Researchers have developed a low-cost visible light communication (VLC) system using commercially available hardware that enables stable data transmission even under strong ambient light. By implementing a newly designed 8B13B coding scheme on an FPGA and interfacing it with a Raspberry Pi, the team achieved reliable outdoor VLC at data rates of up to 3.48 Mbit/s over distances of several meters. The approach addresses key challenges in VLC, including pulse distortion and sunlight interference, and offers a practical path toward intelligent transportation system (ITS) applications.
Visible light communication (VLC) is attracting increasing attention as an alternative wireless technology that uses light emitted from LEDs to transmit data. Because VLC does not rely on radio frequencies, it offers potential advantages in environments where radio communication suffers from congestion, interference, or regulatory constraints. In particular, VLC is considered promising for intelligent transportation systems (ITS), where traffic lights and street lamps could serve as communication infrastructure. However, practical deployment has been prevented by sensitivity to ambient light, waveform distortion in LEDs.
A research team at Tokyo Polytechnic University has now demonstrated a simple and affordable VLC system that overcomes several of these obstacles. The researchers developed a new 8B13B line coding scheme tailored for VLC and implemented serializer/deserializer (SerDes) logic using Verilog HDL on a field-programmable gate array (FPGA). The FPGA is connected to a Raspberry Pi via a standard serial peripheral interface (SPI), allowing data to be transmitted using only widely available components.
The proposed 8B13B coding employs a return-to-zero format and maintains a balanced number of logical "1" and "0" bits, suppressing visible flicker and ensuring stable synchronization. By relying primarily on the rising edges of optical pulses, the system is robust against pulse-width variations caused by LED response characteristics, a phenomenon known as data-dependent pulse width shrinkage.
Experimental evaluations showed that the system achieved a maximum data rate of 3.48 Mbit/s and maintained stable communication over distances of approximately 3 meters under strong ambient light, including direct sunlight exceeding 90,000 lux. The researchers made a receiver having multiple photodiodes and a narrow-band optical filter to suppress background light, enabling reliable operation in outdoor environments relevant to ITS applications.
All key components— including the FPGA, Raspberry Pi, and electronic components of LED driver and photodetector—are commercially available, making the system highly reproducible and cost-effective. The receiver and transmitter circuit diagrams are provided in the paper. The authors have also released the FPGA SerDes source code as open source, encouraging further research, educational use, and adaptation to other platforms.
The proposed VLC system could support future applications such as transmitting intersection or blind-spot video information from traffic infrastructure to vehicles, enhancing safety even in autonomous driving scenarios. Beyond ITS, the researchers note that the system provides a practical educational platform that integrates analog circuits, logic circuits, and software in a single communication system.
Funding
This research was supported by the regular institutional budget of Tokyo Polytechnic University.
Journal
Electron. Signal Process.
Article Title
A study of SerDes logic for visible light communication using 8B13B code
Authors
Tokio Yukiya, Nobuo Nishimiya, Takayuki Uchida
DOI0.
10.55092/esp20250006
