Estimation of rain attenuation over microwave and millimeter bands for terrestrial radio links in Ethiopia

Abstract

While rainfall is a major cause of communication impairment at microwave and millimeter bands, the effect of rain attenuation in the Ethiopian microwave links, has so far remained as unstudied. Therefore, in this paper, the rain rate distribution at 15 minutes integration time is predicted for different percentage of time of the year based on two years of rain intensity data obtained from National Meteorological Agency (NMA) of Ethiopia. The rainfall rate for one minute integration time not exceeded 0.01% of the time is calculated using ITU-R and Chebil designations, it is found that the highest rainfall rate at 0.01 % of time for any location in Ethiopia, does not exceed 64 mm/h. The ITU-R model is then applied to estimate and analyze rainfall attenuation over terrestrial radio links for ten sites in Ethiopia. The attenuation is predicted for frequencies from 1–150 GHz, with variable distances. The results show that Bahirdar is predicted to experience the largest effect of rain attenuation whereas, Dubti, has the lowest attenuation.