Efficient visible light communication drivers using illumination LEDs in industrial environments
Visible light communication (VLC) allows the dual use of lighting and wireless communication systems by modulation of illumination devices. However, to increase the performance, typically, beam-forming measures are taken creating pencil beams, thus contradicting the illumination purpose. In order to optimize the performance trade o between ecient illumination and communication, the switching capabilities of illumination LEDs are examined. Illumination LEDs with standard drivers and without beam-forming show limited applicability for communication purposes as they are not optimized for the necessary switching capability (f 11 MHz) and coherence. Methods to enhance the electrical current by pre-equalisation, biasing, carrier sweeping and current shaping are examined in respect to the illumination LED's communication performance. A novel driver scheme is derived which achieves considerably higher switching frequencies (f 100 MHz) without employing beamforming at the illumination LED. This driver is able to obtain a data rate of up to 200 Mbit/s at a distance of 3.2 m, using on-o keying (OOK) modulation technique. Therefore, it is feasible to apply the LED driver by implementing standardised illumination devices in VLC systems.