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1.引言近年来,发表了许多有关移动无线电话系统的论文,这些文章都是根据频分多路复用的原理写出的。众所周知,频分系统的缺点是邻近信道互相干扰和产生信道间的交叉调制,以至无法利用可用频谱内的所有载频,降低频率的利用率。改进频分系统的有效办法是缩减无线勤务范围。但是,由于信号强度随距离的变化是统计性的,其随机衰落极为严重,因此即使设计较小的频分通信网也是很困难的。
1. INTRODUCTION In recent years, many papers have been published on mobile radiotelephone systems, all of which are based on the principle of frequency division multiplexing. It is well-known that the disadvantage of frequency-division systems is that adjacent channels interfere with each other and cross-channel cross-modulation occurs so that all carrier frequencies in the available spectrum can not be utilized to reduce frequency utilization. An effective way to improve the frequency division system is to reduce the scope of wireless service. However, since the variation of signal strength with respect to distance is statistically significant and its random fading is extremely serious, it is difficult to design even a small frequency-division communication network.