Estimation of Optical Wireless Communication Link Availability Using Meteorological Visibility Data for Major Locations in South Africa

The numerous unique advantages of optical wireless communication (OWC) systems make them a viable complementary technology to microwave and millimeter-wave systems for reliable deployment of multimedia services within the access networks. One of the most significant atmospheric factors responsible for deterioration in the performance of OWC links is Fog. Meteorological visual range measurements less than or equal to 1000 meters are used in the classification of fog into various strata from light fog to dense fog. Low visibility measurements within the aforementioned range indicates that an increased atmospheric scattering attenuation of the transmitted signals is expected, and hence a severe reduction in the availability of the OWClink. Fog visibility data spanning a period of 8 years was obtained from major cities at each of the nine South African provinces and are statistically processed. This paper presents the fog visibility distributions for each province after examining the characteristics of fog events obtained from each of the nine provinces for the same time period. The fog cumulative distributions are then converted into Mie scattering attenuation distributions using various established aerosol scattering models for OWC links transmitting at 850 nm wavelength. The locations considered in this work are not only representative of the various weather conditions in South Africa, but are also major commercial zones with massive potential for OWC systems deployment. These results represent a survey through which a wider assessment of availability and performance of optical wireless communication systems may be performed. Portability of performance metrics to areas which exhibit similar weather patterns may be possible, even outside South Africa.