异步DS-CDMA系统中相对时延对多用户检测的性能影响:分析与评估

Effect of Relative Delay on Performance of Multiuser Detection in Asynchronous DS-CDMA Systems: Analysis and Evaluation

多用户检测技术是DS-CDMA系统中的关键技术之一。在反向链路的基站接收机一端,接收信号是各用户异步发射信号经传输信道后的叠加,许多多用户检测器的输入是对系统中各用户用特征波形匹配滤波后以符号速率采样的信号。然而,异步用户间不同的相对时延将引起不等的部分互相关系数,从而也导致不一样的多用户检测性能。该文分析了平均部分互相关系数的解析表达式并给出了计算方法,采用进化算法求解最大以及最小部分互相关系数存在的相对时延条件,提出了异步系统中多用户检测在平均、最大以及最小部分互相关系数条件下的性能分析与评估方法,对分析和比较多用户检测接收机整体性能具有很大意义。

Multiuser detection is a key technique in DS - CDMA systems. The received signal of uplink receiver is superposition of the spreading signal transmitted by users over asynchronous channels. Many multiuser detectors deal with discrete signal sampled at symbol or chip rate after passing through matched filterers. However, different relative delay between users results in distinct partial correlation coefficients thus bringing about distinct performance of multiuser detectors. It is very important to effectively evaluate the average and extreme performance of system. In this paper, the expression of average partial correlation coefficients is analyzed and the corresponding numerical computation method is proposed. On the other hand, relative delay corresponding to the maximal and minimal correlation coefficients is also solved by the evolution algorithm. Based on the obtained results, the performance of the decorrelating and Minimum Mean Square Error （MMSE） multiuser detectors in asynchronous DS-CDMA systems are evaluated by numerical simulation.