| 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 thesis, 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 lighter and, most importantly, can support significantly higher data rates. Optical communication is characterized by the line of sight property 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 a minimal set of point-to-point optical links that is robust to occasional link failures. We develop patterns for networks with maximum 1, 2 and 3 interfaces per node constraints. We evaluate the robustness of our proposed deployment patterns by simulating three simple 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, thereby minimizing the cost of deployment. |
