2. Wi-Fi
Wi-Fi is a technology that allows electronic devices to connect to a
wireless LAN (WLAN) network.
It mainly uses the 2.4 gigahertz UHF and 5 gigahertz SHF ISM radio
bands.
Wi-Fi compatible devices can connect to the Internet via a WLAN
network and a wireless access point. Such an access point has a range
of about 20 meters (66 feet) indoors and a greater range outdoors.
The Wi-Fi Alliance defines Wi-Fi as any "wireless local area network"
(WLAN) product based on the IEEE 802.11 standards
3. Different Wi-Fi Protocols and Data Rates
Protocol Frequency Signal Max. Data Rate
Legacy 802.11 2.4 GHz FHSS or DSSS 2 Mbps
802.11a 5 GHz OFDM 54Mbps
802.11b 2.4 GHz HR-DSSS 11Mbps
802.11g 2.4 GHz OFDM 54Mbps
802.11n 2.4 or 5 GHz OFDM 600Mbps
802.11ac 5 GHz 256-QAM 1.3Gbps
4. History Of Li-Fi
Harald Haas, who teaches at
the University of Edinburgh
in Scotland, coined the term
"Li-Fi" at his TED Global
Talk in 2011.
He gave a second TED
Global lecture in 2015 on the
use of solar cells as Li-Fi
data detectors and energy
harvesters.
5. Challenges faced by radio spectrum
Capacity
Scarce, Expensive,Lesser Bandwidth
Efficiency
Huge amount of energy needed to cool the base station cabins
Availability
Unavailable in aircrafts
Security
Radio waves penetrate through walls
7. Advantages Of Using Visible Light
Capacity
We have 10,000 times more spectrum
Efficiency
This is data through illumination, high energy efficiency of LED bulbs
Availability
Light is available everywhere. It can be used in airports, hospitals
Security
Light does not penetrate walls.
8. Infrared rays in Remote control
Remote controls creates a simple,
low-speed data stream in 10,000
bits per second.
With Li-Fi we transmit thousands
of data streams in parallel, at even
higher speeds.
9. Working Of Li-Fi
Operational procedure is very simple, if the led is on, you transmit a
digital 1,if its off you transmit a digital 0.
The LEDs can be switched on and off very quickly, which gives nice
opportunities for transmitting data.
Hence all that is required is some LEDs and a controller that code
data into those LEDs.
We have to just vary the rate at which the LED’s flicker depending
upon the data we want to encode .
12. Modulation Techniques
On-off keying
• On-off keying (OOK) denotes the simplest form of amplitude-shift
keying (ASK) modulation
• Presence of a carrier for a specific duration represents a binary one
• Absence of carrier for the same duration represents a binary zero
• It is analogous to unipolar encoding line code.
• It is very easy to generate and decode
13.
14. Li-1st
The first product to be
developed by pure LiFi
This is the worlds first Li-
Fi system
Full duplex
communication with a
capacity up to 5Mbps
downlink x 5Mbps uplink
Has a range of up to three
meters.
15. Li-1st Ceiling Unit
Li-1st Ceiling Unit is
connected to the data network
via a standard Ethernet RJ45
port.
It encodes the data and
transmits it by modulating the
intensity of the LED light.
The Li-1 st ceiling unit receives
and decodes the uplink signal
using an infra-red detector and
optics.
16. Li-1st Desktop Unit
A visible light decoder captures
the continuous sequence of light
intensity changes.
It then decode the binary stream
and transmit it to the client device
via an USB connection.
The desktop unit receives data
from the client device, encodes it
and transmits it to the ceiling unit
using an infra-red emitter.
17. Li-Flame
The Li-Flame is the world’s
first high-speed wireless
network solution using VLC.
Multiple APs throughout an
indoor space allow users to
move from one AP to the
next
There is no interruption in its
high-speed data stream
18. Li Flame Ceiling Unit
Data and power via standard
Ethernet port
Simple installation
Connects to an LED light fixture to
form an atto-cell over a wide area
Multiple access
Handover control enables seamless
switching between APs
19. Li Flame Desktop Unit
Connects to client device via
USB
10Mbps infrared uplink to ceiling
unit
allows user to move from one
AP to the next without losing the
high-speed data connection
Transceiver swivel head can be
adjusted by user to optimise the
connection
Battery-powered and portable
20. Solar Li-Fi
Harald Haas at TED Global
2015 demonstrated solar li-fi.
He showed transmission
of video from a standard
off-the-shelf LED lamp to a
solar cell with laptop acting as
receiver.
21. Solar Li-Fi
The point is to use existing infrastructure like solar panel and
LEDs to close the digital divide and to connect billions of
devices to internet .
The Li-Fi prototype relies on solar energy to power Internet
connections
An LED light source paired with a solar panel becomes a
fully functional transmitter and receiver system for high
speed, secure data transfer
It is possible to use solar cells on the roof of a hut to act as a
broadband receiver from a laser station on a close by hill.
25. Limitations 0f Li-Fi
Light does not penetrate walls so signal contained to one area.
For ideal speeds line of sight is required.
A major challenge facing Li-Fi is how the receiving device
will transmit back to transmitter.
Interferences from external light sources like sun light, normal
bulbs, and opaque materials in the path of transmission will
cause interruption in the communication
26. Conclusion
So, all we would need to do is to fit a small microchip to every
potential illumination device.
This would then combine two basic functionalities: illumination
and wireless data transmission
This could solve the four essential problems that face us in wireless
communication these days
In the future data for laptops, smartphones could be transmitted
through the light in a room.