Bionic Underwater Acoustic Communication By Mimicking Cetaceans Whistles

Over the past few decades,the reliability,data rate,and networking of underwater acoustic(UWA)communication have attracted a wide spread attention.However with the increasing demand of ocean resources,the security of UWA communication is also a vital factor to be considered while designing a UWA communication system.To realize covert underwater acoustic communication,the traditional communication algorithms usually exploit low signal-to-noise ratio(SNR)to hide the communication signal in the background noise.Unlike the traditional algorithms,the bionic covert UWA communication methods use marine mammal's sound or some high-like synthetic signal as a carrier to transmit iniformation,which is most likely to be neglected as oceans noise when detected by the enemy.By this way,the covert communication can be realized.According to the special characteristics of normal distribution,point sound source,moderate frequency and reasonable movement,the cetaceans whistles are chosen to be mimicked,and the bionic UWA communication by mimicking cetaceans whistles is studied in this thesis.The work is explained in detail below:1.The cetaceans whistles are analyzed,and two detection methods are used: matched filter for known whistles and local max detector for unknown whistles.Based on the time-frequency characteristics,a simple classification method is introduced.Then,a model of whistles is built with parameters.2.Based on the whistles model,a bionic UWA communication method is proposed.The transmitter maps the information to the parameters of the whistle model to realize the modulation.The receiver employs maximum likelihood estimator or match filter estimator to estimate the parameters of the received signals,and then realizes demodulation by demapping these parameters to information.The feasibility of the proposed method was verified by simulation and pool experiment.3.Based on the whistles contour,two bionic UWA communication methods are studied.One uses the liner frequency modulated(LFM)signals with different center frequencies combined together to mimic whistles,while the information is modulated in the chirp rate of each LFM signals to realize bionic communication.The other one realizes bioniccommunication by using synthetic whistles whose contour adds a frequency-shift keying modulated signal to carry information.The feasibility and reliability of the proposed method were verified by simulation,sea trial and pool experiment respectively.4.Based on adaptive filter,a bionic UWA communication method is proposed.According to the human audio sensibility,this method uses whale whistle to mask direct sequence spread spectrum(DSSS)signal,which may improve the security of DSSS signal.A adaptive filter is used to extract DSSS signal from the mixed signal,which is the main work in this thesis.Simulation and sea trial verified the feasibility of the proposed method.Thus hree kinds of bionic UWA communication method are studied in this thesis based on cetaceans whistles.The performance of each communication method is analyzed by simulation,pool experiment or sea trial.