Frequency scaling in millimetre-wave rain attenuation estimation for satellite link in tropical regions

Abstract

The congestion at the lower frequency bands is pushing the demands for the usage and operation in the higher bands. The bands above 10 GHz are now required to satisfy the tremendously increasing needs in satellite communication (SatCom) systems. The biggest problem in deploying frequencies above 10 GHz in tropical-equatorial regions is that such areas will experience acute degradation of signal quality due to heavy rainfall throughout the year. A reliable estimation of rain attenuation is required. Dependable fade margins are required in mitigating the harsh signal losses. It is found that data validation for rain attenuation estimation using the frequency scaling technique is not available in any previous studies conducted in tropical regions. It has been suggested that instead of using the conventional method of predicting rain attenuation using the point rainfall rate information, an applicable non-meteorological technique should also be established. A frequency scaling technique can be the alternatives mean to predict rain attenuation when rainfall data is not available. The objectives of the research entail rain-induced attenuation studies for SatCom in tropical regions. They comprise identifying the best fade margin for rain attenuation at various links, formulating a new frequency scaling model with improved accuracy, and validating the proposed model. The methodologies involved in the study encompass the processing of the beacon signals into first-order statistics of rain attenuation. This, later, leads to the generation of monthly and annual rain attenuation Cumulative Distribution Functions (CDFs). The worst month analysis for rain intensity and rain attenuation was also carried out. The signal loss is expected to be appalling in the worst month because of the high occurrence of rain events. The required fade margin was determined from an exceedance at a specific point from the annual CDF. In brief, the frequency scaling model was derived based on the correlation between the attenuation ratio of a higher and lower frequency against the attenuation at a lower frequency. The newly developed formulation was utilized to generate new CDFs of attenuation at different frequencies. The proposed model offers a lower RMSE value and percentage error of 2.8 and 11.3% respectively. In contrast, the generic method suggested by the ITU-R only managed to perform prediction with RMSE value and percentage errors of 28.3 and 28% accordingly. The new model was validated using data set from alternative years and alternate locations. In conclusion, the results from the research demonstrate a model that can be used in the tropical-equatorial region in a way denoting the achievement of fulfilling the stated objectives. The satellite signal performance can be improved by applying developed mitigation techniques with an economically viable cost where dependable fade margins can be attained. The newly developed frequency scaling technique can offer the right margin to achieve the required quality of service (QoS) for future SatCom in supporting near-future 5G communication. Consistent connectivity for high-speed broadband communication demand in delivering digital and internet applications during heavy precipitation can be attained.