Comparative Analysis of ITU-R P.618-14 and Ajayi-Olsen Models for Rain-Induced Signal Attenuation on Aviation Satellite Communication Links in Some Northern Nigeria

Abstract

Rain-induced signal attenuation remains one of the most critical impairments affecting satellite communication links operating above 10 GHz in tropical environments. This study presents a comparative analysis of the ITU-R P.618-14 standard model and the Ajayi-Olsen tropical propagation model for predicting rain attenuation on aviation satellite communication links across four selected states in Northern Nigeria; Abuja/FCT, Kaduna, Jos/Plateau, and Sokoto. Five years of daily rainfall data (2021–2025) obtained from the Nigerian Meteorological Agency (NiMET) were fitted to a Gamma distribution to derive the 0.01% exceedance rain rate (R_0.01) for each station. Both models were applied at Ku-band (12 GHz) and Ka-band (30 GHz). Results reveal that R_0.01 values range from 1.827 mm/hr at Abuja to 4.415 mm/hr at Sokoto. The Ajayi-Olsen model consistently predicts 8–10% higher Ku-band attenuation than ITU-R P.618-14, confirming that the global model underestimates rain attenuation in Northern Nigeria. Ka-band attenuation A_0.01 ranges from 1.911 dB at Abuja to 4.330 dB at Sokoto under ITU-R predictions. A Ku-band correction factor of +10% to ITU-R predictions is recommended for aviation satellite link budget design across Northern Nigeria.