中圖分類號： TN914.42 文獻標識碼： A DOI：10.16157/j.issn.0258-7998.212094 中文引用格式： 潘微宇，趙知勁. 帶殘余頻偏的LSC-DS-CDMA信號偽碼估計[J].電子技術應用，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
直接擴頻序列碼分多址(Direct Sequence Code Division Multiple Access，DS-CDMA)采用高速率的偽碼對信息碼進行擴頻調制，具有較強的隱蔽性和抗干擾能力[1]。DS-CDMA信號可根據擴頻方式分為短碼(Short Code，SC)DS-CDMA和長碼(Long Code，LC)DS-CDMA兩種信號，為了進一步提高保密性，利用長碼對短碼擴頻信號做加擾處理，得到長短碼(Long and Short Code，LSC)DS-CDMA信號。SC-DS-CDMA信號用一周期擴頻碼調制一個信息碼，文獻[2]-[3]分別采用多重信號分類法[2]和平行因子法[3]實現了各用戶偽碼盲估計；文獻[4]利用特征值分解法和Givens矩陣旋轉法來估計SC-DS-CDMA信號各用戶的偽碼，但在尋找Givens矩陣旋轉角度時采用極值法，難以得到最佳旋轉角度，估計性能不佳；LC-DS-CDMA信號用一周期擴頻碼調制多個信息碼，文獻[5-6]通過構建張量模型，分別利用TUCKER分解[5]和CP分解[6]估計LC-DS-CDMA信號的偽碼；文獻[7]采用迭代最小二乘投影算法和庫搜索估計異步LC-DS-CDMA信號各用戶的偽碼；文獻[8]采用矩陣填充理論、奇異值分解和FastICA算法估計LSC-DS-CDMA信號各用戶復合碼，并利用m序列三階相關特性估計出各用戶長短碼；文獻[9]利用FastICA算法分離LSC-DS-CDMA信號各用戶復合碼，并基于分圓陪集理論和三階相關特性估計長短碼。上述研究都只針對理想信號，實際接收信號總會帶有小的殘余頻偏[10]，使得上述方法無法直接使用。文獻[11]-[12]分別利用線性調頻Z變換法和無跡卡爾曼濾波法估計殘余頻偏，但無法完全消除頻偏；文獻[13]利用特征值分解法得到帶殘余頻偏的偽碼，并通過全數字鎖相環(Digital Phase Locked Loop，DPLL)對頻偏進行跟蹤消除，實現了長碼直擴信號的偽碼估計，但并未對LSC-DS-CDMA信號進行研究。
