Optimization in design of underwater sensor networks

Underwater sensor networks will find applications in oceanographic data collection, pollution monitoring, offshore exploration, disaster prevention, assisted navigation and tactical surveillance applications. Underwater acoustic networking is the enabling technology for these applications. Underwater sensor networks consists of variable number of sensors that are deployed to perform collaborative monitoring tasks over a given area. Underwater sensor nodes are interconnected to one or more underwater sinks, which are in charge or relaying data from the ocean bottom to a surface station. Underwater sink are also equipped with horizontal links to communicate with other sensor nodes. Sensors are can be connected to sinks by means of direct links or multi-hop paths. This dissertation presents a new formulation addressing the optimum location of underwater sinks in underwater sensor networks. The problem of locating the underwater sinks consist of finding the position of underwater sinks such that all underwater sensor are within d-hop distance of at least one underwater sinks. It is shown that this problem is NP-complete. However, there is a polynomial time approximation scheme for this problem. We also present two approximation algorithm for this problem. The underwater sink placement problem, in which the underwater sinks are just required to d-hop cover all nodes in the network may introduce bottle neck problem. In order to over come this problem we will introduce balanced sink placement problem, in which each underwater sink will d-hop cover a bounded number of sensor nodes. We also consider a situation when the number of available underwater sinks is bounded for some real time applications. In this case we will introduce some novel methods to locate underwater sinks such that the each sensor node can be covered by an underwater sink via a bounded hop distance.