A Mobile Communications Gateway for AUV Telemetry

Autonomous underwater vehicle (AUV) operators rely on underwater acoustic telemetry for monitoring and control during mission sorties. This requires operators to maintain acoustic communications by remaining nearby, or deploying a moored gateway buoy and remaining within radio frequency (RF) communications range. An autonomous mobile communications and navigations gateway system has been developed by Hydroid and Woods Hole Oceanographic Institution, to extend telemetry capabilities with REMUS AUVs over the horizon, for situations where deploying moored resources is impractical. Hydroid gateways rely on the Micro-modem acoustic modem, developed by the Acoustic Communications Group at Woods Hole Oceanographic Institution. The modem has been designed with signaling characteristics for reliable communication in the challenging shallow water horizontal propagation path, along with a small physical size and low-power electrical requirements, making it an ideal choice for installation in AUVs. This new mobile “Smart Gateway” is carried as a payload on the Liquid Robotics Wave Glider SV2, an autonomous surface vehicle (ASV), which provides significant energy with long endurance and mobility to allow deep water station keeping, and potentially AUV-coordinated transit. Traditional Gateway systems offered by Hydroid and others typically provide a simple serial interface to the deployed acoustic modem, over RF link. The autonomous gateway system described here manages RF and acoustic links without user intervention, using data caching and AUV link discovery to provide disruption tolerant telemetry services to multiple AUVs. In addition to caching data when links are down, the gateway can monitor the acoustic communications link performance, to adjust acoustic modem data rate, when REMUS AUVs are in range. In addition to telemetry services, the system can provide navigation assistance, by means of a moving long-baseline transponder. This paper provides a detailed system description, along with results from recent at-sea testing.