Underwater sensor networks with mobile agents: Experience from the field

This paper reports the experimental results obtained by two research projects, UAN and Thesaurus, in which two different network communication schemes have been implemented in the context of underwater robots cooperation. UAN implemented a complex layered communication scheme including collision avoidance medium access, node addressing and routing strategies, and mobile nodes as adaptable network components able to sustain the communication. Thesaurus is deploying a Time Division Multiplexing network with the explicit objective of supporting the robotic exploration of deep water archaeological sites. The paper examines the approaches and challenges in the design and implementation of both underwater sensor networks. It discusses how the specific application influenced the design and the operation of the communication protocols at the various network layers. Field results are presented to discuss how the network structure impacts on the underwater robot cooperation and on the overall sensing network performance.