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利用小波包变换的多载波调制避免了OFDM技术中由多径效应引起的载波的正交性损失,同时降低了为此加入的循环前缀引起的信噪比损失,因而使用小波包变换的多载波CDMA系统(WPT-CDMA)性能优于传统的OFDM-CDMA系统。但在MIMO多用户传输环境下,接收机端的约束最小均方(CLMS)自适应波束形成算法在信号方向向量存在偏差及采样样本数目较少的情况下,会出现收敛速度慢、输出性能下降、不稳定等问题。针对这些问题本文提出应用在WPT-CDMA系统中的基于最差性能的鲁棒CLMS算法。从理论分析与仿真实验的结果都可以看到系统性能的改善。
The multi-carrier modulation using wavelet packet transform avoids the loss of orthogonality caused by the multipath effect in the OFDM technology and reduces the loss of signal-to-noise ratio caused by the cyclic prefix added for the OFDM technique. Therefore, the use of the wavelet packet transformed multi-carrier CDMA system (WPT-CDMA) outperforms the traditional OFDM-CDMA system. However, under MIMO multi-user transmission environment, the receiver-side constrained Least Mean Square (CLMS) adaptive beamforming algorithm may exhibit slow convergence rate and poor output performance when the signal direction vector is deviated and the number of sampling samples is small. Unstable and other issues. To solve these problems, this paper proposes a robust CLMS algorithm based on the worst performance in WPT-CDMA system. From the theoretical analysis and simulation results can see the improvement of system performance.