A Polynomial Model for Multipath Fading Channel Responses

Multipath fading in microwave digital radio systems can be a major source of outage and, therefore, has been the subject of numerous recent investigations.1"4 One important objective of current activity is to develop a statistical model of fading useful for estimating its effect on specific systems and for indicating possible methods of correction. Two multipath fading characterizations have been proposed recently for terrestrial systems in the channelized common carrier bands. One represents the multipath fading frequency response as that due to an equivalent three-path medium.5 The result is a three-parameter, com1197 plex gain function, where the joint probability distribution for the three parameters describes the fading statistically. The second characterization, which is the subject of this paper, expresses the multipath fading frequency response as a complex polynomial expanded about the channel center frequency.6 Specifically, if Hc{u) JJ . . complex channel gain at any time = complex channel gain during nonfading '