Statistical-dynamical channel modeling of outdoor optical wireless links

The growing need for Earth observation and monitoring systems has stimulated considerable interest in free-space optical wireless (FSO) systems because of the huge bandwidth requirements. However, terrestrial FSO links are severely impacted by weather conditions especially dense fog to a larger extent while, rain and snow to a lesser extent. For the proper deployment of FSO technology requires a better understanding of the free-space channel transmission characteristics as they have major influence on the transmission link properties like link availability, reliability and quality of service. This thesis provides new insight on the fog microphysics, its characterization and the fog attenuation modeling. A comprehensive analysis of the measured fog attenuations is presented by building the discussion through comparison of recorded attenuations at Graz (Austria Milan (Italy), Nice (France) and Prague (Czech Republic). It was observed that fog attenuations in radiation fog environments are much stable when compared with advection fog attenuations, because of the difference in the microclimate and the microphysics involved. The work further proposes novel approaches to compute the exponential distribution, and modified gamma distribution parameters from the measured fog attenuations recorded at Graz and Prague. The newly computed distribution parameters are compared, analyzed and validated against the representative fog events on the basis of statistical analysis, and new fog drop size distribution computation methods are proposed which best approximate the attenuation behavior at a particular location.