Focused Beam Routing Protocol for UnderwaterAcoustic Networks

Multi-hop transmission is considered for large coverage areas in bandwidth-limited underwater acoustic networks. In this paper, we present a scalable routing technique based on location information, and optimized for minimum energy per bit consumption. The proposed Focused Beam Routing (FBR) protocol is suitable for networks containing both static and mobile nodes, which are not necessarily synchronized to a global clock. A source node must be aware of its own location and the location of its final destination, but not those of other nodes. The FBR protocol can be defined as a cross-layer approach, in which the routing protocol, the medium access control and the physical layer functionalities are tightly coupled by power control. It can be described as a distributed algorithm, in which a route is dynamically established as the data packet traverses the network towards its final destination. The selection of the next relay is made at each step of the path after suitable candidates have proposed themselves. The system performance is measured in terms of energy per bit consumption and average packet end-to-end delay. The results are compared to those obtained using pre-established routes, defined via Dijkstra's algorithm for minimal power consumption. It is shown that the protocol's performance is close to the ideal case, as the additional burden of dynamic route discovery is minimal.