Section: 5.14.1.2.2 Sidelink process
Content: The Sidelink process is associated with a HARQ buffer. The sequence of redundancy versions is 0, 2, 3, 1. The variable CURRENT_IRV is an index into the sequence of redundancy versions. This variable is updated modulo 4. New transmissions and retransmissions either for a given SC period in sidelink communication or in V2X sidelink communication are performed on the resource indicated in the sidelink grant as specified in clause 5.14.1.1 and with the MCS selected as specified in clause 5.14.1.1. If the sidelink process is configured to perform transmissions of multiple MAC PDUs for V2X sidelink communication the process maintains a counter SL_RESOURCE_RESELECTION_COUNTER. For other configurations of the sidelink process, this counter is not available. If the Sidelink HARQ Entity requests a new transmission, the Sidelink process shall: - set CURRENT_IRV to 0; - store the MAC PDU in the associated HARQ buffer; - store the sidelink grant received from the Sidelink HARQ Entity; - generate a transmission as described below. If the Sidelink HARQ Entity requests a retransmission, the Sidelink process shall: - generate a transmission as described below. To generate a transmission, the Sidelink process shall: - if there is no uplink transmission; or if the MAC entity is able to perform uplink transmissions and transmissions on SL-SCH simultaneously at the time of the transmission; or if there is a MAC PDU to be transmitted in this TTI in uplink, except a MAC PDU obtained from the Msg3 buffer, and transmission of V2X sidelink communication is prioritized over uplink transmission; and - if there is no Sidelink Discovery Gap for Transmission or no transmission on PSDCH at the time of the transmission; or, in case of transmissions of V2X sidelink communication, if the MAC entity is able to perform transmissions on SL-SCH and transmissions on PSDCH simultaneously at the time of the transmission: - instruct the physical layer to generate a transmission according to the stored sidelink grant with the redundancy version corresponding to the CURRENT_IRV value. - increment CURRENT_IRV by 1; - if this transmission corresponds to the last transmission of the MAC PDU: - decrement SL_RESOURCE_RESELECTION_COUNTER by 1, if available. The transmission of the MAC PDU for V2X sidelink communication is prioritized over uplink transmissions if the following conditions are met: - if the MAC entity is not able to perform all uplink transmissions and all transmissions of V2X sidelink communication simultaneously at the time of the transmission; and - if uplink transmission is not prioritized by upper layer according to TS 24.386[ User Equipment (UE) to V2X control function; protocol aspects; Stage 3 ]  [15]; and - if thresSL-TxPrioritization is configured and the value of the highest priority of the sidelink logical channel(s) in the MAC PDU is lower than thresSL-TxPrioritization.