Rainfall Zoning and Rain Attenuation Mapping for Microwave and Millimetric Applications in Central Africa

Abstract

Rainfall attenuation is among the major factors often considered, in the design of wireless networks, operating at higher bands within microwave and millimeter wave spectrum. At tropical and equatorial locations, not only is the occurrence of rainfall events of serious concern to terrestrial and satellite communication systems, but also the high intensity of rain rates attained during such events. In this paper, daily rainfall measurements from the Rwanda Meteorology Agency (Meteo Rwanda) are obtained for 30 locations within equatorial Rwanda (between latitudes of 1°2'S and 2°45'S and longitudes of 28° 45'E and 30052'E), Central Africa, to develop rain rate and rain attenuation maps for wireless radio links. From these long term annual rainfall measurements spanning a minimum of 10 years at these locations, rainfall rate statistics estimated from appropriate models are applied to determine radio link availabilities between 99% and 99.999%. Furthermore, specific attenuation estimates due to rainfall are proposed from International Telecommunication Union (ITU) recommendations at selected frequencies of the microwave and millimeter bands, for the design of wireless networks. Results obtained from this approach incorporating both rainfall rate zones and specific attenuation over Rwanda, are presented as spatial contour maps representations for different ranges of link availability. It is envisaged that these maps will serve as a useful resource for quick reference for future link design estimates, for terrestrial and satellite networks across Rwanda and Central Africa.