BER Performance of FSO Limited by Shot and Thermal Noise Over Exponentiated Weibull Fading Channels

In this letter, the average bit error rate (ABER) performance of free-space optical links adopting $m$ -ary pulse-position modulation is investigated by considering the effects of both atmospheric turbulence and receiver noise. The atmospheric turbulence is modeled by exponentiated Weibull (EW) distribution with an aperture averaging effect taken into account. For the receiver noise, both shot- and thermal-noise-limited scenarios are studied and compared with log-normal and gamma-gamma distributions. For the shot-noise-limited system, an approximate expression for the ABER is obtained on the basis of the generalized Gauss-Laguerre quadrature rule. The union bound of ABER for the thermal-noise-limited system is also derived and verified by Monte Carlo simulation.