Opportunistic Localization and Synchronization for Underwater Acoustic Sensor Networks

Underwater acoustic sensor networks (UASN) have many applications, such as monitoring environmental quality, exploring underwater targets and more. Node localization and synchronization in UASNs are preliminary tasks. However, the uncertainties of underwater acoustic channels have brought many difficulties to the localization and synchronization of UASNs. In this context, localization and synchronization in UASNs are opportunistic. In this paper, a method of localization and synchronization is proposed for an asynchronous UASN. In this UASN, autonomous underwater vehicles (AUVs) serve as mobile anchor nodes to provide information for synchronizing and localizing the static sensor nodes. To improve service life of the static sensors, a (q, p) duty-cycle working mode is designed for them. Due to the (q, p) working mode and the uncertainties of acoustic channels, this paper analyzes the operating conditions for successfully synchronization and localization. An EM algorithm for synchronization and localization that can handle uncertainties of the mobile anchor positions is proposed. Finally, simulation experiments are provided in order to test the performance of the EM algorithm, the EM method performs better than other algorithms.