Turbo Detection for MIMO–OFDM Underwater Acoustic Communications

An experimental investigation on turbo detection for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) underwater acoustic communications, is presented in this paper. In our detection scheme, the linear symbol estimation benefits from a hybrid soft interference cancelation and a reliability-based detection ordering enabled by the a priori information at the equalizer input. The proposed MIMO–OFDM detector is tested by field trial data collected in the SPACE08 and the ACOMM10 undersea acoustic communication experiments, where convolutional code was adopted in SPACE08 and binary low-density parity-check (LDPC) code was used in ACOMM10. Experimental results show that for both sets of trial data, turbo detection achieves much better performance than the conventional non-iterative detection. Moreover, the results provide guidance on the selection of system parameters including the subcarrier number, the iteration numbers for both the turbo equalization and the LDPC decoding, for achieving a good complexity-performance tradeoff.