Alternating-Signal-Biased System Design and Demonstration for Visible Light Communication

In the literature, previous system designs are mainly focused on the use of direct-current light-emitting diodes (DC-LEDs) with fixed voltage bias. As alternating-current (AC)-LEDs are more energy efficient and becoming more and more popular, a driving system supporting AC-LEDs providing lighting and visible light communication (VLC) functions is highly desirable. This paper investigates the alternating-signal-biased system design for VLC, which combines the AC bias voltage signal and electrical data signal to modulate both DC- and AC-LEDs. In the experiment, a 40-LED array is modulated by our proposed system that makes use of current from AC power source while maintaining nondistorted message signal transmission. On-off-keying and quadrature-phase-shift-keying formats are used, and data rates of 60 and 120 kb/s are demonstrated, respectively. The threshold voltage effect and the system extension to support AC-LED are discussed. The alternating-signal-biased system design supporting both DC- and AC-LEDs is also discussed.