Further results on high-rate MIMO-OFDM underwater acoustic communications

MIMO-OFDM is one viable solution for high data rate transmissions over underwater acoustic channels. Our previous work has reported experimental results for MIMO-OFDM with two transmitters and QPSK modulation. In this paper, we deal with MIMO-OFDM with more transmitters and higher order modulation. With data collected from the RACE experiment at Narragansett Bay, Rhode Island, March 2008, we report MIMO-OFDM performance results of QPSK/8-QAM/16-QAM/64-QAM modulations with two transmitters, QPSK/8-QAM/16-QAM modulations with three transmitters, and QPSK/8-QAM modulations with four transmitters. With large constellations and MIMO spatial multiplexing, very high data rates can be achieved, e.g., a spectral efficiency of 3.5 bits/sec/Hz is approached in three different configurations.