Underwater Networks with Limited Mobility: Algorithms, Systems, and Experiments

This chapter discusses algorithms, systems, and experiments that use limited mobility to enable underwater networks of robots to collect and share observations, and merge these observations into global models. Long-term deployments require minimization of movement and communication to reduce power consumption since there are few charging options underwater. To achieve this minimization, our underwater nodes use a combination of platform and algorithmic approaches. For the platform, the nodes are anchored in position, but adjust their depths in the water, allowing for monitoring of the full water column. Due to the tethering system, energy losses only occur on these depth changes such that once nodes reach a position, they can maintain it for extended periods without any additional energy use. Algorithmically, to position the nodes, we develop a provably convergent decentralized control algorithm to optimize the depths of the nodes for sensing with a more general use for any limited mobility system. In this chapter, we develop the general form of the algorithm, design a specific implementation on our underwater platform for thewater column sensing application, and present the results of several in-situ experiments.