Level Crossing Rate and Average Fade Duration of Satellite-to-UAV FSO Channels

This paper investigates the second-order statistics of the level crossing rate (LCR) and average fade duration (AFD) for the optical wireless channels between a satellite and a vehicle. Specifically, the novel expressions of LCR and AFD for the low earth orbit (LEO) satellite-to-unmanned aerial vehicles (UAVs) laser links are derived in the presence of the generalized misalignments caused by the satellite vibration together with the UAV hovering, which is modeled by a four-parameter Beckmann distribution, and the atmospheric turbulence conditions. The analysis can also be applied to other kinds of vehicles, which, in fact, require simpler channel models. Several numerical examples are presented to quantitatively demonstrate the impact of both atmospheric turbulence and pointing errors on the LCR and AFD. The Monte Carlo simulations are performed to validate the correctness of the theoretical derivations.