Abstract: The underwater acoustic channel is the most complex channel. In order to achieve significant diversity gain in the underwater acoustic channel, a BCH-LDPC coded MIMO-OFDM underwater acoustic communication system was presented and an improved receiver was proposed for the system. The outer encoder and the inner encoder were separated by the V-BLAST encoder in the transmitter. The improved receiver was based on the joint iterative detection and decoding algorithm. Some information was feedback from the outer decoder so as to reduce the operation times of MIMO detection and improve the reliability of the initial soft information. The performance of the system using three different receivers was analyzed by simulation. Simulation results show that the improved receiver can obtain more performance gain and has a significantly lower computational complexity. Besides, the BCH-LDPC coded system can achieve better performance than the separate coding system at high signal-to-noise ratio (SNR), when their system code rates are the same.

Key words: communication, underwater acoustic communications, multiple input multiple output (MIMO), orthogonal frequency-division multiplexing (OFDM), concatenated coding