中图分类号：TN914.42
文献标识码：A
DOI：10.16157/j.issn.0258-7998.212094
中文引用格式：潘微宇，赵知劲. 带残余频偏的LSC-DS-CDMA信号伪码估计[J].电子技术应用，2022，48(6)：58-63.
英文引用格式：Pan Weiyu，Zhao Zhijin. Pseudo code estimation of LSC-DS-CDMA signal with residual frequency offset[J]. Application of Electronic Technique，2022，48(6)：58-63.
Pseudo code estimation of LSC-DS-CDMA signal with residual frequency offset
Pan Weiyu1，Zhao Zhijin1，2
1.School of Communication Engineering，Hangzhou Dianzi University，Hangzhou 310018，China； 2.State Key Lab of Information Control Technology in Communication System of No.36 Research Institute， China Electronic Technology Corporation，Jiaxing 314001，China
Abstract：Aiming at the problem of estimation of long and short code direct spread code division multiple access signal with residual frequency offset, firstly, the signal matrix is constructed by using the periodic piecewise received signals of short code and long code. Secondly, the eigenvalue decomposition method is used to obtain the user eigenvector sub-space with residual carrier, and the digital phase-locked loop is used to track and eliminate the residual frequency offset. Then, the Givens matrix is used to rotate the load matrix composed of eigenvectors, and a whale optimization algorithm combined with random difference and simulated annealing is proposed to find the best rotation angle to minimize variance, so as to estimate the composite code segments of each user and splice them in turn. Finally, Berlekamp-Messay algorithm and correlation operation are used to estimate the long code and short code of each user. Simulation results verify the effectiveness of the proposed algorithm for pseudo code estimation of LSC-DS-CDMA signals with residual frequency offset.
Key words :long and short code direct spread code division multiple access；digital phase locked loop；Givens rotation；whale optimization algorithm；Berlekamp-Massey algorithm
0 引言
直接扩频序列码分多址(Direct Sequence Code Division Multiple Access，DS-CDMA)采用高速率的伪码对信息码进行扩频调制，具有较强的隐蔽性和抗干扰能力[1]。DS-CDMA信号可根据扩频方式分为短码(Short Code，SC)DS-CDMA和长码(Long Code，LC)DS-CDMA两种信号，为了进一步提高保密性，利用长码对短码扩频信号做加扰处理，得到长短码(Long and Short Code，LSC)DS-CDMA信号。SC-DS-CDMA信号用一周期扩频码调制一个信息码，文献[2]-[3]分别采用多重信号分类法[2]和平行因子法[3]实现了各用户伪码盲估计；文献[4]利用特征值分解法和Givens矩阵旋转法来估计SC-DS-CDMA信号各用户的伪码，但在寻找Givens矩阵旋转角度时采用极值法，难以得到最佳旋转角度，估计性能不佳；LC-DS-CDMA信号用一周期扩频码调制多个信息码，文献[5-6]通过构建张量模型，分别利用TUCKER分解[5]和CP分解[6]估计LC-DS-CDMA信号的伪码；文献[7]采用迭代最小二乘投影算法和库搜索估计异步LC-DS-CDMA信号各用户的伪码；文献[8]采用矩阵填充理论、奇异值分解和FastICA算法估计LSC-DS-CDMA信号各用户复合码，并利用m序列三阶相关特性估计出各用户长短码；文献[9]利用FastICA算法分离LSC-DS-CDMA信号各用户复合码，并基于分圆陪集理论和三阶相关特性估计长短码。上述研究都只针对理想信号，实际接收信号总会带有小的残余频偏[10]，使得上述方法无法直接使用。文献[11]-[12]分别利用线性调频Z变换法和无迹卡尔曼滤波法估计残余频偏，但无法完全消除频偏；文献[13]利用特征值分解法得到带残余频偏的伪码，并通过全数字锁相环(Digital Phase Locked Loop，DPLL)对频偏进行跟踪消除，实现了长码直扩信号的伪码估计，但并未对LSC-DS-CDMA信号进行研究。
