Estimation of wave parameters from accelerometry to aid AUV-shore communication

Commercial off-the-shelf autonomous underwater vehicles (AUVs) are commonly equipped with short range radios (for high bandwidth, low-cost close range operation) and satellite modems (for low bandwidth, global operation). In a coastal observatory it should thus be possible to exploit an AUVs' proximity to the coast to use the short range radios when vehicles are within useful communication range of coastal base stations, and to use satellite communications otherwise. Measurements in the coastal ocean using a Slocum glider and a network of elevated, coastal base stations show that the useful communication range depends strongly on two parameters 1) the distance between the vehicle and the base station, and 2) the local sea state experienced by the vehicle. Here we describe measurements of communication quality in a coastal setting over 206 glider surfacing events at ranges between 2.4 and 16 km from the base station. The glider was instrumented with an accelerometer. At each surfacing, the accelerations experienced by the glider due to the local sea state were recorded concurrently with communication quality. Analysis of these measurements provides the first evidence that it is possible to predict communication quality from the sea state at a vehicle's location and the distance between the vehicle and the nearest base station. This enables a simple, yet useful, piece of logic that allows onboard decision making on whether the vehicle should use its short range radio or its satellite modem. We discuss how this finding enables online modification of low-level communication protocol parameters.