Frequency domain turbo equalization for No-CP single-carrier MIMO underwater acoustic communications

This paper proposes a frequency-domain turbo detection scheme for single-carrier, multiple-input, multiple output (MIMO) underwater acoustic (UWA) transmission without using cyclic prefix (CP), aiming to achieve a low detection complexity and a high transmission efficiency simultaneously. The received data stream is divided into consecutive blocks, and each block is equalized in the frequency domain. To enable the frequency-domain equalization, inter-block-interference (IBI) cancellation and CP reconstruction are necessary for each block. The IBI is removed by using the currently estimated channel and the detected symbols from the previous block. The CP reconstruction for the current iteration of the turbo equalization is obtained with the soft symbol estimation from the previous iteration. In the first iteration, there is no a priori soft symbol estimation available, thus the frequency-domain equalizer (FDE) is performed in an approximating style. The detection performance improves over iterations. The proposed scheme has been tested by field trial data measured in the ACOMM09 underwater communication experiment.