基于修正互补序列的MC-DS-CDMA系统抗干扰性能分析

Performance of MCS used in MC-DS-CDMA system

MC-DS-CDMA由于采用了正交频分复用技术,具有高传输速率、抗多径干扰等优点,但是该系统存在占用了大量的频率资源的缺陷.由于采用的常规扩频码不能保证具有良好的自相关与互相关特性,导致其存在很强的多址干扰和非同步干扰,这些限制了系统的容量.该文提出了一种修正互补序列作为扩频码应用于MC-DS-CD MA的新型通信系统.在正交噪声检测(OND)和互补序列理论的基础上,将虚拟码片概念引入到互补序列中.根据虚拟码片的产生算法对整帧数据进行处理构成扩展帧.虚拟码片的加入在扩展帧中形成了无干扰窗口.接收时在此无干扰窗口中对接收数据进行互补序列所特有的相关运算,可以准确恢复原始发送数据.文中对系统进行了模拟仿真,证明了此技术的可行性.该技术的采用使系统可以在使用相对较少子载波的情况下,有效防止由于上行线路传输所产生的非同步干扰和多径干扰,而且可以将多址干扰降低到很低的水平.

The MC-DS-CDMA system, based on orthogonal frequency division multiplexing (OFDM), has some good properties, such as high-speed transmission and restraining multi-path interference. However, it uses significant frequency resources. Because traditional spreading spectral sequence does not have good property of autocorrelation and inter-correlation in the meantime, it leads to multi-access interference. In addition, the interference resulted from absence of synchronization must be considered in this system. Here, a new system of MC-DS- CDMA system using modified complementary sequences is proposed. Based on the theory of complementary sequences and OND, the concept of dummy chip is introduced. According to the algorithm of dummy chips generation, the whole frame data will be processed and becomes the extended frame which is also called modified complementary sequence. The dummy chips in the extended frame become an undisturbed window. When received data is carried on the particular correlating computation of complementary sequence in the undisturbed window, the primitive transmitted data will be restored correctly. The performance has been analyzed and simulated. The result of simulation proved this measure proper and feasible. With the quotation of this technology, the system can efficiently eliminate multi-path interference and the interference resulted from absence of synchronization in the up-link, which also can decrease multi-access interference to a low level under the condition of using less sub-carriers relatively.