Bionic Covert Hydroacoustic Spread Spectrum Communication based on Improved Adaptive Filtering Algorithm

Due to the presence of eavesdroppers in the ocean, the covertness and reliability of communication transmission between Underwater Acoustic Network (UWAN) nodes are further required. In this context, this paper proposes an imitation whale whistle high-order packet spread spectrum covert communication technique based on the improved fast Recursive Least Squares (FRLS) algorithm. The method takes the sperm whale whistle signal as the hidden carrier and utilizes a modulation technique combining high-order M-ary modulation and group spread spectrum (MGSS), which greatly enhances the communication rate. A fast least squares algorithm with adaptive forgetting factor (AFRLS) is proposed at the receiver side to ensure the reliability of the system while greatly reducing the computational complexity. Finally, the feasibility of the method is verified by quantitatively analyzing the imperceptibility of the communication signals using three parameters: the time domain waveform correlation coefficient (WCC), Mel-scale Cepstral Distance (MelD), and Objective Difference Grade (ODG) value.