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本文建立了复合码ＤＳＣＤＭＡ扩频系统的数学模型，推导了多址干扰的数学表示，定义了用户之间的互扰因子，并进行了计算．研究发现：在扩频比相同的条件下，若ＰＮ序列周期大于扩频比，且序列的伪随机性较好，则采用ＷＨｍ／Ｍ复合序列与采用ｍ、Ｍ序列的扩频系统，其互扰因子均呈高斯分布，且数字特征相同；当ＰＮ序列周期等于扩频比时，互扰因子不具有高斯分布特性．该结论不要求扩频比足够大，而且对同步和异步ＤＳＣＤＭＡ通信系统都适用．
This paper establishes a mathematical model of DS-CDMA CDMA system, deduces the mathematical representation of multiple access interference, defines the mutual interference factor between users, and calculates. It is found that if the PN sequence period is greater than the spreading ratio and the pseudo-randomness of the sequence is better under the same spreading conditions, the WHm / M complex sequence and the spread spectrum system using m and M sequences are adopted, The mutual interference factors are Gaussian distribution, and the same digital characteristics; when the PN sequence period equal to the spreading ratio, the mutual interference factor does not have Gaussian distribution. This conclusion does not require spread-spectrum ratio is large enough, but also for synchronous and asynchronous DS-CDMA communication systems are applicable.