Visible Light Communication
Using LED lighting for data transmission — the technology behind LiFi, indoor positioning, and smart city connectivity.
What is VLC?
Visible Light Communication (VLC) uses the visible light spectrum (400-800 THz) to transmit data. Any LED light source can be modulated at high speeds to encode information, turning ordinary lighting into a wireless communication channel.
VLC is the foundational technology behind LiFi, but it's broader than LiFi alone. VLC encompasses any visible light data transmission, including low-data-rate applications like indoor positioning, vehicle-to-vehicle communication, and underwater signaling.
How VLC Works
- Transmitter: An LED light source (ceiling light, traffic light, display screen) is rapidly switched on and off
- Modulation: Data is encoded by varying the LED's intensity — typically using OOK (On-Off Keying), PPM (Pulse Position Modulation), or OFDM
- Channel: Modulated light propagates through the air
- Receiver: A photodiode or image sensor detects the light fluctuations and demodulates the data
Applications Beyond LiFi
- Indoor positioning: VLC-based positioning achieves centimeter-level accuracy for indoor navigation (better than GPS which doesn't work indoors)
- Vehicle-to-vehicle (V2V): Using car headlights and taillights to communicate speed, braking, and trajectory data
- Smart cities: Street lights as data access points and environmental sensors
- Underwater communication: Radio waves don't propagate well underwater, but blue-green light does
- Screen-to-device: High-speed data transfer from displays to smartphones via visible light
- Signage: Retail displays that transmit product information to nearby phones
VLC vs WiFi vs Bluetooth
- Bandwidth: VLC offers higher bandwidth density than WiFi in indoor environments
- Security: Light is naturally contained within rooms — no wall-penetrating signals
- Interference: No electromagnetic interference with existing radio systems
- Infrastructure: Uses existing LED lighting — no additional spectrum allocation needed
- Limitation: Requires line of sight or reflected light; doesn't work in darkness
Standards
IEEE 802.15.7-2018 defines the physical layer (PHY) and medium access control (MAC) for short-range optical wireless communication using visible light. It supports data rates from 11.67 kbit/s to 96 Mbit/s and defines three PHY types for different applications.