Evaluation of underwater acoustic channel capacity in conjunction with application of sweep-spread carrier signals

Since the sweep-spread carrier (S2C) technology uses broadband frequency swept carrier signals with high frequency-sweep rates, the instant frequencies of multipath components have different values, what create sufficient background for their separation in frequency domain. The paper shows that after filtering the receiving signal with a filter, matched to the S2C reference signal, the strength and number of the multipath components significantly decreases. This provides considerable increase of coherence bandwidth of the communication channel and, in consequence, significant increase of achievable data rates. In this way the channel capacity can be substantially enhanced. The paper represents experimental data on evaluation of the underwater acoustic channel capacity during data transmission by use of (a) S2C carrier signal and (b) traditional constant-frequency carrier signal.