Underwater channel characterization for shallow water multi-domain communications

Abstract

The underwater acoustic channel is a difficult communication medium due to its variable link quality which depends on location, time and the environment.This paper reports on underwater channel characterization for shallow water (< 100 m) in the Atlantic offshore of Halifax, Canada. The underwater channel characteristics drives the level of multi-domain robot collaboration possible to characterize a floating target both above- and below-water. RF communications is used between the topside unmanned surface vehicle and unmanned aerial vehicle. Underwater, acoustic modems are used between the submerged part of the unmanned surface vehicle and the unmanned underwater vehicles. The outcome is a multi-domain picture of the floating target from the sensors on these collaborating robots.Before deployment, simulations were performed with a tool that integrates BELLHOP and newly developed complementary analysis capabilities in a MATLAB framework to determine operational ranges from range-dependent attenuation. The main contributions are an underwater acoustic environment-informed approach to placing mobile communicating nodes in a network, the network’s range predictions, channel analysis and a user-friendly GUI to manage the BELLHOP inputs and outputs. The approach and tools are validated in simulations and verified in-water. Transmission losses (TL) and underwater channel characteristics for illustrative cases are presented.