Research On Rain Attenuation And Fade Countermeasures In Ka Band Satellite Communication

Satellite communication system has experienced rapid development for its unique advantage and has become an essential part of telecommunication in the future. It will be the development trend of the future satellite communication to utilize Ka band or higher frequency band to construct the satellite communication system. The influence of rain attenuation in Ka band satellite communication system is extremely serious. It is a main factor that affects the communication capability and the quality of transmission in Ka band satellite communication.It is the most important step that researching fade countermeasures in analyzing rain attenuation, finding the causation and forecasting. With the rising of frequency, the influence to signals of all kinds of factors increases gradually, such as weakening the power of satellite signal, adding system noise temperature, reducing the rate of cross polarization identify. The calculation of rain attenuation is simple on condition that the rainfall is symmetrical. However, as the rainfall is usually complex, accurate calculation of rain attenuation is actually intricacy.It is difficult to establish a precise fade calculation model. Now application to rain attenuation widely used prediction model is ITU-R. Based on the rain data of 13 typical sits in Northeast China, and the character of China terrain, this paper adopts ITU-R model, Rain attenuation on up link 30GHz and down link 20GHz in Ka band satellite orbit position:62°E, 92°E and 122°E is calculated by Matlab. Analyzed Ka band rain attenuation in Northeast China, and summarizes the characters of Ka band satellite communication system in this area.In order to ensure the transmission quality of satellite communication link, we must adopt corresponding compensation methods. Nowadays some typical rain attenuation compensation methods include the technology of dividing and collecting, the technology of power control, adaptive technique. In this paper we put forward an adaptive CDMA scheme. Finally, with its emphasis on the effect of rainfalls on the capabilities of satellite communications, this paper discusses in detail the wave-spreading characteristic of Ka-band satellite communication, in accordance with which, a simulation channel model is built to research rain attenuation compensation. The simulation results indicate the two methods mentioned above is correct and practical.