Diversity combining for long-range acoustic communication in deep water.

A recent experiment showed that coherent long-range acoustic communication is feasible in deep water over a ∼550 km range between a source towed slowly at ∼75 m depth and a horizontal line array towed at 3.5 knots at ∼200 m depth. This letter further demonstrates that diversity combining mitigates channel fading and increases the output signal-to-noise ratio. Using sparse channel-estimate-based equalization, three transmissions are combined successfully to decode a 40 Hz bandwidth (230-270 Hz) 8 phase-shift-keying communication signal, achieving an effective data rate of 17 bits/s at ∼550 km range.