利用沃尔什码扩频的MC-CDMA系统频偏估计算法

Carrier frequency offset estimation algorithm in MC-CDMA systems with Walsh-code spreading

针对多载波码分多址(MC-CDMA)系统上行链路存在的多用户载波频偏问题,提出了一种利用沃尔什码进行扩频的载波频偏估计导频算法.该算法使用全1的沃尔什码作为专用扩频码,对频偏待估计用户的两个相同导频符号进行扩频;在接收端,利用导频的专用扩频码码片与信息符号的扩频码码片不同的均值特性,得到频偏待估计用户的导频接收信号的近似成分,并从中利用辐角值提取方法得到载波频偏估计值.仿真结果表明:在频率选择性衰落信道下,与基于信号子空间分解的自适应训练序列(ATS)算法相比较,该算法降低了计算复杂度,而且频偏估计的性能也很接近ATS算法,适用于系统在信息数据发送的过程中需跟踪频偏变化的场合.

Aiming at the multiple carrier frequency offset（CFO） problem in the uplink of MC-CDMA systems,a pilot algorithm based on Walsh-code spreading is proposed.The all ＂1＂ Walsh-code as the specific spreading code is used to spread two identical pilots of the interested user.At the receiver,by exploiting the different mean value properties between the specific pilot symbols spreading code and data symbols spreading codes,the received interested user＇s pilot signal components can be approximately extracted and accordingly the CFO of the interested user can be obtained with the phase-angle extraction method.Simulation results show that compared with the subspace decompose based ATS algorithm,the proposed estimator has similar CFO estimation performance with lower computation complexity under the frequency fading channel,and is especially suitable for the scenario where CFO needs tracking during the process of data transmission.