Level crossing and fading probabilities in an atmospheric communication link for a non-Markov process

The statistics of light pulses in an atmospheric communication link are studied here. The correlation between light pulses propagating through a turbulent atmosphere is described by a nonexponential function. As this leads to a non-Markov process, the statistics of the pulse sequence are investigated using a multidimensional distribution. The multidimensional calculations were performed for level crossing and fading probability. The results demonstrate in some cases essential differences from the results obtained in Markov approximation. The level crossing probabilities for the non-Markov process have been fitted by analytical expressions which permit the approximate calculations of these probabilities in a simple way.