Publication: Effects of integration time on rain rate distributions for microwave link design based on measurement in Malaysia
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Microwave communication systems -- Malaysia
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The demand for radio frequency spectrum is rapid since the most desirable frequency spectrum is congested; hence 5G and satellite communications are moving forward to the frequency band utilization above 10 GHz. Frequency higher than 10 GHz is subjected to impairment by rain. ITU-R has established rain attenuation prediction methods deduced from the measured rainfall rate with an integration time of 1-minute or less. However, recently, significant discrepancies in ITU-R prediction are found in the measurements of rain attenuation at mmWave bands for short-length propagation links. All researchers used rain intensity from 1- min integration time measurement, as not less than 1-minute data are unavailable. Therefore, this project aims to consider rain rate less than 1-minute integration time, investigate the effects of less than 1-minute integration time on rain rate distribution, and compare rain attenuation predictions using measured rain intensities with different integration times. A real-time rain gauge with a resolution of 10-secs integration time is installed in the International Islamic University Malaysia (IIUM) Gombak. A one-year measured rain rate data with integration times of 10-secs, 20-secs, 30-secs, 1- minute, and 2-minutes are utilized to analyze the effects of integration times on rain intensity distributions and rain attenuation predictions. From the analysis, it is found that at 0.01% probability, rain rates are 123 mm/hr and 191 mm/hr with 1-min and 10-secs integration times, respectively. At 0.1% and 0.001% probabilities, the differences increase to 80% and above. The rain attenuation measured at 26 GHz, 38 GHz, and 73 GHz terrestrial links with 300 m lengths and 12 GHz earth-to-satellite links in Malaysia are compared with those predicted by data from 5 integration times. Predicted attenuation with 10-secs is closer to measurement than 1-min integration time for all three terrestrial links and two satellite links. However, 30-sec integration time data was found close to the measurement for one satellite link. Hence mm-wave short paths in 5G, lower integration time-based rain rate measurement will provide more accurate prediction for path loss and high reliability in the tropical climate.