A clock synchronization independent localization scheme for underwater wireless sensor networks

Almost all the existing range-based localization schemes for underwater wireless sensor networks (UWSNs) assume that clocks of different nodes are well synchronized. However, clock synchronization is very challenging in UWSNs. In this paper, we design a clock synchronization independent localization scheme (CSILS). Instead of trying to estimate distances between unknown nodes and anchor nodes, we design a scheme for obtaining the distance differences based on the local clocks. In order to convert the distance differences into node's location, we propose distance-difference-based maximum likelihood estimation (D-D-BMLE). Finally, we give some suggestions on how to deploy anchor nodes Simulation results show that CSILS works well without clock synchronization when anchor nodes are deployed reasonably. Compared to a clock-synchronization-based localization scheme, CSILS improves localization accuracy with a proper level of localization coverage and communication overhead in terms of mobility model of water currents.