基于判决辅助的异步CDMA信号多伪码序列盲估计算法

Decision-aided-based multiple blind PN code estimation algorithm of asynchronous CDMA signal

针对多径异步码分多址(CDMA)信号多用户伪码盲估计问题,利用发送符号的有限元(FA)特性,提出了一种基于最大似然的判决辅助(DA)算法,构建了信息码、伪码及信道的双层迭代估计结构,实现了异步CDMA信号的高性能多伪码盲估计,并推导了异步体制CDMA信号伪码盲估计问题的Crammer-Rao界(CRB),从而评估了所提算法的性能。仿真实验表明,相比现有常用的迭代最小二乘投影(ILSP)算法,所提算法估计精度性能实现较大提升,接近理论界,在用户数量较多时也能实现较优估计。

Aiming at the problem of blind estimation of multi-user pseudo-code of multi-path asynchronous code division multiple access(CDMA)signal,using the finite element(FA)characteristic of transmitted symbol,a decision aid(DA)method based on maximum likelihood was proposed.A two-step iterative estimation structure for PN code,transmitted bit and channel was designed to realize the estimation of multiple user code in asynchronous CDMA system with superior performance.Moreover,the Cramer-Rao bound(CRB)of PN code estimation in asynchronous CDMA signal was derived to evaluate the performance of proposed method.Simulation indicates significant improvement in performance which is close to the theory bound of the proposed method compared to commonly-used iterative least square with projection(ILSP)method.The method can also achieve superior estimation when the user number increases.