A low-cost distributed networked localization and time synchronization framework for underwater acoustic testbeds

Localization and time synchronization are both essential services for Internet-connected underwater acoustic testbeds. Although the two are mutually coupled, they are often treated separately. We propose a new low-cost distributed networked localization and time synchronization framework for underwater acoustic sensor networks. The proposal is based on decoupling the two problems and solving first the time synchronization then localization using the same set of messages, i.e., with no additional overhead. A coarse, followed by a fine-grained, localization algorithm is adopted to accurately estimate the location of an unknown node. The solution is robust to noisy range measurements. The proposed scheme is implemented in a testbed based on Teledyne Benthos Telesonar SM-975 underwater modems and tested extensively in Lake LaSalle at the University at Buffalo. Experiments and simulations in terms of root mean square error (RMSE) demonstrate that the proposed scheme can achieve a high accuracy for a limited energy budget.