Large Delay Underwater Sensor Networks Clock Synchronization With Mobile Beacon

Recently, a various of science technology has been matured, WSN, the short forwireless sensor networks has been applied to more different fields. With the increasinginterests in economy, industry and agriculture, underwater wireless sensornetworks(UWSN) received people’s tremendous attention. Construction of UWSN hasmore importance on exploring the ocean activities, collecting information, monitoringthe danger, researching the fishery resources, developing seabed resources, exploitingocean economy.Clock synchronization is one of critical services needed by WSN. In ocean,UWSN mainly adopts acoustic communication, there are several factors such as lowspeed transmission, Doppler shift, large energy consumption, limited hardware and thevariability of the marine environment that affect the data transfer in the water, so mostexisting WSN synchronization can not be applied to UWSN directly. In this paper, wecome up with a new clock synchronization algorithm, called "Ma-Sync", which is amobile-assisted clock synchronization algorithm for large delay UWSN. It exploitsmobile beacon node to assist clock synchronization and utilizes the relationshipbetween distance and propagation delay to compute the clock skew and offset. In thissense, it is a novel clock synchronization approach, eliminates the effect of largepropagation delay without special deployment and additional hardware.Based on Ma-Sync clock synchronization, we realize the communication of thenodes and the communication between nodes and computer. In order to make theexperiment be similar to underwater, we put delay in one of them. In computer, we getthe time stamps, then compute the clock skew by java program. The program includesthe time information and the formulas get from the Ma-Sync. After correcting the time of the receiver, the time of the sender equal to the receiver, we can prove the validity ofMa-Sync. Simulation result shows Ma-Sync algorithm can reduce energy consumptionduring the synchronization process and improve clock synchronization precisioncompared with other clock synchronization algorithm.