On the k-factor distribution and diffraction fading for Southern Africa

In previous presentations, we have discussed models for determining the probability density function (pdf) of the effective earth radius factor for Botswana as a means of predicting k-factor variation. These models are based on the radiosonde measurement data obtained over three years in Botswana. In this presentation, we compare the k values obtained via the curve-fitting model for Botswana and Durban, South Africa. We compare the median k-factor values and k values exceeded 99.9% of the time. Two design examples show that the type of terrain plays a major role in diffraction fading resulting from k-factor variation. While designing with k=4/3 only results in losses of 2 dB and 5 dB for Durban and Botswana links, respectively, multiple obstructions would result in higher fades. Moreover, the gentler terrain in Botswana results in lower losses that would have been the case if the k-factor for Durban had been 1.1. Also we observe that 99.9% link availability would be harder to attain in Durban than in Botswana, due to the higher k-factor variability and hillier terrain in Durban.