Visible Light Communication (VLC): Concepts and Use Cases

What is VLC?

Visible Light Communication is the name given to the type of communication in which data is sent through the modulation of light waves from the visible spectrum, ranging from 380 nm to 750 nm wavelengths. In general, any system in which information can be transmitted using some kind of light visible to human eyes can be named as Visible Light Communication.

Key VLC concepts.

1. Transmitters

LEDs are used as transmitters in VLC systems. Most commercially available light bulbs contain several LEDs. These light bulbs contain a driver responsible for controlling the current passing through the LEDs, directly influencing the intensity of the illumination. In other words, the current arriving at the LED is controlled by transistors, which manipulate the light signals that the LED emits at high frequency, and thus makes the communication imperceptible to human eyes.

2. Receivers

Receivers are responsible for capturing light and converting it into electrical current. Normally, photodiodes are used as receivers in Visible Light Communication systems. However, photodiodes are extremely sensitive, and capture waves beyond the spectrum of visible light, such as ultraviolet and infrared. They also saturate easily, in an external environment and exposed to sunlight, for example, and the photodiode would fail to receive data due to high interference. For this reason, other components can be used to capture light. One of them is the smartphone camera itself, which allows any cell phone to receive data sent by a VLC transmitter. In addition to these devices, LEDs themselves can be used as receivers because they feature photo-sensing characteristics.

3. Dual functionality

Dual Functionality: LEDs used for VLC can also serve a dual function of both lighting sources and data transmitter, thus proving highly effective in lighting up an environment that also requires communication. 

High Bandwidth: VLC enjoys a higher bandwidth than traditional RF communication, owing to a huge spectrum in visible light. Ideally, under flawless conditions, it can go as high as several Gbps.

4. Line of Sight

VLC requires a line of sight or considerable light reflection, unlike RF communications, to establish perfect communication; hence, it is best suited for indoor environments under controlled lighting.

Interference-VLC is immune to EMI, hence very useful in places where RF communications may be disrupted or restricted, such as in hospitals and airplanes.

5. Modulation Technique

Some modulation techniques employed by VLC are: On-Off Keying, Pulse Width Modulation, and Orthogonal Frequency Division Multiplexing-all of these work on changing the intensity of light to send data.

Use Cases of VLC

1. Indoor High-Speed Wireless Networking (Li-Fi):

The most important application of VLC is Li-Fi, or Light Fidelity. It involves the use of LED lighting as a source of delivering high-speed Internet. It can deliver much higher data rates compared to Wi-Fi, even several gigabits per second in offices, homes, and industrial environments with LED lighting.

2. Indoor Positioning Systems (IPS):

VLC has been applied to indoor navigation and location-based service in shopping malls, museums, airports, and hospitals. The building will send information about location, modulating the light in LED fixtures to VLC-capable devices, enabling users to move with ease within indoor spaces that may be hard to navigate where GPS signals are weak.

3. Automotive and Transportation Communication:

VLC may utilize car headlights and taillights to provide Vehicle-to-Vehicle and V2X communications with infrastructure. These can be useful in vehicle-to-vehicle safety communications, where automobiles "talk" to each other in order to avoid collision, or even share real-time traffic information.

In addition, they can interact with the vehicles to update them regarding traffic lights and avoid any accidents.

4. Smart Lighting System:

VLC can be installed in smart city and smart home lighting systems for efficient communication and automation. For example, street lights can communicate with IoT devices or cars to enable real-time data or lighting controls considering environmental conditions.

5. Underwater Communication:

Because of its extremely limited range in water and very slow speed in water, underwater communication performance is poor while using traditional RF. VLC is applicable in underwater communication because the wavelength of visible light could go much further and faster in water, especially in clear water. Marine exploration, underwater robotics, and underwater sensor networks are some such applications which could benefit from this.

6. Medical Applications

In such places, VLC can be used for wireless communication with no possibility of EMI that could interfere with sensitive medical equipment. It also can be used to achieve very precise indoor navigation for hospital staff and data communication between different devices within operating rooms.

7. Airplane Cabin Communication:

VLC can be used on aircraft to provide systems of onboard entertainment and passenger communications without interfering with the avionic of the airplane. LEDs installed for cabin lighting can act simultaneously as data transmitters, thus enabling a high-speed internet connection or media streaming.

8. Retail and Advertising:

With VLC, proximity marketing for retail could be enabled, meaning that store lighting can send out offers or product information directly to the customer's smartphone or tablet while browsing different sections of the store.

9. Augmented Reality (AR) and Virtual Reality (VR):

VLC can enable low-latency communication for AR and VR applications, which demand high-speed, high-bandwidth communication for an immersive experience.