Hybrid time-frequency domain equalization for single-carrier underwater acoustic communications

Abstract

Single-carrier block transmission (SCBT) has a great potential for providing higher bandwidth efficiency over frequency-selective channels with reduced computational complexity and low peak-to-average power ratio (PAPR). In this paper we propose a hybrid time-frequency domain equalization method for pseudorandom noise (PN) based single-carrier block transmissions. The proposed hybrid time-frequency domain equalizer includes two parts: a multi-channel frequency domain equalizer and a single channel adaptive time domain decision feedback equalizer (DFE). Bidirectional DFE and time-reversal diversity processing to cancel both residual post-cursor and pre-cursor intersymbol interference (ISI) is extended to hybrid time-frequency domain equalizer.Underwater acoustic communication systems with single transmitter and multiple receivers have been designed and tested in lake in 2011. At a distance of 1.8 km, the useful data rates around 1500-7000 bps were achieved with uncoded bit error rate (BER) 10--3-10--5 using the presented schemes. Experiment shows the performance can be enhanced by 1.5-3.8 dB in terms of output signal-to-noise ratio (SNR). A sea experiment was conducted with single transmitter and single receiver in 2012. At a distance of 625 m, the useful data rates around 8750 bps were achieved with uncoded bit error rates 10--2-10--3 using the presented schemes. Experiment shows the performance can be enhanced by 1.6-2 dB in terms of output SNR.