الفهرس 
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Abstract
Free-space optical (FSO) communication links are thought to be most negatively impacted by fog and sandstorms. Several probabilistic models for signal attenuation in various types of fog have been proposed in the literature. To the best of our knowledge, there is no prior probabilistic signal attenuation model for dusty channels. As a result, in this study, the probabilistic behaviour of the FSO channel during sandstorms was analyzed using real-time data from the Egyptian Meteorological Authority and propose the negative-exponential (NE) distribution as a statistical model for signal attenuation in dust. A probability distribution function (PDF) is then derived for the random dust channel state. Also, a closed-form channel state distributional formulation is derived for a stochastic FSO channel model that considers both dust effects and Gamma-Gamma (G-G) atmospheric turbulence induced fading as it models strong, moderate and weak turbulence. Next, closed formulas are derived for both the average bit-error rate (BER) and outage probability for the FSO system operating in this channel environment. Using the forms derived, it can be shown that the dust storm has a significant impact on the system’s performance. Finally, to overcome this degradation, utilizing a hybrid FSO and radio frequency (RF) wireless communication system was suggested. The received signals are combined using the wellknown diversity selection combining (SC) technique. Further, the hybrid system’s performance was compared to that of an FSO-only system. Our results showed that, at all dust densities, the adopted system successfully improved the performance by utilizing the complementary features of FSO and RF channels.