Research On Time Delay Estimation Algorithm Based On Distributed Underwater Acoustic Location

Distributed underwater acoustic localization system which depends on time delay estimation,the positioning accuracy is often heavily dependent on the time delay estimation accuracy.and for underwater acoustic signal channel is time dispersion rapid fading,which is time-varying?space-variant?multi-path?dispersion and unstable,middle and far distance channel' band width has been greatly limited.The main research of this paper is based on the three questions of distributed localization: first,multiple access interference caused by other points to single node time delay estimation when limited in a fixed number of location node;second,degradation of time delay estimation performance caused by the Doppler-shift,which results from the relative movement between the target and the location node;third,methods to improve the ability of time delay estimation under the circumstance of low SNR.First,improved form the prospect of the low-related signal's design and modulation method,a low-related window signal for localization has been put forward,based on BOC model.GMW signal has been used to construct related signal assembles,in which any two arbitrary signal has a low-related window of fixed length.Multiple access interference of other points will be efficiently reduced when some point receives synchronously.Thus,BOC modulation method has curbed sidelobe of related output function's vertex within a digit.Additionally,Combined time delay estimation algorithm which is can resistance the Doppler Shift and the multiple access interference has been proposed when researched time delay estimation methods for the Doppler Shift Estimation and multiple access interference.The signal used in emission are Chirp signal and sequences with low crosscorrelation,the signal form is time domation superposition and frequency-domain separation.In receiving port,Fractional Fourier Transform is used to efficiently estimate Chirp's pretty good energy concentration and detection ability,make frequence compensation for the sequences with low crosscorrelation,Chirp signal interference removal in the frequency domain.the sequences with low crosscorrelation to synchronize and receive in the end.The system can accurately estimate the time delay under with Doppler Shift and multiple access interference.Finally,a self-adaptable time delay estimation algorithm based on Wavelet Transform is given,with the foundation of the research of time delay estimation of low SNRbackground in underwater acoustic distributed localization.Using Wavelet Transform's multi-scale transformation propriety,noise in signal's subjective frequency band is greatly mortified without attenuation of the original signal's energy.And this promotion in time delay estimation compared with traditional method has been justified by computer stimulation and experiment.