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.

This paper considers the cyclostationary nature of digital signals when determining crosstalk interference between such signals in multipair cable. This approach is necessary as the interference is only relevant at the decision instants in the receivers of the disturbed systems and any time variation of this interference with respect to the sampling instants changes the effect of this interference; previous studies in the area have ignored the cyclostationary nature of the digital signal. Expressions for the time-varying mean and variance of far-end and near-end crosstalk (FEXT and NEXT) have been derived. These expressions demonstrate the inherently smaller time variation of the NEXT interference when compared to the FEXT interference. An interesting result is that the calculation of the time-averaged value of the variance of FEXT and NEXT interference still requires the use of the cyclostationary properties of the digital signal. The results of this paper are extended and applied to various examples of the engineering of digital line systems in multipair cable in Part II of this paper.

In this paper, the results of Part I are applied to the engineering of primary-level digital line systems in multipair cable operating in either a nonsynchronous or a synchronous network. It is shown that the erstwhile incorrect assumption that crosstalk interference from digital line systems is wide sense stationary, and not cyclostationary, leads to an overestimation of system margin of less than 1 dB. It is also shown that the change from a nonsynchronous to a synchronous network leads to a reduction in system margin which is difficult to quantify exactly, but it is typically less than 2.5 dB for FEXT and 1.5 dB for NEXT. The paper concludes with a consideration of the cyclostationary nature of block,encoded digital signals such as 4B3T, MS43, etc., and extends some of the results of Part I.