High-Rate Information Transmission for Underwater Channels: Path-Specific Beamforming and Doppler Compensation

In this article, we present path-specific beamforming and Doppler compensation in the context of a single-input multiple-output single-carrier system for underwater acoustic communications. We address scenarios in which the multipath channel exhibits different Doppler shifts on different propagation paths. The proposed algorithm draws upon the use of beamforming to isolate the multipath signals, which are subsequently fed to a multi-channel fractionally-spaced decision-feedback equalizer (DFE). In addition to the conventional DFE, a delay-locked loop (DLL) is coupled with a phase-locked loop (PLL) to perform adaptive online resampling. The DLL eliminates the need of front-end resampling, even in high Doppler regimes. The performance is demonstrated through simulation and using an experimental underwater transmission, showing excellent results in terms of data detection mean squared error (MSE) and bit error rate (BER).