CHARACTERIZATION OF RAIN FADE DYNAMICS FOR KU BAND SATELLITE COMMUNICATION SYSTEM IN A TROPICAL LOCATION

Abstract

Rain fade has always been regarded as the main obstacle to satellite communication operating at higher frequencies, particularly in the tropics. The dynamic characteristics of rain fade such as fade duration and fade slope, are important parameters for system engineers to design and plan fade mitigation techniques for highly reliable Ku-band services and other higher frequency bands. Twenty – four (24) consecutive months (January 2017 – December 2018) of received signal strength data at 12.245 GHz (Ku- band) from EUTELSAT-W4 (geostationary at 36 E) was collected concurrently with rain intensity data at The Federal University of Technology, Akure (7.17 N, 5.18 E) Nigeria. The number of events exceeding the duration threshold at minimum attenuation of 1 dB is 4361, while at 15 dB attenuation, the number of events is 240 for the year 2017. In 2018 the 1 dB attenuation recorded 8455 occurrences and 15 dB attenuation is 206. The measured fade duration was compared with ITU-R P 1623 model and the Cheffena- Amaya prediction model. The results showed that the ITU-R model is in close relation to the measured data, whereas, Cheffena-Amaya model overestimates the measurement for all the durations considered. The ITU-R fade duration model was modified based on the measured data using the Levenberg-Marquardart method to suit the study location. The comparative analysis of the modified ITU-R model has minimum statistical values of an average prediction error of Mean value of -0.51246, Standard Deviation value of 0.78614, and Root Mean Square value of 0.91236. The proposed modified ITU-R prediction model is recommended to be adopted for Nigeria climate. These findings can be utilized for planning and designing fade mitigation techniques to overcome severe rain effects on earth-to-satellite microwave links operating at Ku- band in the tropical regions.