16.9.6.1 General

Sidelink supports SL DRX for unicast, groupcast, and broadcast. Similar parameters as defined in clause 11 for Uu (on-duration, inactivity-timer, retransmission-timer, cycle) are defined for SL to determine the SL active time for SL DRX. During the SL active time, the UE performs SCI monitoring for data reception (i.e., PSCCH and 2nd stage SCI on PSSCH). The UE may skip monitoring of SCI for data reception during SL DRX inactive time.

The actual parameters supported for each cast type (unicast, groupcast, broadcast) are specified in the following clauses.

The SL active time of the RX UE includes the time in which any of its applicable SL on-duration timer(s), SL inactivity-timer(s) or SL HARQ retransmission timer(s) (for any of unicast, groupcast, or broadcast) are running. In addition, the slots associated with announced periodic transmissions by the TX UE and the time in which a UE is expecting CSI report following a CSI request (for unicast) are considered as SL active time of the RX UE. The time for the unicast link establishment procedure and the time for the PC5 RRC reconfiguration with initial SL DRX configuration procedure as specified in clause 5.28.2 of TS 38.321 [6] are considered as SL active time of the RX UE.

The TX UE maintains a set of timers corresponding to the SL DRX timers in the RX UE(s) for each pair of source/destination L2 ID for unicast or destination L2 ID for groupcast/broadcast. When data is available for transmission to one or more RX UE(s) configured with SL DRX, the TX UE selects resources taking into account the active time of the RX UE(s).

The UE can determine from SIB12 whether the gNB supports SL DRX or not.