LiFi Technology

1. What is LiFi?

LiFi, also known as "Light Fidelity" is a wireless optical networking technology, which uses light emitting diodes (LEDs) to transmit data.  In 2011, professor Harald Haas made a LiFi demonstration at the TED (Technology, Entertainment, Design) Global Talk on Visible Light Communication (VLC). You can watch the demonstration on the link below;

VLC uses light as medium to deliver high-speed communication in a manner similar to Wi-Fi and complies with the IEEE standard IEEE 802.15.7. The IEEE 802.15.7 is a high-speed, bidirectional and fully networked wireless communication technology-based standard similar to Wi-Fi’s IEEE 802.11.

2. How does LiFi work?

LiFi is a high speed, bidirectional, and fully networked wireless communication of data using light. LiFi constitutes of several lightbulbs that form a wireless network.

When an electrical current is applied to a LED light bulb a stream of light (photons) is emitted from the bulb. LED bulbs are semiconductor devices, which means that the brightness of the light flowing through them can be changed at extremely high speeds. This means that the signal can be sent by modulating the light at different rates. The signal can then be received by a detector that interprets the changes in light intensity (the signal) as data.  Also when the LED is ON, you transmit a digital 1 and when it is OFF you transmit a 0.  

The intensity modulation cannot be seen by the human eye, and thus communication is just as seamless as other radio systems, allowing the users to be connected where there is LiFi enabled light. Using this technique, data can be transmitted from a LED light bulb and back at high speeds.

3. Working Principle of LiFi

To use the LiFi technology from a visible light point of view, a user will typically require a transmitter such as LED light and a receiver made up of a photodetector material. The transmitter is connected to the network to modulate digital data along with the flickering light which emits from the LED light source. The receiver then receives such light and decodes the information modulated with the corresponding light rays.

The transmitter in a LiFi system is an LED which generates white light. This can be achieved in one of two ways. The first technique involves the combination of red green and blue (RGB) LEDs to produce white light. The second technique involves using a blue Indium Gallium Nitride (InGaN) emitter that excites a yellow phosphor coating to emit white light.  The white LED chips are typically grouped in arrays to create a combined emitter with higher radiant output flux. Since the transmitter serves the dual purpose of illumination and data transmission, the illuminance requirement of the task area determines the transmitted power of the LEDs used.

The receiver frontend is usually made up of a photodiode, pre-amplifier, an optical concentrator, and an optional optical filter. Received light passes through the optical filter which cuts out background radiation and the slow component from the yellow phosphor emission at the transmitter.  The filtered light is converged onto the Photodiode by a collimator lens. The Photodiode converts the received light to an electrical current which is pre-amplified and passed onto signal processing components.

4. Visible Light Communication

Visible Light Communication, also known as VLC, can be defined as the transmission of data through the use of light sources emitting at visible wavelengths between 400 and 800 THz (780–375 nm).  It is a subset of optical wireless communications technologies.

The VLC market is in its infant stage. There is a growing demand for an alternative wireless communication technology due to the crowding of the Radio Frequency (RF) bandwidth. This will result in the adoption of VLC technology on a global scale. As the VLC technology is based on LEDs, it does not face distortions or spectrum deficits and can transfer data at tremendous speeds.

5. LiFi vs WiFi

LiFi uses light for data transmission while WiFi uses electro-magnetic waves at radio frequencies for data transmission. Due to less interference incurred by light compare to radio frequency waves, it is used in more dense environments.

LiFi covers distance of about 10 meters while WiFi covers about 30 meters.