| Summary: | This paper analyzes the impact of generalized selection multiuser scheduling on the performance of the multiple-input–multiple-output (MIMO) free-space optical (FSO) communication system. We consider a general scenario that the point-to-multipoint system consists of a central transmitter equipped with <inline-formula> <tex-math notation="LaTeX">$K$</tex-math></inline-formula> aperture groups containing <inline-formula> <tex-math notation="LaTeX">$M$</tex-math></inline-formula> transmit apertures and <inline-formula> <tex-math notation="LaTeX">$K$</tex-math></inline-formula> users equipped with <inline-formula> <tex-math notation="LaTeX">$N$</tex-math></inline-formula> receive apertures communicating over gamma–gamma turbulence FSO channels. For the MIMO links between the central node and user, we derive the combining signal-to-noise ratio (SNR) distributions of MIMO repetition coding and MIMO transmit laser selection. Then, a statistics analysis is presented for the multiuser diversity scheme in which the user with the <inline-formula><tex-math notation="LaTeX">$k$ </tex-math></inline-formula>th best combining SNR is selected. Based on the analysis, the closed-form expressions of the outage probability are derived, and the diversity benefit provided by the channel fluctuations is further discussed. Numerical results verify the accuracy of these analytical results.
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