In simple terms, Li-Fi can be
thought of as a light-based Wi-Fi. That is, it uses light instead of radio
waves to transmit information. And instead of Wi-Fi modems, Li-Fi would use
transceiver-fitted LED lamps that can light a room as well as transmit and
receive information. Since simple light bulbs are used, there can technically
be any number of access points.
This technology uses a part of
the electromagnetic spectrum that is still not greatly utilized- The Visible
Spectrum. Light is in fact very much part of our lives for millions and
millions of years and does not have any major ill effect. Moreover there is
10,000 times more space available in this spectrum and just counting on the
bulbs in use, it also multiplies to 10,000 times more availability as an
infrastructure, globally.
It is possible to encode data in
the light by varying the rate at which the LEDs flicker on and off to give
different strings of 1s and 0s. The LED intensity is modulated so rapidly that
human eyes cannot notice, so the output appears constant.
More sophisticated techniques
could dramatically increase VLC data rates. Teams at the University of Oxford
and the University of Edinburgh are focusing on parallel data transmission
using arrays of LEDs, where each LED transmits a different data stream. Other
groups are using mixtures of red, green and blue LEDs to alter the light's
frequency, with each frequency encoding a different data channel.
Li-Fi, as it has been dubbed, has
already achieved blisteringly high speeds in the lab. Researchers at the
Heinrich Hertz Institute in Berlin, Germany, have reached data rates of over
500 megabytes per second using a standard white-light LED. Haas has set up a
spin-off firm to sell a consumer VLC transmitter that is due for launch next
year. It is capable of transmitting data at 100 MB/s - faster than most UK
broadband connections.
