Rain fade impairment analysis for Earth-to-space radio links using site diversity techniques in Delta State, Nigeria

Abstract

Site diversity is a fade mitigation technique that employs two or more spatially separated receiving stations to reduce the adverse effects of rain attenuation on satellite communication links. Its effectiveness is particularly important in tropical regions where intense convective rainfall frequently degrades Earth-to-space radio communications. This study investigates rain fade impairment and evaluates the effectiveness of site diversity for Ku-band Earth-to-space radio links in Warri, Delta State, Nigeria, a tropical coastal environment with high rainfall intensity. Rain rate and received signal level measurements collected during the peak rainy months of 2024 were analysed to generate cumulative distribution functions (CDFs) for rainfall occurrence and attenuation statistics. The study adopted the ITU-R P.618-11 and P.618-12 propagation models to estimate rain attenuation and diversity gain for both single-site and joint-site configurations. Results show that rain attenuation increases with rainfall intensity and becomes particularly severe for rainfall rates exceeding 70 mm/h. Maximum single-site attenuation values of 54.83 dB and 25.12 dB were observed during rainfall intensities of 200 mm/h in July and August, respectively. The application of site diversity reduced attenuation significantly, producing maximum diversity gains of 13.76 dB, 5.27 dB, 5.22 dB, and 4.10 dB for July, April, August, and October, respectively. Negative diversity gains observed at low rainfall intensities indicate periods of high spatial correlation between rain cells, during which diversity effectiveness is reduced. The findings validate the applicability of the ITU-R site diversity model under tropical convective rainfall conditions and provide localized propagation information for the design and optimization of reliable Ku-band satellite communication systems in the Niger Delta region of Nigeria.