AUV-Aided joint time synchronization and localization of underwater target with propagation speed uncertainties

Abstract

The accurate sensor localization is one of the most basic requirements for the Underwater Acoustic Sensor Networks (UASNs) in many applications. However, in harsh underwater environment, the existence of propagation speed variation with depth (i.e., stratification effect) and asynchronous clock generally affects the ranging estimation, and in turn significantly decreases localization accuracy. Taking into account these specific characteristics of UASNs, we first propose an efficient Autonomous Underwater Vehicle (AUV) aided joint localization and time synchronization solution for UASNs, subjected to stratification effect constraint, in which AUV acts as a mobile anchor and broadcasts beacon signals periodically to provide localization reference for unknown target sensors. Next, since the estimation accuracy of localization and synchronization is very sensitive to the accuracy of the AUV locations, the joint localization and synchronization method in the case of inaccurate AVU locations is considered. Then, Cramer Rao Lower Bound (CRLB) analyses are presented for both accurate and inaccurate AVU locations cases. Finally, numerical simulation results show that the proposed method in this paper outperforms the existing ones in terms of estimation errors.