Future Tech: Li-Fi

What if the lights in your home were your WiFi? That’s the question that a new and interesting technology called Li-Fi seeks to answer.

The term “Li-Fi” was coined by Harold Haas at his 2011 TED Talk. Haas is a research at the University of Edinburgh and a co-founder of pureLiFi, a startup tech company that focuses on making consumer grade Li-Fi products. But…you’re probably asking….what is Li-Fi? Li-Fi is exactly how it sounds. Instead of using radio waves like Wi-Fi, Li-Fi uses visible light to transmit high-speed wireless data. It’s a somewhat similar concept to fiber optics which also uses light to transmit data along a wire. In most examples, LEDs are used as the source of light as they consume very little energy. The LEDs would be switched on and off very rapidly (faster than the human eye can see) and those series of on/off would be translated into electrical signals by a receiver. Li-Fi is still relatively new but the primary drivers will be Internet of Things (IoT), vehicle to vehicle communications and anything that requires short range, high speed wireless communications.

How_VLC_works

Li-Fi vs Wi-Fi

  • The visible light spectrum (as opposed to radio waves which is what Wi-Fi uses) is about 10,000 times larger than the entire radio frequency spectrum. Li-Fi is not subject to “spectrum crunch” inherent in radio waves.
  • Researchers have been able to reach speeds of up to 224 Gbps in a lab. Even bouncing off walls, up to 70Mbps have been reached. Pilot programs have been done in office/industrial settings with speeds up to 1Gbps. Theoretical max speeds of 802.11ac Wi-Fi is 1.2Gbps
  • Doesn’t penetrate opaque walls which can allow sensitive data to only be radiated in certain locations without fear of eavesdropping outside. Wi-Fi signals can be sniffed outside of the room

Disadvantages

  • Light must be on all the time to send data (although technically the light could be lowered enough where human eyes can’t detect it but still be “on”)
  • Must use LEDs. Traditional incandescent bulbs would not work.
  • Costly to retrofit existing lighting to LEDs + networking.
  • Limited to indoor use. Outdoor use is useless because of sunlight.
  • Requires line of sight or ability to actually “see” the actual light or photons.

[disclaimer: If you don’t like techie talk, skip this next paragraph]

The IEEE has developed a standard for visible light communication (802.15.7) that defines the physical and MAC layers. However, the standard has not kept up with the latest advancements in VLC such as optical orthogonal frequency division multiplexing (O-OFDM). Fortunately, VLC can also take advantage of 802.11 protocols except using visible light instead of radio waves.

[back to regular talk]

PureLiFi has a product to market called LiFi-X which consists of a USB dongle about the size of a Chromecast and an access point (AP). The AP is able to connect to different LED light fixtures to create an atto-cell. So far, the state of Li-Fi is similar to how Wi-Fi was when it first became mainstream in the early 2000s. It will be interesting to see if this “5G” technology will take off in the future.

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