On Optimal Non-Equally Spaced M-PAM in Dimmable Visible Light Communication

In this letter, channel capacity of dimmable visible light communication systems with M-ary pulse amplitude modulation (M-PAM) channel input alphabets is investigated. Mutual information is maximized considering both the probability input distribution and the M-PAM levels simultaneously. Schemes with non-equally spaced M-PAM levels are obtained as a result of this maximization process and they lead to gains in capacity when compared with previous schemes proposed in the literature.