Biologically inspired underwater acoustic communication based on discrete cosine transform

Abstract

Reliable underwater communication is a challenging problem due to the scarce bandwidth and spreading loss. In the presence of eavesdroppers, it adds a further complexity as the secure end to end communication is also necessitated. In this context, we propose a biologically inspired, watermark technology based underwater acoustic communication method using discrete cosine transform (DCT) of the cetacean sounds. The information-modulated pseudo-noise sequence is embedded into the select DCT frequency points of the broadband cetacean sound with a certain weight. The final transmitted signal is obtained by inverse discrete cosine transform after information modulation. At the receiver end, the synchronization is achieved through the cross-correlation between the received watermarked signal and the original cetacean sound. After extracting the selected DCT frequency points of each received sound sub-unit, the demodulation is conducted by the sequence correlation based on the local library. Similarity between the watermarked signal and the original cetacean sound is evaluated through the waveform correlation coefficient and PESQ score. Simulation and lake experiment verified the feasibility of the proposed biologically inspired communication method. A reliable communication rate of 54.92 bps was achieved at a distance of 1.22 km with the mean waveform correlation coefficient and PESQ score over 0.85 and 3.6 respectively in the lake trial and the bit error rate is lower than 10-3.