Robust grid-based deployment schemes for underwater optical sensor networks

Underwater sensor networks have received significant attention from the research community in recent years. Since radio signals face excessive absorption in the underwater environment, acoustic communication has been the dominant physical layer medium in the literature. Although acoustic communication has long range and omni-directional characteristics like terrestrial radio, it suffers from excessive propagation delay in water and very low bandwidth. In this paper, we consider the design of an optical underwater sensor network based on low cost LEDs and photodiodes. Such an optical communication system has shorter range compared to acoustic systems but is cheaper and can support significantly higher bandwidth. Optical communication requires line of sight which makes optical links vulnerable to occasional failures due to underwater organisms and moving particles. We consider a grid based deployment of underwater sensor nodes and the selection of a topology based on point-to-point optical links that is robust to occasional link failures. We develop patterns for networks with at most 3 interfaces per node constraints. We evaluate the robustness of our proposed deployment patterns by simulating three resilient routing protocols on these patterns and demonstrate that our patterns support a high degree of robustness even though they use only a fraction of all potential links in the grid graph.