In any digital communication system (even for very simple wired communication), there is a specific mechanism for synchronization. In case of simple / short distance wired system the device gets synchronized by edge (falling or rising) of a specific bit pulse. In a little bit complicated wired system, they use a sequence of bit pattern often called 'preamble' for synchronization.
In Wireless communication environment, the factors currupting the timing are more diverse and aggravating. Therefore, we would need more efficient and sophisticated mechanism to guarantee the synchronization. Usually in cellular system(at least 3G, 4G, 5G system), we use one or more types of specific signal for downlink synchronization and use RACH process for uplink synchronization.
Different Radio Technology use different types of Sync signals and Synchronization process.