Progressive Multichannel Equalization Based on Beamforming for Underwater Acoustic Multipath Channel

The multi-channel equalizer can utilize spatial diversity gain to reduce inter-symbol interference (ISI) in underwater acoustic (UW A) communication system more effectively. However, it also significantly increase the system complexity and bring a lot of noise. Beam-domain processing can reduce the number of equalization channels by performing beamforming to multi-channel received signals, thus reducing system complexity In practice, however, the optimal number of array sensors is usually hard to predict. In this paper, a progressive beam-domain multi-channel decision feedback equalizer (DFE) is proposed. The proposed method can adaptively adjust the number of array sensors being used according to the desired performance, thereby achieving a good trade-off between performance and complexity. This method works in an iterative way. When the decoding of the current iteration fails, the receiver will increase the number of sensors at the next iteration until the decoding succeeds or the output signal-to-noise ratio (SNR) of the equalizer begin to decrease. Numerical simulation results show that the proposed method enjoys lower complexity under good channel conditions while maintains good performance in poor channel conditions.