Wireless Underwater Sensor Networks

In the report a wireless sensor network for passive as well as active acoustic surveillance under water is described. A feasible use is surveillance of an area at sea like the entrance to a harbour or a base. With other sensors the network also has a civilian use, e.g. for environmental surveillance. The network has a decentralised architecture and a large part of the signal processing is done locally within each node or in a group of network nodes, after which the result is presented to the operations centre or similarly. Being autonomous and wireless the system is rapidly deployed, and covert if needed. The major part of the report deals with the design of the communications protocols for the network. Designing network protocols for the underwater acoustic channel is a great challenge. To achieve reasonable capacities, protocols need to be tailored to the specific scenario. In particular the MAC protocol is important to design properly. In the report we discuss two different protocol solutions, one based on Aloha and one on TDMA. The solution based on Aloha is simple to implement but gives an expected low throughput in the network. A TDMA solution, on the other hand, can be made fairly efficient when tailored to our specific scenario.