Section: 5.4.4 Scheduling Request
Content: The Scheduling Request (SR) is used for requesting UL-SCH resources for new transmission. When an SR is triggered, it shall be considered as pending until it is cancelled. All pending SR(s) shall be cancelled and sr-ProhibitTimer and ssr-ProhibitTimer shall be stopped when a MAC PDU is assembled and this PDU includes a BSR which contains buffer status up to (and including) the last event that triggered a BSR (see clause 5.4.5), or, if all pending SR(s) are triggered by Sidelink BSR, when a MAC PDU is assembled and this PDU includes a Sidelink BSR which contains buffer status up to (and including) the last event that triggered a Sidelink BSR (see clause 5.14.1.4), or, if all pending SR(s) are triggered by Sidelink BSR, when upper layers configure autonomous resource selection, or when the UL grant(s) can accommodate all pending data available for transmission. If the MAC entity has resources for SR configured on only one of SPUCCH and PUCCH, that SR resource is valid for all logical channels. If the MAC entity has resources for SR configured on both PUCCH and SPUCCH, MAC entity shall consider all logical channels that have triggered an SR (and at retxBSR-Timer expiry, MAC entity shall consider all logical channels, belonging to a LCG, with data available for transmission): - PUCCH resources for SR are valid if logicalChannelSr-Restriction is not configured, or if logicalChannelSr-Restriction allows SR on PUCCH, for any of the logical channels; - SPUCCH resources for SR are valid if logicalChannelSr-Restriction is not configured, or if logicalChannelSr-Restriction allows SR on SPUCCH, for any of the logical channels. If an SR is triggered and there is no other SR pending, the MAC entity shall set the SR_COUNTER and the SSR_COUNTER to 0. As long as one SR is pending, the MAC entity shall for each TTI: - if no UL-SCH resources are available for a transmission in this TTI: - Except for NB-IoT: - if the MAC entity has no valid PUCCH nor valid SPUCCH resource for SR configured in any TTI: - if the MAC entity is a MCG MAC entity and rach-Skip is not configured; or - if the MAC entity is a SCG MAC entity and rach-SkipSCG is not configured: - initiate a Random Access procedure (see clause 5.1) on the corresponding SpCell and cancel all pending SRs; - else if this TTI is not part of a measurement gap or Sidelink Discovery Gap for Transmission, and if transmission of V2X sidelink communication is not prioritized in this TTI as described in clause 5.14.1.2.2: - if the MAC entity has at least one valid SPUCCH resource for SR configured for this TTI and if ssr-ProhibitTimer is not running: - if SSR_COUNTER < dssr-TransMax: - increment SSR_COUNTER by 1; - instruct the physical layer to signal the SR on one valid SPUCCH resource for SR; - start the ssr-ProhibitTimer. - else: - notify RRC to release SPUCCH for all serving cells; - if the MAC entity has no valid PUCCH resource for SR configured in any TTI: - notify RRC to release PUCCH for all serving cells; - notify RRC to release SRS for all serving cells; - clear any configured downlink assignments and uplink grants; - initiate a Random Access procedure (see clause 5.1) on the SpCell and cancel all pending SRs. - if the MAC entity has at least one valid PUCCH resource for SR configured for this TTI and if sr-ProhibitTimer is not running: - if SR_COUNTER < dsr-TransMax: - increment SR_COUNTER by 1; - instruct the physical layer to signal the SR on one valid PUCCH resource for SR; - start the sr-ProhibitTimer. - else: - notify RRC to release PUCCH and SPUCCH for all serving cells; - notify RRC to release SRS for all serving cells; - clear any configured downlink assignments and uplink grants; - initiate a Random Access procedure (see clause 5.1) on the SpCell and cancel all pending SRs. - For NB-IoT: - if the MAC entity has no valid resource for SR together with acknowledgement of the data in this TTI and no valid PRACH resource for SR configured in any TTI: - initiate a Random Access Procedure (see clause 5.1), and cancel all pending SRs in the first subframe containing PRACH for preamble transmission. - else: - if the MAC entity has valid resource for SR together with acknowledgement of the data in this TTI: - instruct the physical layer to signal the SR together with acknowledgement of the data. - cancel, if any, initiated Random Access Procedure for SR. - else: - if the MAC entity has valid PRACH resource for SR configured in this TTI and sr-ProhibitTimer is not running: - instruct the physical layer to signal the SR on one valid PRACH resource for SR. - start the sr-ProhibitTimer in the subframe containing the last repetition of the corresponding SR transmission. NOTE 1: The selection of which valid PUCCH/SPUCCH resource for SR to signal SR on when the MAC entity has more than one valid PUCCH/SPUCCH resource for SR in one TTI or overlapping TTIs is left to UE implementation. NOTE 2: SR_COUNTER is incremented for each SR bundle. sr-ProhibitTimer is started in the first TTI of an SR bundle.