Research On Detection,recognition And Separation Technologies For The Multi-carrier Mixed Signal

With the development of information technology and the wide application of the orthogonal frequency division multiplexing(OFDM)technology,the influence from the multi-carrier mixed signal is becoming more serious in the information reconnaissance and spectrum surveillance areas,especially for non-cooperative receiving,which does not only degrade the demodulation performance,but also restricts the application of the correlative technology.Therefore,this dissertation focuses on the processing techniques of the multi-carrier mixed signal,including the detection and recognition technology,the parameter estimation technology,the multi-channel blind source separation technology and single-channel blind source separation technology.Furthermore,a novel wireless communication scheme based on the baseband mixed signal waveform is proposed.The main contributions of this dissertation are summarized as follows.1.For the multi-carrier mixed signal,its detection and recognition algorithm is derived,which is the first problem in the processing,and the corresponding algorithms are different when the modulation types are diverse.Here,one of the mixed signals is considered as the interference of the other OFDM signal,and the single-carrier interference and multi-carrier interference are recognized by the high-order cumulant and spectrum characteristic,respectively.The detection and recognition algorithm is the premise of the subsequent processing.2.The OFDM+OFDM mixed signal is proved to be the cyclostationary signal.Based on the characteristic,this dissertation discusses the parameter estimation algorithms of the multi-carrier mixed signal,which make use of the high-order cyclic cumulant and cyclic auto-correlation function.Combined with the square spectrum,these algorithms can accurately estimate the correlative parameters,including the symbol rate,frequency offset,sub-carrier number and delay,etc.Besides,the Cramer-Rao bound of the parameter estimation is derived.3.A novel two-channel blind source separation algorithm is proposed,which is based on reconstruction and cancellation.This dissertation does not introduce its application scene,but also discusses its pivotal technologies,including the data transmission technology and reconstruction and cancellation technology based on the parameter tracking and adaptive filter.Furthermore,this dissertation analyzes the influencing facters of the performance,and discusses the relation between the demodulation quality of the objective signal and the performance of the reconstruction and cancellation algorithm.4.A novel and low-complexity single-channel blind source separation algorithm is proposed,which first applies the Gibbs sampling theroy and QRD-M decomposition algorithm to separate the mixed signal,and it can be applied to the single-carrier mixed signal and multi-carrier mixed signal,whose corresponding realization principles and methods are disscussed,respectively.Compared with the existing single-channel blind source separation algorithms,the proposed algorithm does not only keep good separation performance,but also tremendously reduces the computation complexity.5.The baseband mixed signal waveform is proposed,which simultaneously satisfies the requirements of the spectrum efficiency and anti-intercepting ability.In this scheme,the baseband mixed signal is used to construct the transmission signal,and the only difference between the signals is the delay.Comparaed with the existing anti-intercepting communication scheme based on the mixed signal,the novel scheme does not only improve the anti-intercepting ability,especially with anti-multi-antannasintercepting ability,but also keeps very high spectrum efficiency.