A Statistical Model of Multipath Fading on a Space-Diversity Radio Channel

Occurrences of multipath fading limit the performance quality of high-speed digital radio systems operating on line-of-sight microwave radio paths. Extensive field measurement programs have been imple2185 merited to evaluate the performance of a number of digital radio systems operating in different configurations under various conditions.1-5 These studies have indicated the universal need for some form of dynamic channel equalization, and for space diversity reception, on many paths, to meet performance requirements. While field measurements provide a good means of evaluating the operation of radio systems, they require considerable time, effort, and expense. Furthermore, they suffer from the vagaries of nature in that multipath fading is a randomly occurring phenomenon with variable characteristics from month to month.5,6 To reduce the need for field measurements, a statistical model of multipath fading was developed.6,7 This model, used in conjunction with characterization measurements performed on a radio in the laboratory, allows predictions to be made of the system performance under multipath conditions when operating in a nondiversity configuration.8-10 The results presented here extend the previous work by providing a statistical model for multipath fading in a space-diversity configuration. The data base used for modeling was obtained by transmitting a wideband (8-PSK digital radio) signal at 6 GHz over a 26.4-mile path from Atlanta to Palmetto, Georgia. The received power at a number of frequencies in a 24.2-MHz band was measured simultaneously on both a horn reflector and a parabolic dish antenna separated by 30 feet.