Bandwidth-efficient MIMO underwater acoustic communications with frequency-domain equalization

This paper proposes a bandwidth-efficient frequency-domain equalization (FDE) for single carrier (SC) underwater acoustic (UWA) communications with multiple transducers and hydrophones. The proposed algorithm implements an overlapped-window FDE by partitioning a large block into small subblocks. A decision-directed channel estimation scheme is also proposed to track the channel variation by the detect symbols. The proposed algorithm is tested by undersea data collected during the Rescheduled Acoustic Communications Experiment (RACE) in March 2008. The experimental results demonstrate the proposed receive algorithm effectively tracks the time variation of the channel impulse responses and significantly improves the performance of uncoded bit error rate (BER). Compared with traditional SC-FDE system, the proposed overlapped-window FDE achieves 74.4% and 84.6% average BER reduction for the 400 m and 1000 m range systems, respectively at the same data efficiency and has only 8.4% transmission overhead, which is much smaller than over 20% of other existing UWA OFDM and SC-FDE systems at the same BER level.