Contrasting space-time schemes for MIMO FSO systems with non-coherent modulation

For the case of multiple-input multiple-output (MIMO) free-space optical (FSO) communication systems, we consider the suitability of the spatial multiplexing scheme when on-off keying modulation is employed. We show that, even with the optimal maximum likelihood detection at the receiver, the performance is worse, compared to the case of repetition coding (RC) under the condition of equal transmission rate. This confirms the quasi-optimality of the RC scheme for MIMO FSO systems.