Mutual decentralized synchronization for intervehicle communications

Data exchange among vehicles can improve road safety and capacity. Most of the proposed intervehicle data communication systems require intervehicle synchronization. Synchronization must be done in a decentralized manner. We propose a new mutual decentralized synchronization system. Using a devoted carrier frequency, each vehicle transmits a continuous periodic train of pulses. The aim of the synchronization system is to make these periodic pulses synchronous to indicate the start of data slots in slotted ALOHA types of media access protocol. Each vehicle measures the power of pulses of other vehicles as well as the time difference between other pulses and its own pulse. Using this information, each vehicle shifts its own pulse transmission time toward a weighted average of other pulse transmission times. Eventually, all periodic pulse trains are synchronized. The system performance is evaluated in nonfading and fading channels.