共查询到17条相似文献,搜索用时 171 毫秒
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在低信噪比条件下检测出直接序列扩频(DSSS)信号后,要恢复出原始信息,估计出扩频码序列是非常关键的,因此有必要研究DSSS信号的扩频码序列估计算法。提出了一种基于改进的协方差矩阵迭代算法应用于估计扩频码序列。理论分析和计算机仿真实验都表明了该算法能在低信噪比下估计出扩频码序列,与其他一些扩频码序列估计算法如基于投影子空间的算法、基于神经网络的算法相比,具有运算量更小等优势。 相似文献
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在直接序列扩频(DSSS)通信对抗系统中,伪码(PN)序列估计是一个重要的研究课题.针对在某些情况下权值向量不收敛的问题,提出了一种基于快速正交投影逼近子空间跟踪(OPAST)算法和滑动窗技术的直扩信号PN码序列估计算法,对非同步接收DSSS信号按照宽窗口分段,利用快速OPAST算法提取主特征向量,滑动窗技术实现码同步.该算法迭代权值向量具有正交性以及良好的收敛性,同时解决了常见相位模糊问题.算法具有较低复杂度,数据存储量少,易于硬件实现与实时处理.仿真结果表明,在-10 dB的较低信噪比背景环境中,该快速OPAST算法可以正确有效地估计出PN码序列. 相似文献
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为了实现对直接序列扩频通信信号的非协作接收,提出了一种新的基于子空间分析和盲信号处理算法的负信噪比同步码分多址(CDMA)信号伪码全盲估计方法。该方法突破了以往直接序列扩频信号伪码估计技术单用户假设的局限,更加贴近实际应用。理论分析和计算机仿真表明了该方法的有效性。 相似文献
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针对低信噪比下同步多用户非周期长码直扩信号的扩频序列估计问题, 提出了一种基于嵌套迭代最小二乘投影算法的扩频序列估计方法.首先, 将同步多用户非周期长码直扩信号等效为含有缺失数据的相应的短码直扩信号.然后, 利用最大似然估计理论对相应的短码直扩信号进行数学分析, 构建扩频序列估计的数学模型.最后, 利用一种嵌套迭代最小二乘投影算法来实现扩频序列的估计.研究表明, 该算法在低信噪比(小于-10 dB)情况下, 对多用户(多达10路)扩频序列的估计有着良好的性能表现. 相似文献
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针对下变频后含有残余载波的周期长码直扩信号PN(Pseudo-Noise)码盲估计难题,在已知码片速率和PN码周期前提下,该文提出一种结合矩阵特征值分解和数字锁相环(Digital Phase Locked Loop, DPLL)的PN码盲估计方法。该方法首先将带有残余载波的周期长码直扩信号等效建模为虚拟多用户短码直扩信号模型,利用矩阵特征值分解和模糊酉矩阵的方法估计出含有残余载波的PN码,然后利用DPLL对残余载波的频率和相位进行跟踪和估计并最终消除残余载波,最后根据特定约束条件(如m序列、Gold序列)去除分段相位模糊,最终估计出PN码序列。理论分析和仿真结果表明,提出的方法能够有效地工作在较低信噪比下,且表现出良好的性能。 相似文献
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Blind classification of the short-code and the long-code direct sequence spread spectrum signals 总被引:1,自引:0,他引:1
Direct sequence spread spectrum (DSSS) signals are now widely used for communications. According to the relationship between spreading factor and code length, the DSSS signals can be divided into two types: the short-code (SC) and the long-code (LC) DSSS. For the cooperative receivers, the above type information is known in advance. However, under the non-cooperative contexts, such information becomes one of the unknown parameters of interest. To extract this information, a blind algorithm that is based on the second-order statistics of the matrix norms of the signal correlation matrices is proposed in this study. A set of correlation matrices is constructed from the received signal samples following which the matrix norm of each correlation matrix is computed and normalised by the maximum. Then, by comparing the variance of the normalised matrix norms with a preset threshold, the type of the received DSSS signal can be identified. Simulation results verify the capability of the proposed method in various scenarios, such as multipath fading channel and multiple access interference. 相似文献
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Soft synchronization of direct sequence spread-spectrum signals 总被引:1,自引:0,他引:1
A new technique for soft synchronization of direct-sequence spread-spectrum (DSSS) signals is presented. The technique, referred to as the dominant mode despreading (DMDS) algorithm, exploits the eigenstructure of a frequency-channelized DSSS signal to estimate the spreading code and underlying message sequence of the signal. Unlike other despreading techniques, the estimate of the code and data improves steadily with the number of code repeats. The technique is applicable to arbitrary spreading codes and message sequences and can operate in environments containing arbitrary levels of white background noise, and for signals with arbitrary unknown timing phase or carrier frequency offset. The technique requires the DSSS signal to have a constant-modulus spreading code and unrelated message and code-repeat rates. This paper introduces the basic technique, theoretically analyzes the algorithm to prove convergence under infinite time-average conditions, and demonstrates the algorithm via computer simulation for a single DSSS signal received in the presence of white Gaussian noise 相似文献
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本文针对非周期长码直扩信号参数估计难的问题,建立了非周期长码直扩信号的一种表示模型;推导分析了非周期长码直扩信号延迟相乘后的自相关函数,此自相关函数具有周期性峰值,两个相邻峰值之间的间隔倒数就是扩频码的码片速率;同时还推导分析了噪声对此自相关函数的影响,合理选择延迟量理论上可以消除噪声影响;根据上述特点,提出了一种非周期长码直扩信号的扩频码码片速率估计方法。该方法首先估计基带信号延迟相乘后的自相关函数,然后消除噪声产生的峰值,最后通过估计峰值间隔,得到扩频码的码片速率估计。仿真结果表明了本方法的有效性。 相似文献