Modeling of Ka-band slant path rain attenuation for hilly tropical region

Abstract

Experimental measurement of satellite signal at 20.2 GHz using GSAT-14 satellite beacon has been carried out over the hilly tropical location Umiam, Shillong during 2017–2019. Collocated rainfall measurements have been done using a laser precipitation monitor for the same duration. The data have been analyzed to understand the signature of orographic rainfall on the Ka-band signal and to achieve the highest possible reliability of signal reception for a high rainfall tropical location. Complementary cumulative distribution of experimentally obtained rain attenuation is compared with that of conventional ITU-R model calculated rain attenuation and recently developed Chang Sheng model predicted rain attenuation values. The result shows severe overestimation of the actual measurement by both the ITU-R model and Chang Sheng model. The Chang Sheng model is further modified with the orographic adjustment factor for predicting orographic rain attenuation. The model was developed based on the data of 2017–18 and validated using the measured attenuation of the year 2019. The performance of the proposed model is evaluated in terms of RMSE and correlation coefficient. The value of the correlation coefficient has been found to be 0.988, and the RMSE value has been found to be around 3.0986, which indicates the acceptable performance of the proposed model. The proposed model is further optimized for operational elevation angle range, rain rate range, and frequency range. The proposed model will help in optimizing the power utilization in the Uplink Power Control technique for rain attenuation mitigation over high rainfall hilly regions.