SMP-Sync: Time synchronization using seawater movement pattern for underwater wireless networks

Time synchronization in underwater environment is challenging due to high propagation, high-channel access delay and mobility of sensor nodes. Therefore, in our research, we suggest novel time synchronization based on features of underwater environment, called “SMP-Sync”. To show motivation of our research, we define error factors over linear-regression in time synchronization and propose a method to handle those errors. Especially, it controls the instant of transmission by exploiting the feature of seawater movement and node deployment. Moreover, the protocol uses more accurate time information by removing channel access delay from the timestamp. The SMP-Sync is also practical on the underwater sensor network requiring low-power consumption because the SMP-Sync conducts time synchronization with smaller transmission and reception times compared with previous works. Finally, simulation results show that the SMP-Sync reduced time error by 2.5ms and 0.56ms compared with TSHL and MU-Sync respectively, reducing communication overhead.