Journal Article

An Open-Source QAM MODEM for Visible Light Communication in FPGA for Real-Time Applications

Ricci, Stefano

2026

Overview

Visible Light Communication (VLC) is a transformative paradigm poised to revolutionize the automotive and numerous other sectors. As the demand for high data rates and low latency applications grows, the limited bandwidth of standard white LED-based lamps—typically restricted to a few MHz—presents a significant bottleneck. While high-order modulation schemes like Quadrature Amplitude Modulation (QAM) offer superior spectral efficiency, their computational complexity often hinders real-time implementation. Consequently, the existing literature lacks experimental validation of low-latency real-time VLC links. This work addresses this challenge by proposing a modified algorithm that is implemented in a resource-efficient QAM modulator/demodulator (MODEM) for an FPGA. The algorithm includes the synchronization loop. The proposed MODEM is available as open-source code and provides a scalable foundation for researchers to explore low-latency real-time VLC links. Experimental results demonstrate successful 2, 4, and 6 Mb/s links using 4-, 16-, and 64-QAM constellations, respectively, over a white-phosphor-power LED. We measured a latency of less than 1.3 μs.

• Publisher: MDPI AG,Multidisciplinary Digital Publishing Institute (MDPI)
• Subject: Algorithms / Bandwidths / Communication / Digital integrated circuits / Field programmable gate arrays / FPGA / Light emitting diodes / low-latency / Modems / Optimization techniques / Quadrature Amplitude Modulation (QAM) / Real time / Transmitters / VHDL / Visible Light Communications (VLC)