li-filightfidelity-130813102733-phpapp02 [autosaved].pptx
TRANSCRIPT
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Wireless data is growing exponentially
YouTube
In 2011, ~ 140 views for every personon earth (over 1 Trillion views)
72 hours of video are uploaded toYouTube every minute
25% of global YouTube views comefrom mobile devices
Internet video traffic is growing at 48% CAGR
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leading to RF Spectrum
Shortage
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PRESENT SCENARIO
Radio Spectrum is congested but the demand forwireless data double each year .Every thing, it
seems want to use wireless data but the capacity isdrying up.
So what can carry this excess demand in the future .
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PRESENT SCENARIO
1.4 Million 5 Billion
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Cost and Expensive Less Bandwidth compared to other spectrums
Insufficient spectrum for increasing data
Efficiency
Millions of basestations consume huge amount
of energy for1.Transmitting the radio waves2.To cool the base station cabins
5% Efficiency
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Available within the range of Base stations Limited availabity
Unavailable in aircraftsSecurity: Less secure(passes through the walls)
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How to fix the problem?
Identify new spectrum, or
Enhance spectrum reuse (smaller cells), or
Both measures jointly
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Electromagnetic Spectrum
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RadioWaves
InfraredRays
VisibleRays
UltravioletRays
X- RaysGamaRays
Gama rays cant be used as they could be dangerous.X-rays have similar health issues.Ultraviolet light is good for place without people, but other wise
dangerous for the human body.Infrared, due to eye safety regulation, can only bse used with lowpower.
HENCE WE LEFT WITH THE ONLY THE VISIBLE - LIGHT SPECTRUM.
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.
Radio waves Visible lights
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WHAT IS LiFi ?
Li-Fi is transmission of data through
illumination, sending data through aLED light bulb that varies in intensityfaster than human eye can follow
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History of Li-Fi
The technology truly beganduring the 1990's in countrieslike Germany, Korea, andJapan where they discoveredLED's could be retrofitted tosend information. HaraldHaas continues to wow theworld with the potential to use
light for communication
Harald Haas
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How LI-FI Works ?
Very simply, if the LED is on, you transmit a digital 1, ifit's off you transmit a digital 0.
They can be switched on and off very quickly,which gives nice opportunities for transmitting data.
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Block Diagram
DataModulation
(PPM/FSK)
LightSource
DataDemodulation
(PPM/FSK)
PhotoDetector
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Digital Modulation Tech.
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Transmitting element
LED
Fluorescent Lamp
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Receiving element
(Detector)
Avalanche Photo Diode
Image Sensors
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VLC Vs. IR and RF
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Indoor VLC configurations
(a) Directedline-of-sight (LOS) link
(b) Non-directed LOS link
(c) Diffuse link
(d) Quasi diffuse link
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Economic value
A free band that does not need license.
High installation cost but very low maintenance cost.
Cheaper than Wi-Fi.
Theoretical speed up to 1 GB per second : Less time & energyconsumption.
No more monthly broadband bills.
Lower electricity costs.
Longevity of LED bulb : saves money.
Light doesn't penetrate through walls : secured access.
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Advantages
Safe for health
Secure
No interference on RF signals
High speed
Challenging Problems Connectivity while moving
Multiuser support
Dimming
Shadowing
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Solutions to Challenging problems
Solution for connectivity
This problem is similar to the connectivity problem in cellular network whenyou move from one area of the city to another area while speaking with cell-phone
The solution is called handover, using which the user is transferred from oneBS to another
Handover is done in the area that two BSs have common coverage
Similar solution can be used in signal processing domain for VLC
The user can be transferred from one light source to another in the area thatis under the coverage of both
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Solutions to Challenging problems
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
CDMA has been adopted and developed for optical systems
Optical orthogonal codes (OOC) are used as signature pattern for users
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Solutions to Challenging problems
Solution for shadowing
As shown before, the impulse response in VLC systemshas two parts
When the line-of-sight (LOS) part (which is received viadirect path) is blocked, the impulse response is only thesecond part
Then the data can be recovered using the second partwhich is indeed the received data from the indirect paths(multipath signal)
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POTENTIAL APPLICATION OF LI-FI
Li Fi technology is still in its infancy .However some areaswhere it seems perfectly applicable are:-
TRAFFIC LIGHTS
Traffic lights can communicate to the car and witheach other.
Cars have LED-based headlights, LED-based cack lights,and cars can communicate with each other andprevent accidents in by exchanging information.
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INTRINSICALLY SAFE
ENCIRONMENTS
Visible Light is more safe than RF, hence it can be usedin places where RF can't be used such as petrochemicalplants , airplanes etc.
PUBLIC INTERNET HOTSPOTS
There are millions of street lamps deployed aroundthe world.
Each of these street lamps could be a free access
point.
POTENTIAL APPLICATION OF LI-FI
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ON OCEAN BEDS
Li-Fi can even wok underwater were Wi-Fi fails
completely, thereby throwing open endless opportunitiesfor military/navigation operations.
POTENTIAL APPLICATION OF LI-FI
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. An USB Li-fi Key
designed byOLEDCOMM for tablet.
Li-Fi router for PC by
OLEDCOMM, a Frenchcompany.
OLEDCOMM hasrecently designed a Li-FiDongle for Smartphones.
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Future Prospects
This research report categorizes the global
VLC technology market; based on
component, applications, and geography.
Li-Fi uses light-emitting diodes (LEDs)
which are rapidly gaining in popularity for
standard lightbulbs and other domestic
and commercial purposes. They areexpected to be ubiquitous in 20 years.
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Still under research
What will be the effect ofinterferences from external lightsources like sun light & normalbulbs?
what about the limited bandwith
of the existing copper cablesused for electrical connections ?
where do the connections uplink,how serious are the modificationsneeded to the power grid ?
how will other devices react ifyou inject a high frequency intomains ?
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Concluding Remarks
Li-Fi is enabled by advanced digital transmission technologies
Li-Fi will enable many new applications
Optical attocell networks based on Li-Fi:
Are the glue between future energy efficient illumination and cellularcommunications;
Harness unregulated, unused and vast amount of electromagneticspectrum;
Enable ever smaller cells without the need for new infrastructure;
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Any Queries ?
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