Mutual decentralized synchronization for inter-vehicle communications

Data exchange among vehicles improves road safety and capacity. Most of the proposed inter-vehicle communication systems require synchronization to 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 synchronize these periodic pulses to be pointers to the start of data slots in slotted ALOHA. Each vehicle measures the power of pulses of other vehicles as well as the time difference between other pulses and its own pulse. Each vehicle shifts its own pulse transmission time towards a weighted average of other pulse transmission times. Eventually all periodic pulse trains are synchronized. The system performance is evaluated in a non-fading and multi-path fading channels.