Demonstrating a real–time QAM–16 visible light communications utilizing off-the-shelf hardware

This study aims to design, implement, and demonstrate a one-way real-time VLC system through DCO-OFDM using QAM–16 as the Mapper (Modulator). The system was divided into two units, namely VLC Server (transmitter) and Client (receiver), based on a low-bit rate transmission applications with running text, which is often found in digital signage. The uniqueness of this report focuses on the use of low-cost components for VLC transceivers, including DSP and ASP. In this condition, DCO-OFDM digital blocks were embedded within the generic-purpose Microcontroller as DSP (STM32F4 Development board), with available and widely assessed libraries being utilized for implementation in the proposed system, to speed up the DSP development process. Meanwhile, the ASP contained a linear LED driver as a substitute for the commercial Bias-T function, as well as the AFE receiver with the Op-Amps circuit blocks. The developmental approach of the VLC system was also carried out by simulation and realistic implementation, where the productions of the DSP and ASP sections, especially the DCO-OFDM with the QAM–16 mapper and the AFE receiver, were performed on MATLAB® and SPICE®, respectively. Additionally, the transfer of QAM–16 modulated data was realistically performed by observing the impact of the optical channel distance changes on the behavior of the constellation diagram.