On the performance of multiplexing FSO MIMO links in log-normal fading with pointing errors

In this paper, we employ a spatial multiplexing scheme with M transceivers to increase the data rate of a free-space optical (FSO) system. In our proposed scheme, each transmitter sends independent information toward the center of its related receiver aperture. We analyze the performance of the proposed scheme in terms of average achievable rate. To compare the performance of our proposed scheme with its spatial diversity FSO system counter-part, we define a case in which M transmitters send the same information. To facilitate performance analysis, we also derive the analytical expressions for spectral efficiency of both spatial multiplexing and diversity configurations, which reduces the (M + 2)-dimensional integration of spatial multiplexing and (M
²
+ 2)-dimensional integration of spatial diversity FSO systems to a two-dimensional integration in both configurations. The adequacies of our analytical results are thoroughly confirmed by numerical simulations.