HydroNode: an underwater sensor node prototype for monitoring hydroelectric reservoirs
Proceedings of the Seventh ACM International Conference on Underwater Networks and Systems
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The Earth is a water planet. The largely unexplored vastness of the ocean, covering about two-thirds of the surface of Earth, has fascinated humans for as long as we have records. There is interest in monitoring the marine environment for scientific exploration, commercial exploitation, and military applications such as coastline protection and submarine detection. SEA-Swarm (Sensor Equipped Aquatic Swarm) is a novel underwater sensor network architecture. It consists of a large number of low cost untethered underwater sensors that operate and move as a group (swarm) with water current and dispersion. A SEA Swarm enables 4D (space and time) monitoring of local underwater events such as contaminants and intruders. Due to radio signal attenuation, unlike ground-based sensor technology, underwater networks are based on acoustic communications. Due to the very different environment properties and also the unique nature of the applications, the protocols developed for ground-based sensor networks are not directly applicable to SEA-Swarm networks. Among the many potential applications, we address underwater surveillance. More specifically, we consider coastline protection and submarine detection. In this scenario, sensors forward events to mobile sinks, such as unmanned submarines which then take direct action or report to control center. We describe the building blocks that enable this application: localization, mobility model and communication. Localization is required to tag sensed data. It is also essential for position based routing algorithms. A realistic mobility model that captures the physical movement of the sensor nodes with ocean currents is essential for this study. The mobility model impacts connectivity, coverage and deployment of these network. The realistic mobility model has been implemented in the simulator. Finally, communication issues are addressed by presenting a location service, studies on network coding and describing the benefits of opportunistic routing in underwater networks. The Location Service provides location information enabling geographic routing in underwater. Network Coding works by combining packets while they are being routed. It improves robustness and throughput in multicast applications. Opportunistic Routing allows the packet to be forward even if it was not received by the designated neighbor nodes. It can help mitigate underwater acoustic medium challenges, such as high bit error rate, temporary loss of connectivity due to shadow zones, limited bandwidth and communication signal spreading.