Joint Time Synchronization and Localization for Underwater Acoustic Sensor Networks

Time synchronization and localization for underwater acoustic sensor networks (UASNs) face new challenges in several aspects. Since an acoustic signal propagates slowly underwater, the propagation delay cannot be neglected. Hence, time synchronization is tightly coupled with localization. Furthermore, underwater sensor nodes have stringent energy constraints, and they are expected to have a long lifetime. To overcome these challenges, in this paper we propose a joint time synchronization and localization scheme for an asynchronous UASN, where static nodes are synchronized and localized with the help of a mobile node. The mobile node broadcasts packets for synchronization and localization periodically, and the period is carefully designed to avoid collisions. To save energy, the static nodes work in a (q, p) duty-cycle schedule, which impacts the packet receiving for the static node. Consequently, the probability for the static nodes to be successfully synchronized and localized is analyzed. It sheds lights on the design of system parameters to achieve a high probability. Moreover, simulation results indicate the efficiency of the proposed scheme.