Embodiments of a User Equipment (UE), Generation Node-B (gNB) and methods of communication are disclosed herein. The UE may attempt to decode sidelink synchronization signals (SLSSs) received on component carriers (CCs) of a carrier aggregation. In one configuration, synchronization resources for SLSS transmissions may be aligned across the CCs at subframe boundaries in time, restricted to a portion of the CCs, and restricted to a same sub-frame. The UE may, for multiple CCs, determine a priority level for the CC based on indicators in the SLSSs received on the CC. The UE may select, from the CCs on which one or more SLSSs are decoded, the CC for which the determined priority level is highest. The UE may determine a reference timing for sidelink communication based on the one or more SLSSs received on the selected CC.