Study of the seasonal characteristics of rainfall rate in Southwestern Nigeria and its effect on induced attenuation in earth-satellite communications

Abstract

Tropospheric propagation channel modeling is gaining more attention in the scientific community, especially in the applications of the upcoming high-frequency satellite communication systems. Channel modeling is essential to predict link performance, for example, in the area of Bit-Error-Ratio (BER) in a single-user scenario and in a multi-user scenario, especially in the areas of throughput and latency. This study investigates the seasonal characteristics of rainfall rate and rain-induced attenuation in terms of exceedance and worst-month rain statistics over selected tropical locations in Nigeria. The coefficient of variation (CV) of rain rate has also been analyzed to examine the variability of rainfall rate due to the inhomogeneity nature of the chosen region. The GPM satellite 30-min rain rate data has been used for rain attenuation prediction through a 30-min to 1-min metric conversion model. Validation of rain attenuation was conducted through a two-year (2013–2014) beacon measurement of rain attenuation at 12.275 GHz at the Akure site. The ITU-R 618–13 (2017) rain attenuation model has been modified based on the rain attenuation beacon measurement. The modified ITU-R model has produced a least root mean square error (RMSE) of 6.4 when compared to the ITU-R model with 23.5 RMSE. The attenuation difference reduces as the frequency difference moves to the upper frequency bands. The ITU-R model overestimates the calculations from the GPM-derived results, which indicates the modification of the ITU-R model for the tropical location. Spatial variation of attenuation at 30 GHz revealed intensive and dry seasons exhibited the highest and lowest attenuation induced values, respectively. The results can be applied to power-enhanced satellite systems to achieve good signal availability in the study areas.