ANALYSIS OF RAIN ATTENUATION OF RADIO SIGNALS USING MEASUREMENT OF DROP SIZE DISTRIBUTION IN A TROPICAL LOCATION

Abstract

This research gives the analysis and modeling of rain drop size distribution in Akure, a tropical location. Three years (2013-2015) data of rainfall parameters (rain rate, number of drops and fall velocity) were obtained from communication research group, Department of Physics, The Federal University of Technology Akure, Nigeria. The rainfall parameters were measured using vertically-pointing Micro Rain Radar. The drop sizes were classified into drizzle, widespread, shower and thunderstorm rain types based on rain rate values. An estimation approach was used to obtain its equivalent drop diameter. Gamma distribution was employed as a result of its strong correlation coefficient compared to other distributions. Parameters associated with gamma distribution were estimated using method of moment based on the third, fourth and sixth moments. The result was compared with the drop size distribution of other tropical region; such as Rwanda and Durban. The results obtained were then applied to the computation of specific attenuation based on Mie scattering function at 25.33oC for frequency window of 10 - 60 GHz. Result shows that drop diameters and fall speed increases with height considerably. The specific rain attenuation also increases with frequency. However, performance above 40 GHz relative to increase in frequency in the frequency window considered shows no significant change in the extinction coefficient. The estimated attenuation statistic from this work will be useful for future studies on millimeter wave communication systems for this region.