Experimental results with HF underwater acoustic modem for high bandwidth applications

We present a robust, video-capable modem designed for wireless underwater acoustic communication. The difficult nature of the underwater acoustic channel necessitates explicit Doppler compensation and mitigation of severe multipath. Due to the relatively low propagation speed of sound in water, platform mobility causes severe Doppler that cannot be treated as in RF wireless communicaiton, as a frequency shift or through a global rescaling. We model the underwater acoustic channel with explicit time-varying Doppler and multipath, and derive the turbo resampling equalizer (TRE) that tracks and mitigates these phenomena. Building on previous work, we demonstate experimental results achieving data rates in excess of 1 Mbps over 100 m in shallow water, and successfully transmit live video over a 5 m underwater acoustic channel from a rapidly moving transmitter with speeds in excess of 3 m/s and accelerations in excess of 7m/s2.