Visible Light Communication

The Visible Light Spectrum

Visible light communication operates in the visible spectrum between 380 and 750 THz (wavelengths 400–700 nm). This spectrum is globally unlicensed — no spectrum allocation, no regulatory fees, no coordination required:

The IEEE 802.11bb Light Communications standard extends into near-infrared (800–1000 nm) for practical implementations, maintaining the same principles while avoiding visible flicker perception.

IEEE Standards for VLC

IEEE 802.15.7 (VLC)

The IEEE 802.15.7 task group developed the VLC physical and MAC layer standards:

• 802.15.7-2011: Original VLC standard; OOK and variable OOK modulation; up to 96 Mbps; fixed infrastructure
• 802.15.7-2018: Added mobility support (VLC receiver in motion), PWM dimming control, Visible Light Position (VLP) capability, color-shift keying (CSK)
• 802.15.7r: Next-generation VLC (in development); planned data rates up to 1 Gbps; enhanced mobility

IEEE 802.11bb (Light Communications)

Ratified in 2023, IEEE 802.11bb is the global standard for Light Communications, specifying PHY and MAC for light-based internet access:

• Scope: Uplink and downlink operations using visible and near-infrared light
• Minimum throughput: 10 Mbps at MAC data service access point
• Hybrid Coordination Function (HCF): Channel access mechanism for light communications
• Interoperability: Among solid-state light sources with different modulation bandwidths
• Physical layer: Specified for integration with IEEE 802.11 MAC
• Chair: Nikola Serafimovski (pureLiFi)
• Technical Editors: Volker Jungnickel (Fraunhofer HHI) for PHY, Harry Bims for MAC

Modulation Schemes for VLC

LED Characteristics for VLC

The LED light source fundamentally limits VLC data rates. Standard lighting LEDs were not designed for communications:

Li-Fi: Bidirectional VLC for Internet Access

Li-Fi (Light Fidelity) extends VLC beyond simple point-to-point messaging to bidirectional wireless internet access using modulated LED or laser light:

pureLiFi Products

• Light Antenna ONE™: First qualified Li-Fi module for mass device integration, designed for IEEE 802.11bb compliance; smartphone and device integration ready
• Kitefin XE: Room-filling Li-Fi with gigabit backhaul; multi-user access point
• Kitefin Tactical: Mission-deployable Li-Fi for defense; ruggedized, rapid deployment
• LiFi Cube™: Plug-and-play Li-Fi gateway; desktop form factor

Key Li-Fi Advantages

• Military-grade security: Light does not penetrate walls; signal contained within room
• No RF interference: Safe for hospitals, aircraft, mines, explosive environments
• No spectrum licensing: Visible light spectrum is globally unlicensed
• Dual-use: Same LED luminaires provide illumination + communications
• High density: Each Li-Fi cell is confined to one room; no co-channel interference

Visible Light Position (VLP)

VLC enables centimeter-level indoor positioning by triangulation from multiple LED transmitters:

• TOA (Time of Arrival): Requires sub-nanosecond timing; LEDs lack precise time synchronization
• TDOA (Time Difference of Arrival): More practical; measures TDOA between LED pairs
• RSS (Received Signal Strength): Most common; path loss model from known LED positions
• Accuracy: 3–4 LED transmitters enable centimeter-level positioning
• Applications: Indoor asset tracking, robot navigation, smartphone navigation in malls/airports

IEEE 802.15.7-2018 includes the Visible Light Position (VLP) annex, standardized the use of VLC infrastructure for positioning.

VLC vs Other Optical Wireless Technologies

Physical Layer Constraints

• Line-of-sight preferred: VLC performance degrades without direct LOS; diffuse VLC possible but lower rates
• Ambient light interference: Sunlight and fluorescent lights create noise; receivers use optical filters and modulation schemes to reject ambient
• Eye safety: IEC 62471 photobiological safety standard; laser-based VLC must meet Class 1M or Class 1 limits; LEDs are generally safe
• Coverage limited to illuminated area: Each LED illuminates a specific area; full coverage requires LED grid deployment

Research and Development

Key research institutions advancing VLC/Li-Fi:

• Fraunhofer HHI (Heinrich Hertz Institute): World record 10 Gbps VLC (2020); IEEE 802.11bb PHY technical editor
• Oxford University: Optical wireless communications group; OFDM for VLC, massive MIMO optical
• pureLiFi: Commercial Li-Fi systems; integrated circuit design
• COMSYS (University of Edinburgh): VLC channel modeling, modulation optimization

Note: VLC and Li-Fi remain emerging technologies with limited mass-market adoption. IEEE 802.11bb ratification (2023) is expected to accelerate device integration and deployment. The primary barriers are receiver cost, ambient light rejection performance, and the need for LED infrastructure upgrades in existing buildings.