Mitigation of Atmospheric Turbulence Impact on the Free Space Optical Communication using Space-Time Coding Based on MISO

Free-space optical communication has many advantages such as high bandwidth, high security and can be a good alternative for radio systems. The performance of this system could be degraded due to atmospheric turbulence. Turbulence-induced refractive index changes in the medium in the path between transmitter and receiver which leads fluctuation in light intensity on receiver. The gamma-gamma distribution is popularly accepted for modeling the received intensity fluctuations in the near-ground free-space optical communication. Turbulence can cause fading in mobile communication. In the third generation mobile communication systems, to overcome the fading phenomenon, multi-transmitter and multi-receiver MIMO structure is used. In this paper, mitigation of the turbulence effects, based on practical considerations, and using a MISO structure with space time-codes with aperture averaging method with gamma-gamma distribution has been studied. Simulation results show that the design link (MISO with 4 transmitter and 10km range) has BER of less than 10-6 even in the presence of strong turbulence.