A novel broadband COFDM modulation scheme for robust communication over the underwater acoustic channel

An UWA communication system that uses coherent pseudo-random-phase carrier COFDM modulation is presented. The system shares the advantages of the correlating receiver of the direct sequence spread spectrum system and COFDM modulation. A feature of the new system is the use of a pseudo-random Gaussian noise signal as a channel sounding probe to measure the complex channel transfer function for frequency domain equalization. The equalizer uses the least squares autoregressive algorithm, which has been modified to accommodate the multi-carrier OFDM signal structure for frequency domain equalization. In this paper, an outline of the structure of the COFDM system and the method of frequency domain equalization are described. The bit-error-rate probabilities of three system configurations are then discussed under different multipath/Doppler channel conditions.