Spectral-Efficient PAM Modulations for Dimmable Visible Light Communication Systems

Abstract

In visible light communications (VLC), the bulbs are used to provide communication and illumination simultaneously. Therefore, it is important to design modulation schemes, which are capable of adjusting the illumination level. The simplest approach to achieve this is compensating an all-one or an all-zero sequence, which however is spectrally inefficient. In this paper, we propose to use the constant sum codes to construct spectral-efficient dimmable pulse amplitude modulation (PAM) for VLC. We also present an efficient algorithm based on graph expanding to design the mapping for the proposed dimmable PAM. Numerical results show that the spectral efficiencies of the proposed dimmable PAM are higher than those of the state-of-the-arts. Numerical results also show that the proposed dimmable PAM performs better than the state-of-the-arts in coded VLC. These results show the potential advantages of the proposed dimmable PAM.