8 Sidelink Operation

38.3043GPPNRRelease 17TSUser Equipment (UE) procedures in idle mode and in RRC Inactive state

8.1 NR sidelink communication, and V2X sidelink communication, and NR sidelink discovery

The UE may transmit or receive NR sidelink communication if it fulfils the condition(s) defined in TS 38.331 [3], clause 5.8.2. When UE is in-coverage for sidelink operation as defined in clause 8.2, the UE may perform NR sidelink communication according to SIB12, and when out-of-coverage for sidelink, the UE may perform NR sidelink communication according to SL-V2X-PreconfigurationNR or according to SIB12 of the cell on the frequency which provides inter-carrier NR sidelink configuration, as specified in TS 38.331 [3]. The UE shall not perform NR sidelink communication according to SL-V2X-PreconfigurationNR if the UE detects a cell providing NR sidelink configuration or inter-carrier NR sidelink configuration for the frequency UE is interested to perform NR sidelink communication on.

The UE may transmit or receive V2X sidelink communication if it fulfills the condition(s) defined in TS 36.331[6], clause 5.10.1d. When UE is in-coverage for sidelink operation as defined in clause 8.2, the UE may perform V2X sidelink communication according to SIB13/ SIB14 of the cell on an NR frequency.

The U2N Remote UE, the U2N Relay UE, or both may transmit or receive NR sidelink relay discovery (i.e., as specified in TS 23.304 [22]) if it fulfills the condition(s) defined in TS 38.331 [3].

For NR sidelink broadcast and groupcast, the UE may obtain SL DRX configuration from SIB12 (for in-coverage UE, as defined in clause 8.2, in RRC_IDLE and RRC_INACTIVE state) or SL-PreconfigurationNR (for UE out-of-coverage).

For inter-UE coordination (IUC) information configuration, the UE may obtain it from SIB12 (for in-coverage UE, as defined in clause 8.2, in RRC_IDLE and RRC_INACTIVE state) or SL-PreconfigurationNR (for UE out-of-coverage).

8.2 Cell selection and reselection for Sidelink

The requirements defined in this clause for sidelink operation (including sidelink relay operations) apply for UEs in RRC_IDLE, RRC_INACTIVE and in RRC_CONNECTED.

When UE is interested to perform NR sidelink communication on non-serving frequency, it may perform measurements on that frequency or the frequencies which can provide inter carrier NR sidelink configuration for that frequency for cell selection and reselection purpose in accordance with TS 38.133[8]. When UE is interested to perform V2X sidelink communication on non-serving frequency, it may perform measurements on that frequency or the frequencies which can provide inter carrier V2X sidelink configuration for that frequency for cell selection and intra-frequency reselection purpose in accordance with TS 38.133[8].

If the UE detects at least one cell on the frequency which UE is configured to perform NR sidelink communication on fulfilling the S criterion in accordance with clause 8.2.1, it shall consider itself to be in-coverage for NR sidelink communication on that frequency. If the UE cannot detect any cell on that frequency meeting the S criterion, it shall consider itself to be out-of-coverage for NR sidelink communication on that frequency.

If the UE detects at least one cell on the frequency which UE is configured to perform V2X sidelink communication on fulfilling the S criterion in accordance with clause 8.2.1, it shall consider itself to be in-coverage for V2X sidelink communication on that frequency. If the UE cannot detect any cell on that frequency meeting the S criterion, it shall consider itself to be out-of-coverage for V2X sidelink communication on that frequency.

If the UE has selected a cell on a non-serving frequency for V2X sidelink communication, it shall perform additional intra-frequency reselection process to select a better cell for sidelink operation on that frequency in accordance with clause 8.2.1.

If the UE has selected a cell on a non-serving frequency for NR sidelink communication, it shall perform additional reselection process to select a better cell for sidelink operation in accordance with clause 8.2.1.

8.2.1 Parameters used for cell selection and reselection triggered for sidelink

When evaluating S criterion, R criterion (ranking) or inter-frequency cell reselection criterion, as defined in clause 5.2.3.2, clause 5.2.4.6 and clause 5.2.4.5 respectively, for cell selection/reselection triggered for NR sidelink communication or V2X sidelink communication on a non-serving frequency, UE shall perform the evaluation as follows:

– The UE shall use cell selection/reselection parameters broadcast by the concerned cell (i.e. selected cell for the sidelink operation) for the evaluation.