说明：  在无线通信体系中,由于开放的通信信道条件,卫星通信系统中通信链路容易受到平均大气条件的影响,尤其是采用Ka波段的高频信号的系统,容易受到降雨造成的雨衰影响,严重影响了系统的有效性和可靠性。
(In a wireless communication system, the communication channel open, average atmospheric conditions vulnerable to the communication link in satellite communication system, especially the system of high frequency signal using Ka band, vulnerable to the influence of rain attenuation caused by rainfall, seriously affect the validity and reliability of the system. In digital systems, channel coding is often used to improve reliability, while modulation is used to ensure effectiveness. Low order modulation and large redundancy coding are adopted to improve the reliability.)