A capacity-approaching coding scheme for M-PAM VLC systems with dimming control

Abstract

A visible light communication (VLC) system with intensity modulation and direct detection is considered. A channel coding scheme based on a binary low-density parity-check (LDPC) code and M-ary pulse amplitude modulation (PAM) is designed. The LDPC encoder is followed by a many-to-one mapper. This mapper induces the input distribution for the non-equally spaced M-PAM alphabet under a desired dimming target. No auxiliary coding technique for DC-balance is needed. The coded scheme using non-equally probable M-PAM levels outperforms the use of equally probable levels showing capacity-approaching performance. Moreover, the scheme is flicker-free for typical information rates of a VLC system. The main advantage of the proposed scheme is that it does not incur any coding rate loss compared to other similar schemes in the literature.