Evaluation of some rain attenuation prediction models for satellite communication at Ku and Ka bands

Abstract

Propagation of radio waves between terrestrial and earth-space links at frequencies above 10 GHz are adversely affected by weather, especially rain. Rain-induced attenuation is an important propagation effect that has to be considered in satellite communication system design. Prediction of rain attenuation for earth-space links in North Central Nigeria at Ku and Ka bands is investigated using five rain attenuation models: The ITU-R P.618 model, Bryant model, Garcia-Lopez model, Svjatogor model and Simple attenuation model (SAM). The main objective is to determine the optimal rain attenuation prediction models for satellite communication in this region. 33 years (1983-2015) daily rainfall data obtained from the Nigerian Meteorological Agency (NIMET) were used. Three elevation angles were considered: 55o 42.5o and 23o. The results obtained showed that the ITU-R P.618, Garcia-Lopez and Bryant models performed best in this region. Also, attenuation ranged from 14 dB to 16 dB at 55o elevation angle, 15 dB to 16 dB at 42.5o elevation angle and 20 dB to 22 dB at 23o elevation angle for exceedance time percentage of 0.01% at Ku-band in all the stations. For the Ka-band, attenuation varied between 33 dB and 37 dB at 55o elevation angle, 33 dB and 37 dB at 42.5o elevation angle and between 42 dB and 48 dB at 23o elevation angle for same 0.01% exceedance time percentage. From the values of rain attenuation predicted for 0.01% time exceedance, availability of signal is possible at 42.5o and 55o elevation angles but impossible at 23o elevation angle at Ku-band. At Ka-band, the predicted rain attenuation values for 0.01% time exceedance have shown that availability of signal is impossible at all three elevation angles, which implies total signal fade out during such rainfall events in the region.