2.2 无线情况
We now turn to electromagnetic
现在讨论无线情况下的电磁
propagation in the wireless environment, 波传播，为简单起见，主要讨论下
we focus on the downlink, base station
行链路即从基站到移动终端的情
As a terminal（终端） moves，changing the conditions of reception（接收） at either end，signal amplitudes（幅度） will fluctuate randomly，resulting in SO-called fading（衰落） of the signal．
无线传播环境在无线移动通 信系统中起着重要的作用。
它决定了系统的性能，决定 了系统是否适合进行实时语音信 息传输，或者适合数据传输，或 者其他类型的通信。
所以，在介绍无线通信其他 方面之前，有必要对无线介质某 些方面的影响详细地讲解一下。
The radio or wireless path normally described in wireless systems corresponds to the radio link between a mobile user station and the base station with which it communicates．It is the base station that is，in turn， connected to the wired network over which communication signals will travel．
