Improving the availability of terrestrial FSO links over log normal atmospheric turbulence channels using dispersive chirped Gaussian pulses

Probability of fade estimation for FSO links with time dispersion and turbulence modeled with the gamma–gamma or the I-K distribution

“…Their variations affect the refractive index of the atmosphere, n( ) and hence, the mathematical expression for its estimation, as a function of the wavelength, (in m), can be obtained from [9,10,36,37] and (8), as:…”

“…Thus, by expressing the refractive index as a function of the angular frequency, ω, the propagation constant, i.e., ˇ(ω) = ωn(ω)c −1 , is given as, [9,10]:…”

“…In order to estimate the variations in the link's probability of fade, taking into account both the GVD and the atmospheric turbulence effects, for a terrestrial, horizontal, FSO link which employs chirped Gaussian longitudinal pulses as information carriers, the normalized irradiance arriving at the receiver is obtained from (2) and [10] as:…”

“…However, due to the higher data rate transmission it has to be taken into account the group velocity dispersion (GVD) caused by the atmospheric propagation of the laser beam, which was assumed to be negligible for shorter and slower links. This phenomenon, affects the shape of the pulse, i.e., carrier of the information bit and thus, their detection is (usually) more difficult and its impact on the performance of the whole system can be either detrimental or, under specific circumstances, beneficial [9,10].…”

“…The availability of the links can be evaluated by means of the probability of fade [10,28]. In this work, turbulenceinduced fading is modeled using the I-K, or the gamma-gamma (GG) distribution models.…”