Adaptation of a Hydroacoustic Communication Channel with OFDM Technology to the Negative Influence of a Drifting Ice Cover

Field investigations of the influence of a drifting ice cover on the probability of bit errors in a hydroacoustic communication channel constructed by the orthogonal frequency-division multiplexing (OFDM) technology were carried out. Quantitative estimates of the effect of drifting ice on a multifrequency phase-modulated OFDM signal reflected from the lower ice surface have been determined. The negative influence is seen in the broadening of the carrier frequency spectrum and in the reduction of the mutual correlation of phase-frequency shifts between carrier frequencies at the reception point. As a result of the spectrum broadening and jump-like changes in the phase of information signals, there is a sharp increase in the probability of bit errors during the reception. Methods are proposed for choosing optimum broadband OFDM-signal parameters allowing the negative influence of the ice cover to be neutralized and the signal transmission through a hydroacoustic communication channel with given characteristics to be implemented.