Time synchronization for underwater sensor networks based on multi-source beacon fusion

Time synchronization is the foundation for collaboration among sensor nodes. Acoustic communication and restricted mobility of sensor nodes are two unique characteristics of underwater sensor networks (UWSNs), negating the effect of terrestrial synchronization schemes. Existing UWSN time synchronization protocols focus on point to point synchronization, incompatible for large-scale networks. Moreover, some of them require special hardwares and deployment conditions. In this paper, we propose MulSync, a scalable synchronization protocol for multi-hop UWSNs. MulSync includes the synchronization communication scheme to exploit acoustic communication nature of broadcast. The skew and offset are estimated by performing linear regression three times over a set of time stamp pairs gathered through message exchange. Three linear regressions are exploited to make full use of the time reference information delivered from multi-source beacons. Simulation results demonstrate that MulSync achieves high accuracy at low message overhead and time cost.