Section: 5.14.1.5 TX carrier (re-)selection for V2X sidelink communication
Content: The MAC entity shall consider a CBR of a carrier to be one measured by lower layers according to TS 36.214[ Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer; Measurements ]  [6] if CBR measurement results are available, or the corresponding defaultTxConfigIndex configured by upper layers for the carrier if CBR measurement results are not available. If the TX carrier (re-)selection is triggered for a Sidelink process according to clause 5.14.1.1, the MAC entity shall: - if there is no configured sidelink grant on any carrier allowed for the sidelink logical channel where data is available as indicated by upper layers (TS 36.331[ Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification ]  [8] and TS 24.386[ User Equipment (UE) to V2X control function; protocol aspects; Stage 3 ]  [15]): - for each carrier configured by upper layers associated with the concerned sidelink logical channel: - if the CBR of the carrier is below threshCBR-FreqReselection associated with the priority of the sidelink logical channel: - consider the carrier as a candidate carrier for TX carrier (re-)selection for the concerned sidelink logical channel. - else: - for each sidelink logical channel, if any, where data is available and that are allowed on the carrier for which Tx carrier (re-)selection is triggered according to clause 5.14.1.1: - if the CBR of the carrier is below threshCBR-FreqKeeping associated with priority of the sidelink logical channel: - select the carrier and the associated pool of resources. - else: - for each carrier configured by upper layers on which the sidelink logical channel is allowed, if the CBR of the carrier is below threshCBR-FreqReselection associated with the priority of the sidelink logical channel; - consider the carrier as a candidate carrier for TX carrier (re-)selection. The MAC entity shall: - if one or more carriers are considered as the candidate carriers for TX carrier (re-)selection: - for each sidelink logical channel allowed on the carrier where data is available and Tx carrier (re-)selection is triggered: - select one or more carrier(s) and associated pool(s) of resources among the candidate carriers with increasing order of CBR from the lowest CBR. NOTE 1: It is left to UE implementation how many carriers to select based on UE capability. NOTE 2: It is left to UE implementation to determine the sidelink logical channels among the sidelink logical channels where data is available and that are allowed on the carrier for which Tx carrier (re-) selection is triggered. NOTE 3: If the MAC entity is configured by the upper layer to receive a sidelink grant dynamically on the PDCCH, it is left to UE implementation to determine which carriers configured by upper layer in sl-V2X-ConfigDedicated, as specified in TS 36.331[ Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification ]  [8] are considered as selected carriers for the sidelink synchronization procedures in clauses 5.10.7, 5.10.8 and 5.10.8a of TS 36.331[ Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification ]  [8].