Study On The Prediction Model Of Rain Attenuation On Microwave And Millimeter-wave Propagation

With the development of high-capacity and high-speed communication technology,various radio communication systems with frequency above 10 GHz is widely used.Rain attenuation is an important factor affecting the performance of those radio systems and an important basis for system reliability design.Rain attenuation prediction accuracy has important application value for microwave and millimeter wave system design and system performance evaluation.Based on the rain attenuation database from the International Telecommunication Union(ITU-R),the performance of the existing rain attenuation prediction models is analysised.A new rain attenuation prediction model for terrestrial line-of-sight(LOS)links and slant links is proposed.Based on mesoscale numerical weather model,the feasibility of short-term numerical prediction of rain attenuation is explored.Finally,the regional distribution characteristics of slant links rain attenuation in C hina combined with the design of satel ite communication system are analyzed.The main innovations are as follows:1.Analyzing the contradiction between path adjustment factor based on cylindrical rain cells and measured data in traditional rain attenuation prediction model,a theoretical model of rain attenuation was established based on exponential cell distribution(EXC ELL),and the concept of rain rate adjustment factor was put forward.The main characteristics of meas ured rain attenuation data can be explained more reasonably by using rain rate adjustment factor than by traditional path adjustment factor.The results show that the theoretical model of rain attenuation based on EXC ELL rain cell is more reasonable than the traditional cylindrical rain cel.2.A new rain attenuation prediction model for slant links is proposed.Based on the analysis of rainfall attenuation data of ITU-R slant links,the variation characteristics of rainfall rate adjustment factors with rainfall rate,path length,percentage of time,rain height and elevation angle are analyzed.The relationship between rainfall rate adjustment factors and strong correlation parameters such as rainfall rate,path length and elevation angle is established.A new rain attenuation prediction model for slant links using full probability rain rate is developed.The new model is compared with several existing models.The results show that the new model has better accuracy,stability and robustness and the anomalous behaviors found in existing rain attenuation prediction models are also improved.3.A new rain attenuation prediction model for terrestrial LOS links is proposed.By analyzing the rain attenuation data of ITU-R terrestrial LOS links,the model establishes the relationship between rain rate adjustment factor and the parameters such as rain rate and path length,and predicts the rain attenuation wit h different time of percentage by using the full probability rain rate.The prediction accury of the model is superior to that of other rain attenuation prediction models using full probability rain rate distribution,and equivalent to the model using probability transformation.The model prediction process is simpler and more convenient,and it overcomes the shortcoming of ITU-R method that cannot predict the rain attenuation for other percentage of time with the exceeded rain rate of 0.01% of an average year is unavailable.4.In order to meet the requirement of radio system operation and support,a short-term prediction method for rain attenuation region is proposed by combining WRF with the theory of rain attenuation taking advantage of the advantages of numerical weather model in time-space distribution prediction of radio environmental parameters.By comparing with the observation data of the rain gauge and the sounding instrument,the WRF model can accurately predict the meteorological parameters needed for the rain attenuation prediction.The feasibility of short-term forecast of regional rain attenuation is explored.The results are in good agreement with the trend of the measured results.Finally,the difference of rain rate data from different sources and different prediction models on the prediction attenuation is analyzed.Combined with the satellite communication system in China,the effects of rainfall rate data from different sources and different prediction modes on the prediction results of rainfall attenuation are analyzed and compared with the measured Ka band slant link rain attenuation data in China.The difference of communication design process between Ka/Q/V band satellite communication system and X/Ku band system is analyzed.It can provide important reference for the engineering application of Ka/Q/V band satellite communication system.