Three-Dimensional Spatial Coding Based on Hybrid Pulse Width and Pulse Position Modulation for Simultaneous Data Transmission and Brightness Control on RGB LED Arrays

A three dimensional (3D) spatial coding scheme is proposed for simultaneous control of illumination and data transmission in a Visible Light Communication (VLC) system with RGB LEDs arrays . The proposed and experimentally tested coding is based on hybrid Multi-Pulse Position Modulation (M-PPM) for data encoding, in which the number of pulses (slots) control the amount of current delivered to the LED such as the Pulse Width Modulation (PWM). The implemented VLC system complies with the dual functionality, indoor lighting and data transmission, also proposes an alternative solution for the problem of the interdependence between the speed of data transmission and the variation of the levels of illumination. In this paper, the feasibility of implementing the proposed scheme using low cost elements and using digital demodulation is demonstrated. A constant transmission speed of 6 Kbps was obtained with two 10W RGB LEDs at 0.9 meters from the OPT101 photodetector of Texas Instruments, with a range of illumination ranging between 25% and 85% of the possible light power of the sources LED.