Maximum Effective Bit Rate Estimation for Wireless Optical Communication Links with Time Diversity Over Strong Turbulence Channels
The free space optical communication systems exhibit significant research and commercial interest in the last few years due to their capability of achieving optical wireless communications with high and secure data rate transmission and low installation and operational cost, without need of licensing. On the other hand, the unstable conditions of the atmosphere, which is the propagation path of the laser beam that carries the information signal, and especially the atmospheric turbulence effect, affects mainly its intensity and causes random irradiance fluctuations at the receivers end. This phenomenon causes a significant reduction in the systems availability and performance (BER) In order to overcome this reduction, many methods have been studied, from which the diversity techniques are a very efficient solution. In this work, we investigate a timediversity scheme for free space optical channels under strong turbulence conditions modeled with the K distribution. We concentrate on the estimation of the maximum effective bit rate of the link, which is limited by the finite capacity of the optical channel, as well as on the multiple transmission of the same part of the information signal in order to achieve much better performance characteristics using the time diversity scheme. Thus, we extract closed form mathematical expressions for the estimation of the maximum effective bit rate, for both, fast and slow, fading statistics. Finally, we present numerical results for many practical cases.