Low frequency phase coherent communications in the Sicily Strait

Low frequency (950-1450 Hz) quadrature phase shifted keying signals were transmitted between a bottom mounted source and vertical array during the 1999 Adventure Bank experiment in the Sicily Strait at a distance of 10 km. The purpose of this experiment was to minimize the effect of Doppler shift/spread due to source motion so that the effect of the environment can be better diagnosed. Temporal and spatial coherence of the signal are measured to analyze the performance of beamforming and spatial diversity versus the number of phones using a sparse equalizer. It is shown that by choosing phones according to spatial coherence and combining beamforming with diversity, bit error rates of the order of 10^-3 were achieved consistently over a period of ~9 hours with a signal-to-noise ratio as low as ~1 dB at the phone level