Date Added: Dec 2009
Atmospheric effects can significantly degrade the reliability of free-space optical communications. One such effect is scintillation, caused by atmospheric turbulence, refers to random fluctuations in the irradiance and phase of the received laser beam. This paper investigates the use of multiple lasers and multiple apertures to mitigate scintillation. Since the scintillation process is slow, the authors adopt a block fading channel model and study the outage probability under the assumptions of orthogonal pulse-position modulation and non-ideal photo detection. Assuming perfect receiver Channel State Information (CSI), the authors derive the Signal-to-Noise Ratio (SNR) exponents for the cases when the scintillation is lognormal, exponential and gammagamma distributed, which cover a wide range of atmospheric turbulence conditions.