For the purpose of investigating the performance of digital radio systems, Telecom Australia established and conducted over a three year period (1982-1984), a 140 Mbit/s 16 QAM digital radio field experiment. In parallel with this experiment, analytical work was undertaken to develop an "outage prediction method" to assist with route design. This paper presents the observations and conclusions drawn from this work. Emphasis is placed on the aspects which relate to system design. We show that for digital radio outage prediction, a radio path can be characterized for multipath fading by the probability of occurrence of multipath fading and the mean echo delay, while the radio equipment can be characterized by a set of normalized parameters. The performance improvements achieved through the use of adaptive equalization and space-diversity are highlighted. Finally, we present a methodology for considering the performance of digital radio systems in the presence of interference and thermal noise, and present results for system performance with adjacent channel interference.

Outage in digital microwave radio systems during multipath fading is highly correlated with the channel amplitude dispersion. This characteristic is exploited in a new digital microwave radio system measurement technique which yields dispersion signatures. These dispersion signatures can be readily applied to assess the effects of time varying channels on digital radio equipment. Thus, dispersion signatures can be used for in-service monitoring of equipment operation during actual fading. Routine maintenance assessment and laboratory evaluation of digital microwave radio equipment can also be readily carried out. The laboratory evaluation results can be used for system design both with and without diversity.