Time-domain receiver design for MIMO underwater acoustic communications

In this paper, we propose a time-domain receiver design scheme for high data rate single carrier multiple-input, multiple-output (MIMO) underwater acoustic communications. In this scheme, each received packet is artificially partitioned into blocks for processing. The MIMO channel is initially estimated using training blocks at the front of transmitted packets from all transducers. With the estimated MIMO channel, one data block following the training blocks is equalized. The phase rotation in the equalized data block is compensated by a group-wise phase correction operation, before symbol detection. The newly detected data block along with K - 1 previous data (or pilot) blocks are utilized to re-estimate the channel, which is employed to equalize the next new data block. The block-wise processing procedure is repeated until all blocks in the received packet are processed and demodulated. The proposed receiver scheme is tested with MakaiEx05 experimental data measured at Kauai, Hawaii, in September 2005. Processing results show that it works effectively with 2 times 8 BPSK, QPSK and 8PSK transmissions at the symbol period of 0.1 milliseconds. The average uncoded bit error rate (BER) is on the order of 8 times 10^-4 for BPSK, 3 times 10^-2 for QPSK, and 8 times 10^-2 for 8PSK transmission.