Hierarchical and Nonhierarchical Three-Dimensional Underwater Wireless Sensor Networks

In some underwater sensor networks, sensor nodes may be deployed at various depths of an ocean making those networks threedimensional (3D). While most terrestrial sensor networks can usually be modeled as two dimensional (2D) networks, these underwater sensor networks must be modeled as 3D networks. This leads to new research challenges in the area of network architecture and topology. In this paper, we present two different network architectures for 3D underwater sensor networks. The first one is a hierarchical architecture that uses a relatively small number of robust backbone nodes to create the network where a large number of inexpensive sensors communicate with their nearest backbone nodes, and packets from a backbone node to the sink is routed through other backbone nodes. This hierarchical approach allows creating a network of smaller number of expensive backbone nodes while keeping the mobile sensors simple and inexpensive. Along with network topology, we also study energy efficiency and frequency reuse issues for such 3D networks. The second approach is a nonhierarchical architecture which assumes that all nodes are identical and randomly deployed. It partitions the whole 3D network space into identical cells and keeps one node active in each cell such that sensing coverage and connectivity are maintained while limiting the energy consumed. We also study closeness to optimality of our proposed scheme.