A bidirectional coherent acoustic communication system for underwater vehicles

An acoustic modem for bidirectional communication with an unmanned underwater vehicle has been developed and installed on the Florida Atlantic University Ocean Explorer. The modem is used to test and demonstrate two-way phase-coherent communications between surface platforms and AUVs. However, in addition to serving as a testbed for investigating specific issues associated with high-rate vehicle communications, the modem has been used in actual practice to transmit vehicle status information, CTD data and compressed images to observers on the surface in near real-time. The system includes both medium frequency (2-4 kHz) and high frequency (20-30 kHz) transmission capability for short and medium range data uplink, as well as a towed array for reception at the medium frequency (MF) and a small vertical array for use at the high frequency (HF). The communication system has been tested in Florida, New England and the Bahamas where ranges of 2 km at HF and 4 km at MF have been achieved at burst rates of 6700 bps and 1670 bps respectively in water depths of 10-30 m.