Attenuation of millimetre wave radio signal at worst hour rainfall rate in a tropical region: A case study, Nigeria

Abstract

The classical sub-6 GHz spectrum currently being used by wireless networks cannot support the requirement of 5G and higher upcoming mobile communication networks due to its limited bandwidth. Millimeter Wave (MMW) radio systems operating at 30 to 300GHz band provides higher bandwidth, frequency reuse and communications security but suffers greatly from atmospheric, environmental and rain attenuation. The attenuation of millimeter wave radio signal at worst hour rainfall rate was therefore investigated. The data was collected from the Tropospheric Data Acquisition network (TRODAN), the International Institute for Tropical Agriculture (IITA) and the Federal University of Technology, Akure. The rainfall rates were measured at 5 and 1-minutes integration time and the Lavergnat and Gole model was used for the conversion of the measured 5 minute to equivalent 1-minute values. The results revealed that throughout the study period, about 66.67% of the sites recorded the worst rainfall events at the 15 hours Local Time (LT). The range of rainfall rate at 0.01% exceedance was 1.18 to 62 mm/hr while at 0.001% it ranged from 51.50 to 116 mm/hr. The specific attenuation at the threshold frequency of 200 GHz at the 0.01% exceedance ranged from 1.638 to 6.175 dB/km. The clear signal band frequency threshold was 60 GHz and the path attenuation ranged from 15.34 dB to 20.43 dB. These results suggest the inclusion of the estimated attenuation values by radio propagation engineers in designs for this region.