【作者】 王悦；

【导师】 刘晓志；

【作者基本信息】 东北大学 ， 信号与信息处理， 2013， 硕士

【摘要】 直接序列扩频(Direct Sequence Spread Spectrum,DS-SS)信号具有抗多径、抗干扰、低截获概率、多址复用等优点,在军事和民用通信领域有着广泛的应用。对于非合作方如通信侦察、无线电频谱监测及非法通信电台的定位跟踪等,需要截获信号并在未知扩频序列条件下实现信号的解扩以完成传输信息的恢复,因此开展DS-SS信号的盲解扩研究在通信对抗领域具有重要的意义。本文针对非合作通信情况下长码直扩信号的扩频码序列估计问题,采用独立分量分析(Independent Component Analysis,ICA)方法进行研究,主要工作如下：首先,介绍了直接序列扩频信号盲估计的研究现状和发展趋势,对DS-CDMA系统与直接序列扩频通信系统的信号模型进行了分析,研究了独立分量分析的基本原理。其次,对CDMA模型与ICA的模型进行了分析,在此基础上研究了一些传统扩频序列盲估计算法。针对传统算法只适用于短码扩频序列盲估计的现状,本文提出了一种周期长码直接序列扩频信号模型——虚拟多用户模型,该模型可以把长码扩频信号等效成短码信号,并应用Fast-ICA算法对其进行了盲解扩研究。仿真实验结果表明,本文提出的模型适用于长码信号的扩频序列盲估计,且具有很好的估计性能。再次,基于虚拟多用户系统模型,对长码信号进行分段估计,并对传统Fast-ICA算法的预处理过程进行改进,提出了无需白化的Fast-ICA算法。将改进的算法应用于周期长码直接序列扩频信号的模型中,仿真证明,该方法的收敛速度更快,能正确的估计出扩频序列。最后,对本文的研究工作进行了总结,并对未来的研究工作进行了展望。更多还原

【Abstract】 Direct Sequence Spread Spectrum (DS-SS) signal has the advantages of multi-path, anti-jamming, low probability of intercept, multiple access multiplexing, which is widely used in military and civilian communication fields. For non-cooperative communication situations such as reconnaissance, monitoring of radio spectrum and tracking of illegal radio communication, intercepting signal and despreading signal for restoring information transmission in the condition of unknown spread spectrum sequence is necessary, so carrying out DS-SS signal blind despreading research in communication countermeasure fields has important significance.In this thesis, aiming at the problem of estimation of the spread spectrum code sequence of long code DS-SS signal in the non-cooperative case, Independent Component Analysis (ICA) method is adopted to research, the main work is as follows:First of all, the research status and development trend of blinding estimation to DS-SS signal are introduced, and the signal model of DS-CDMA system and DS-SS communication system is analysed.The basic principle of the ICA is discussed.Secondly, on the basis of the analysis of CDMA and ICA model, some traditional blind estimation algorithms of spreading spectrum sequence are studied. Aiming at the present situation that the traditional algorithms can be only applied into blind estimation of short-code DS-SS signal. A signal model of the new cycle long code DS-SS, virtual multi-user model, is proposed, which can make the long code spread spectrum signal equale to short code signal, and then the Fast-ICA algorithm can be applied to this model. Simulation results show that, the model proposed in this thesis can be applied in blind estimation of long code signal, and the estimation performance is satisfied.Thirdly, on the basis of virtual multi-user mode, the long code signal is estimated piecewise and the preprocessing of traditional Fast-ICA algorithm is improved, then the Fast-ICA algorithm without whitening is proposed. The improved algorithm is applied to estimate long code DS-SS signal, simulation results show that the convergence speed of this method is faster, which can estimate the spread spectrum sequence correctly at the same time.Finally, the research of this thesis is summarized, and the future research is prospected.更多还原