2. CONTENTS
Present Scenario
Introduction
Basic Concepts
How Li-Fi Works?
Li-Fi Construction
Comparisons
Advantages
Limitations
Solutions to problems
Conclusion
3. Wireless data is growing
exponentially…
YouTube
In 2011, ~ 140 views for every person on earth (over 1
Trillion views)
72 hours of video are uploaded to YouTube every minute
25% of global YouTube views come from mobile devices
Internet video traffic is growing at 48% CAGR
5. Present Scenario
1.4 Million
5 Billion
Radio Spectrum is congested but the demand for wireless data
double each year .Every thing, it seems want to use wireless data
but the capacity is drying up.
6. How to fix the problem?
Identify new spectrum, or
Enhance spectrum reuse (smaller cells), or
Both measures jointly
7.
8. Introduction
Li-Fi is a VLC, visible light communication, technology
developed by a team of scientists including Dr. Gordon Povey,
Prof. Harald Haas and Dr. Mostafa Afgani at the university of
Edinburgh.
Li-Fi is now part of the Visible Light Communication (VLC) PAN
IEEE 802.15.7 standard. “Li-Fi” is typically implemented using
white LED light bulbs.
LI-FI is transmission of data through illumination ,sending data
through a LED light bulb that varies in intensity faster than
human eye can follow.
10. Basic Concepts
LED i.e. Light emitting diode can be switched on and off faster since
operating speed of LED is less than 1 μs, than the human eye can
detect, causing the light source to be appear continuously.
This invisible on-off activity enables a kind of data
transmission using binary codes: switching on and LED is a
logical ‘1’, switching it off is a logical ‘0’.
It is possible to encode data in the light by varying the rate at
which LED’s flicker on and off to give different strings of 1s
and 0s.
15. Limitations/Challenges
Light can't pass through solid objects, and thus the signal
may be lost
Connectivity while moving
Multiuser support
Dimming
Shadowing
16. Solutions to Challenging problems
Solution for connectivity
The solution is called “handover”, using which the user is transferred from
one BS to another
Handover is done in the area that two BS’s have common coverage
The user can be transferred from one light source to another in the area that
is under the coverage of both
17. Contd..
Solution for multiuser support
One solution is time division multiplexing (TDM)
Each frame is divided into equal time slots
Each user transmit data in one time slot in a predefined order
The other solution is code division multiple access (CDMA)
Codes are assigned to users
Each user transmit its data using the assigned signature pattern
It is used in 3G and 4G cellular networks
18. Contd..
Solution for shadowing
As shown before, the impulse response in VLC systems has two parts
When the line-of-sight (LOS) part (which is received via direct path)
is blocked, the impulse response is only the second part
Then the data can be recovered using the second part which is
indeed the received data from the indirect paths (multipath signal)
19. Conclusion
Li-Fi will make are lives more technology driven in the
near future.
With its magic of light it can make our world a greener,
safer, cleaner and moreover a brighter place to live.
20. References
http://en.wikipedia.org/wiki/Li-Fi
http://teleinfobd.blogspot.in/2012/01/what-is-lifi.html
technopits.blogspot.comtechnology.cgap.org/2012/01/ 11/a-lifi
world/
www.lificonsortium.org/
the-gadgeteer.com/2011/08/29/li-fi-internet-at-the-speed-oflight/
http://www.digplanet.com/wiki/Li-Fi
Visible-light communication: Tripping the light
fantastic: A fast and cheap optical version of Wi-Fi is coming”,
Economist, dated 28Jan 2012
