BER of MIMO FSO link with Alamouti coding and SEC

Diversity combining at both transmitter and receiver end can successfully mitigate the degradation caused by atmospheric turbulence in free space optical (FSO) links. In this paper, we derive the bit error rate (BER) expression of a 2 × L multiple input multiple output (MIMO) FSO link operating over gamma-gamma fading channel. Alamouti space time coding is considered at the transmitter while the receiver employs switch-and-examine combining (SEC). Numerical results for on-off keying (OOK) modulation are provided and are compared with Monte Carlo simulations.