多载波码分多址系统的上行等效空时多用户检测

Uplink Equivalent Space-Time Multiuser Detection for Multicarrier Code-Division Multiple Access Systems

针对多载波码分多址(MC CDMA)系统传统频域符号检测方法解码效率低的问题,提出了基站使用任意阵MC CDMA系统的特殊等效空时直接序列码分多址模型,其特点是定义了具有循环卷积结构的特征波形,从空时联合角度刻画了矢量信道特征,克服了频域模型不能理想描述矢量信道的痼疾.同时,为系统构造了基于上行矢量信道冲激响应盲估计的最小均方误差等效空时多用户检测器,其性能是线性最优的.仿真结果表明,当系统信噪比为8dB并且负载因子(即活动用户数与扩频增益之比)不超过85%时,即使单天线也比4天线传统频域等增益合并符号检测方法的解码效率至少要高出20dB.

Conventional frequencydomain symbols detection schemes for multicarrier codedivision multiple access (MCCDMA) systems pose very low decoding efficiency. To combat this challenge, an equivalent spatialtemporal direct sequence CDMA model is developed in details for MCCDMA systems with arbitrary antenna arrays over frequencyselective fading channels.In this model, by exploiting the novelly defined signature waveform with the cyclic convolution structure, the spatialtemporal signature of vector channels is elegantly described. Successively, an uplink equivalent spatialtemporal minimum meansquared error multiuser detector is derived. This multiuser detector is linearly optimum, and is constructed on the blindly estimated vector channel impulse response. As demonstrated by computer simulation results, this proposed scheme, even with single antenna, outperforms the conventional frequencydomain equalgain combing (EGC) symbols detection scheme with four antennas. Concretely, when the signaltonoise ratio is 8 dB and the system loading factor (namely, the ratio of active users to the spreading gain) does not overrun 85% , the decoding efficiency of the above proposed scheme measured by rooted meansquared error surpasses that of EGC 20 dB at least.