Research On Ka-band Satellite Communication System’s Rain Attenuation Characteristics And Compensation Method Based On OFDM Technology

Satellite communications for its many advantages features, has become animportant and indispensable component in modern communications system. With thegrowth of business needs, using Ka-band (30/20GHz) constitutes satellitecommunication system is the future trend of development. For Ka-band satellitecommunication systems, the attenuation caused by the rainfall is an important factoraffecting the quality of satellite communication transmission.To solve this problem, this paper summarizes the current application anddevelopment of Ka-band satellite communications in the world, introduces themechanism and impact of rain attenuation, the internationally popular rain attenuationprediction model ITU-R and calculated the values of Chinese65sites’ Ka-band103°E geostationary orbit satellite uplink20GHz and downlink30GHz rain attenuation.Through the Ku-band actual measurement of rainfall attenuation value in three years2011-2013, transform the rain attenuation data into Ka-band using conversion formulaand proof the ITU-R rain attenuation prediction model is validated in Changchun area,as the same time the lognormal distribution and exponential curve fitting analysisusing the least squares method.To ensure the quality of transmission Ka-band satellite communication, we proposetechnique power compensation based on OFDM technology. Combined with theOFDM channel characteristic and rain attenuation actual measurement data, try tobuild the OFDM transmission attempt to the satellite communication systemsimulation and analysis. The results show that with the increase if the number ofcarriers in the OFDM system, the utilization of a substantial increase in the system,and the BER performance is reduced. Individual pursuit channel utilization or errorrate is not comprehensive; you can find a channel utilization and error performance balanced approach to improve transmission performance.Finally, the power compensation method of rain attenuation based on the basicalgorithm, by increasing the transmit power can be achieved effectively offset the lowSNR environments. The rain attenuation at high SNR environment, arising from therain attenuation although the system is not completely offset error, but the errorperformance of the system has been greatly improved, thereby reducing the impact ofrain attenuation of the transmitted signal. Simulation analysis, this method proved tobe an effective power compensation method.