Single-carrier underwater acoustic communication combined with channel shortening and dichotomous coordinate descent recursive least squares with variable forgetting factor

In this study, the authors propose a novel decision feedback equaliser (DFE)-based receiver, which combines channel shortening methods and dichotomous coordinate descent (DCD) recursive least squares (RLS) adaptive algorithm with variable forgetting factor (VFF). The proposed receiver can obtain its performance gain via two aspects: (i) reducing the computing complexity by channel shortening method, such as passive time reversal (pTR) filter or minimised mean-square error (MMSE) filter and (ii) improving the performance of the receiver, such as a lower bit error rate and mean-square error. Underwater acoustic (UWA) channel has the features of long multi-path spread and time-varying property. When the multi-path spread is very long, pTR or MMSE filter is used as a channel shortening pre-processing method to reduce the computing complexity in the DFE receiver. When the channel is time varying, VFF is incorporated into DCD-RLS adaptive algorithm to improve the tracking capability of the DFE receiver. The proposed receiver is appealing for practical implementations. Numerical examples and lake experimental results show that, the proposed DFE receiver can achieve a better performance in the UWA communication system.