The unique properties of underwater acoustic communications, such as large and time-varying propagation, low and range dependent bandwidth, and adverse operating environment make the synchronization of Underwater Acoustic Sensor Networks (UWASNs) very challenging. In this dissertation, to enhance synchronization performance we address three crucial issues of UWASNs: time-varying propagation, consistency of timestamps being used and bandwidth efficiency. We show that, if not mitigated, time-varying propagation would lead to a very poor synchronization for UWASNs. To address the issue, we propose a low complexity algorithm, which employs a simple preprocessing method to obtain delay compensated timestamps and avoids the assumption of static underwater node. The extensive simulation results demonstrate that with a much lower computational complexity compared with alternative approaches in the literature, the proposed approach achieves an improved precision in synchronization. We identify the importance of consistency analysis of the timestamps obtained in adverse underwater environment by showing that collisions, which are not uncommon during data transmission, may cause inconsistent timestamps. We propose a robust synchronization algorithm for underwater networks, which identifies and eliminates the inconsistent timestamps by utilizing the concept of Cook’s distance and achieves an enhanced synchronization as shown through extensive simulations. As available bandwidth is extremely limited and energy consumption is critical in underwater networks, exchanging many two-way signals for synchronization would deteriorate the system performance noticeably.
|Qualification||Doctor of Philosophy|
|Publication status||Unpublished - 2012|