Evaluating Time Diversity Performance on an On-board Processing Satellite to Earth Station Downlink

A method for assessing the performance of time diversity (TD) along a single downlink path is proposed. The evaluation is done using TD gain, which is obtained from joint distribution of similar retransmitted rain attenuation time series separated by finite time delay. Statistics use to assess the performance of TD are obtained from analyses of measurements from the most recent British Atmospheric Data Centre (BADC) database. TD is presented in this paper as a suitable fade mitigation scheme for increasing link availability and improving the quality of service in broadcast systems. Prior to achieving a model of TD, analyses of propagation datasets (November 2005) and extraction of attenuation statistics have been carried out. These statistics are necessary for the modeling process and for the design of a satellite link between any two earth stations having a separation distance in excess of the mean rain cell size which is roughly 10 Km. Comparisons are made with ITU-R model and some useful conclusions deduced.