A New Selective Fading Model: Application to Propagation Data

Performance prediction of a digital radio system on a line-of-sight microwave channel requires an accurate statistical model of the channel. Because different digital radio systems may have different sensitivities to the various channel impairments, the model must be complete to the extent that it must be capable of duplicating the amplitude and phase (at least approximately) of all observed channel conditions. To facilitate laboratory measurements and computer simulations for calculating outage, the model should be realizable as a practical test circuit and should have as few parameters as possible. Most important, the parameters should be statistically well behaved. Two types of models have been generally considered for line-of-sight microwave radio channels: power series type models1-3 and multipath models.4"6 A power series model will require a few terms only if the channel is a multipath medium with a small spread of delays relative to the reciprocal bandwidth of the channel.3 This implies that one must understand the channel as a multipath medium to understand the behavior of a power series model. Hence, we have limited our characterization efforts to multipath models. The basis for this study is the simple three-ray multipath fade.7 If the fading in a channel can be characterized by a simple three-path model, the channel will (as shown in Section II) have a voltage transfer function of the form H(u) = a[ 1 - be±j(u~"°)Tl (1)