对于移动通信系统主要有两类衰落：大规模衰落和小规模衰落。大规模衰落表示由于大范围内移动而引起的平均信号能量的减少或路径损耗。而小规模衰落则表现为两种机制：信号的时延扩展和信道的时变特性。对于无线应用，信道的时变特性是由于发射机和接收机相对移动而造成传输路径的变化。这些传播条件的变化速率影响衰落率。如果存在大量反射路径而不存在视行信号分量，此时的小规模衰落称为瑞利衰落(Rayleigh fading)，接收信号的包络由瑞利概率分布函数统计描述。这种衰落也就是这次实验我准备研究的-system for mobile communications fading there are two main categories : large-scale and small-scale fading fading. In view of large-scale decline of large scale movement of the average energy of the signal path to reduce or loss. And the decline of small-scale, it was manifested as two mechanisms : signal delay expansion and channel time-varying characteristics. For wireless applications, channel time-varying characteristics as transmitter and receiver relative movement caused transmission path changes. These conditions spread of the rate changes affect the rate of decline. If there is a large number of pathways exist without depending on the signaling component, At that time, the decline of small-scale known as Rayleigh fading (Rayleigh fading). The received signal envelope from Rayleigh