Multi-Resampling Equalizer for Underwater Acoustic Single Carrier Communication

Wideband Doppler effect is a significant challenge for underwater acoustic communication (UAC). In this paper, we propose a novel multi-resampling equalizer to solve the Doppler problem caused by relative motion. In this equalizer, the received signal is resampled in parallel, then passed through a feedforward filter (FFF), and combined to suppress the wideband Doppler effect. The combined signal is passed through a phase lock loop (PLL) and a feedback filter (FBF) to eliminate the residual Doppler effect and residual intersymbol interference. The coefficients of these filters are updated by recursive least squares (RLS). Compared to conventional timescale estimation-based equalizers, the proposed equalizer does not need to send two segments of LFM. Thus, it reduces the power consumption and transmission time. At the same time, it does not need to receive a complete segment of communication data to demodulate, improving communication's realtime performance. Finally, the experiments are presented to demonstrate the validity of the proposed equalizer. The results show great improvement compared to conventional timescale estimation-based equalizer.