Research On Bionic Covert Underwater Acoustic Communication Technology Based On Digital Watermarking

In the 21st century,underwater acoustic communication(UAC)plays an vital role in Marine resources development,national defense construction and information technology countermeasure.With the development of the new era,more and more attention has been focused on the security and concealment of UAC for the need of national defense.In order to achieve convert communication,traditional covert UAC usually transmits communication signals with such a little power that they can be easily hidden in the noise of the ocean,which make it difficult for the enemy to detect them,but there are still some shortcomings including shorter communication distance and lower-level safety.By contrast,the biomimetic covert UAC uses the calls of creatures in the ocean or natural sounds as communication signals.When the signals are discovered,the enemy will recognize them as inherent ocean sounds and exclude them.In this paper,the reconstructed fin whale sound is used as the carrier to study the covert UAC technology of imitating fin whale sound,the project supported by the National Fund 61771412"Research on the Real-time Perception Method and Key Technology of Underwater Acoustic Speech Communication Performance".The main work of this paper is as follows:(1)Analyze the characteristics of underwater acoustic(UWA)channel and its influence on UAC as well as model the UWA channel in shallow sea and Bellhop model,flat terrain channel and Dickins terrain channel in deep sea.(2)Based on the robustness of the watermarking algorithm to decrease the multipath effect,the author implemented the Patchwork on DCT(Discrete Cosine Transform)domain and time domain audio watermarking(AW)algorithm without UWA channel estimation and equalization.In the same condition,the imperceptibility and robustness of two algorithms are evaluated.The simulation results show that the imperceptibility of the two algorithms is excellent,while the DCT algorithm on Patchwork has better robustness.Moreover,a cyclic error-correcting code is added on the basis of the original algorithm to improve its robustness.(3)Study the covert UAC technology of imitating fin whale sound.First,the Chirplet transform is used to reconstruct the fin whale sound as the carrier signal,and secret information,embed into the carrier signal through the AW algorithm based on Patchwork DCT domain and time domain is extracted through the UWA channel.The study simulates respectively in different conditions in ocean to evaluate the imperceptibility and robustness of the system.The results show that the imperceptibility of the two algorithms is better,but the robustness of the former to counteract the multipath effect is more effective than the latter.