Rain attenuation prediction on earth-to-satellite microwave link in Libya as a case study

Abstract

Earth-to-satellite microwave links are revolutionary communication systems that supports high-speed data rate. It can accommodate a large number of users with increased spectral efficiency and high throughput. However, performances of those links operating in Ku, Ka, and V-bands are degraded by the environment and strongly attenuated by rain. Rain attenuation is the most significant consideration and challenge for higher frequency bands. Hence, it is essential for the satellite link designer to take into account rain fade margin accurately before system implementation. Rain rate is the main measured parameter to predict of rain attenuation. Rainfall statistical data measured and recorded in Libya with 3-hours integration time for the period of 30 years are collected. The prediction methods require one minute integration time rain intensity. Therefore, collected data were analysed and processed to convert into one minute rain rate cumulative distribution in Libya. Several prediction models for conversion of one minute rain rate have been utilized by considering different climatic conditions. A suitable prediction model is recommended to predict one-minute rain rate distribution for microwave link design in Libyan environment. Chieko and Yoshio is recommended in the calculation of one-minute rain rate cumulative distribution under Libyan climatic conditions. The model proposed by International Telecommunication Union-Radio wave Propagation (ITU-R) is used to predict and investigate rain fade based on converted 1-minute rain rate data. C, Ku-band downlink at 4-12 GHz rain fading is not a considerable factor in Libya. The further result shows a fade marginal difference of about 15 dB between Ku- and Ka-band frequencies for 99.99% availability of time in coastal regions. As well as the results obtained at V-band downlink shows that 99.99% availability is possible in all the southern part stations in Libya. It is observed that the ITU-R model seems to under estimate the rain attenuation in northeast and northwest in Libyan costal line. Rain fade predicted at five locations are used for performance analysis in terms of link spectral efficiency and throughput. Taking into account of rain fade margin at different outage probabilities. Findings will enable the earth-to-space link designer to determine the optimum transmitting power to mitigate rain fade. Results and analysis of this research will be a very useful resource to design highly reliable earth-to-satellite communication links in Libya.