Analysis of Multipath Fading Effects

Abstract

Multipath fading has a severe effect on the performance of wireless communication systems. Because of either refraction from the ionosphere or obstructions in the path of a transmitting and receiving device, received signals do involve varying delays. in assessing the impact of multipath propagation on various wireless systems, a quantitative estimate of the system outage is the figure of merit. Systems outages are often assessed with equipment signatures (receiver's tolerance to selective fading) and are highly dependent on the statistics of fading. Multipath fading effects are analyzed from a theoretical perspective. A four state Markov model I derived in parallel with a predefined three-state birth-death model. A formula for reacquisition hyserisis induced outages is shown to yield accurate predictions when compared with actual counts on simulated fades. These predictions are also shown to be more accurate than Ranade's empirical asymptotic result. Outages would be diminished if equalizers can be used to mitigate very large notch depths. A fundamental limit exists, however for the fade notch depths to which an equalizer can remove dispersion without enhancing the thermal noise to an unacceptable amount. A way to deduce the limit is provided and analyzed.