the highest priority, among the logical channels that satisfy all the following conditions and the MAC CE(s) that satisfies CAPC and destination requirement, if any, for the SL grant associated to the SCI:

5 >

if a Source Layer-1 ID and a Destination Layer-1 ID contained in the COT initiator's SCI or COT sharing information match to the 8 LSB of the corresponding Destination Layer-2 ID and the 16 LSB of a Source Layer-2 IDs relating to the transmission from the responding UE and the cast type indicator in the SCI is set to unicast; or if a Destination Layer-1 ID contained in the COT initiator's SCI or COT sharing information matches to the 16 LSB of a Destination Layer-2 ID relating to the transmission from the responding UE and the cast type indicator in the SCI is set to groupcast or broadcast; and

5 >

if a CAPC value of the SL data has an equal or smaller CAPC value than a CAPC value indicated in the COT sharing information; and

5 >

SL data is available for transmission; and

5 >

SBj > 0, in case there is any logical channel having SBj > 0; and

5 >

sl-configuredGrantType1Allowed, if configured, is set to true in case the SL grant is a Configured Grant Type 1; and

5 >

sl-AllowedCG-List, if configured, includes the configured grant index associated to the SL grant; and

5 >

sl-HARQ-FeedbackEnabled is set to disabled, if PSFCH is not configured for the SL grant associated to the SCI.

2 >

else if sl-BWP-DiscPoolConfig or sl-BWP-DiscPoolConfigCommon is not configured according to TS 38.331; and

2 >

if the new transmission is not associated to a sidelink grant on SL-PRS Dedicated resource pool:

3 >

select a Destination associated to one of unicast, groupcast and broadcast, that is in the SL Active time for the SL transmission occasion if SL DRX is applied for the destination, and having at least one of the MAC CE and the logical channel and pending SL-PRS transmission(s) with the highest priority, among the logical channels that satisfy all the following conditions and MAC CE(s), if any, and SL-PRS(s), if any, for the SL grant associated to the SCI:

4 >

SL data is available for transmission; and

4 >

SBj > 0, in case there is any logical channel having SBj > 0; and

4 >

sl-configuredGrantType1Allowed, if configured, is set to true in case the SL grant is a Configured Grant Type 1; and

4 >

sl-AllowedCG-List, if configured, includes the configured grant index associated to the SL grant; and

4 >

sl-HARQ-FeedbackEnabled is set to disabled, if PSFCH is not configured for the SL grant associated to the SCI; and

4 >

allowed on the carrier where the SCI is transmitted, if the carrier is configured by upper layers according to TS 38.331 and TS 23.287, if multiple carrier frequencies are configured and if the MAC entity has been configured with Sidelink resource allocation mode 2; and

4 >

having a priority whose associated sl-threshCBR-FreqReselection is no lower than the CBR of the carrier when the carrier is (re-)selected in accordance with clause 5.22.1.11, if multiple carrier frequencies are configured and if the MAC entity has been configured with Sidelink resource allocation mode 2.

1 >

else: (i.e., the sidelink grant is associated with SL-PRS Dedicated resource pool)

2 >

select a Destination corresponding to the cast type of the SL grant and having pending SL-PRS transmission(s) with the highest priority for the SL grant associated to the SCI.

1 >

select the logical channels satisfying all the following conditions among the logical channels belonging to the selected Destination when the new transmission is not associated to a sidelink grant on Dedicated SL-PRS resource pool:

2 >

SL data is available for transmission; and

2 >

sl-configuredGrantType1Allowed, if configured, is set to true in case the SL grant is a Configured Grant Type 1; and.

2 >

sl-AllowedCG-List, if configured, includes the configured grant index associated to the SL grant; and

2 >

having a priority whose associated sl-threshCBR-FreqReselection is no lower than the CBR of the carrier when the carrier is (re-)selected in accordance with clause 5.22.1.11, if multiple carrier frequencies are configured if the MAC entity has been configured with Sidelink resource allocation mode 2; and

2 >

CAPC value of the SL data has an equal or smaller CAPC value than a CAPC value indicated in the COT sharing information if MAC decides to use the shared COT; and

2 >

sl-HARQ-FeedbackEnabled is set to the value that satisfies the following conditions:

3 >

if PSFCH is configured for the sidelink grant associated to the SCI and the UE is capable of PSFCH reception:

4 >

sl-HARQ-FeedbackEnabled is set to enabled, if sl-HARQ-FeedbackEnabled is set to enabled for the highest priority logical channel satisfying the above conditions; or

4 >

sl-HARQ-FeedbackEnabled is set to disabled, if sl-HARQ-FeedbackEnabled is set to disabled for the highest priority logical channel satisfying the above conditions.

3 >

else:

4 >

sl-HARQ-FeedbackEnabled is set to disabled.

5.22.1.4.1.3 Allocation of sidelink resources p. 182

The MAC entity shall for each sidelink grant associated with Shared SL-PRS resource pool:

1 >

if there is SL-PRS pending for transmission for the selected destination:

2 >

erive Transport Block Size for a new transmission for SL-SCH assuming SL-PRS can be transmitted in the sidelink grant according to clause 8.1.3.2 in TS 38.214;

2 >

if all the SL-SCH data within logical channel with higher priority than that of the SL-PRS can be allocated with resources:

3 >

determine that the pending SL-PRS can be transmitted in the sidelink grant.

2 >

else:

3 >

determine that the pending SL-PRRS cannot be transmitted in the sidelink grant;

3 >

derive the Transport Block Size for a new transmission for SL-SCH with no SL-PRS according to clause 8.1.3.2 in TS 38.214.

The MAC entity shall for each SCI corresponding to a new transmission for SL-SCH:

1 >

allocate resources to the logical channels as follows:

2 >

logical channels selected in clause 5.22.1.4.1.2 for the SL grant with SBj > 0 are allocated resources in a decreasing priority order. If the sPBR of a logical channel is set to infinity, the MAC entity shall allocate resources for all the data that is available for transmission on the logical channel before meeting the sPBR of the lower priority logical channel(s);

2 >

decrement SBj by the total size of MAC SDUs served to logical channel j above;

2 >

if any resources remain, all the logical channels selected in clause 5.22.1.4.1.2 are served in a strict decreasing priority order (regardless of the value of SBj) until either the data for that logical channel or the SL grant is exhausted, whichever comes first. Logical channels configured with equal priority should be served equally.

The UE shall also follow the rules below during the SL scheduling procedures above:

the UE should not segment an RLC SDU (or partially transmitted SDU or retransmitted RLC PDU) if the whole SDU (or partially transmitted SDU or retransmitted RLC PDU) fits into the remaining resources of the associated MAC entity;
if the UE segments an RLC SDU from the logical channel, it shall maximize the size of the segment to fill the grant of the associated MAC entity as much as possible;
the UE should maximise the transmission of data;
if the MAC entity is given a sidelink grant size that is equal to or larger than 12 bytes while having data available and allowed (according to clause 5.22.1.4.1) for transmission, the MAC entity shall not transmit only padding;
A logical channel configured with sl-HARQ-FeedbackEnabled set to enabled and a logical channel configured with sl-HARQ-FeedbackEnabled set to disabled cannot be multiplexed into the same MAC PDU.

The MAC entity shall not generate a MAC PDU for the HARQ entity if the following conditions are satisfied:

there is no Sidelink CSI Reporting MAC CE generated for this PSSCH transmission as specified in clause 5.22.1.7; and
there is no Sidelink DRX Command MAC CE generated for this PSSCH transmission as specified in clause 5.22.1.8; and
there is no Sidelink Inter-UE Coordination Request MAC CE generated for this PSSCH transmission as specified in clause 5.22.1.9; and
there is no Sidelink Inter-UE Coordination Information MAC CE generated for this PSSCH transmission as specified in clause 5.22.1.10; and
the MAC PDU includes zero MAC SDUs and the MAC PDU is not associated with SL-PRS transmission on Shared SL-PRS resource pool.

Logical channels shall be prioritised in accordance with the following order (highest priority listed first):

data from SCCH;
Sidelink CSI Reporting MAC CE;
Sidelink Inter-UE Coordination Request MAC CE and Sidelink Inter-UE Coordination Information MAC CE;
Sidelink DRX Command MAC CE;
data from any STCH or SL-PRS.

5.22.1.4.2 Multiplexing of MAC Control Elements and MAC SDUs p. 183

The MAC entity shall multiplex MAC CEs and MAC SDUs in a MAC PDU according to clauses 5.22.1.4.1 and 6.1.6.

5.22.1.5 Scheduling Request p. 183

In addition to clause 5.4.4, the Scheduling Request (SR) is also used for requesting SL-SCH resources for new transmission when triggered by the Sidelink BSR (clause 5.22.1.6) or the SL-CSI reporting (clause 5.22.1.7) or SL-DRX Command indication. The Scheduling Request (SR) is also used for requesting SL-PRS resources for new transmission when triggered by SL-PRS resource request (clause 6.1.3.74). If configured, the MAC entity performs the SR procedure as specified in this clause unless otherwise specified in clause 5.4.4. For a sidelink logical channel or for SL-CSI reporting or for SL-DRX Command indication or for Sidelink consistent LBT failure recovery or for SL-PRS Resource Request, at most one PUCCH resource for SR is configured per UL BWP.

The SR configuration of the logical channel that triggered the Sidelink BSR (clause 5.22.1.6) is also considered as corresponding SR configuration for the triggered SR (clause 5.4.4). The value of the priority of the triggered SR corresponds to the value of priority of the logical channel that triggered the SR.

Each sidelink logical channel and Sidelink consistent LBT failure recovery may be mapped to zero or one SR configuration, which is configured by RRC. If the SL-CSI reporting procedure is enabled by RRC, the SL-CSI reporting is mapped to one SR configuration for all PC5-RRC connections. The SR configuration of the SL-CSI reporting triggered according to 5.22.1.7 is considered as corresponding SR configuration for the triggered SR (clause 5.4.4). The value of the priority of the triggered SR triggered by SL-CSI reporting corresponds to the value of the priority of the Sidelink CSI Reporting MAC CE. The SR configuration of the SL-CSI reporting is considered as corresponding SR configuration for the triggered SR of SL-DRX Command indication triggered according to 5.28.3. The value of the priority of the triggered SR triggered by SL-DRX Command indication corresponds to the value of the priority of the Sidelink DRX Command MAC CE. The SR configuration of the Sidelink consistent LBT failure recovery triggered according to 5.31.2 is considered as corresponding SR configuration for the triggered SR (clause 5.4.4). The value of the priority of the triggered SR triggered by Sidelink consistent LBT failure recovery corresponds to the value of the priority of the SL LBT failure MAC CE. SL-PRS resource request may be mapped to zero or one SR configuration, which is configured by RRC. The value of the priority of the triggered SR triggered by SL-PRS resource request corresponds to the lowest value of the priority of all SL-PRS(s) indicated in the SL-PRS Resource Request MAC CE.

All pending SR(s) triggered according to the Sidelink BSR procedure (clause 5.22.1.6) prior to the MAC PDU assembly shall be cancelled and each respective sr-ProhibitTimer shall be stopped when the MAC PDU is transmitted and this PDU includes an SL-BSR MAC CE which contains buffer status up to (and including) the last event that triggered a Sidelink BSR (see clause 5.22.1.4) prior to the MAC PDU assembly.

All pending SR(s) triggered according to the Sidelink consistent LBT failure recovery (clause 5.31.2) shall be cancelled and each respective sr-ProhibitTimer shall be stopped when the MAC PDU is transmitted and this PDU includes an SL LBT failure MAC CE that indicates Sidelink consistent LBT failure or when all the triggered Sidelink consistent LBT failure(s) for an SL BWP is cancelled.

All pending SR(s) triggered according to the Sidelink BSR procedure (clause 5.22.1.6) shall be cancelled and each respective sr-ProhibitTimer shall be stopped when the SL grant(s) can accommodate all pending data available for transmission in sidelink.

If there is pending SR triggered by Sidelink consistent LBT failure recovery which has no corresponding SR configuration, MAC entity initiate a Random Access procedure (see clause 5.1) on the Serving Cell and cancel the pending SR.

The pending SR triggered according to the SL-CSI reporting for a destination shall be cancelled and each respective sr-ProhibitTimer shall be stopped when the SL grant(s) can accommodate the Sidelink CSI Reporting MAC CE when the SL-CSI reporting that has been triggered but not cancelled or when the triggered SL-CSI reporting is cancelled due to latency non-fulfilment as specified in 5.22.1.7. The pending SR triggered according to the SL-DRX Command indication for a destination shall be cancelled and each respective sr-ProhibitTimer shall be stopped when the SL grant(s) can accommodate the Sidelink DRX Command MAC CE when the SL-DRX Command indication that has been triggered but not cancelled. All pending SR(s) triggered by either Sidelink BSR or Sidelink CSI report or Sidelink DRX Command indication shall be cancelled, when RRC configures Sidelink resource allocation mode 2.

All pending SR(s) triggered according to the SL-PRS Resource Request procedure (clause 5.22.1.12) prior to the MAC PDU assembly shall be cancelled and each respective sr-ProhibitTimer shall be stopped when the MAC PDU is transmitted and this PDU includes an SL-PRS Resource Request MAC CE which contains status of the pending SL-PRS transmission(s) up to (and including) the last event that triggered a SL-PRS Resource Request (see clause 5.22.1.12) prior to the MAC PDU assembly.

All pending SR(s) triggered according to the SL-PRS Resource Request procedure (clause 5.22.1.12) shall be cancelled and each respective sr-ProhibitTimer shall be stopped when the SL grant(s) can accommodate the all the pending SL-PRS transmission(s).

5.22.1.6 Buffer Status Reporting p. 184

The Sidelink Buffer Status reporting (SL-BSR) procedure is used to provide the serving gNB with information about SL data volume in the MAC entity.

RRC configures the following parameters to control the SL-BSR:

sl-periodicBSR-Timer, configured by periodicBSR-Timer in sl-BSR-Config;
sl-retxBSR-Timer, configured by retxBSR-Timer in sl-BSR-Config;
sl-logicalChannelSR-DelayTimerApplied;
sl-logicalChannelSR-DelayTimer, configured by logicalChannelSR-DelayTimer in sl-BSR-Config;
sl-logicalChannelGroup.

Each logical channel which belongs to a Destination is allocated to an LCG as specified in TS 38.331. The maximum number of LCGs is eight.

The MAC entity determines the amount of SL data available for a logical channel according to the data volume calculation procedure in TS 38.322 and TS 38.323.

An SL-BSR shall be triggered if any of the following events occur:

1 >

if the MAC entity has been configured with Sidelink resource allocation mode 1:

2 >

SL data, for a logical channel which belongs to an LCG of a Destination, becomes available to the MAC entity; and either

3 >

this SL data belongs to a logical channel with higher priority than the priorities of the logical channels containing available SL data which belong to any LCG belonging to the same Destination; or

3 >

none of the logical channels which belong to an LCG belonging to the same Destination contains any available SL data.

in which case the SL-BSR is referred below to as 'Regular SL-BSR';

2 >

UL resources are allocated and number of padding bits remaining after a Padding BSR has been triggered is equal to or larger than the size of the SL-BSR MAC CE plus its subheader, in which case the SL-BSR is referred below to as 'Padding SL-BSR';

2 >

sl-retxBSR-Timer expires, and at least one of the logical channels which belong to an LCG contains SL data, in which case the SL-BSR is referred below to as 'Regular SL-BSR';

2 >

sl-periodicBSR-Timer expires, in which case the SL-BSR is referred below to as 'Periodic SL-BSR'.

1 >

else:

2 >

Sidelink resource allocation mode 1 is configured by RRC and SL data is available for transmission in the RLC entity or in the PDCP entity, in which case the Sidelink BSR is referred below to as 'Regular SL-BSR'.

For Regular SL-BSR, the MAC entity shall:

1 >

if the SL-BSR is triggered for a logical channel for which sl-logicalChannelSR-DelayTimerApplied with value true is configured by RRC:

2 >

start or restart the sl-logicalChannelSR-DelayTimer.

1 >

else:

2 >

if running, stop the sl-logicalChannelSR-DelayTimer.

For Regular and Periodic SL-BSR, the MAC entity shall:

1 >

if sl-PrioritizationThres is configured and the value of the highest priority of the logical channels that belong to any LCG and contain SL data for any Destination is lower than sl-PrioritizationThres; and

1 >

if ul-PrioritizationThres is configured and the value of the highest priority of the logical channels that belong to any LCG and contain UL data is equal to or higher than ul-PrioritizationThres according to clause 5.4.5:

2 >

prioritize the LCG(s) for the Destination(s).

1 >

if the Buffer Status reporting procedure determines that at least one BSR has been triggered and not cancelled according to clause 5.4.5 and the UL grant cannot accommodate an SL-BSR MAC CE containing buffer status only for all prioritized LCGs having data available for transmission plus the subheader of the SL-BSR according to clause 5.4.3.1.3, in case the SL-BSR is considered as not prioritized:

2 >

prioritize the SL-BSR for logical channel prioritization specified in clause 5.4.3.1;

2 >

report Truncated SL-BSR containing buffer status for as many prioritized LCGs having data available for transmission as possible, taking the number of bits in the UL grant into consideration.

1 >

else if the number of bits in the UL grant is expected to be equal to or larger than the size of an SL-BSR containing buffer status for all LCGs having data available for transmission plus the subheader of the SL-BSR according to clause 5.4.3.1.3:

2 >

report SL-BSR containing buffer status for all LCGs having data available for transmission.

1 >

else:

2 >

report Truncated SL-BSR containing buffer status for as many LCGs having data available for transmission as possible, taking the number of bits in the UL grant into consideration.

For Padding SL-BSR:

1 >

if the number of padding bits remaining after a Padding BSR has been triggered is equal to or larger than the size of an SL-BSR containing buffer status for all LCGs having data available for transmission plus its subheader:

2 >

report SL-BSR containing buffer status for all LCGs having data available for transmission;

1 >

else:

2 >

report Truncated SL-BSR containing buffer status for as many LCGs having data available for transmission as possible, taking the number of bits in the UL grant into consideration.

For SL-BSR triggered by sl-retxBSR-Timer expiry, the MAC entity considers that the logical channel that triggered the SL-BSR is the highest priority logical channel that has data available for transmission at the time the SL-BSR is triggered.

The MAC entity shall:

1 >

if the sidelink Buffer Status reporting procedure determines that at least one SL-BSR has been triggered and not cancelled:

2 >

if UL-SCH resources are available for a new transmission and the UL-SCH resources can accommodate the SL-BSR MAC CE plus its subheader as a result of logical channel prioritization according to clause 5.4.3.1:

3 >

instruct the Multiplexing and Assembly procedure in clause 5.4.3 to generate the SL-BSR MAC CE(s);

3 >

start or restart sl-periodicBSR-Timer except when all the generated SL-BSRs are Truncated SL-BSRs;

3 >

start or restart sl-retxBSR-Timer.

2 >

if a Regular SL-BSR has been triggered and sl-logicalChannelSR-DelayTimer is not running:

3 >

if there is no UL-SCH resource available for a new transmission; or

3 >

if UL-SCH resources are available for a new transmission and the UL-SCH resources cannot accommodate the SL-BSR MAC CE plus its subheader as a result of logical channel prioritization according to clause 5.4.3.1; or

3 >

if the set of Subcarrier Spacing index values in sl-AllowedSCS-List, if configured for the logical channel that triggered the SL-BSR, does not include the Subcarrier Spacing index associated to the UL-SCH resources available for a new transmission; or

3 >

if sl-MaxPUSCH-Duration, if configured for the logical channel that triggered the SL-BSR, is smaller than the PUSCH transmission duration associated to the UL-SCH resources available for a new transmission:

4 >

trigger a Scheduling Request.

A MAC PDU shall contain at most one SL-BSR MAC CE, even when multiple events have triggered an SL-BSR. The Regular SL-BSR and the Periodic SL-BSR shall have precedence over the padding SL-BSR.

The MAC entity shall restart sl-retxBSR-Timer upon reception of an SL grant for transmission of new data on any SL-SCH.

All triggered SL-BSRs may be cancelled when the SL grant(s) can accommodate all pending data available for transmission. All BSRs triggered prior to MAC PDU assembly shall be cancelled when a MAC PDU is transmitted and this PDU includes an SL-BSR MAC CE which contains buffer status up to (and including) the last event that triggered an SL-BSR prior to the MAC PDU assembly. All triggered SL-BSRs shall be cancelled, and sl-retx-BSR-Timer and sl-periodic-BSR-Timer shall be stopped, when RRC configures Sidelink resource allocation mode 2.

5.22.1.7 CSI Reporting p. 186

The Sidelink Channel State Information (SL-CSI) reporting procedure is used to provide a peer UE with sidelink channel state information per carrier as specified in clause 8.5 of TS 38.214.

RRC configures the following parameters to control the SL-CSI reporting procedure:

sl-LatencyBoundCSI-Report, which is maintained for each PC5-RRC connection.

The MAC entity maintains an sl-CSI-ReportTimer for each carrier of a pair of the Source Layer-2 ID and the Destination Layer-2 ID corresponding to a PC5-RRC connection. sl-CSI-ReportTimer is used for an SL-CSI reporting UE to follow the latency requirement signalled from a CSI triggering UE. The value of sl-CSI-ReportTimer is the same as the latency requirement of the SL-CSI reporting in sl-LatencyBoundCSI-Report configured by RRC.

The Sidelink CSI Reporting MAC CE can only be transmitted on the carrier where the SL-CSI request is received.

The MAC entity shall for each carrier of a pair of the Source Layer-2 ID and the Destination Layer-2 ID corresponding to a PC5-RRC connection which has been established by upper layers:

1 >

if the SL-CSI reporting has been triggered for a carrier by an SCI and not cancelled:

2 >

if the sl-CSI-ReportTimer for the triggered SL-CSI reporting is not running:

3 >

start the sl-CSI-ReportTimer for the carrier.

2 >

if the sl-CSI-ReportTimer for the triggered SL-CSI reporting expires:

3 >

cancel the triggered SL-CSI reporting for the carrier.

2 >

else if the MAC entity has SL resources allocated for new transmission on the carrier where the corresponding SL-CSI request is received and the SL-SCH resources can accommodate the SL-CSI reporting MAC CE and its subheader as a result of logical channel prioritization:

3 >

instruct the Multiplexing and Assembly procedure to generate a Sidelink CSI Reporting MAC CE as defined in clause 6.1.3.35;

3 >

stop the sl-CSI-ReportTimer for the triggered SL-CSI reporting of the carrier;

3 >

cancel the triggered SL-CSI reporting of the carrier.

2 >

else if the MAC entity has been configured with Sidelink resource allocation mode 1:

3 >

trigger a Scheduling Request.

5.22.1.8 Void

5.22.1.9 IUC-Request transmission |R17| p. 187

The Sidelink Inter-UE Coordination Request transmission procedure is used to trigger a peer UE to transmit Sidelink Inter-UE Coordination Information.

RRC configures sl-TransmissionStructureForPSCCHandPSSCH parameter to control the inter-UE coordination request procedure. For a resource pool in a SL BWP where sl-TransmissionStructureForPSCCHandPSSCH is configured as interlaceRB, the Enhanced Inter-UE coordination Request MAC CE is used. Otherwise, the Inter-UE coordination Request MAC CE is used.

5.22.1.10 IUC-Information Reporting |R17| p. 187

5.22.1.10.1 General p. 187

The Sidelink Inter-UE Coordination Information reporting procedure is used to provide a peer UE with inter-UE coordination information as specified in clause 8.1.4 of TS 38.214. The Sidelink Inter-UE Coordination Information reporting procedure can be triggered by Sidelink Inter-UE Coordination Request MAC CE or condition (See TS 38.331 and TS 38.214). Unicast for preferred resource set and non-preferred resource set and Groupcast/Broadcast for non-preferred resource set are supported for inter-UE coordination information transmission triggered by a condition other than explicit request reception. Unicast for preferred resource set and non-preferred resource set is supported for inter-UE coordination information transmission triggered by an explicit request.

RRC also configures sl-TransmissionStructureForPSCCHandPSSCH parameter to control the inter-UE coordination Information reporting procedure. For a resource pool in a SL BWP where sl-TransmissionStructureForPSCCHandPSSCH is configured as interlaceRB, the Enhanced Inter-UE coordination Information MAC CE is used. Otherwise, the Inter-UE coordination Information MAC CE is used.

RRC configures the following parameter to control the SL-IUC Information reporting procedure:

sl-LatencyBoundIUC-Report, which is maintained for each PC5-RRC connection.

The MAC entity maintains an sl-IUC-ReportTimer for each pair of the Source Layer-2 ID and the Destination Layer-2 ID corresponding to a PC5-RRC connection. sl-IUC-ReportTimer is used for an SL-IUC Information reporting UE to follow the latency requirement signalled from an IUC-Information triggering UE. The value of sl-IUC-ReportTimer is the same as the latency requirement of the SL-IUC Information in sl-LatencyBoundIUC-Report configured by RRC.

The MAC entity shall for each pair of the Source Layer-2 ID and the Destination Layer-2 ID corresponding to a PC5-RRC connection which has been established by upper layers:

1 >

if the SL-IUC Information reporting has been triggered by an SL-IUC Request MAC CE (and/or an SCI) and not cancelled:

2 >

if the sl-IUC-ReportTimer for the triggered SL-IUC Information reporting is not running:

3 >

start the sl-IUC-ReportTimer.

2 >

if the sl-IUC-ReportTimer for the triggered SL-IUC Information reporting expires:

3 >

cancel the triggered SL-IUC Information reporting.

2 >

else if the MAC entity has SL resources allocated for new transmission and the SL-SCH resources can accommodate the SL-IUC Information MAC CE and its subheader as a result of logical channel prioritization:

3 >

instruct the Multiplexing and Assembly procedure to generate a Sidelink Inter-UE Coordination Information MAC CE as defined in clause 6.1.3.53;

3 >

stop the sl-IUC-ReportTimer for the triggered SL-IUC Information reporting;

3 >

cancel the triggered SL-IUC Information reporting.

5.22.1.10.2 Reception of IUC-Information Reporting p. 188

Upon the reception of SL-IUC Information MAC CE from another UE, the MAC entity shall:

1 >

if sl-InterUE-CoordinationScheme1 enabling reception/transmission of preferred resource set and non-preferred resource set is configured by RRC:

2 >

if the SL-IUC Information MAC CE contains a non-preferred resource set and if the UE is configured to use full sensing or partial sensing in the resource pool where the non-preferred resource set is located:

3 >

indicate the received non-preferred resource set to physical layer.

5.22.1.11 TX carrier (re-)selection |R18| p. 188

The MAC entity shall consider a CBR of a carrier to be one measured by lower layers according to TS 38.215 if CBR measurement results are available, or the corresponding sl-DefaultTxConfigIndex configured by upper layers if CBR measurement results are not available.

If the TX carrier (re-)selection is triggered for a Sidelink process according to clause 5.22.1.1, 5.22.1.2 or 5.22.1.3.3, the MAC entity shall:

1 >

if there is no selected sidelink grant on any carrier allowed for the sidelink logical channel where data is available as indicated by upper layers (TS 38.331 and TS 23.287):

2 >

for each carrier configured by upper layers associated with the concerned sidelink logical channel:

3 >

if the CBR of the carrier is below sl-threshCBR-FreqReselection associated with the priority of the sidelink logical channel:

4 >

consider the carrier as a candidate carrier for TX carrier (re-)selection for the concerned sidelink logical channel.

1 >

else:

2 >

for each sidelink logical channel, if any, where data is available and that are allowed on the carrier for which Tx carrier (re-)selection is triggered according to clause 5.22.1.1, if the CBR of the carrier is below sl-threshCBR-FreqKeeping associated with priority of the sidelink logical channel, for each sidelink logical channel, if any, where data is available and that are allowed on the carrier for which Tx carrier (re-)selection is triggered according to clause 5.22.1.1:

3 >

select the carrier and the associated pool of resources.

2 >

else:

3 >

for each carrier configured by upper layers on which the sidelink logical channel is allowed, if the CBR of the carrier is below sl-threshCBR-FreqReselection associated with the priority of the sidelink logical channel:

4 >

consider the carrier as a candidate carrier for TX carrier (re-)selection, for each carrier configured by upper layers on which the sidelink logical channel is allowed.

The MAC entity shall select a carrier on which the SL-CSI Request was received as a carrier for transmission of a Sidelink CSI Reporting MAC CE. The MAC entity shall for the Sidelink CSI Reporting MAC CE select any pool of resources among the pools of resources except the pool(s) in sl-BWP-DiscPoolConfig, sl-BWP-DiscPoolConfigCommon, sl-BWP-PoolConfigA2X or sl-BWP-PoolConfigCommonA2X, if configured or Dedicated SL-PRS resource pool, if configured.

The MAC entity shall select a carrier on which a Sidelink Inter-UE Coordination Request was received as a carrier for transmission of a Sidelink Inter-UE Coordination Information MAC CE. The MAC entity shall for the Sidelink Inter-UE Coordination Information MAC CE select any pool of resources among the pools of resources except the pool(s) in sl-BWP-DiscPoolConfig, sl-BWP-DiscPoolConfigCommon, sl-BWP-PoolConfigA2X or sl-BWP-PoolConfigCommonA2X, if configured or Dedicated SL-PRS resource pool, if configured.

The MAC entity shall perform the TX carrier (re-)selection such as TX carrier (re-)selection for the logical channel when TX carrier (re-)selection for a Sidelink Inter-UE Coordination Request MAC CE, and/or a Sidelink DRX Command MAC CE is triggered.

The MAC entity shall:

1 >

if one or more carriers are considered as the candidate carriers for TX carrier (re-)selection:

2 >

if Tx carrier (re-)selection is triggered, for each sidelink logical channel allowed on the carrier where data is available:

3 >

select one or more carrier(s) among the candidate carriers with increasing order of CBR from the lowest CBR, and select the associated pool(s) of resources:

4 >

if sl-HARQ-FeedbackEnabled is set to enabled for the sidelink logical channel:

5 >

select one pool of resources configured with PSFCH resources among the pools of resources except the pool(s) in sl-BWP-DiscPoolConfig or sl-BWP-DiscPoolConfigCommon, sl-BWP-PoolConfigA2X or sl-BWP-PoolConfigCommonA2X, if configured or Dedicated SL-PRS resource pool, if configured.

4 >

else:

5 >

select any pool of resources among the pools of resources except the pool(s) in sl-BWP-DiscPoolConfig or sl-BWP-DiscPoolConfigCommon, sl-BWP-PoolConfigA2X or sl-BWP-PoolConfigCommonA2X, if configured or Dedicated SL-PRS resource pool, if configured.

2 >

else if Tx carrier (re-)selection is triggered, for a Sidelink DRX Command MAC CE or a Sidelink Inter-UE Coordination Request MAC CE:

3 >

select any pool of resources among the pools of resources except the pool(s) in sl-BWP-DiscPoolConfig, sl-BWP-DiscPoolConfigCommon, sl-BWP-PoolConfigA2X or sl-BWP-PoolConfigCommonA2X, if configured or SL-PRS dedicated resource pool, if configured.

5.22.1.12 SL-PRS Resource Request |R18| p. 190

SL-PRS transmission can be triggered either by lower layer signalling from the peer UE or the UE's own upper layers. The SL-PRS Resource Request procedure is used to provide gNB with information about the triggered SL-PRS transmission.

The MAC entity shall, if Sidelink resource allocation scheme 1 for SL-PRS transmission is configured:

1 >

if aperiodic SL-PRS is triggered:

2 >

trigger the SL-PRS Resource Request.

1 >

else if periodic SL-PRS is triggered:

2 >

notify RRC to send SL-PRS Resource Request.

The MAC entity shall:

1 >

if SL-PRS Resource Request is triggered and not cancelled:

2 >

if UL-SCH resources are available for a new transmission and these UL-SCH resources can accommodate the SL-PRS Resource Request MAC CE plus its subheader as a result of logical channel prioritization:

3 >

instruct the Multiplexing and Assembly entity to generate the SL-PRS Resource Request MAC CE.

2 >

else:

3 >

trigger a Scheduling Request for the SL-PRS Resource Request MAC CE as specified in clause 5.4.4.

The SL-PRS Resource Request MAC CE may be cancelled when SL grant can accommodate all the pending SL-PRS transmissions. The SL-PRS Resource Request MAC CE shall be cancelled when a MAC PDU is transmitted and this PDU includes a SL-PRS Resource Request MAC CE that indicates request for all the pending SL-PRS transmission(s) since the last event the MAC CE is triggered.