移动通信课件第1讲.ppt

Mobile Wireless Communications 移动无线通信 Chapter 2 Chapter 2 Characteristics of the mobile radio Characteristics of the mobile radio environment-propagation environment-propagation phenomena phenomena 第第2 2章章无线介质中传播现象的特性无线介质中传播现象的特性 Radio (无线的) propagation (传播) conditions play a critical role in the operation of mobile wireless systems . They determine the performance of these systems , whether used to transmit real-time voice messages , data , or other types munication traffic . It thus behooves (有益于) us to describe the impact (影响) of the wireless medium wireless medium (无线介质) in some detail (详细的), before moving on to other aspects of the wireless communication process . ?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 municates . It is the base station that is , in turn , connected to the work over munication signals will travel . Modern wireless systems are usually divided into many geographically distinct areas called cells , each controlled by a base station . ?无线通信或无线线路一般都?被描述为无线系统中移动用户终?端和它所通信的基站之间的通信?链路,而基站则连接着可传输信?号的有线网络。??现代的通信系统一般在区域?上被分为很多小区, 每个小区设?有一个基站。本章主要过论一个小区内信号在基站和移动终端之间进行传输时的传播环境。 The focus here is on one cell and the propagation conditions encountered by signals traversing (穿过) the wireless link (链路) between base station and mobile terminal . The wireless link (链路) is made up of a two-way path (收发双用信道): a forward path (前向通路), downlink (下行链路), from base station to mobile terminal ; a backward path (反向通路), uplink (上行链路), from mobile terminal to base station . ?无线链路由收发双用信道组成:前向通路即下行,是从基站到移动?终端;反向通路即上行,是从移动终端到基站。 The propagation (传播) or transmission (传播) conditions over this