Selection Transmit Diversity for FSO Links Over Strong Atmospheric Turbulence Channels

In this letter, transmit laser selection for multiple-input-single-output free-space optical communication systems with intensity modulation and direct detection over strong atmospheric turbulence channels is analyzed. Assuming channel side information at the transmitter and receiver, a transmit diversity technique based on the selection of the optical path with a greater value of scintillation has shown to be able to extract full diversity as well as providing better performance compared to other alternatives recently proposed such as orthogonal space-time block codes and repetition codes. Simulation results are further demonstrated to confirm the analytical results obtained for a diversity order of two.