Spherical Color-Shift Keying for Visible Light Communication Systems

In this paper, we propose the novel spherical colorshift keying (SCSK) schemes for visible light communication (VLC) systems, which can improve the system fidelity comparing to the conventional color-shift keying (CSK) techniques. Specifically, the constant-intensity constraint in conventional CSK schemes requires that the constellation symbols remain on a two-dimensional intensity plane. We propose to expand the envelope of CSK constellations to three-dimensional space subjected to a new spherical intensity constraint, such that the minimum Euclidean distance (MED) is enlarged. Furthermore, we convert the constellation design problem to the new spherical circle packing (SCP) problem, then solve it with the aid of the proposed spherical quasi-physical (SQP) model, where the socalled spherical heuristic quasi-physical algorithm (SHQPA) is employed to obtain the optimal SCSK constellations. Simulation results demonstrate that the new schemes can achieve beneficial gains upon their conventional counterparts.