Synchrosqueezed Transforms Algorithm And Its Application In Chaotic Secure Communications

Chaotic secure communications have been one of the hottest issues in the field of information and communication in recent 40 years.While achievements have been made in this area,some critical issues,such as the improvement of synchronization performance,the accurate extraction of harmonic signal and anti-jamming ability have not been well addressed.Although the synchrosqueezed transforms have advantages in the accurate extraction of harmonic signals,it fails to be directly applied in chaotic secure communications.The challenges lie in the selection of the mother wavelet,rapid implementation and optimization of algorithms,noise reduction,etc.This dissertation attempts to present the theoretical analysis,explore the algorithm optimization of synchrosqueezed transforms,and propose a design of chaotic secure communication scheme based on synchrosqueezed transforms.The main results are as follows:(1)The theory and algorithm implementation of wavelet synchrosqueezed transform(WSST)are studied.We discuss and analyze the influence factor of WSST,such as the mother wavelet,the wavelet threshold,etc.WSST is not sensitive to the choice of mother wavelet,but to its parameters.So we propose an optimal design method for the parameters of the mother wavelet,based on Renyi entropy of time-frequency distribution.In this method,the optimal parameters are determined by calculating the minimum Renyi entropy,so as to achieve the optimal time-frequency distribution.(2)The theory and implementation of first-order STFT synchrosqueezed transform(FSST1)and second-order STFT synchrosqueezed transform(FSST2)are studied.The theorems on the robustness properties of FSST1 and FSST2 are established and proved.We verify that both FSST1 and FSST2 are robust to bounded perturbations.Based on the requirement that the algorithm must be quickly implemented on digital signal processor in industrial application,the filter implementation algorithms based on FSST1 and FSST2 are proposed.(3)New schemes of stochastic chaotic secure communication based on SST are proposed.In order to improve anti-jamming ability and universality of chaotic systems in secure communication,a chaotic secure communication scheme based on WSST mean square asymptotic synchronization is proposed.In order to improve the stability and convergence rate of the synchronization system,a chaotic secure communication scheme based on FSST2 mean square exponential synchronization is proposed.In order to improve the reliability of secure communication,a random chaotic secure communication scheme based on WSST finite time synchronization is proposed.