码分多址信号的解调

在码分多址(CDMA)系统中，窄带信号被乘以叫作扩频信号的宽带信号。扩频信号是一个伪随机代码序列，此码片速率比消息数据速率高若干数量级。随着民用通信步入移动通信年代，CDMA由于功率谱密度低、安全性能好、抗干扰能力强等优点而迎合了当今移动通信的需求。在北美洲，CDMA已经被采纳作为数字语言通信的一种方法，这种数字蜂窝系统由高通公司提出和研究，并被电信业协会(TIA)作为标准，即IS-95标准。该文以IS-95前向业务信道为例，为CDMA信号的解调过程提供了初步的框架，并给出了解调过程中一些关键问题的解决方法。

The Demodulation of CDMA Signals

In code division multiple access(CDMA) systems, the narrowband message signal is multiplied by a very large bandwidth signal called the spreading signal. The spreading signal is a pseudo-noise code sequence that has a chip rate which is orders of magnitudes grater than the data rate of the message. As the commercial communications step into a new era of mobile communications, the qualities of CDMA, such as low power-density, privacy, and a high immunity to interference, etc, are desirable in these areas. In North America, CDMA has been adopted as one multiple-access method for digital cellular voice communications. This digital cellular communication system was proposed and developed by qualcomm and has been standardized and designated as IS-95 by the telecommunications industry association(TIA). In this paper, the IS-95 is used as an example to provide the primary framework of the demodulation process of the CDMA forward traffic channels, and the solution to some key problems during demodulation process is presented.