Biologically inspired covert underwater acoustic communication using high frequency dolphin clicks

To meet the requirements of covert underwater acoustic communication, a bionic camouflage scheme is proposed. We use sounds of marine mammals as communication signal to deceive the unintended receiver and achieve covert communication. An ultra-short duration, wide bandwidth pulse that imitates high frequency clicks of dolphin is adopted as the information carrier. We use multi-pulse modulation technique to improve anti-jamming capability. Each single pulse in the frame series which contain one bit information is modulated by the time hopping (TH) code in time domain. The frame series are modulated by pulse position modulation (PPM) technique as a whole. Transmitted reference scheme is adopted to mitigate the received signal affected by severe underwater acoustic channel. Theoretical analysis and simulation results obtained by using channel response measured at sea show that it can achieve short-range covert underwater acoustic communication benefiting from biologically inspired camouflage of communication signal.