Site Diversity Prediction at a Tropical Location From Single-Site Rain Measurements Using a Bayesian Technique

Abstract

Site diversity is one of the few fade mitigation techniques that are actively explored to overcome the serious fading condition encountered in high-frequency satellite communication, particularly over tropical regions. However, the study of site diversity performance is limited over tropical regions due to unavailability of simultaneous fade measurements from multiple locations as well as the lack of data on spatial rain pattern from radar measurements. We propose here a copula-based Bayesian approach to study the site diversity performance utilizing only a single location's drop size distribution measurement. Study of diversity performance has been done for Ahmedabad, India, utilizing 3 years of disdrometer data. Effects of frequency, elevation angle, and site separation on diversity gain are investigated using the proposed method. Results are compared with two ITU-R models, site diversity results from Italy, a temperate region, and Singapore, another tropical location. The spatial correlation obtained through this technique is also compared with radar observations in Oklahoma, a totally different climatic regime. The simple ITU-R model is found to be underpredicting the diversity gain significantly for the present location whereas the explicit ITU-R model shows overprediction above 8 dB for single-site rain attenuation values. Comparison with measurements at Italy shows similar diversity gains for low single-site attenuation values. The results reported for Singapore matches well with the present method. The study indicates room for improvement in the present ITU-R model considering the different nature of tropical rain and that the proposed method is suitable for such a purpose.