D LIGHTpbrvits

7/28/2019 D LIGHTpbrvits

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A PAPER ON

D-LIGHT-The future wireless communication based on visible light spectrum.

P.B.R.VISVODAYA INSTITUTE OF TECHNOLOGY & SCIENCE,KAVALI ,S.P.S.R.NELLORE(DST),PIN:524201.

Submitted by:

R.DEEPAK III/IV B.Tech, P.SAI JAWAHAR III/IV B.Tech,

10731A0488, 10731A0470,

[email protected] [email protected]

PH:8374272526 PH:8125633176
mailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]


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Abstra

ct

White LEDs are set to penetrate many areas of everyday life.

An interesting property of these devices (in addition to their

lightening capabilities) is that they can be utilized for data

transmission. In the past, primarily OOK (on-off keying) hasbeen used for digital data modulation of such devices. OOK

imposes limitations on the achievable data rates. Visible

Light Communication uses light emitting diodes (LEDs), for

the dual role of illumination and data transmission. Using the

visible light spectrum, which is free and less crowded than

other frequencies, wireless services can be piggy-backed over

existing lighting installations. With this leading edge technology,

data including video and audio, internet traffic, etc, can be

transmitted at high speeds using LED light. In addition, where

security of local communication is important eg defense and

finance applications, D-Light technology offer a secure medium

for communication in an office/building environment

Keywor

ds

White LEDs, Low-voltage lines, On-Off Keying, Green VLC,

LVX

I.

Introduction

In the 21th century, high speed data transmission will play an

important role in our daily life. Multimedia information is

envisaged to be available at any place and at any time. Wirelessnetworks constitute a key element to achieving these goals.

However, radio frequency bandwidth at frequency ranges

which allow reasonable spatial coverage is a limiting factor.

Therefore, alternative wireless transmission means have to be

explored. Visible light communication using white LEDs offers

the potential for such alternative.

The main reasons are as follows:

White LEDs are currently penetrating many areas of our

everyday life. They are envisaged to replace high energy

consuming light bulbs in private and business homes and

even in street lamps.

Moreover, they can be used in headlights of planes and

trains, front and back lights in

cars and trains, and for object illumination in museums,

etc.

Bandwidth is not limited.

Existing local power line infrastructure can potentially be

utilized.

Transmitters and receivers devices are cheap, and there

is no need for expensive RF units.

As lightwaves do not penetrated opaque objects, they

cannot be eavesdropped. It is very difficult for an intruder

to (covertly) pick up the signal from outside the room. Visible light radiations are undoubtedly free of any health

concerns.

II. What is

VLC ?

VLC (Visible light communication) involves two-way


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communication using the medium of light. Photons, which can

be seen by the human eye, carry an embedded signal, which is

unseen. This 'signal within a signal' is the foundation of LVX's

patent protected technology and separates LVX technology

from other one-way lighting technologies which do not both

communicate and provide visible light.

A significant attribute of LEDs is their ability to switch on and

off thousands of times per second. No other lighting technology

has this capability. This switching occurs at ultra-high speeds,

so far beyond what the human eye can detect, that the lightappears to be constantly on. Amazingly, the technology can

transmit a signal even when the light appears off. These

embedded signals are emitted from the LEDs in the form of

binary code; 'off' equals zero and 'on' equals one. When LVX

equipment and devices are placed throughout a building of

geographical area, a comprehensive wireless communication

network can be created.

A. How LEDs

Work?

Light Emitting Diodes are lights that are used extensively in

electronic devices, consumer products and equipment. Their

uses vary from signaling, signage and illumination. They are

preferred over other illuminating technologies because of

their small size, versatility, longevity, and most importantly

because of their high energy efficiency. Recent advances

in semiconducting material science and manufacturing

techniques have positioned LED technology to be the preferred

choice for general indoor and outdoor lighting applications.

while the development of Light Emitting Diodes has evolved

steadily throughout the past few decades, the science of

LEDs is fundamentally the same. A diode produces light on

an atomic level when electrons jump from a higher to a lowerstate (quantum jump). Certain semiconducting materials

facilitate this phenomenon when low voltage electrical

current passes through them. In order for this to happen, two

different semiconducting materials are bonded together. One

is negatively charged while the other is positively charged.

An electrical current induces the electrons to jump from the

negatively charged material to the positively charged material.

Subatomic particles in the form of photons are released in this

movement. Photons are perceived as light.

Through research and experimentation, engineers and

scientists have developed a variety of LED lighting solutions

for many different applications. LEDs can produce many

intensities of light-output and any color within the visible light

spectrum. Today, the improvements and color quality of LEDs

can be utilized in general illumination solutions for buildings

and roadways.

LEDs are fundamentally different from other lighting

technologies. Fluorescent and incandescent technologies

use heat to produce light. LEDs do not. They produce very

little heat. In fact, the lighting industry refers to them as

cool lights and recognizes them as the most sustainable


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lighting technology today. They are significantly more energy

efficient than incandescent lights and do not contain any of the

hazardous materials such as mercury, that other lights Homes

are connected to electric grid by low-voltage lines (LV). Low

Voltage lines are distributed to each power plug in every room

in a house. More than 99 percent of homes in the United States

have access to electricity, whereas connectivity level is far

less for cable and phone lines. Thus, a combination of MV andLV power lines can be an appropriate candidate for providing

broadband access to every home in the country. The

characteristics of LV power lines are very well known, and there

are a variety of research activities in this area to exploit different

features of LV grids.

Indoor wireless connectivity is always appealing to consumers

because of its ease of use. One of the conventional wireless

access systems is Wi-Fi. But these systems and similar other

wireless schemes suffer from many shortages, including

interference, not being able to provide quality of service (QoS),

adequate coverage and most importantly, security.

A better alternative for high-speed wireless home networking,

delivering voice/video/data (Triple Play) is to use optical

wireless, indoors. Use of conventional lasers for optical indoor

communications has not been feasible as yet because of the

high cost of laser sources. Instead of lasers, LEDs can be used as

communications transmitters connected to electric grid,

receiving high-bit-rate signals via BPL.

Fig. 1: Visible Light Communications Using Visible Light LEDs

Recently, WHITE LEDs emerged in the market and are

considered as future lamps. Apparently, in the near future,

the low cost, efficient and miniature WHITE LEDs will replace

the incandescent and fluorescent lamps. Researchers pledge

that by 2012, these devices will reach seven watts and 1000

luminescence. This is brighter than a 60-watt bulb, yet draws a

current provided by four D-size batteries. A Japanese research

team suggested using the same WHITE LEDs not only for lighting

the homes but also as light sources for wireless in-house

communications. Using this new and developing technologyalong with MV-LVpower-lines communications can create a

revolution in the area of consumer networking because of its

efficiency and affordability. Therefore, in future, you turn on the

lights for indoor low-cost lighting and you receive broadband

via the same through modulated WHITE LED light.


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B. Visible Light Communication

System

Visible Light Communication system are presently being

developed by scientists seeking to create ultra high-speed,

high security, biologically friendly communications networks

that allow the creation and expansion of seamless computing

applications using very large bandwidth high-frequency pulsed

light instead of radio waves and microwaves.

Such systems use modulated light wavelengths emitted (and

received) by a variety of suitably adapted standard sources,such as indoor and outdoor lighting, displays, illuminated signs,

televisions, computer screens, digital cameras and digital

cameras on mobile phones for communication purposes,

primarily through the use of white Light Emitting Diodes

(LEDs).

Their use may help provide both partial and full solutions

to a number of technological problems: increasingly limited

availability of conventional bandwidths for electronic equipment;

possible communications interference with sensitive electrical

equipment; data security; and perceived negative health

consequences when exposed to raised radiofrequency andmicrowave levels.

III. LED (Light Emitting Diode) VLC

TECHNOLOGY

LED (Light Emitting Diode) Visible Light Communications (VLC)

systems are recognized as creating a possible valuable addition to

future generations of technology, which have the potential to

utilize light for the purposes of advanced technological

communication at ultra high speed surpassing that of current

wireless systems. One of the goals of researchers is to allow 100

megabits of data transference per second (Mbps) in offices and

homes by modulation of light from upgraded lighting systems.If it is developed correctly, the possibility exists that many of the

problems associated with present day infrared, radiowave and

microwave communications systems (and lighting technology)

could be at least partially resolved, and a more biologically

friendly system made available to industries and the general

public.

A further advantage is that VLC systems can transmit data more

securely over short distances than radiofrequency/microwave

communications devices whose signals can be easily detected

outside the rooms and buildings they originate in.

A. Visible Light Communication using

White LEDs

Fig. 2: Possible future deployment scenario


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In the 21th century, a wide variety of multimedia services will

be available at any place, and at any time. For this reason the

demand for broadband wireless data transmission is

increasing. Radio and optical wireless transmissions are both

possible candidates to realize such wireless systems. However,

for radio frequency transmission, the availability of free radio

frequency resources is becoming a limiting factor. Therefore,

alternative wireless transmission means have to be explored.

Visible light communication utilizing white light emitting diodes(LEDs) is a potential alternative to realize such high speed

wireless links. However, only little research has been done in

this area, and many open questions exist. The optical channel is a

challenging medium and there are numerous considerations

which must be taken into account when designing high speed

indoor optical wireless links. Non-directed line-of-sight (LOS)

and diffuse links are accompanied with a high optical path loss

and multipath propagation. Multipath propagation results in

multipath dispersion giving rise to inter-symbol interference

(ISI), which is one of the primary impairments to achieving

high speed communication. In addition to this, wireless

optical communication links must be capable of operating inenvironments where intense ambient light levels exist, which

degrades link performance. Finally, all these factors must be

overcome without breaching eye safety regulations, which place

limitations on the maximum optical transmit power which can

be used. The research project will investigate the properties of

white LEDs when they are used as optical transmitters and

examine new optical wireless transmission techniques to

overcome existing problems.

B. Visible Light Communications opportunity

equals10,000

!

The answer to life, the universe and everything might be 42,

but I will use some pseudo mathematics to show that the

VLC opportunity equates to 10,000!

1. There are approximately 1.4 million cellular base station

masts worldwide (Masts).

2. There are approximately 14 billion light bulbs in the

world (Bulbs).

Each light bulb represents a future opportunity to introduce

VLC technology and turn each light bulb into a miniature base

stations (no mast required). I therefore suggest that the VLC

opportunity (VLC) can be calculated as:

Now lets consider the opportunity from another dimension,

that of the available spectrum. Wireless radio transmission

uses frequencies from a few kHz up to 10s of GHz. If we dont

consider fixed satellite links as wireless (no mobility) then

wireless communications extends up to about 40GHz. So:

3. Wireless radio bandwidth ~ 40GHz (Radio)

Now consider the visible light spectrum which extends from


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400THz to 790THz. So:

Visible bandwidth ~ (790-400)THz = 390THz

(Visible)

Therefore the VLC opportunity in terms of available bandwidth

can be calculated as:

So the opportunity of using VLC can be considered to be four

orders of magnitude greater than alternatives when measured

in terms of access points relative to cellular access points, or

when measured in terms of the available bandwidth relative to

radio. Of course the key message is not really that VLC=10,000, itis that the opportunity for VLC is immense, but the real

challenge may lie in making VLC access points 10,000 times

cheaper than a cellular base station. However, if you consider

that the average cellular base station might cost $10,000, this

challenge does look realistic.

C. How Green is Visible Light

Communications?

To address VLCs green credentials I firstconsider what makes

it green. Here are my top 3 reasons:

1. VLC helps stimulate the demand for LED lighting and white

LED bulbs and fixtures are now highly efficient. If we were

all to switch over to LED illumination the energy savings

would be colossal.

2. The power consumed by VLC in transmitting data is small

compared to RF communications equipment.

3. VLC eliminates the need for some items of communications

equipment, this too reduces the energy required to produce

the communications equipment.

So having considered why VLC is green from a qualitative point

we are left with the trickier task of determining how white it

could be based on a quantitative analysis. To do this we must

make a few assumptions and then calculate the savings ingreen house gasses (based on CO2 emissions) resulting from a

switch to VLC solutions.

We will make the assumption that white LED VLC technology

will be used in place of incandescent lamps and Wi-Fi, we will

also assume that the savings in energy will savings will be

obtained generating less electricity from fossil fuels. From the

qualitative analysis we can identify three areas where energy

can be saved.

1. Operational energy savings by using white LED compared

with incandescent.

2. Operational energy savings by using VLC instead of Wi-

Fi

3. Embodied energy savings by manufacturing white LED

VLC lamps instead of incandescent light bulbs and Wi-Fi

access points.

I have calculated the operational energy of a typical white LED

lamp as 18kWhr per year based on a duty cycle of 4 hours per

day. The energy used in a Wi-Fi per year is 53kWhr as compared

to 3kWhr of additional energy required for VLC over and above

the energy required for illumination.

The embodied energy per year in a Wi-Fi (based on an average

lifetime of 3 years) is 16kWhr. While the embodied energy in a

VLC light bulb and transceiver circuit has been estimated at1.0kWhr (based on a lifetime of 10 years). The embodied

energy in an incandescent bulb is 0.4kWhr based on 0.8 year

lifetime.

Given that there are 14 billion incandescent light bulbs and

300 million Wi-Fis, replacing all of these by VLC lamps would

save about 897 billion kWhr of energy.

This is laid out in the table below:


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AnnualEnergy

Embodied

EnergyVolume Total

Energy

Incandescent

bulb89.3

kWhr0.4 kWhr 14 billion 1226 b

kWhr

Wi-Fi 53kWhr

16 kWhr 300 million 21 bkWhr

VLC 21kWhr

1.0 kWhr 14 billion 308 bkWhr

Total Savings 897 bkWhr

2

:

will require cooperation and agreement from a number of

different bodies. However, success should bring a low-cost high

data-rate infrastructure that can increase wireless capacity

substantially.

This is equivalent to a reduction of 870 million tonnes of CO

per year if less fossil fuel is used to generate the electricity.

Alternatively we can consider the savings in terms of nuclear

power stations. A modern nuclear power plant generates about

8-10 TWhr of electricity per year. So the saving is equivalent

to eliminating the need for 100 nuclear power stations!

IV. VLC

Applications

A wide range of applications would benefit from using white

LEDs Visible Light Communications:

1. WiFi Spectrum Relief - Providing additional bandwidth

in environments where licensed and/or unlicensed

communication bands are congested

2. Smart Home Network Enabling smart domestic/industrial

lighting; home wireless communication including media

streaming and internet access3. Commercial Aviation Enabling wireless data

communications such as in-flight entertainment and

personal communications

4. Hazardous Environments- Enabling data communications

in environments where RF is potentially dangerous, such

as oil & gas, petrochemicals and mining

5. Hospital and Healthcare Enabling mobility and data

communications in hospitals

6. Defence and Military Applications Enabling high data

rate wireless communications within military vehicles and

aircraft

7. Corporate and Organisational Security Enabling the use

of wireless networks in applications where (WiFi) presents a

security risk

8. Underwater Communications Enabling communications

between divers and/or remote operated vehicles

9. Location-Based Services Enabling navigation and

tracking inside buildings.

V.

Conclusion

VLC based on white LEDs appears to be an important potential

component in expanding useable bandwidth, protectingsensitive electrical equipment and data, creating more

biologically friendly communications technology, and helping

develop seamless computing applications.

VLC offers the advantage of a communications channel in an

unregulated, unlicensed part of the electromagnetic spectrum.

In applications where a visible beam is desirable for security it

can provide high data rates. There are a number of technical

and regulatory challenges to be overcome; rapid technicalprogress is being made, but the challenges of standardization


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