Constellation Design for Complex Colour Shift Keying Aided Optical OFDM Systems

Colour shift keying (CSK) and optical orthogonal frequency division multiplexing (OOFDM) are among the promising high-rate transmission technologies for visible light communication (VLC). Existing methods that combine CSK and OOFDM typically assume the use of conventional CSK constellations such as those defined by the IEEE 802.15.7 standard. However, such a straightforward CSK-OOFDM combination distorts the colour balance and the modulated VLC signal is therefore no longer white. In this paper, we design optimised CSK constellations that work in the complex domain under a given colour constraint. Simulation results demonstrate the effectiveness of the new design method, which not only produces new constellations with an improved normalised minimum Euclidean distance (NMED) compared with the traditional counterparts, hence improves the achievable bit error rate (BER) performance, but also eliminates the colour balance distortion issue of conventional CSK-OOFDM systems.