Pair-wise collision-based underwater time synchronization

Time synchronization is a critical issue for Underwater Wireless Sensor Networks (UWSN). Although numerous time synchronization algorithms have been proposed for terrestrial wireless sensor networks, none of them could be applied to UWSN directly. This is because underwater time synchronization offers two fundamental challenges compared with terrestrial wireless sensor networks, i.e., (1) long propagation delay and (2) sensor node mobility. We propose a novel time synchronization approach called Coll-Sync to address the above challenging problems, which is a pair-wise collision-based time synchronization scheme for mobile underwater acoustic sensor networks. Coll-Sync adopts collision and packet meetings in a long propagation process to eliminate the effect of node mobility. In this paper, we indicate that collision and packet meetings contain highly useful information that can be leveraged to improve time synchronization. Through comprehensive experiments, we show that our proposed Coll-Sync greatly outperforms existing time synchronization schemes in both precision and energy saving.