这一信道模型能够描述由电离层和对流层反射的短波信道，以及建筑物密集的城市环境。12瑞利衰落只适用于从发射机到接收机不存在直射信号（LoS，Line of Sight）的情况，否则应使用莱斯衰落信道作为信道模型-This channel model is able to describe the HF channel reflected by the ionosphere and troposphere, as well as building a dense urban environment. 12 Rayleigh fading only applies to from the transmitter to the receiver there is no direct signal (LoS, Line of Sight), otherwise use Rician fading channel as the channel model