Spread-spectrum Signal In The Complex Environment Parameter Estimation And Identification,

The direct sequence code division multiple access(DS-CDMA) has already been widely used in wireless communications due to its many advantages, such as large capacity, anti-jammer capability, universal frequency reuse and low power spectrum. Especially during the past twenty years, the direct sequence system has been greatly applied to military communication equipment, such as satellite navigation(GPS, GLONASS),LEO satellite communication, wireless sensor networks. The military communication surroundings, which are always varied and different with traditional communication surroundings, call for new parameter estimation technology of direct sequence (DS) signal.Under non-cooperation direct sequence communication, blind recognition of DS signal and blind estimation of the parameter are important to spy the enemy transmitter. The receiver of missile guided by satellite must estimate the parameter of high dynamical DS signal. In the military communications, varied kinds of interference exist, which will greatly influence the parameter estimation. All the above conditions will challenge the traditional arithmetic, which estimate the parameter of DS signal. In order to improve the performance of DS system applied in military surroundings, new parameter arithmetic should be made to adapt to the corrupt surroundings.In this paper, parameter estimation under three kinds of corrupt surroundings was discussed, Non-cooperation DS system, High dynamical DS system and DS system under tone interference. The main contents are as follow:Chapter 1 is an introduction of this paper. The history of blind parameter estimation of DS signal, parameter estimation of high dynamical DS signal and parameter estimation of DS signal under interference is introduced.Chapter 2: Blind parameter estimation of MPSK-DS signal is discussed. The spectral correlation of MPSK-DS signal is first analyzed, and the close expression was got. Base on the spectral correlation of MPSK-DS signal, this paper propose a new arithmetic to estimate the carry frequency and chip rate of MPSK-DS signal. Cumulant invariants were proposed to classification of MPSK-DS signals, after manipulating interpolation and phase difference on MPSK-DS signals.Chapter 3: Blind estimation of direct sequence code was discussed. Sampling the received DS signal, and a new model was built. Based on this model, PCA (principlecomponent analysis) was proposed to estimate the direct sequence code of single-user DS signal; ICA(independent component analysis) was propose to estimate direct sequence of DS signal with asynchronous multi-users and multi-path interference; the method incorporating PCA ,FFT and costas loop was proposed to estimate both the direct sequence and frequency of single-user DS signal.Chapter 4: Parameter estimation of high dynamical DS signal was discussed. A method based on phase difference was proposed to GPS bit synchronization. A loop cascaded by AFC(auto frequency control) and PLL(phase lock loop) was proposed to tracking carrier of high dynamic carrier.Chapter 5: Parameter estimation of DS signal under tone interference was discussed. The despread close expression of tone interference was obtained based on time-domain analyses. The baseband model of costas loop and DLL under tone interference were also built, the tracking locus was analyzed.Chapter 6 : The research work was summarized. The work should be further investigated was pointed.