Mote-based underwater sensor networks: Opportunities, challenges, and guidelines

Most underwater networks rely on expensive specialized hardware for acoustic communication and modulation. This has impeded wide scale deployments of underwater sensor networks and has forced researchers to use simulations to investigate these systems. To address these issues, this paper examines a system that integrates off-the-shelf acoustic hardware built-in to sensor modules with software modems for establishing underwater acoustic links. Because the hardware in our system is readily available, we have conducted several rounds of field experiments to evaluate it. Building on our recent field experiments in a river, canal, pond, and swimming pool, this paper outlines the technical and logistical challenges for deploying software-driven underwater sensor networks. The design choices include methods for signal modulation at the sender, and symbol synchronization, signal filtering, and signal demodulation at the receiver. We also discuss higher layer communication protocol issues, with a focus on cross-layer optimization, as well as practical solutions to logistical deployment challenges, such as waterproofing and casing, calibration, and fouling. The design guidelines in this paper lay the groundwork for further development of software-driven of underwater sensor networks.