A method based on time-frequency masking for MFSK underwater acoustic communication signal enhancement

Abstract

Because of the lower propagation speed and the complexity of the underwater acoustic channel, completely avoiding the access-collision of the common channel in the underwater acoustic networks is difficult. To deal with the multiple access interference (MAI) caused by the access-collision, we have proposed a signal enhancement method based on time-frequency (T-F) masking and the approximate W-disjoint Orthogonality (WDO) caused by the sparsity of the MFSK signals in the time and frequency domain. More specifically, because of the MFSK signals sparsity, we consider the MAI canceling as the separation of mixtures of MFSK signals by using time-frequency masking, if the WDO of the MFSK mixtures is close to one. First, we demonstrate the level of approximate WDO of the MFSK signals in various orders. Then, according to the WDO of the MFSK signals, we separate the mixtures by using the ideal T-F mask, and compare their bit error ratio (BER) performance with different bit rates and signal-noise ratios. The simulation result demonstrates that when the signal is sparse enough, using the T-F masking can recover the transmitted data from the mixtures.