Further Results on Frequency-Domain Channel Equalization for Single Carrier Underwater Acoustic Communications

A frequency-domain channel equalization and phase correction method was proposed in a previous work published in Oceans´07 conference, in which 10^-4 BER performance was presented for fixed-to-fixed source/receiver channels. The method is improved by using minimum mean square error (MMSE) estimation in channel updates rather than least squares estimation. It is applied to moving-to-fixed channels in the AUVFest´07 ocean experiment where single-carrier wideband transmission was employed with quadrature phase shift keying modulation. The moving source channels exhibit higher Doppler shift and larger Doppler drift than the fixed-to-fixed channels. Therefore, the number of symbols required for initial phase estimation is increased from 2 to 8 symbols when the group- wise phase correction algorithm is applied to the moving sources. Thirty-six packets with data block length of 512 symbols have been processed and 34 of them achieved an uncoded Bit Error Rate (BER) lower than 10^-2. The overall uncoded BER performance of all 36 packets is 1.81 times 10^-3 which is slightly higher than that of the fixed-to-fixed channels.