Light Fidelity (Li-Fi) is a bidirectional, high speed , fully networked wireless communication technology similar to Wi-Fi. Li-Fi was first put forward by Professor Harald Haas,University of Edinburgh, during a TED Talk in 2011. Li-Fi is a form of visible light communication and a subset of optical wireless communications (OWC) and could be a complement to RF communication (Wi-Fi or Cellular network), or even a replacement in contexts of data broadcasting. It is so far measured to be about 100 times faster than some Wi-Fi implementations, reaching speeds of 224 gigabits per second.
Bidirectional, high speed, fully networked wireless
communication technology like Wi-Fi.
First proposed by Professor Harald Haas, University
of Edinburg in 2011, that...
Light bulbs can act as wireless routers.
Will form visible light communication VLC.
A subset of optical wireless communication OWC.
Could be complement to RF communication Wi-Fi or
Could even replace all for data broadcasting.
It is about 100 times faster than some Wi-Fi systems.
Speeds up to 224 gigabits per second.
Can use visible light or infra red and near ultraviolet
Uses LED as source.
Current to LED is switched on/off at a rate too high
to be noticed by human eye.
LED can be dimmed to below human visibility.
It is short range communication as light can not
Hence more secure from hacking.
Direct line of sight not required as light reflects
VLC uses visible light between 400THz(780nm) to
800THz(375nm) as optical carrier for data
transmission and illumination.
It uses fast pulses of light to transmit information
Main components of system are-
A high brightness white LED as source.
A silicon photodiode which is highly responsive to
visible wavelength region.
LED is switched on/off to generate „1‟ and „0‟.
As flicker rate is very high, it appears constant to
Light bulbs used as data communication medium to
PC, Laptop, Tablet and PDA .
All devices have photo-detector connected to them.
Unlike RF communication, LI-FI is very useful in
electromagnetic sensitive areas such as aircraft
cabins, hospitals, nuclear power plants..
Li-Fi can work under water where Wi-Fi fails.
Transmits on visible light spectrum, which is 10,000
times larger than entire RF spectrum.
Data rates of over 10 Gbits/s is much faster than
typical fast broadband.
Li-Fi is expected to be about 10times cheaper than
But Li-Fi has shorter range than Wi-Fi.
Li-Fi is highly efficient as LED consumes less energy
as compared to Wi-Fi.
No licencing required for Li-Fi.
No harmful radiation for living beings in Li-Fi.
Radio waves can penetrate through walls, hence can
be intercepted and misused, while light can not
penetrate walls, hence highly secure.
TECHNOLOGY SPEED DATA DENSITY
Fire Wire (IEEE 1394)
800 Mbps *****
USB 3.0 5Gbps *****
THUNDERBOLT (Apple) 2 X 10 Gbps *****
Wi-Fi-IEEE (802.11N) 150 Mbps *
Bluetooth 3 Mbps *
IrDA 4 Mbps ***
Wi-Gig 2 Gbps **
Giga-IR 1 Gbps ***
Li-Fi >10 Gbps ****
Part of visible light communication is modelled after
As IEEE 802.15.7 is getting obsolete, it fails to
accommodate latest technological development in
field of optical wireless communication such as...
Optical orthogonal frequency division multiplexing
O-OFDM optimized for-
high data rates,
New standards required for optical wireless
However IEEE802.15.7 defines physical layer(PHY)
and media access control(MAC) layer.
Standard delivers required data rates to transmit
audio, video and multimedia services.
Standard accounts for
Optical transmission mobility,
Compatibility with lighting system of building,
Interference due to ambient light
MAC layer linking with other layers such as TCP/IP
Defines three PHY layers with different rates:-
PHY I established for outdoor application from 11.67Kbps
PHY II permits data rates from 1.25Mbps to 96Mbps.
PHY III used for many emission sources with modulation
method colour shift keying(CSK). 12Mbps to 96Mbps
Modulation method for PHY I and PHY II are on-off
keying(OOK) and variable pulse position
Manchester coding for PHY I and PHY II includes
clock inside transmitted data by representing logic
“0” with OOK symbol „01‟ and logic “1” by OOK
Symbols sent with a DC component to avoid light
extinction during long runs of “0”s.
Constant current of electricity supplied to an LED
light bulb can be varied up and down at extremely
high speed invisible to human eye.
There is photo-detector to receive light signal and a
signal processing element to convert data into
Data fed into an LED light bulb are sent at high
speed to photo-detector/photodiode to be converted
into electrical signal.
Enhanced method is array of LEDs for parallel data
transmission to increase data rate.
Or a mixture of red, green and blue LEDs to alter
light frequencies for data channel multiplexing.
LED and photodiode are used to send and detect
Voltage regulator and level shifter on both side
to maintain voltage level.
Prof. Harald Haas demonstrated in 2011,
transmission of video by LED light bulb with a speed
more than 10Mbps.
In 2011, German scientists succeeded in creating
800Mbps wireless network by using normal red,
green, blue and white LED light bulbs.
Subsequently, in 2012, Haas setup a company
pureLiFi with aim to become world leader in VLC.
PureLiFi demonstrated the first commercially
available Li-Fi system, the Li-1st, at 2014 Mobile
World Congress in Barcelona.
PureLi-Fi Demo had three Li-Fi access points, brick-
sized boxes attached to LED down-lighters covering
area of 20sq.m.
Boxes turned light bulbs to wireless antenna.
Dongle plugged into laptop or tablet, acts as wireless
modem to received data.
Dongle plugged via USB also provided power.
Dongle has sensor to catch light and infra red
component to send signal.
Overhead lights also have networking component:
for multiple users to connect to single light
To move from one light source to another without
PureLiFi already have two products in market:
Li-Flame Ceiling Unit to connect to an LED light
Li-Flame Desktop Unit which connects to a device
PureLiFi is adding this functionality to off-the-shelf
light bulbs and plugging dongles to devices to
PureLiFi COO Burchardt aims to incorporate this
inside devices and LED bulb as application-specific
integrated circuit (ASIC) or System-on Chip(SoC)
Medical Electronics:- Radio waves block signals from
monitoring equipment in hospitals, especially OT.
Li-Fi can be safely used in medical establishments
with 10000times more spectrum.
Airlines: Wi-Fi hampers with working of airlines.
High speed Li-Fi connections can be safely provided
inside airplanes for each seat.
Smarter Power Plants : Power plants need fast
interconnected data system to monitor demand, grid
integrity, core temperature etc. without radiation
Li-Fi could offer safe, abundant connectivity for all
such sensitive areas.
It will give additional benefit of drastic power saving
in terms of technology and use of LED bulbs.
On Road: Li-Fi can communicate with LED lights of
vehicles to reduce accidents.
Street lamps can be changed to Li-Fi lamps to
Road blocks and congestions can be controlled by
intimating the drivers about traffic.
Under Sea: For under water ROVs, large cables
supply power and allow signal transmission with
Limitation of length and risk of damage to wires.
Sea exploring becomes efficient if instead of wires,
high powered lamps fitted at bottom, are used to
send Li-Fi signals to ROVs.
Vessels can also use headlamps to communicate with
other vessels or land.
Data processing and transfer becomes faster and
Multiuser Communication: Li-Fi helps to share
multiple information at a single instance.
Broadcasting and multiple accessing can be made
Ceiling lights, street lights etc. can be used as
hotspots to spread internet using VLC at low cost.
Under Li-Fi technology, every bulb can be made to
Li-Fi will lead to cleaner, greener, safer and brighter
Will solve problems of RF bandwidth shortage.
Li-Fi is authentic and very efficient alternative to RF
Li-Fi and Wi-Fi are complementary technologies that
will work well in many situations.
Line-of-sight is major drawback of Li-Fi outdoors.