Adaptive multichannel combining and equalization for underwater acoustic communications

TLDR

Practical receivers based on these structures face difficulties in underwater acoustic channels due to extended time‑varying multipath and phase instabilities. The authors propose a receiver that overcomes these problems by jointly performing adaptive mean‑squared error diversity combining, multichannel carrier‑phase synchronization, and decision‑feedback equalization. Its performance is demonstrated on experimental telemetry data from deep and shallow water long‑range acoustic channels. The authors derive a theoretically optimal multichannel receiver for intersymbol interference channels, present suboptimal linear and decision‑feedback equalizer variants, and show experimentally that joint equalization of few channels yields superior coherent PSK and QAM reception.

Abstract

A theoretically optimal multichannel receiver for intersymbol interference communication channels is derived, and its suboptimal versions with linear and decision feedback equalizer are presented. A practical receiver based on any of these structures encounters difficulties in the underwater acoustic channels in which the extended time-varying multipath is accompanied by phase instabilities. A receiver that overcomes these problems by jointly performing adaptive mean-squared error diversity combining, multichannel carrier-phase synchronization and decision feedback equalization is proposed. Its performance is demonstrated on the experimental telemetry data from deep and shallow water long-range acoustic channels. Presented results indicate superior quality of coherent PSK and QAM reception obtained through joint equalization of very few channels.