It’s
impossible to avoid Wi-Fi in today’s world. It’s everywhere; your neighbors
have it, it’s free in coffee shops, and essential for smartphones. We all know
Wi-Fi, but what is Li-Fi? Li-Fi, like Wi-Fi, enables electronic devices like
computers, laptops and smartphones to wirelessly connect to the Internet. Even
though Wi-Fi was also originally intended for such devices, it is widely used
today to connect all sorts of things: printers, televisions, speakers,
headphones, and even running shoes! In simple terms, Li-Fi is equivalent to
Wi-Fi, but using light waves instead of radio signals. Li-Fi uses the light
waves from LED light bulbs – that are rapidly replacing incandescent light
bulbs for their energy saving and safety - to transmit data so it provides
illumination and wireless data communications. Imagine a modern LED light bulb –
fitted with Li-Fi technology – in your living room, or office, or in a lamp on
your desk, or by your bedside. Anywhere that is illuminated by the Li-Fi
enabled LED, can also communicate via Li-Fi.
What
Is LiFi?
The term LiFi was coined by Professor Harald Haas, and
is recognized by the IEEE standardization
committee for Optical Wireless Communications. LiFi is high-speed, bidirectional,
networked and mobile wireless communications using light (as opposed to traditional radio
frequencies). With LiFi technology, data travels
in the visible light spectrum through LEDs. This makes it possible to
provide wireless internet access at speeds of
over 100 Gbps, although this is still in the Lab.
Although Li-Fi can be used to off-load data from existing Wi-Fi networks,
implementations may be used to provide capacity for the greater downlink demand
such that existing wireless or wired network infrastructure may be used in a
complementary fashion.
LiFi is the use of the visible
light portion of the electromagnetic spectrum to transmit information at very
high speeds. This is in contrast to established forms of wireless communication
such as Wi-Fi which use traditional radio frequency (RF) signals to transmit
data.
With
LiFi, data is transmitted by modulating the intensity of the light, which is
then received by a photo-sensitive detector, and the light signal is
demodulated into electronic form. This modulation is performed in such a way
that it is not perceptible to the human eye.
LiFi
is a category of Optical Wireless Communications (OWC). OWC includes infra-red
and ultra-violet communications as well as visible light. However, LiFi is
unique in that the same visible light energy used for illumination may also be
used for communication.
How Does Li-Fi Work?
When a constant current is applied to an LED light bulb a constant
stream of photons are emitted from the bulb which is observed as visible light.
If the current is varied slowly the output intensity of the light dims up and
down. Because LED bulbs are semi-conductor devices, the current, and hence the
optical output, can be modulated at extremely high speeds which can be detected
by a photo-detector device and converted back to electrical current. The
intensity modulation is imperceptible to the human eye, and thus communication
is just as seamless as RF. Using this technique, high speed information can be
transmitted from an LED light bulb.
Radio frequency communication
requires radio circuits, antennas and complex receivers, whereas Li-Fi is much
simpler and uses direct modulation methods similar to those used in low-cost
infra-red communications devices such as remote control units. Infra-red
communication is limited in power due to eye safety requirements, whereas LED
light bulbs have high intensities and can achieve very large data rates.
Ranjan Tyagi
Batch 2015-17
Symbiosis Institute of Telecom Management