li-filightfidelity-130813102733-phpapp02 [autosaved].pptx

7/27/2019 li-filightfidelity-130813102733-phpapp02 [Autosaved].pptx

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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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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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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.



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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.



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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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