On the use of wavelength and time diversity in optical wireless communication systems over gamma–gamma turbulence channels

Abstract

Optical wireless communication or free space optical systems have gained significant research and commercial attention in recent years due to their cost-effective and license-free high bandwidth access characteristics. However, by using the atmosphere as transmission media, the performance of such a system depends on the atmospheric conditions that exist between transmitter and receiver. Indeed, for an outdoor optical channel link, the existence of atmospheric turbulence may significantly degrade the performance of the associated communication system over distances longer than 1 or even 0.5km. In order to anticipate this, particular attention has been given to diversity methods. In this work, we consider the use of wavelength and time diversity in wireless optical communication systems that operate under weak to strong atmospheric turbulence conditions modeled by the gamma–gamma distribution, and we derive closed form mathematical expressions for estimating the system's achievable outage probability and average bit error rate. Finally, numerical results referred to common practical cases are also obtained in order to show that wavelength and time diversity schemes enhances considerably these systems’ availability and performance.