基于加权WHT的软判决序列快速估计算法

利用WHT(Walsh Hadamard Transform)进行PN序列估计,存在抗误码性能不足、受序列多项式抽头数限制等问题。针对这些问题,该文提出一种基于加权WHT的软判决序列快速估计算法。首先,对硬判决容错似然限、多项式抽头数制约因素进行理论分析。然后,将序列软信息引入到序列频次系数中提高估计性能;对WalshHadamard矩阵进行列加权处理,改变矩阵二元元素性质,降低多抽头对估计性能的影响。同时,进行序列控制状态选择,将多抽头多项式转化为少抽头多项式进行估计。仿真结果表明,该算法性能较WHT算法性能提高约1.5dB,基本不受估计多项式抽头和阶数限制。

A Soft Fast Estimation Method of PN Sequence Based on Weighting Walsh Hadamard Transform (WHT)

The issue of poor error-tolerance and polynomial taps restriction of Walsh Hadamard Transform (WHT) estimation method is studied and a novel soft fast PN sequence estimation algorithm based on weighting Walsh Hadamard Transform is proposed in this paper. Firstly, the theory analysis about error-tolerance likelihood bound of sequence hard-decision and restrictive factor of estimation polynomial taps is performed. Based on this analysis, the sequence soft information are taken to sequence frequency-coefficient to improve estimation performance, and the Walsh Hadamard matrix is column-weighted to change its binary property, which can decrease the polynomial taps influence to estimation performance. Meanwhile, the sequence control state are chosen to decease the estimation polynomial taps in the essence. The simulation results show that the proposed method is irrelevant with the order and tapped number of generator polynomial, and its performance is improved 1.5 dB than WHT.