Prediction of satellite link rain attenuation using radar reflectivity for tropical climate in Malaysia

Abstract

The requirements of wireless communications in Malaysia, both civilian and military will evidently include wideband capacity satellite systems. Prior to satellite launching, the precise rain fade margin has to be identified. At the moment, most prediction models for the link rain fade margin are not able to offer accurate estimation when compared to actual measurement. Current available rain attenuation prediction models are also regarded as "not universally applicable", and involve gross generalization as well as over simplification by using only point rainfall rate at 0.01% of time exceedance and speculated rain heights. Radar reflectivity data which are available at almost all points of the affected slant path link are believed to be capable of providing a more relevant rain attenuation estimation. This research was carried out in collaboration with the Malaysian National Space Agency (ANGKASA) and Malaysian Meteorology Department (MMD). RazakSAT`s data and one-year radar data had been analyzed. The overall objective of this research is the derivation of a new technique using radar information, believed to be capable of generating a more reliable annual statistics of rain attenuation compared to previously proposed methods. In this research, the information from a radar had been exploited in estimating the rain attenuation using vertical and horizontal variability of rain events. The sub-objectives of the study involved quantification of knowledge concerning propagation effects, determination of climatological influences and production of refined propagation models for satellite communications. Tasks involved include derivation of relationship between radar reflectivity and actual satellite link attenuation at X-band frequency using the regression technique. The one-year rain events were classified where the characteristics had been deliberated to acquire vertical profile reflectivity (VPR) and the empirical rain height values. All information are important for attenuation predictions, link budget estimation, microwave system planning, slant path rain attenuation modelling and remote sensing of the Earth's surface. The new technique achieves reduced error of only 4.13% variation. This is certainly a great improvement as compared to the ITU-R estimation. ITU-R estimation has percentage error of 58.21% variation. The findings of this research will be valuable for the future designers in configuring the best communication establishment for satellite system operating in the tropics.