In a previously published paper [Opt. Express26(17), 22182 (2018)], the performance of a LDPC coded OAM-based UCA FSO system exploring linear equalization with channel estimation over atmospheric turbulence has been analyzed. We find that some concepts and descriptions in [Opt. Express26(17), 22182 (2018)] are inconsistent and paradoxical. In this comment, we point out the referred inconsistency and paradox one by one and present the correct explanations.
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