A new formulation for rain scatter interference

Fundamental to frequency management and spectrum efficiency is the need to share the available radio spectrum among a number of services in such a way that maximum exploitation and minimum interference are achieved simultaneously. One of the most widespread applications in which spectrum is shared between two services is that of terrestrial and satellite-based radio communications systems, where it is of primary importance to protect sensitive earth station receivers operating to satellites in the geostationary orbit from harmful interference from terrestrial transmitters using the same frequency bands. A new model for the path loss in rain scatter has been developed in which the earth station elevation angle is now an input parameter, in order to derive more reliable and more widely applicable estimates of rain scatter interference. This paper describes the rain scatter process and the development of the new formulation, together with comparisons between the resulting predictions of path loss with those derived from the existing model. Comparisons are also given between the new model and the predicted path losses and experimental measurements of rain scatter interference obtained within the COST 210 project, which considered the influence of the atmosphere on interference between radio communications systems at frequencies above 1 GHz, and led to the rain scatter model in Recommendation P.452-9.