Abstract: A new spreading scheme is introduced for nullifying the multi-access interference(MAI)for CDMA systems. For the synchronous systems, this scheme can keep the orthogonality among the codes used to different users in multipath environments and, therefore, cancel the MAI completely. In alternation, the multi-symbols of a user are overlapped and can, however, be calculated. The simulation shows the effectiveness of this approach for reducing bit error rate(BER) while the system throughputs remain unchanged. In addition, the band efficiency is also discussed.

Key words: CDMA, spreading scheme

摘要： 提出了一种可以在多径环境下消除CDMA多址干扰的新扩频方案。在同步发射条件下，该方法在多径环境下保持了多用户码的正交性，因此完全消除了多址干扰。而各自用户的信息符号可通过解方程的方法从多径叠加信号中分离得到。仿真结果表明该方法可以在保持系统信息吞吐量不变的条件下，降低误码率。另外，还对带宽效率进行了讨论。

关键词: CDMA, 扩频方案