High-frequency channel characterization for M-ary frequency-shift-keying underwater acoustic communications

Many (>100) packets of pseudo-random signals transmitted during the TREX04 experiments are analyzed in this paper to deduce the narrowband signal envelope amplitude statistics over a wide band (15–19kHz) of frequencies. The envelope amplitude statistics are found to be non-Rayleigh-type with a long-tail distribution at high amplitudes. Long-term and short-term fading statistics are deduced from the data, exhibiting near lognormal and Rayleigh distributions, respectively. The combined distribution is closely approximated by a K-distribution, which fits the measured amplitude distributions well over a wide band of frequencies.