Robust TDA-MAC for practical underwater sensor network deployment: lessons from USMART sea trials

In this paper, we present the results of deploying the first test prototype of the USMART low cost underwater sensor network in sea trials in Fort William, United Kingdom, on 29 June 2018 and 3 July 2018. We demonstrate the first ever hardware implementation of the Transmit Delay Allocation MAC (TDA-MAC) protocol for data gathering in underwater acoustic sensor networks (UASNs). The results show a successful application of TDA-MAC to remote environmental monitoring, integrating a range of sensor nodes developed by the universities of Heriot-Watt, York, Newcastle and Edinburgh. We focus on the practical challenges and their mitigation strategies related to TDA-MAC to increase its robustness in real-world deployments, compared with theoretical and simulation-based studies. The lessons learned from the sea trials reported in this paper prompted several crucial modifications to TDA-MAC which form a solid foundation for further work on the development of TDA-MAC based UASNs.