Space-Time Coded MPSK Coherent MIMO FSO Systems in Gamma-Gamma Turbulence
Coherent free-space optical communication employing M-ary phase-shift keying is investigated for space-time coded Multiple-Input Multiple-Output (MIMO) systems over Gamma-Gamma turbulence channels. The proposed space-time coded system offers an efficient utilization of coherent free-space optical channel capacity by exploiting the degree of freedom at both the transmitter and receiver ends. Such a system design is particularly suitable for turbulence channels. Novel closed-form error rate expressions are presented for the proposed MIMO system using a series expansion approach. In addition, asymptotic symbol-error rate and truncation error analyses are performed.