Statistical Modeling of a Shallow Water Acoustic Communication Channel

A mathematical model for the impulse response of a time-varying shallow water acoustic channel is proposed. The channel is modeled as a superposition of multiple propagation paths, whose lengths and relative delays are calculated from the channel geometry. Each path is characterized by a frequency-dependent path loss, and an additional random time-variation, expressed as a multiplicative distortion. Experimental signals collected during a 2008 test in the Narragansett Bay off the coast of North America are used to assess the statistical properties of the channel. Ricean distribution, conditioned on a timevarying mean, is found to be a good match for the path gain. Measurements of the average received power over short time intervals are made to assess the channel coherence, and to test the possibility of developing a feedback-based channel state prediction for power control or adaptive modulation.