基于恒模特性的QPSK-DSSS信号扩频序列估计  

Spreading Sequence Estimation Based on Constant Modulus Property for QPSK-DSSS Signals

作　　者：张花国[1,2] 魏平[1] 

机构地区：[1]电子科技大学电子工程学院,四川成都611731 [2]通信信息控制和安全重点实验室,浙江嘉兴314033

出　　处：《航空学报》2013年第6期1389-1396,共8页Acta Aeronautica et Astronautica Sinica

基　　金：国家自然科学基金(61201282);通信信息控制和安全重点实验室基金(9140C130304120C13064)~~

摘　　要：针对非合作低信噪比条件下的QPSK-DSSS信号,提出一种基于恒模特性的扩频序列估计算法。该算法首先将单用户QPSK-DSSS信号等效为两用户的BPSK-DSSS信号,其次通过对信号协方差矩阵进行特征分解,估计出由同相与正交两路扩频序列张成的二维信号子空间,最后利用扩频序列的恒模特性消除特征分解带来的酉阵模糊问题,实现扩频序列的精确估计。本文提出算法实现简单,相对目前现有传统算法具有较低的计算复杂度,而且计算机仿真表明:本文提出算法在低信噪比条件下具有优良的估计性能。In this paper, a spreading sequence estimation algorithm based on constant modulus property is proposed for the QPSK-DSSS signals in low signal to noise ratio and non-cooperative scenarios. First, the single-user QPSK-DSSS signal can be equivalently represented as a two-user BPSK-DSSS signal, and then the two-dimensional signal subspace spanned by the in-phase and quadrature binary spreading sequences is estimated by the eigen-decomposition of the covariance matrix. Fi- nally, to estimate the spreading sequences accurately, its constant modulus property is exploited to cope with the unitary matrix ambiguity resulting from eigen-decomposition. The proposed algorithm is simple and easy to implement, and has a lower computational complexity compared to existing methods. And simulation results demonstrate the significant perform- ance gains of the proposed algorithm in low signal to noise ratio situations.

关 键 词：QPSK—DSSS信号 扩频序列 信号子空间 恒模特性 酉阵模糊 

分 类 号：V557.5[航空宇航科学与技术—人机与环境工程] TN911.6[电子电信—通信与信息系统]