OFDM系统中基于子空间加权的时延估计算法  

A time delay estimation algorithm based on weighted subspace in OFDM system

作　　者：苏佳[1] 李铭 侯艳丽[1] SU Jia;LI Ming;HOU Yanli(School of Information Science and Engineering,Hebei University of Science and Technology,Shijiazhuang,Hebei 050018,China)

机构地区：[1]河北科技大学信息科学与工程学院,河北石家庄050018

出　　处：《河北科技大学学报》2022年第6期587-593,共7页Journal of Hebei University of Science and Technology

基　　金：河北省重点研发计划项目(21355901D,20355901D)。

摘　　要：针对低信噪比条件下正交频分复用(orthogonal frequency division multiplexing,OFDM)系统利用MUSIC算法(multiple signal classification)进行时延估计时,特征值分解得到的信号子空间和噪声子空间不能完全正交导致算法性能下降的问题,提出一种基于子空间加权的时延估计算法——WMUSIC算法(weighted multiple signal classification)。算法对信道频域响应估计的协方差矩阵进行特征分解,利用噪声特征值的幂级数对噪声子空间进行加权处理,同时采用信号特征值的倒数对信号子空间进行加权处理,以修正MUSIC算法的伪谱,通过谱峰搜索得到时延估计值。仿真结果表明,与MUSIC算法相比,WMUSIC算法具有更高的时延估计精度,在信噪比为-8 dB时,估计精度在两径条件下提升71.46%,三径条件下提升19.48%。WMUSIC算法有效解决了低信噪比条件下MUSIC算法伪谱谱峰存在混叠导致谱峰搜索误差较大的问题,可以完成较为准确的时延估计任务,提高了低信噪比条件下OFDM系统的时延估计性能。When the MUSIC(multiple signal classification)algorithm is used by the orthogonal frequency division multiplexing(OFDM)system to perform time delay estimation under the condition of low SNR(signal-noise ratio),the signal subspace and the noise subspace obtained by eigenvalue decomposition may not be completely orthogonal,which leads to the MUSIC algorithm performance degradation.In order to solve the problem,a time delay estimation algorithm based on the weighted subspace—WMUSIC(weighted multiple signal classification)algorithm was proposed.The proposed algorithm performed eigen-decomposition of the covariance matrix of channel frequency domain response estimation,weighted the noise subspace by the power series of the noise eigenvalues,and at the same time used the reciprocals of the signal eigenvalues to weight the signal subspace to correct the pseudo-spectrum of the MUSIC algorithm and obtained the delay estimation value through spectral peak search.The simulation results show that,compared with MUSIC algorithm,WMUSIC algorithm has higher time delay estimation accuracy.Specifically,when the SNR is-8 dB,the estimation accuracy can be improved by 71.46%with two paths and 19.48%with three paths.The WMUSIC algorithm effectively solves the problem of relatively large errors in spectral peak search caused by spectral peaks aliasing for MUSIC algorithm with low SNR.The proposed WMUSIC can complete more accurate time delay estimation,which provides a reference for improving the performance of time delay estimation in OFDM system under low SNR conditions.

关 键 词：无线通信技术 正交频分复用 时延估计 MUSIC算法 子空间加权 

分 类 号：TN911.7[电子电信—通信与信息系统]