Underwater delay tolerant routing in action

Underwater Sensor Networks (UWSN) have several applications in aquatic environments ranging from target tracking to environmental monitoring. Harsh nature of underwater environments and different conditions and properties of the medium compared to on-ground environment pose some challenges when it comes to the design of a robust system. One of these challenges is the continuously moving aquatic flows, and at sometimes the autonomously moving nodes, that lead to a continuously varying network topology. When the nodes within the network are sparse, this variation requires special attention when designing a data routing protocol for such networks. Delay tolerant networks (DTN) account for this variation through the allowance of some permissible amounts of delay when transferring the data from a source node to a destination node. In this work, a DTN routing protocol for UWSN is designed. During the design process, the main properties of UWSN were taken into consideration. For example, continuous motion of nodes was dealt with through the use of state tables to keep the one-hop neighbor and hop count information. Additionally, collision avoidance was alleviated through the use of random time intervals between control packet transmissions. The protocol was successfully implemented in Aqua-Net architecture. Lab tests were also conducted successfully using Benthos acoustic modems in the University of Connecticut´s UWSN lab. Results demonstrated that data packets can be successfully sent from source to destination with the assistance of auxiliary control packets within permissible delays.