一种用于多码CP-DS-CDMA系统的混合时频域均衡器

A hybrid time-frequency domain equalizer for multicode CP-DS-CDMA systems

提出了一种新的用于基于循环前缀的多码直接序列扩频码分多址接入(CP-DSCDMA)系统的混合时频域均衡器。该均衡器包括一个前向频域线性均衡器(FDLE)和一个反向时域线性预测器(TDLP)。依据最小均方误差(MMSE)准则导出了该均衡器的最优系数,并证明了前向频域均衡器系数与反向时域线性预测器阶数无关,因此只需改变反向线性预测器的结构就可以灵活地调整系统性能。通过结合块交织处理,该均衡器能利用解扩后在符号级的判决结果,来增强反馈信号的可靠性。计算机仿真结果表明在多码CP-DS-CDMA系统中该均衡器比现有的频域线性均衡器有3dB的性能提高。

This paper proposes a new hybrid time-frequency domain equalizer for cyclic prefix assisted mnlticode direct sequence code division multiple access （CP-DS-CDMA） systems. The proposed equalizer consists of a feedforward frequency domain equalizer （FDE） and a feedback time domain linear predictor （TDLP）. The optimal coefficients of the proposed equalizer are derived based on the minimum mean square error （MMSE） criterion and it is shown that the optimal coefficients of the feedforward FDE are independent of the order of the feedback TDLP. By only adjusting the structure of TDLP, the whole system performance can be flexibly changed. Furthermore, when combined with a block interleaver, the proposed equalizer can benefit from the feedback of the decisions at symbol level, which are obtained after dispreading and have higher reliability than the decisions at the chip level before dispreading. The simulation results show that the proposed scheme can achieve 3dB performance improvement over the conventional linear frequency domain equalizer in mnlticode CP-DS-CDMA systems.