影响LMDS系统无线信道特性的几个主要因素

Impact of Main Factor on Radio Channel of LMDS System

对工作于厘米或毫米波段的LMDS系统而言 ,无线信道的特性对系统是否稳定可靠起着关键性的作用。同工作于该波段的卫星通信系统一样 ,雨衰是影响系统性能的主要因素 ;相反对移动通信影响较大的多径衰落对实现视距传输、在用户端采用高增益强定向性天线的LMDS系统影响并不大。此外 ,植被和建筑阻挡以及尘暴的影响也不容忽视。笔者就这几方面因素的影响情况逐一讨论 ,并提出相应的估计模型和改善方法。

Characteristics of radio channel play a key role in stabilization and reliability of LMCS/LMDS system at centimeter and millimeter. Rain specific attenuation has been recognized as a principal cause for impact system performance in LMDS and satellite communications systems operating in the same frequency band. In contrast to mobile communication system, multipath is not a typically problem for LMDS system, because directional antennas are used and the antennas are sufficiently high providing a line of sight propagation path between the transmitter and receiver. Moreover, the effects of buildings, foliage, and dust storms shouldn't be ignored. The impact of these factors on signal propagation and propose corresponding models is discussed. At the last,antenna height and directivity are used in the classification of statistical channel models for LMDS.