TDD-CDMA系统中一种新的多用户干扰抑制方案

传统的多用户处理是在上行进行的,本文提出了应用于TDD-CDMA系统中下行方向的一种多用户处理方案.在TDD-CDMA系统中,可以利用上行信道参数对下行信道参数做出估计.本文提出了一种实时利用信道参数来降低CDMA中的多用户干扰的方法.在该方案中,其多用户处理的基本思路是通过优化系统的多用户扩频码字和解扩码字来降低多用户干扰.为了达到最大的信干比,本文提出了系统扩频码选择的优化准则,它能够充分利用信道的特性.本文根据一定的迭代算法给出优化问题的解.数值分析结果表明,采用上述方案的CDMA系统相对于采用Gold码的系统能够极大地降低多用户干扰,提高信干比.

Analysis of KM(M) Sequences as Spreading Codes for CDMA Systems with RAKE Receiver

Conventional multiuser interference canceling is always done in the uplink.In this paper,a novel multiuser processing scheme used in the downlink of TDD-CDMA (Time division dupler-code division multiple access) systems is proposed.In TDD-CDMA systems,the downlink multipath channel parameter can be estimated from the uplink.In this paper,we use the instantaneous channel parameter to calculate the spreading spectrum code and despreading code for different users.We present the optimal criterion of the generation of the spreading code and despreading code,so that the multiple access interference can be greatly reduced.Numerical results show that our scheme can geratly increase the signal to interference and noise ratio,compared with conventional CDMA systems which use Gold sequence as the spreading code.