Apple patents car-to-car sync method for when GPS signals drop

1. A method, performed by a user equipment (UE), for sidelink synchronization for new radio vehicle-to-everything (NR V2X) communication in a wireless communication system, the method comprising: performing an initial sidelink synchronization by: detecting a valid synchronization source, wherein the valid synchronization source is a first detected synchronization source for sidelink communication, and triggering, without regard to a priority associated with the valid synchronization source, synchronization and sidelink communication with the detected valid synchronization source; deriving a sidelink synchronization signal (SLSS) identifier (ID) and physical sidelink broadcast channel (PSBCH) content, wherein deriving the SLSS ID and the PSBCH content is based at least in part on whether the UE is directly synchronized with a global navigation satellite system (GNSS), indirectly synchronized with the GNSS, directly synchronized with the base station, indirectly synchronized with the base station, or synchronized with an independent synchronization source, wherein the PSBCH content includes a different synchronization hop information field, timing information field, and original synchronization source field that indicates whether the original synchronization source is a GNSS, network, or independent synchronization source based on a type of synchronization, and wherein the SLSS ID is randomly selected from a pre-configured range of SLSS IDs for independent synchronization sources; directly synchronizing with the GNSS after the initial sidelink synchronization in response to detecting the GNSS; determining a loss of GNSS synchronization for the UE; and performing, in response to the loss of GNSS synchronization, synchronization with a serving base station for the UE, wherein the serving base station is timing aligned with the GNSS timing of the UE.