STATISTICAL ESTIMATION OF FADE DEPTH AND OUTAGE PROBABILITY DUE TO MULTIPATH PROPAGATION IN SOUTHERN AFRICA

This study builds on the earlier work by Odedina and Afullo on Multipath fading in Durban. Their work was based on multipath measurements in Durban over a 6.73 km Line-of-Sight (LOS) link. This submission uses the geoclimatic factor approach and ITU-R recommendations P530-14 to obtain the multipath fading occurrence in five cities in South Africa, including Durban. Three-year radiosonde data is used in estimating the percentage of time that a certain fade depth is exceeded and hence outage probability due to atmospheric multipath propagation, assuming the given fade depth leads to the received signal falling below the squelch level. We employ the Inverse Distance Square technique to estimate point refractivity gradient not exceeded for 1% of the time in the lowest 65 m above the ground for five locations within South Africa. Standard error of the mean and confidence interval for both annual averages and seasonal averages of point refractivity gradient is calculated to reflect possible deviation in the given readings. These values of point refractivity gradient obtained are used in determining the geoclimatic factor K. The results presented show monthly, seasonal and annual variation of both point refractivity gradient and geoclimatic factor K. The results confirm that the geoclimatic factor K is region based. The percentage of time a given fade depth is exceeded for a single frequency increases rapidly with increasing path length. This is due to the fact that as the path length increases so do the multiple reflections leading to multipath propagation, which can result in either signal enhancement or multipath fading. A comparison of fade depth and outage probabilities is made with the earlier work in Durban and Rwanda in Central Africa.