The covert underwater acoustic comm

The covert underwater acoustic communication realized from the perspective of bionics draws an increasing interest in recent researches. Inspired by the frequency hopping spectrogram pattern, a bionic underwater acoustic communication method is proposed by using cetacean whistle as communication carrier. The basic idea is to generate synthetic whistle with different spectrogram to transmit the information. The whistle is first modeled after extracting the whistle contour from the noise-polluted recordings. Then a synthetic whistle with a special spectrogram pattern which mimics the whistle spectral characteristic is generated to modulate the information. The bionic communication frame is the combination of the original whistle and the synthetic whistles which are used for synchronization and information modulation respectively. After synchronization, the each received symbol is extracted and correlated with the locally generated signals. The information demodulation is conducted by the correlation peak decision. Finally the bionic effect of communication signals is analyzed through time-frequency correlation coefficient and Mel frequency cepstrum coefficient. Simulation and sea trial verified the feasibility of the proposed method. Less than uncoded bit error rate is achieved with the correlation coefficient over 0.9 at a distance of 8.5km in the sea trial.