| Satellite communication system has experienced rapid development for its unique advantage and has become an essential part of telecommunication in the future. With people's growing needs of wide bandwidth multimedia services, the C(6/4GHz), X(8/7GHz), Ku(14/12GHz) band can't meet the needs of large bandwidth, high speed, small aperture terminal applications, etc. While the Ka band satellite communication system has such merits: Huge bandwidth available, Small disturbance, Small terminal equipment, etc. so it can offer brand-new method for some new services, such as high speed satellite communication, kilo mega bits bandwidth digital transmission , high definition TV (HDTV) and personal communication, etc. It is the development of the future satellite communication to use Ka band or higher frequency band to construct the satellite communication system. Thus, the research and development of Ka band satellite communication system has attached its great importance for the satellite communication service development of our country.Rainfall has become one of the key factors which influence the transmission quality, because it has great attenuation to the electronic wave transmission of Ka band satellite communication system. Therefore, in order to ensure the transmission quality, reliability and economical efficiency, we must master the rainfall attenuation influence of earth station setting areas accurately while the designing the earth-space satellite communication links.The paper introduced the present study status of rain attenuation home and abroad and mechanism of the rain attenuation, physical characters of the rainfall, discussed two wide application rain attenuation prediction models: ITU-R model and DAH model. ITU-R rain attenuation prediction model has its characters of convenient use, less input parameters and wide application domain. Distributions of rain attenuation were given for the satellite communication system (the satellite orbit position: 62°E, 92°E and 122°E) in the Ka-band under the condition of linear polarization. These distributions are calculated from rainfall data and geography parameter at the 65 typical stations of China based on the ITU-R model. Further, we anglicized the rain attenuation character of Ka band satellite communication system, with combination of the geographical and climatic distribution, and we obtained some useful results: (1) The serious Ka band rain attenuation areas are located in the southeast seashore of China, while the modest rain attenuation areas are located in the northwest. It proved that the primary rain attenuation influence factor is the minute rainfall rate of 0.01% time. From the contour map of minute rainfall rate, we can see that, the he heavy rainfall areas are coincident with serious rain attenuation areas. (2)The elevation also affects the rain attenuation heavily. The reason is the elevation determines the length of the slant path, and this result in the variation of the rain attenuation. The result can be employed in designing the Ka band satellite communication system reasonably, reducing the rain attenuation affection and providing the basic theoretic data for the research of Ka band satellite communication system in China. When discussing the compensative methods of rain attenuation, we introduced several representative methods such as site diversity, frequency diversity and up link power control technology. Then introduced some methods based on adaptive algorithm. Such as adaptive forward error correction, adaptive TDMA and adaptive CDMA .Based on the Ka band rain attenuation of 65 typical stations in China, through the analysis of the concrete data, we concluded the terrain character of Ka band satellite communication system in China: (1)with a vast territory, the rainfall in China distributes extremely unevenly, for the rain rate is the primary factor which affects the rain attenuation. So the distribution of the rain attenuation is uneven too. The terrain difference is significant. The biggest rain attenuation site is located...
|
PDF Full Text Request