Real Time Implementation of a Hybrid Differential Manchester-PWM Encoding for Constant Data Rate under Variable Brightness in VLC Systems

A Hybrid Differential Manchester-PWM encoding for data transmission and brightness control is implemented in a real time system and successfully integrated to a visible light communication architecture. The proposed digital modulation, allows simultaneous control of brightness maintaining data transmission at constant bit rate. Transmission data is generated using a ZedBoard™ development kit, which has a ARM Cortex-A9 processor and a Artix-7 FPGA. The resulting electrical signal feeds a driver of a commercial white illumination light-emitting diodes (LEDs). We experimentally demonstrate a constant transmission speed of 50Kbps using three 10W white LEDs at a distance of 0.9 meters, with a range of brightness between 10% and 90% of the maximum luminous flux of the LED sources.