Design and Analysis of an Optically-Fitted DCSK System for VLC Systems

This letter investigates the feasibility of using differential chaos-based modulation in visible light communication (VLC) systems. Taking into account both the complexity and the lack of consideration for illumination of previously studied schemes, a novel modulation scheme called optically-fitted differential chaos shift keying (Of-DCSK) is proposed to improve the bandwidth efficiency of VLC systems. The proposed Of-DCSK scheme utilizes flexible information duration to represent the information bits “0” and “1”, rather than using traditional positive and negative value for information bits, which is proved to be feasible and advantageous in terms of improving system performance, i.e., average system optical power, bandwidth efficiency, and bit error rate (BER). The aforementioned three performance metrics are derived with mathematical expressions in line-of-sight (LOS) environments, and later compared with simulated results. The numerical results reveals that (i) the Of-DCSK scheme outperforms the traditional DCSK scheme in VLC communications, and (ii) the novel scheme provides a promising bandwidth-efficient modulation solution for VLC systems, where parameters <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> (visible light flicker and dimming) and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> (spreading factor) can be used to adjust flickering and dimming ranges using chaos signal length as well as spread factor.