5.15 Bandwidth Part (BWP) operation

38.3213GPPMedium Access Control (MAC) protocol specificationNRRelease 17TS

5.15.1 Downlink and Uplink

In addition to clause 12 of TS 38.213 [6], this clause specifies requirements on BWP operation.

A Serving Cell may be configured with one or multiple BWPs, and the maximum number of BWP per Serving Cell is specified in TS 38.213 [6].

The BWP switching for a Serving Cell is used to activate an inactive BWP and deactivate an active BWP at a time. The BWP switching is controlled by the PDCCH indicating a downlink assignment or an uplink grant, by the bwp-InactivityTimer, by RRC signalling, or by the MAC entity itself upon initiation of Random Access procedure or upon detection of consistent LBT failure on SpCell. Upon RRC (re-)configuration of firstActiveDownlinkBWP-Id and/or firstActiveUplinkBWP-Id for SpCell except for PSCell when SCG is deactivated (see clause 5.29) or activation of an SCell, the DL BWP and/or UL BWP indicated by firstActiveDownlinkBWP-Id and/or firstActiveUplinkBWP-Id respectively (as specified in TS 38.331 [5]) is active without receiving PDCCH indicating a downlink assignment or an uplink grant. Upon RRC (re-)configuration of firstActiveDownlinkBWP-Id for PSCell when SCG is deactivated, the DL BWP is switched to the firstActiveDownlinkBWP-Id as specified in TS 38.331 [5]. The active BWP for a Serving Cell is indicated by either RRC or PDCCH (as specified in TS 38.213 [6]). For unpaired spectrum, a DL BWP is paired with a UL BWP, and BWP switching is common for both UL and DL.

For each SCell a dormant BWP may be configured with dormantBWP-Id by RRC signalling as described in TS 38.331 [5]. Entering or leaving dormant BWP for SCells is done by BWP switching per SCell or per dormancy SCell group based on instruction from PDCCH (as specified in TS 38.213 [6]). The dormancy SCell group configurations are configured by RRC signalling as described in TS 38.331 [5]. Upon reception of the PDCCH indicating leaving dormant BWP, the DL BWP indicated by firstOutsideActiveTimeBWP-Id or by firstWithinActiveTimeBWP-Id (as specified in TS 38.331 [5] and TS 38.213 [6]) is activated. Upon reception of the PDCCH indicating entering dormant BWP, the DL BWP indicated by dormantBWP-Id (as specified in TS 38.331 [5]) is activated. The dormant BWP configuration for SpCell or PUCCH SCell is not supported.

For each activated Serving Cell configured with a BWP, the MAC entity shall:

1> if a BWP is activated and the active DL BWP for the Serving Cell is not the dormant BWP:

2> transmit on UL-SCH on the BWP;

2> transmit on RACH on the BWP, if PRACH occasions are configured;

2> monitor the PDCCH on the BWP;

2> transmit PUCCH on the BWP, if configured;

2> report CSI for the BWP;

2> transmit SRS on the BWP, if configured;

2> receive DL-SCH on the BWP;

2> (re-)initialize any suspended configured uplink grants of configured grant Type 1 on the active BWP according to the stored configuration, if any, and to start in the symbol according to rules in clause 5.8.2;

2> if lbt-FailureRecoveryConfig is configured:

3> stop the lbt-FailureDetectionTimer, if running;

3> set LBT_COUNTER to 0;

3> monitor LBT failure indications from lower layers as specified in clause 5.21.2.

1> if a BWP is activated and the active DL BWP for the Serving Cell is dormant BWP:

2> stop the bwp-InactivityTimer of this Serving Cell, if running.

2> not monitor the PDCCH on the BWP;

2> not monitor the PDCCH for the BWP;

2> not receive DL-SCH on the BWP;

2> not report CSI on the BWP, report CSI except aperiodic CSI for the BWP;

2> not transmit SRS on the BWP;

2> not transmit on UL-SCH on the BWP;

2> not transmit on RACH on the BWP;

2> not transmit PUCCH on the BWP;

2> clear any configured downlink assignment and any configured uplink grant Type 2 associated with the SCell respectively;

2> suspend any configured uplink grant Type 1 associated with the SCell;

2> if configured, perform beam failure detection and beam failure recovery for the SCell if beam failure is detected.

1> if a BWP is deactivated:

2> not transmit on UL-SCH on the BWP;

2> not transmit on RACH on the BWP;

2> not monitor the PDCCH on the BWP;

2> not transmit PUCCH on the BWP;

2> not report CSI for the BWP;

2> not transmit SRS on the BWP;

2> not receive DL-SCH on the BWP;

2> clear any configured downlink assignment and configured uplink grant of configured grant Type 2 on the BWP;

2> suspend any configured uplink grant of configured grant Type 1 on the inactive BWP.

Upon initiation of the Random Access procedure on a Serving Cell, after the selection of carrier for performing Random Access procedure as specified in clause 5.1.1, the MAC entity shall for the selected carrier of this Serving Cell:

1> if PRACH occasions are not configured for the active UL BWP:

2> if the UE is a RedCap UE; and

2> if initialUplinkBWP-RedCap is configured:

3> switch the active UL BWP to BWP indicated by initialUplinkBWP-RedCap.

2> else:

3> switch the active UL BWP to BWP indicated by initialUplinkBWP.

2> if the Serving Cell is an SpCell:

3> if the UE is a RedCap UE; and

3> if initialDownlinkBWP-RedCap is configured:

4> switch the active DL BWP to BWP indicated by initialDownlinkBWP-RedCap.

3> else:

4> switch the active DL BWP to BWP indicated by initialDownlinkBWP.

1> else:

2> if the Serving Cell is an SpCell:

3> if the active DL BWP does not have the same bwp-Id as the active UL BWP:

4> switch the active DL BWP to the DL BWP with the same bwp-Id as the active UL BWP.

1> stop the bwp-InactivityTimer associated with the active DL BWP of this Serving Cell, if running.

1> if the Serving Cell is SCell:

2> stop the bwp-InactivityTimer associated with the active DL BWP of SpCell, if running.

1> perform the Random Access procedure on the active DL BWP of SpCell and active UL BWP of this Serving Cell.

If the MAC entity receives a PDCCH for BWP switching of a Serving Cell, the MAC entity shall:

1> if there is no ongoing Random Access procedure associated with this Serving Cell; or

1> if the ongoing Random Access procedure associated with this Serving Cell is successfully completed upon reception of this PDCCH addressed to C-RNTI (as specified in clauses 5.1.4, 5.1.4a, and 5.1.5):

2> cancel, if any, triggered consistent LBT failure for this Serving Cell;

2> perform BWP switching to a BWP indicated by the PDCCH.

If the MAC entity receives a PDCCH for BWP switching for a Serving Cell(s) or a dormancy SCell group(s) while a Random Access procedure associated with that Serving Cell is ongoing in the MAC entity, it is up to UE implementation whether to switch BWP or ignore the PDCCH for BWP switching, except for the PDCCH reception for BWP switching addressed to the C-RNTI for successful Random Access procedure completion (as specified in clauses 5.1.4, 5.1.4a, and 5.1.5) in which case the UE shall perform BWP switching to a BWP indicated by the PDCCH. Upon reception of the PDCCH for BWP switching other than successful contention resolution, if the MAC entity decides to perform BWP switching, the MAC entity shall stop the ongoing Random Access procedure and initiate a Random Access procedure after performing the BWP switching; if the MAC decides to ignore the PDCCH for BWP switching, the MAC entity shall continue with the ongoing Random Access procedure on the Serving Cell.

Upon reception of RRC (re-)configuration for BWP switching for a Serving Cell while a Random Access procedure associated with that Serving Cell is ongoing in the MAC entity, the MAC entity shall stop the ongoing Random Access procedure and initiate a Random Access procedure after performing the BWP switching.

Upon reception of RRC (re-)configuration for BWP switching for a Serving Cell, cancel any triggered LBT failure in this Serving Cell.

The MAC entity shall for each activated Serving Cell configured with bwp-InactivityTimer:

1> if the defaultDownlinkBWP-Id is configured, and the active DL BWP is not the BWP indicated by the defaultDownlinkBWP-Id, and the active DL BWP is not the BWP indicated by the dormantBWP-Id if configured; or

1> if the UE is not a RedCap UE, and if the defaultDownlinkBWP-Id is not configured, and the active DL BWP is not the initialDownlinkBWP, and the active DL BWP is not the BWP indicated by the dormantBWP-Id if configured; or

1> if the UE is a RedCap UE, and if the defaultDownlinkBWP-Id is not configured, and initialDownlinkBWP-RedCap is not configured, and the active DL BWP is not the initialDownlinkBWP; or

1> if the UE is a RedCap UE, and if the defaultDownlinkBWP-Id is not configured, and initialDownlinkBWP-RedCap is configured, and the active DL BWP is not the initialDownlinkBWP-RedCap:

2> if a PDCCH addressed to C-RNTI or CS-RNTI indicating downlink assignment or uplink grant is received on the active BWP; or

2> if a PDCCH addressed to G-RNTI or G-CS-RNTI configured for multicast indicating downlink assignment is received on the active BWP; or

2> if a PDCCH addressed to C-RNTI or CS-RNTI indicating downlink assignment or uplink grant is received for the active BWP; or

2> if a MAC PDU is transmitted in a configured uplink grant and LBT failure indication is not received from lower layers; or

2> if a MAC PDU is received in a configured downlink assignment for unicast or MBS multicast:

3> if there is no ongoing Random Access procedure associated with this Serving Cell; or

3> if the ongoing Random Access procedure associated with this Serving Cell is successfully completed upon reception of this PDCCH addressed to C-RNTI (as specified in clauses 5.1.4, 5.1.4a and 5.1.5):

4> start or restart the bwp-InactivityTimer associated with the active DL BWP.

2> if the bwp-InactivityTimer associated with the active DL BWP expires:

3> if the defaultDownlinkBWP-Id is configured:

4> perform BWP switching to a BWP indicated by the defaultDownlinkBWP-Id.

3> else:

4> if the UE is a RedCap UE; and

4> if initialDownlinkBWP-RedCap is configured:

5> perform BWP switching to the initialDownlinkBWP-RedCap.

4> else:

5> perform BWP switching to the initialDownlinkBWP.

NOTE: If a Random Access procedure is initiated on an SCell, both this SCell and the SpCell are associated with this Random Access procedure.

1> if a PDCCH for BWP switching is received, and the MAC entity switches the active DL BWP:

2> if the defaultDownlinkBWP-Id is configured, and the MAC entity switches to the DL BWP which is not indicated by the defaultDownlinkBWP-Id and is not indicated by the dormantBWP-Id if configured; or

2> if the UE is not a RedCap UE, and if the defaultDownlinkBWP-Id is not configured, and the MAC entity switches to the DL BWP which is not the initialDownlinkBWP and is not indicated by the dormantBWP-Id if configured; or

2> if the UE is a RedCap UE, and if the defaultDownlinkBWP-Id is not configured, and initialDownlinkBWP-RedCap is not configured, and the MAC entity switches to the DL BWP which is not the initialDownlinkBWP; or

2> if the UE is a RedCap UE, and if the defaultDownlinkBWP-Id is not configured, and initialDownlinkBWP-RedCap is configured, and the MAC entity switches to the DL BWP which is not the initialDownlinkBWP-RedCap:

3> start or restart the bwp-InactivityTimer associated with the active DL BWP.

Upon initiation of the Random Access procedure, after selection of the carrier for performing Random Access procedure as specified in clause 5.1.1, if the UE is a RedCap UE in RRC_IDLE or RRC_INACTIVE mode, the MAC entity shall:

1> if initialUplinkBWP-RedCap is configured for the selected carrier:

2> perform the Random Access procedure as specified in clause 5.1 by using the BWP configured by initialUplinkBWP-RedCap.

1> else:

2> perform the Random Access procedure as specified in clause 5.1 by using the BWP configured by initialUplinkBWP.

1> if initialDownlinkBWP-RedCap is configured:

2> if the Random Access procedure was initiated for SI request (as specified in TS 38.331 [5]) and the Random Access Resources for SI request have been explicitly provided by RRC, and if the selected carrier is SUL carrier:

3> monitor the PDCCH on the BWP configured by initialDownlinkBWP.

2> else:

3> monitor the PDCCH on the BWP configured by initialDownlinkBWP-RedCap.

1> else:

2> monitor the PDCCH on the BWP configured by initialDownlinkBWP.

5.15.2 Sidelink

In addition to clause 16 of TS 38.213 [6], this clause specifies requirements on BWP operation for sidelink.

The MAC entity is configured with at most a single SL BWP where sidelink transmission and reception are performed.

For a BWP, the MAC entity shall:

1> if the BWP is activated:

2> transmit SL-BCH on the BWP, if configured;

2> transmit S-PSS and S-SSS on the BWP, if configured;

2> transmit PSCCH on the BWP;

2> transmit SL-SCH on the BWP;

2> receive PSFCH on the BWP, if configured;

2> receive S-PSS and S-SSS on the BWP, if configured;

2> receive SL-BCH on the BWP, if configured;

2> receive PSCCH on the BWP;

2> receive SL-SCH on the BWP;

2> transmit PSFCH on the BWP, if configured;

2> (re-)initialize any suspended configured sidelink grant of configured grant Type 1.

1> if the BWP is deactivated:

2> not transmit SL-BCH on the BWP, if configured;

2> not transmit S-PSS and S-SSS on the BWP, if configured;

2> not transmit PSCCH on the BWP;

2> not transmit SL-SCH on the BWP;

2> not receive PSFCH on the BWP, if configured;

2> not receive SL-BCH on the BWP, if configured;

2> not receive S-PSS and S-SSS on the BWP, if configured;

2> not receive PSCCH on the BWP;

2> not receive SL-SCH on the BWP;

2> not transmit PSFCH on the BWP, if configured;

2> suspend any configured sidelink grant of configured grant Type 1;

2> clear any configured sidelink grant of configured grant Type 2;

2> cancel, if any, triggered Scheduling Request procedure for sidelink;

2> cancel, if any, triggered Sidelink Buffer Status Reporting procedure;

2> cancel, if any, triggered Sidelink CSI Reporting procedure;

2> cancel, if any, triggered Sidelink DRX Command MAC CE;

2> cancel, if any, triggered Sidelink IUC-Request transmission procedure;

2> cancel, if any, triggered Sidelink IUC-Information Reporting procedure.