Performance of diversity combining techniques for FSO-MIMO system

In free space communication, for transmitting data in the order of giga bits, usually radio frequency is required, as an alternative technique free space optical communication (FSO) can be used. The main drawback of free space optical communication is atmospheric turbulence and beam wander. Atmospheric turbulence causes random fluctuations in transmitting laser beam which gives rise to scintillation. Compared to the large data rates, scintillation process is slow in optical transmission. In order to mitigate this harmful effect of atmospheric turbulence and beam wander, multiple input and multiple output (MIMO) is used. The mitigation of scintillation is achieved through multiple lasers and multiple output apertures, thereby creating a multiple input multiple output (MIMO) channel. In MIMO system different diversity combining techniques are used. In this paper, threshold combining technique is proposed and the error performance is analyzed for FSO-MIMO system.