Decision Feedback Equalizer with Feedback Filters for Receiver Channels on Underwater Acoustic Communication

In underwater acoustic communication, channel responses are characterized by time-varying environment and multipath signals with large amplitudes and lags. To deal with such channels, a decision feedback equalizer has been used for everal decades now, in many cases with a single carrier modulation scheme. The equalizer consists of feedforward and feedback filters and digital phase locked loops. A feedback filter is used on the synthesized signals over received signals for all channels, whereas a feedforward filter is used on a received signal of the corresponding channel. In this study, a decision feedback equalizer with feedback filters for receiver channels is proposed. Furthermore, the demodulation performance of the equalizer is evaluated using previous experimental data. The results of the evaluation show that the proposed equalizer improves the performance in demodulation of some slots. In cases of the other slots, the performance is almost the same as that of conventional equalizer. This indicates that the proposed equalizer can offer demodulation performance equal to or better than that offered by conventional equalizer.