MIMO-OFDM for High Rate Underwater Acoustic Communications
University of Connecticut Storrs United States
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Multiple-input multiple-output MIMO techniques have been actively pursued in underwater acoustic communications recently to increase the data rate over the bandwidth-limited channels. In this paper, we present a MIMO system design, where spatial multiplexing is applied with OFDM signals. The proposed receiver works on a block-by-block basis, where null subcarriers are used for Doppler compensation, pilot subcarriers are used for channel estimation, and a MIMO detector consisting of a hybrid use of successive interference cancellation and soft MMSE equalization is coupled with LDPC channel decoding for iterative detection on each subcarrier. The proposed design has been tested using data recorded from three different experiments. A spectral efficiency of 3.5 bitssecHz was approached in one experiment, while a data rate of 125.7 kbs over a bandwidth of 62.5 kHz was achieved in another. These results suggest that MIMO-OFDM is an appealing solution for high data rate transmissions over underwater acoustic channels.