Tech Explained: LiFi

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The demand for high-speed WiFi increases every day. Cisco estimates that by 2019 more than ten billion mobile devices will exchange 35 quintillion bytes of information each month. That does not even factor in Internet of Things devices. To meet this demand, it may soon be possible to transmit data using Light Fidelity (LiFi) instead of, or in addition to, WiFi. So how, exactly, can data be transmitted using light?

The idea of using light to send information has been around for more than a century. Alexander Graham Bell sent the first wireless telephone message on the photophone – a device he invented in 1880. The photophone used vibrations of lightwaves from sunlight focused on a mirror. However, LiFi uses fluctuations in light-emitting diodes (LEDs) to transmit information. The technology was first demonstrated in 2011 by researcher Harold Haas, who created the first LiFi transmitter using off-the-shelf parts.

An LED light bulb is a semiconductor, which means that the current of electricity to the bulb can fluctuate at extremely high speeds. Using signal processing technology, data is first encoded as a series of variations in the current. This data is then sent out as light fluctuations too rapid to be picked up by the human eye. A photodiode in the receiver detects the fluctuations in the light and ‘decodes’ the signal. In effect, the light bulb acts as a wireless router.

Researchers have demonstrated that LiFi can transmit information at speeds as high as 224 gigabits per second. This is the equivalent of downloading around 18 movies every second. In an office setting, researchers have been able to achieve download speeds up to 100 times faster than the average WiFi.

Because LiFi does not create electromagnetic interference, it could function around equipment sensitive to such interference, such as in hospitals, on oil rigs or underwater. Existing LED bulbs can be easily converted to become LiFi transmitters. Such a process would only require the addition of a single microchip, therefore creating a cost-effective, quick transition. Any light source – bus shelters, street lights, tourist information kiosks – could provide data transmission as well as light. Another advantage of LiFi is that anything that blocks light also blocks the signal. This reduced the risk of data leaking through home or office walls.

There are some drawbacks to the technology, however. In very bright daylight, the receivers have difficulty distinguishing the signal from the background light. To overcome this, it may be necessary to develop smart architecture solutions, such as having light follow the user. What is clear is that, as more and more devices feature such sensors, it threatens to swamp the existing WiFi infrastructure. LiFi is one possible solution. This has not escaped the notice of electronics businesses like electronics giant Siemens or Haas’s company, pureLiFi, who are rapidly developing plug-and-play systems to make LiFi available for a wide range of applications. Does LiFi have the potential to replace WiFi?

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