Datum 2014
LiFi
L
Light Fidelity
The New way of Data Transfer
ARAVIND SAKTHIVEL M
B.Sc CT (G1) - IV
i-Fi (or light fidelity), refers to wireless
Chair of Mobile Communications at the University of
communication systems
Edinburgh and co-founder of a spin-out company, pure
using
light
from light-emitting diodes as a medium
LiFi.
instead of traditional radio frequencies, as in
technology using the trademark Wi-Fi.
Li-Fi signals work by switching bulbs on and
off incredibly quickly – too quickly to be noticed by the
human eye. And although Li-Fi bulbs would have to be
kept on to transmit data, the bulbs could be dimmed to
the point that they were not visible to humans and yet
still functional.
The term Li-Fi was coined by Harald Haas
from the University of Edinburgh in the UK. VLC
Li-Fi is expected to be ten times cheaper than
communication
is
modeled
after
communication
Wi-Fi. Li-Fi has the advantage of being able to be used
protocols established by the IEEE 802 workgroup. This
in electromagnetic sensitive areas such as in aircraft
standard defines the physical layer (PHY) and media
and nuclear power plants without causing interference.
access control (MAC) layer. The standard is able to
The light waves cannot penetrate walls which makes a
deliver enough data rates to transmit audio, video
much shorter range, though more secure from hacking,
and multimedia services. It takes count of the optical
relative to Wi-Fi. Direct line of sight isn’t necessary for
transmission mobility, its compatibility with artificial
Li-Fi to transmit signal.
lighting present in infrastructures, the defiance which
may be caused by interference generated by the
Light reflected off of the walls can carry 70
Mbps. Both Wi-Fi and Li-Fi transmit data over the
ambient lighting. The MAC layer allows to use the link
with the other layers like the TCP/IP protocol.
electromagnetic spectrum, but whereas Wi-Fi utilises
radio waves, Li-Fi uses visible light. While the US Federal
The standard defines three PHY layers with different
Communications Commission has warned of a potential
rates:
spectrum crisis because Wi-Fi is close to full capacity,
Li-Fi has almost no limitations on capacity. The visible
light spectrum is 10,000 times larger than the entire
The PHY I was established for outdoor application
and works from 11.67 kbit/s to 267.6 kbit/s.
radiofrequency spectrum.Researchers have reached
data rates of 10 Gbps, which is more than 250 times
faster than superfast broadband. Researchers have
The PHY II layer allows to reach data rates from
1.25 Mbit/s to 96 Mbit/s.
proven that speeds over 10 Gbps are possible. The Li-Fi
market is projected to be worth over $6 billion per year
by 2018. Short range, low reliability and high installation
costs are the potential drawbacks. Professor Harald
Haas is widely recognised as the “father of LiFi.” He is
6
The PHY III is used for many emissions sources
with a particular modulation method called color
shift keying (CSK). PHY III can deliver rates from
12 Mbit/s to 96 Mbit/s.