Visible light communications employing PPM and PWM formats for simultaneous data transmission and dimming

Abstract

A visible light communication system with simultaneous brightness control and data transmission is experimentally demonstrated in this paper. A pulse-width modulation (PWM) scheme is adopted for brightness control of the light-emitting diode and pulse-position modulation (PPM) superimposed on top of PWM is used for data communications. We show that independent control of light dimming is possible while transmitting data within a typical room environment, provided the PWM dimming period is an integer multiple of the PPM slot duration. To validate this, we show the measured eye diagrams for a range of dimming levels. In addition, we qualitatively illustrate examples of different dimming levels by changing the dimming level while maintaining the PPM data stream.