Characteristics of multipath signals and demodulation performance in underwater acoustic communication with a fast-moving terminal

Abstract Underwater acoustic communication with a fast-moving terminal in shallow water remains challenging due to time-varying channels characterized by multipath signals with significant delays and amplitudes, as well as various Doppler shifts. Recently, two types of decision feedback equalizers have been proposed: one designed to address nonuniform variations in reception time of a direct signal, and another aimed at mitigating Doppler shifts in multipath signals, specifically for vertical communication in deep water. In this study, simulations were conducted to investigate how channels with a fast-moving terminal in shallow water degrade demodulation performance, by evaluating the characteristics of individual multipath signals and performance of these equalizers under such conditions. The results reveal that the individual characteristics and setting parameters for equalizers determine performance. Furthermore, the equalizers designed for vertical channels in deep water also improve the performance in channels with a fast-translating terminal in shallow water.