Channel Estimation Based Equalizer for Underwater Acoustic Multiple-Input-Multiple-Output Communication

Multiple-input-multiple-output (MIMO) underwater acoustic communication offers a promising way to improve the data rate under very limited bandwidth underwater channels. However, MIMO underwater acoustic suffers from not only inter-symbol interference (ISI) but also co-channel interference (CoI), which pose significant difficulties to the conventional channel equalizer. Designed to overcome ISI, the traditional channel estimation based decision feedback equalizers (CE-DFE) will experience substantial performance loss, because the impact of CoI is not taken into account. In this paper, first, we modify the calculation of filter coefficients for the traditional CE-DFE to accommodate the presence of CoI. Second, we propose CE-DFE with interference cancellation (IC) for MIMO underwater acoustic communication by adding IC filters. The filter coefficients for proposed CE-DFE with IC are derived using channel estimates. Furthermore, the performance of the traditional CE-DFE, our modified CE-DFE, and our proposed CE-DFE with IC in terms of maximum access error, excess error, and output signal-to-noise ratio is analyzed. Finally, both simulation results and sea trial results demonstrate the effectiveness of the proposed methods.