Recognition Method For The Bionic Cetacean Sounds Camouflage Covert Communication Trains

The bionic camouflage covert underwater acoustic communication technology simulates or uses cetacean sounds to transmit information,and realizes the concealed communication through camouflage and deception,which has the advantages of simultaneously taking into account concealment and long-distance,and has been received great attention.Underwater acoustic signal recognition is the key step of underwater acoustic confrontation,which is of great significance to obtain the initiative of battlefield.However,at present,the anti-detection and recognition methods of the bionic cetacean sounds covert underwater acoustic communication signals are very rare.Based on this fact,this paper focuses on the recognition problems of the bionic cetacean sounds covert underwater acoustic communication signals,and explores the bionic communication signal characteristics of two typical bionic click and whistle,then proposes two effective recognition methods for bionic cetacean sounds covert underwater acoustic communication signals.The main work is as follows:1.Six species of cetaceans with a wide range of distribution are selected,and the main characteristics of their clicks and whistles,such as the duration,time interval,frequency band distribution and the time-frequency contour,are analyzed.Then,the coding principles of bionic click communication trains modulated by time delay difference and bionic whistle communication trains modulated by variable time lengths of LFM signals are introduced,and the main characteristics of the two bionic cetacean sounds communication signals,such as the duration,time interval,frequency band distribution and the time-frequency contour,are analyzed.Further,the distributions of the above main characteristics of the real cetacean sounds and bionic cetacean sounds communication signals are compared to support for the recognition of bionic communication signals.2.Focused on the recognition problem of bionic click communication signals modulated by time delay difference,a bionic communication signal recognition method based on the statistical characteristics of ladder-like change of the click time interval is proposed.An endpoint detection method based on dynamic window energy ratio is proposed to locate the clicks accurately.The time interval of bionic click communication trains presents a ladder-like distribution,however,the time interval of real click trains is nearly random distribution.According to the difference distribution of the time intervals,a recognition method of bionic click communication trains based on support vector machine is developed.Taking the time intervals of the real click trains of different cetaceans,such as sperm whale and killer whale,and the time intervals of bionic click communication trains,as training datasets,the support vector machine classification technology is used to recognize bionic click communication trains.3.Focused on the recognition problem of bionic whistle communication signals modulated by variable time lengths of LFM signals,a bionic communication signal recognition method based on whistle time-frequency contour frequency mutation point and its distribution characteristics is proposed.According to the difference between the time-frequency contour of the bionic whistle communication signal and the real whistle,which the time-frequency contour of the bionic whistle communication signal has time-frequency mutation points with fixed frequency but the time-frequency contour of the real whistle continuously changes,the difference characteristics of the frequency mutation point and instantaneous frequency curve’s linearity and duration are analyzed.Based on the different distributions of these proposed characteristics,the recognition method of bionic whistle communication signal based on CART decision tree is developed,and simulations verify the effectiveness of the recognition method.4.Based on the two bionic communication signal recognition methods proposed above,a software for bionic cetacean sounds communication signals is developed.The experimental system is built,and the lake experiment is carried out,verifing the effectiveness of the above two recognition methods and recognition software in actual underwater acoustic environment.