LIFI

LIFI Prof. Harald Haas is a technology of high brightness light emitting diodes(LED).It is bidirectional ,high speed and fully networked wireless communication.   

LiFi is designed to use LED light bulbs similar to those currently in use in many energy-conscious homes and offices. However, LiFi bulbs are outfitted with a chip that modulates the light imperceptibly for optical data transmission. LiFi data is transmitted by the LED bulbs and received by photoreceptors.

LiFi's early developmental models were capable of 150 megabits-per-second (Mbps). Some commercial kits enabling that speed have been released. In the lab, with stronger LEDs and different technology, researchers have enabled 10 gigabits-per-second (Gbps), which is faster than 802.11ad. 

Benefits of LiFi:

·        Higher speeds than Wi-Fi.

·        10000 times the frequency spectrum of radio.

·        More secure because data cannot be intercepted without a clear line of sight.

·        Prevents piggybacking.

·        Eliminates neighboring network interference.

·        Unimpeded by radio interference.

·        Does not create interference in sensitive electronics, making it better for use in environments like hospitals and aircraft.

By using LiFi in all the lights in and around a building, the technology could enable greater area of coverage than a single WiFi router. Drawbacks to the technology include the need for a clear line of sight, difficulties with mobility and the requirement that lights stay on for operation.

History

Professor Harald Haas, from the University of Edinburgh in the UK, is widely recognised as the original founder of Li-Fi. He coined the term Li-Fi and is Chair of Mobile Communications at the University of Edinburgh and co-founder of pureLiFi

The general term visible light communication (VLC), includes any use of the visible light portion of the electromagnetic spectrum to transmit information. The D-Light project at Edinburgh's Institute for Digital Communications was funded from January 2010 to January 2012.^[20] Haas promoted this technology in his 2011 TED Global talk and helped start a company to market it.^[21] PureLiFi, formerly pureVLC, is an original equipment manufacturer(OEM) firm set up to commercialize Li-Fi products for integration with existingLED-lighting systems.^[22][23]

In October 2011, companies and industry groups formed the Li-Fi Consortium, to promote high-speed optical wireless systems and to overcome the limited amount of radio-based wireless spectrum available by exploiting a completely different part of the electromagnetic spectrum.^[24] A number of companies offer uni-directional VLC products which is not the same as Li-Fi.

VLC technology was exhibited in 2012 using Li-Fi.^[25] By August 2013, data rates of over 1.6 Gbit/s were demonstrated over a single color LED.^[26] In September 2013, a press release said that Li-Fi, or VLC systems in general, do not require line-of-sight conditions.^[27] In October 2013, it was reported Chinese manufacturers were working on Li-Fi development kits.^[28]

In April 2014, the Russian company Stins Coman announced the development of a Li-Fi wireless local network called BeamCaster. Their current module transfers data at 1.25 gigabytes per second but foresee boosting speeds up to 5 GB/second in the near future

Standards[edit]

Like Wi-Fi, LiFi is wireless and uses similar 802.11 protocols; but it usesvisible light communication (instead of radio frequency waves), which has much wider bandwidth.

One part of VLC is modeled after communication protocols established by theIEEE 802 workgroup. However, the IEEE 802.15.7 standard is out-of-date, it fails to consider the latest technological developments in the field of optical wireless communications, specifically with the introduction of opticalorthogonal frequency-division multiplexing (O-OFDM) modulation methods which have been optimized for data rates, multiple-access and energy efficiency.^[30] The introduction of O-OFDM means that a new drive for standardization of optical wireless communications is required.

Nonetheless, the IEEE 802.15.7 standard defines the physical layer (PHY) and media access control (MAC) layer. The standard is able to deliver enough data rates to transmit audio, video and multimedia services. It takes into account optical transmission mobility, its compatibility with artificial lighting present in infrastructures, and the interference which may be generated by ambient lighting. The MAC layer permits using the link with the other layers as with the TCP/IP protocol.^{[citation needed]}

The standard defines three PHY layers with different rates:

·         The PHY I was established for outdoor application and works from 11.67 kbit/s to 267.6 kbit/s.

·         The PHY II layer permits reaching data rates from 1.25 Mbit/s to 96 Mbit/s.

·         The PHY III is used for many emissions sources with a particular modulation method called color shift keying (CSK). PHY III can deliver rates from 12 Mbit/s to 96 Mbit/s.^[31]

The modulation formats recognized for PHY I and PHY II are on-off keying(OOK) and variable pulse position modulation (VPPM). The Manchester coding used for the PHY I and PHY II layers includes the clock inside the transmitted data by representing a logic 0 with an OOK symbol "01" and a logic 1 with an OOK symbol "10", all with a DC component. The DC component avoids light extinction in case of an extended run of logic 0's.^{[citation needed]}

The first VLC smartphone prototype was presented at the Consumer Electronics Show in Las Vegas from January 7–10 in 2014. The phone uses SunPartner's Wysips CONNECT, a technique that converts light waves into usable energy, making the phone capable of receiving and decoding signals without drawing on its battery.^[32][33] A clear thin layer of crystal glass can be added to small screens like watches and smartphones that make them solar powered. Smartphones could gain 15% more battery life during a typical day. This first smartphones using this technology should arrive in 2015. This screen can also receive VLC signals as well as the smartphone camera.^[34]The cost of these screens per smartphone is between $2 and $3, much cheaper than most new technology.^[35]

Philips lighting company has developed a VLC system for shoppers at stores. They have to download an app on their smartphone and then their smartphone works with the LEDs in the store. The LEDs can pinpoint where they are located in the store and give them corresponding coupons and information based on which aisle they are on and what they are looking at.^[36]

Technology details[edit]

Facebook Official Page LIFI TECHNOLOGYThis OWC technology uses light from light-emitting diodes (LEDs) as a medium to deliver networked, mobile, high-speed communication in a similar manner to Wi-Fi.^[3] Li-Fi could lead to the Internet of Things, which is everything electronic being connected to the internet, with the LED lights on the electronics being used as Li-Fi internet access points.^[4] The Li-Fi market is projected to have a compound annual growth rate of 82% from 2013 to 2018 and to be worth over $6 billion per year by 2018.^[5]

Visible light communications (VLC) works by switching bulbs on and off withinnanoseconds,^[6] which is too quickly to be noticed by the human eye. Although Li-Fi bulbs would have to be kept on to transmit data, the bulbs could be dimmed to the point that they were not visible to humans and yet still functional.^[7] The light waves cannot penetrate walls which makes a much shorter range, though more secure from hacking, relative to Wi-Fi.^[8][9] Direct line of sight isn't necessary for Li-Fi to transmit a signal; light reflected off the walls can achieve 70 Mbit/s.^[10][11]

Li-Fi has the advantage of being useful in electromagnetic sensitive areas such as in aircraft cabins, hospitals and nuclear power plants^{[citation needed]}without causing electromagnetic interference.^[8][9] Both Wi-Fi and Li-Fi transmit data over the electromagnetic spectrum, but whereas Wi-Fi utilises radio waves, Li-Fi uses visible light. While the US Federal Communications Commission has warned of a potential spectrum crisis because Wi-Fi is close to full capacity, Li-Fi has almost no limitations on capacity.^[12] The visible light spectrum is 10,000 times larger than the entire radio frequency spectrum.^[13]Researchers have reached data rates of over 10 Gbit/s, which is more than 250 times faster than superfast broadband.^[14][15] Li-Fi is expected to be ten times cheaper than Wi-Fi.^[7] Short range, low reliability and high installation costs are the potential downsides.^[5][6]

PureLiFi demonstrated the first commercially available Li-Fi system, the Li-1st, at the 2014 Mobile World Congress in Barcelona.^[16]

Bg-Fi is a Li-Fi system consisting of an application for a mobile device, and a simple consumer product, like an IoT (Internet of Things) device, with color sensor, microcontroller, and embedded software. Light from the mobile device display communicates to the color sensor on the consumer product, which converts the light into digital information. Light emitting diodes enable the consumer product to communicate synchronously with the mobile device. ^{[17][18] [19]}

Why only vlc

·        Gama rays cant be used as they could be

·        X rays have similar health issues

·        Ultraviolet light is good for place without people, but otherwise dangerous for the human body

·        Infra red, due to eye safety regulation can only bse used with low powe.

·         

How does lifi work?

This digital data in the form of light. On the other end this light is detected by photosensitive devices.next this light is amplified and processed and then fed to the device. The heart of this technology is new generation high brightness LEDs.If led is on we transmit signal 1 and if the led is off, we transmit signal 0.a controller is connected at the back side of these led bulbs to code data to these leds

Parameters	Light fidelity	Wireless fidelity
Speed for data transfer	Faster transfer speed(>1Gbps)	Data transfer speed (150Mbps)
Medium through which data transfers occurs	Used light as a carier	Used radio spectrum
Spectrum range	Visible light spectrum has 10,000 time broad spectrum in comparison to radio frequency	Radio frequency spectrum range less thean visible light spectrum.
Cost	Cheaper than wifi because free band doesn’t need license

 Abstract of Li-Fi Technology
Whether you’re using wireless internet in a coffee shop, stealing it from the guy next door, or competing for bandwidth at a conference, you’ve probably gotten frustrated at the slow speeds you face when more than one device is tapped into the network. As more and more people and their many devices access wireless internet, clogged airwaves are going to make it increasingly difficult to latch onto a reliable signal.
But radio waves are just one part of the spectrum that can carry our data. What if we could use other waves to surf the internet? One German physicist,DR. Harald Haas, has come up with a solution he calls “Data Through Illumination”—taking the fiber out of fiber optics by sending data through an LED light bulb that varies in intensity faster than the human eye can follow. It’s the same idea behind infrared remote controls, but far more powerful.
Haas says his invention, which he calls D-Light, can produce data rates faster than 10 megabits per second, which is speedier than your average broadband connection. He envisions a future where data for laptops, smartphones, and tablets is transmitted through the light in a room. And security would be a snap—if you can’t see the light, you can’t access the data.
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. The term Li-Fi was coined by Prof. Haas when he amazed people by streaming high-definition video from a standard LED lamp, at TED Global in July 2011. Li-Fi is now part of the Visible Light Communications (VLC) PAN IEEE 802.15.7 standard.
“Li-Fi is typically implemented using white LED light bulbs. These devices are normally used for illumination by applying a constant current through the LED. However, by fast and subtle variations of the current, the optical output can be made to vary at extremely high speeds. Unseen by the human eye, this variation is used to carry high-speed data,” says Dr Povey, , Product Manager of the University of Edinburgh's Li-Fi Program ‘D-Light Project’.


Introduction
In simple terms, Li-Fi can be thought of as a light-based Wi-Fi. That is, it uses light instead of radio waves to transmit information. And instead of Wi-Fi modems, Li-Fi would use transceiver-fitted LED lamps that can light a room as well as transmit and receive information. Since simple light bulbs are used, there can technically be any number of access points.
This technology uses a part of the electromagnetic spectrum that is still not greatly utilized- The Visible Spectrum. Light is in fact very much part of our lives for millions and millions of years and does not have any major ill effect. Moreover there is 10,000 times more space available in this spectrum and just counting on the bulbs in use, it also multiplies to 10,000 times more availability as an infrastructure, globally.
It is possible to encode data in the light by varying the rate at which the LEDs flicker on and off to give different strings of 1s and 0s. The LED intensity is modulated so rapidly that human eyes cannot notice, so the output appears constant.
More sophisticated techniques could dramatically increase VLC data rates. Teams at the University of Oxford and the University of Edinburgh are focusing on parallel data transmission using arrays of LEDs, where each LED transmits a different data stream. Other groups are using mixtures of red, green and blue LEDs to alter the light's frequency, with each frequency encoding a different data channel.
Li-Fi, as it has been dubbed, has already achieved blisteringly high speeds in the lab. Researchers at the Heinrich Hertz Institute in Berlin, Germany, have reached data rates of over 500 megabytes per second using a standard white-light LED. Haas has set up a spin-off firm to sell a consumer VLC transmitter that is due for launch next year. It is capable of transmitting data at 100 MB/s - faster than most UK broadband connections.


Genesis of LI-FI
Harald Haas, a professor at the University of Edinburgh who began his research in the field in 2004, gave a debut demonstration of what he called a Li-Fi prototype at the TEDGlobal conference in Edinburgh on 12th July 2011. He used a table lamp with an LED bulb to transmit a video of blooming flowers that was then projected onto a screen behind him.
During the event he periodically blocked the light from lamp to prove that the lamp was indeed the source of incoming data. At TEDGlobal, Haas demonstrated a data rate of transmission of around 10Mbps -- comparable to a fairly good UK broadband connection. Two months later he achieved 123Mbps.


How Li-Fi Works?
Li-Fi is typically implemented using white LED light bulbs at the downlink transmitter. These devices are normally used for illumination only by applying a constant current. However, by fast and subtle variations of the current, the optical output can be made to vary at extremely high speeds.
This very property of optical current is used in Li-Fi setup. The operational procedure is very simple-, if the LED is on, you transmit a digital 1, if it’s off you transmit a 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. All one has to do is to vary the rate at which the LED’s flicker depending upon the data we want to encode.
Further enhancements can be made in this method, like using an array of LEDs for parallel data transmission, or using mixtures of red, green and blue LEDs to alter the light’s frequency with each frequency encoding a different data channel. Such advancements promise a theoretical speed of 10 Gbps – meaning one can download a full high-definition film in just 30 secon


Application of Li-Fi Technology
You Might Just Live Longer
You Might Just Live Longer For a long time, med ical technology has lagged behind the rest of the wireless world. Operating rooms do not allow Wi-Fi over radiation concerns, and there is also that whole lack of dedicated spectrum. While Wi-Fi is in place in many hospitals, interference from cell phones and computers can block signals from monitoring equipment.
Li-Fi solves both problems: lights are not only allowed in operating rooms, but tend to be the most glaring (punintended) fixtures in the room. And, as Haas mentions in his TED Talk,Li-Fi has 10,000 times the spectrum of Wi-Fi, so maybe we can, I dunno, delegate red light to priority medical data. Code Red!
Airlines
Airline Wi-Fi. Ugh. Nothing says captive audience like having to pay for the "service" of dialup speed Wi-Fi on the plane. And don’t get me started on the pricing.
The best I’ve heard so far is that passengers will "soon" be offered a "high-speed like" connection on some airlines. United is planning on speeds as high as 9.8 Mbps per plane.
Uh, I have twice that capacity in my living room. And at the same price as checking a bag, I expect it. Li-Fi could easily introduce that sort of speed to each seat's reading light. I’ll be the guy WoWing next to you. Its better than listening to you tell me about your wildly successful son, ma’am.
Smarter Power Plants
Wi-Fi and many other radiation types are bad for sensitive areas. Like those surrounding power plants. But power plants need fast, inter-connected data systems to monitor things like demand, grid integrity and (in nuclear plants) core temperature. The savings from proper monitoring at a single power plant can add up to hundreds of thousands of dollars.
Li-Fi could offer safe, abundant connectivity for all areas of these sensitive locations. Not only would this save money related to currently implemented solutions, but the draw on a power plant’s own reserves could be lessened if they haven’t yet converted to LE
D lighting.
Undersea Awesomeness
Underwater ROVs, those favourite toys of treasure seekers and James Cameron,operate from large cables that supply their power and allow them to receive signals from their pilots above. ROVs work great, except when the tether isn’t long enough to explore an area, or when it gets stuck on something.

If their wires were cut and replaced with light —say from a submerged, high-powered lamp —then they would be much freer to explore. They could also use their headlamps to communicate with each other, processing data autonomously and referring findings periodically back to the surface, all the while obtaining their next batch of orders.

It Could Keep You Informed and Save Lives

Say there’s an earthquake in New York. Or a hurricane. Take your pick —it’s a wacky city. The average New Yorker may not know what the protocols are for those kinds of disasters. Until they pass under a street light, that is.

Remember, with Li-Fi, if there’s light, you’re online. Subway stations and tunnels, common dead zones for most emergency communications, pose no obstruction. Plus, in times less stresssing cities could opt to provide cheap high speed Web access to every street corner.

How it is different?

Li-Fi technology is based on LEDs for the transfer of data. The transfer of the data can be with the help of all kinds of light, no matter the part of the spectrum that they belong. That is, the light can belong to the invisible, ultraviolet or the visible part of the spectrum. Also, the speed of the internet is incredibly high and you can download movies, games, music etc in just a few minutes with the help of this technology.
Also, the technology removes limitations that have been put on the user by the Wi-Fi. You no more need to be in a region that is Wi-Fi enabled to have access to the internet. You can simply stand under any form of light and surf the internet as the connection is made in case of any light presence. There cannot be anything better than this technology.


Uses in Various Areas
Can be used in the places where it is difficult to lay the optical fiber like hospitals. In operation theatre LiFi can be used for modern medical instruments. In traffic signals LiFi can be used which will communicate with the LED lights of the cars and ccident numbers can be decreased.
Thousand and millions of street lamps can be transferred to LiFi lamps to transfer data. In aircraft LiFi can be used for data transmission.It can be used in petroleum or chemical plants where other transmission or frequencies could be hazardous.


Advantages of LI-FI
 Li-Fi can solve problems related to the insufficiency of radio frequency bandwidth because this technology uses Visible light spectrum that has still not been greatly utilized.
 High data transmission rates of up to 10Gbps can be achieved.
 Since light cannot penetrate walls, it provides privacy and security that Wi-Fi cannot.
 Li-Fi has low implementation and maintenance costs.
 It is safe for humans since light, unlike radio frequencies, cannot penetrate human body. Hence, concerns of cell mutation are mitigated.
Disadvantage of LI-FI
 Light can't pass through objects.
 A major challenge facing Li-Fi is how the receiving device will transmit back to transmitter.
 High installation cost of the VLC systems.
 Interferences from external light sources like sun, light, normal bulbs, opaque



Conclusion
The possibilities are numerous and can be explored further. If his technology can be put into practical use, every bulb can be used something like a Wi-Fi hotspot to transmit wireless data and we will proceed toward the cleaner, greener, safer and brighter future.
The concept of Li-Fi is currently attracting a great deal of interest, not least because it may offer a genuine and very efficient alternative to radio-based wireless. As a growing number of people and their many devices access wireless internet, the airwaves are becoming increasingly clogged, making it more and more difficult to get a reliable, high-speed signal.
This may solve issues such as the shortage of radio-frequency bandwidth and also allow internet where traditional radio based wireless isn’t allowed such as aircraft or hospitals. One of the shortcomings however is that it only work in direct line of sight.

Li-Fi Technology in Wireless Communication

ABSTRACT
Li-Fi or Light Fidelity refers to 5G Visible Light Communication systems using light-emitting diodes as a medium to high-speed communication in a similar manner as Wi-Fi.[13] In the days where internet has become a major demand, people are in a search for Wi-Fi hotspots. Li-Fi or New Life of data communication is a better alternative to Wi-Fi in wireless communication. This paper proposes a survey on Li-Fi Technology. The Li-fi technology was invented by Professor Harald Hass of University of Edinburgh. Li-Fi has more capacity in terms of bandwidth in visible region therefore it does not poke its nose in other communications which uses radio frequency range, without taking its frequency bands. Li-Fi has thousand times greater speed than Wi-Fi and provides security as the visible light is unable to penetrate through the walls, which propose a new era of wireless communication.[18] The concept of Li-Fi is data communication on fast flickering of light which is not detected by human eye but it is focused on photo detector which converts the on-off state into binary digital data. It has gained a huge popularity in two years of its invention. Such technology has brought not only greener but safer and cheaper future of communication.[14]

KEYWORDS: LED (Light Emitting Diode),Wi-Fi (Wireless Fidelity),Li-Fi (Light Fidelity),VLC (Visible Light Communication),RF (Radio Frequency).

2) INTRODUCTION
The concept of Li-fi is currently attracting a great deal of interest, not least because it offers a genuine and very efficient alternative to RF.As a growing number of people and their recent device access wireless internet, the airwaves are becoming increasingly clogged and unavailability of free bandwidths to every device, making it more and more difficult to get a reliable, high speed signal. The opportunity to exploit a completely different part of the electromagnetic spectrum is very appealing. Li-Fi has other advantages over Wi-Fi, such as safe to use at nuclear power plants, thermal power stations where Wi-Fi cannot be used.[16] In such stations RF waves can be harmful and can cause accident, to communicate in such regions only visible light spectrum can be safe. Apart from adverse regions Li-fi can also be used in all places where Wi-Fi can be used. Li-fi is present wherever there is availability of light, in turn eradicating the necessity of having hot-spots only at selected places. There are four criterions to judge on the working of Li-Fi and Wi-Fi that is, capacity, efficiency, availability and security. Both Li-fi and Wi-Fi uses electromagnetic spectrum for data transmission, but whereas Wi-Fi utilizes radio waves, Li-Fi uses visible light communication in the range of 100Mbps. The present paper deals with the VLC which provide a wide and fast data rate like 500Mbps. In this paper, the comparison is made between Wi-Fi and Li-Fi technology. This paper also discusses the working, implementation and improvements in Li-fi technology.[18]

This paper is organized as follows. Section 2 discusses the introduction to Li-fi and Wi-fi. In section 3, the history and future scope of Li-Fi technology has been discussed. Section 4 discusses LI-Fi communication with other devices. Working of LI-Fi technology is discussed in section 5. In section 6, physical layer, modulation formats and frequency spectrum that is related with Li-Fi communication has been discussed. Section 7 deals with the Li-Fi system which was designed by Chinese professor Chi Nan. In Section 8, comparison is made between the Li-Fi, Wi-Fi and bluetooth technology. Finally, section 9 presents conclusion.

3) HISTORY AND FUTURE OF LI-FI
The technology underpinning Li-Fi was pioneered by German Physicist Harald Hass, currently based at University of Edinburgh in UK. Haas coined the term Li-Fi(Light Fidelity) in 2011 in the context of a talk presenting the new technology at the TED (Technology Entertainment and Design) Global conference.[7][17] The word quickly entered common parlance as an instantly recognizable alternative to Wi-Fi. Both terms are examples of abbreviations linguists sometimes describe as clipped forms( i.e. Wi-Fi=wireless fidelity, Li-Fi= light fidelity).[15]Haas’s research project, originally known as D-light(short for Data Light), is now set to launch a prototype Li-Fi application under the name of newly-formed company VLC(Visible Light Communication) Ltd., which was setup to commercialize the technology.[16]

The Li-Fi technology can be used for various purposes, it matters the data transmission through LEDs thus all the screens which illuminate light can be served as a platform for data communication. The screen of the mobile phone, television, bulbs can act as a source of light. On the other hand, the receiving platform, the photo detector can be replaced by a camera in mobile phone for scanning and retrieving data. Its other applications are Li-fi for desktops, smartcard Li-fi, Li-fi for schools, hospitals, Li-fi in cities, smart guides, museums, hotels, fairgrounds, events indoor and LBS(Location-based Services), access control and identification crisis, malls, airport and dangerous environments like thermal power plants.[8][11]

4) OUTLOOK OF LI-FI

In figure 1.1 shows how the Li-Fi cloud will get communicated with others devices. Li-fi using visible light instead of gigahertz radiowaves.Currently there are 1.4 billion base stations which consume more energy and its efficiency is less than 5 percent and we have a total of approximately 5 million mobile phones which transfer more than 600 terabytes of data every month which showcase the fact that wireless has become utility. Li-Fi is free of complex network of wires and box which is installed in the case of Wi-Fi. This is a digital system that translates the classic binary language of zeros and ones in light pulses off or on, respectively, through tiny LED bulbs on and off a million of times per second. The pioneers of data transmission through blinking of LEDs can create wireless internet access with data transmission speeds of close to 10Gbit/s, theoretically, allowing a high-definition film to be downloaded in 30 seconds which is 250 times faster than superfast broadband. These benefits come at a fivefold transits currently offering fiber optic lines, to benefit from this technology requires a luminous router (which can adhere cheaply and easily into any conventional electric bulb) which is capable of emitting the binary signal.[12][15]

5) HOW THE BASIC LIGHT IS CONVERTED INTO ELECTRICITY

Vacuum equations, electromagnetic waves and speed of light

Figure 1.2 is a 3D diagram shows a plane linearly polarized wave propagating from left to right with the same wave equations from left to right

Where E = E₀ sin(−ωt + k ⋅ r) and B = B₀ sin(−ωt + k ⋅ r)

In a region with no charges (ρ = 0) and no currents (J = 0), such as in a vacuum, Equation 1 is reduced Maxwell’s equations:

…(1)

Taking the curl (∇×) of the curl equations, and using the curl of the curl identity ∇×(∇×X) = ∇(∇·X) − ∇²X we obtain the wave equations (2)

…(2)

Which identify

C is the speed of light in free space. In materials with relative permittivity ε_r and relative permeability μ_r, the phase velocity of light becomes

which is usually less than c.

In addition, E and B are mutually perpendicular to each other and the direction of wave propagation, and are in phase with each other. A sinusoidal plane wave is one special solution of these equations. Maxwell’s equations explain how these waves can physically propagate through space. The changing magnetic field creates a changing electric field through Faraday’s law. In turn, that electric field creates a changing magnetic field through Maxwell’s correction to Ampère’s law. This perpetual cycle allows these waves, now known as electromagnetic radiation, to move through space at velocity c.

BOUND CURRENT AND CHARGE

Figure1.3 Left: schematic view of how an assembly of microscopic dipoles produces opposite surface charges as shown at top and bottom. Right: How an assembly of microscopic current loops add together to produce a macroscopically circulating current loop. Inside the boundaries, the individual contributions tend to cancel, but at the boundaries no cancelation occurs.

When an electric field is applied to a dielectric material its molecules respond by forming microscopic electric dipoles – their atomic nuclei move a tiny distance in the direction of the field, while their electrons move a tiny distance in the opposite direction. This produces a macroscopic bound charge in the material even though all of the charges involved are bound to individual molecules. For example, if every molecule responds the same, similar to that shown in the figure, these tiny movements of charge combine to produce a layer of positive bound charge on one side of the material and a layer of negative charge on the other side. The bound charge is most conveniently described in terms of the polarization P of the material, its dipole moment per unit volume. If P is uniform, a macroscopic separation of charge is produced only at the surfaces where P enters and leaves the material. For non-uniform P, a charge is also produced in the bulk.

Somewhat similarly, in all materials the constituent atoms exhibit magnetic moments that are intrinsically linked to the angular momentum of the components of the atoms, most notably their electrons. The connection to angular momentum suggests the picture of an assembly of microscopic current loops. Outside the material, an assembly of such microscopic current loops is not different from a macroscopic current circulating around the material’s surface, despite the fact that no individual magnetic moment is traveling a large distance. These can be described using the magnetization M.

The very complicated and granular bound charges and bound currents, therefore can be represented on the macroscopic scale in terms of P and M which average these charges and currents on a sufficiently large scale so as not to see the granularity of individual atoms, but also sufficiently small that they vary with location in the material. As such, the Maxwell’s macroscopic equations ignores many details on a fine scale that can be unimportant to understanding matters on a gross scale by calculating fields that are averaged over some suitable volume.[21] This Table 1 shows Maxwell’s equations.

6) WORKING OF LI-FI

In Figure 1.4, shows the binary data are captured by few light receptors are required, and are installed on all types of connected devices, from computers to tablets, to phones, televisions or appliances. Matter experts make clear that the light pulses are imperceptible to the human eye, without causing damage or discomfort of any kind. In addition, any lamp or flashlight can become a hotspot. How Li-fi works is simple: You have a light on one end (an LED), and a photodetector (light sensor) on the other. If the LED is ON, the photo detector registers a binary one;otherwise it’s a binary zero. Flash the LED enough times and you build up a message. Use an array of LEDs, and perhaps a few different colors, and very soon you are dealing with data rates in the range of hundreds or megabits per second, this is accomplished by the flickering of LED light bulbs to create binary code (on = 1, off = 0), and is done at higher rates than the human eye can detect. The more LEDs in your lamp, the more data it can process.[10]

Figure 1.5 shows brief connection of internet with LED and information retrieved on the computer. One LED transfers data at a slower rate, so millions of LEDs with one micron size are installed in the bulb. The reduction of size of LEDs does not decrease its capability to transfer data or intensity on the opposite it increases the efficiency of one light bulb to transmit the data at an unexpectedly higher rates. Furthermore, these micro-LEDs are ultimately just pixels — and at one micron, these LEDs would be a lot smaller than those in your Smartphone’s retina display. You could have a huge array of these LEDs that double up as a room’s light source and a display— and provides networking capability on the side. Perhaps a next-next-generation console would communicate with your gamepad, Smartphone, and other peripherals via a Li-Fi-equipped TV. It indeed provides a highway lighting that illuminates the road, provides up-to-date traffic info/warnings, and provides internet access to your car, plus all of the devices on-board.

Figure 1.6 is the model of li-fi led lights, on a more general level; Li-Fi might be used to extend wireless networks throughout the home, workplace, and in commercial areas. Li-Fi is restricted by line of sight, so it won’t ever replace Wi-Fi, but it could augment it nicely. Instead of trying to find the perfect sweet spot for your home’s Wi-Fi router, it would be much simpler if every light in your house simply acted as a wireless network bridge. It’s shown in the figure 1.7. While Li-Fi is still in its early stages, the technology could provide an alternative to using radio waves for wireless Internet access. Currently, household Wi-Fi routers and mobile telecommunication towers depend on radio signals to send data wirelessly. But the amount of radio spectrum is limited.[12]

7) LI-FI COMMUNICATIONS

This section deals with physical layer, modulation formats and frequency spectrum that is related with Li-Fi communication. The IEEE 802.15.7 standard defines the physical layer (PHY) and media access control (MAC) layer. The standard is able to deliver enough data rates to transmit audio, video and multimedia services. It takes into account the optical transmission mobility, its compatibility with artificial lighting present in infrastructures, the deviance which may be caused by interference generated by the ambient lighting. The MAC layer allows using the link with the other layers like the TCP/IP protocol. The standard defines three PHY layers with different rates:

• The PHY I was established for outdoor application and works from11.67 kbit/s to 267.6 kbit/s.
• The PHY II layer allows to reach data rates from 1.25 Mbit/s to 96 Mbit/s.
• The PHY III is used for many emissions sources with a particular modulation method called color shift keying (CSK). PHY III can deliver rates from 12 Mbit/s to 96 Mbit/s.
The modulation formats recognized for PHY I and PHY II are the coding on-off keying (OOK) and variable pulse position modulation (VPPM). The Manchester coding used for the PHY I and PHY II layers include the clock inside the transmitted data by representing a logic 0 with an OOK symbol “01” and a logic 1 with an OOK symbol “10”, all with a DC component. The DC component avoids the light extinction in case of an extended line of logic 0. Optical Orthogonal Frequency Division Multiplexing (O-OFDM) modulation methods which have been optimized for data rates, multiple-access and energy efficiency which can be used for Li-Fi communication. The new high-speed optical wireless models used in both indoors and outdoors. The Li-Fi provides resources for OEM [Original Equipment Manufacturer] and ODM [Original Design Manufacturers]developers to create exciting new products. With the emergence of high-speed cable connections like Thunderbolt and USB 3.0, the stage is set for a wireless equivalent. While Wi-Fi is very popular for pervasive 100+ Mbps service, multi-Gigabit short-range optical wireless interconnects provide an alternative to the proposed Gigabit RF solution. Some of the advantages of optical wireless communications include:
a) Scalability to 10+ Gbps, b) A wide variety of beaming angles and distances,
c) No spectrum license required, d) High physical link security,
e) No RF interference and f) No possible harmful RF radiation.

The technology is ideal for wireless docking, data links with kiosks and mobile displays, medium-range beaming, data showers and optical cellular networks. Users will be able to enjoy a wireless RF-free user environment with data rates that can transfer a 2-hour HDTV video in less than 30 seconds and wirelessly link their bus-connected heavy-lifting peripheral cabinets located elsewhere in the room.[11]

For communication purpose light wave carry data in a fast manner, but in radio wave the data transfer rate is slow. So for that reason we are looking for light wave communication. It is shown by the figure 1.8.There is a disadvantage that light does not penetrate through the walls and no communication in darkness, so if one moves from one room to another he will need a wired bulb in that room too.[6][18]
8) LI-FI AT RETAILER’S SHOP

OLEDCOMM sold the first ever commercially available products based on Li-Fi technology, contributing hence to reduce the radio electromagnetic wave pollution. From your LED you can listen to music, play videos and ultimately connect to internet.[19] But a Professor Chi, from Fudan University showed this technology at China International Industry Fair in Shanghai. This system needed no complex Wi-Fi routers that use radio signals, but only relies on light to send and retrieve data wirelessly. Figure 1.7 shows the Li-Fi system using retail components which has been designed by Chinese professor Chi Nan . Chi’s system runs at 150Mbps by using small number of LED but the speed can be increased to the maximum of 3.5 Gbps. Both transmitter and receivers are installed with LED and chip that process the signals. As the progress is going on, the size of the system is reducing from a play station console to PC laptops. As there are several problems to be resolved there could be an estimate of another five years before the technology can enter the market as consumer products.[3][4][5]

9) COMPARISON OF WIRELESS NETWORKS

10) CONCLUSION
In this paper, a survey on Li-Fi technology has been discussed. From this 5G Li-Fi technology, we can see that the Li-Fi is an advanced approach on design, having the best ever design of internet by largely reducing the size of device which transfers data, implementation- by means of having more than 1.4 million light bulbs all over the world if replaced by such LEDS can provide feasible access, and last but not the least enormous applications compared to any other networks in various fields which cannot be imagined by on use networks. Although there are some disadvantages, but can be eliminated by careful further research. Li-Fi has provided a step forward invention in the world of growing hunger communication, this is safe to all biodiversity including humans and progressing towards a greener, cheaper and brighter future of technologies.
11) REFERENCES
1)https://www.google.co.in/search?q=comparison+between+bluetooth,+wifi,lifi&source=lnms&tbm=isch&sa=X&ei=iS64UqasBoaSrgfS8YGIBQ&ved=0CAcQ_AUoAQ&biw=1360&bih=666
2)https://www.google.co.in/search?q=electromagnetic+spectrum&source=lnms&tbm=isch&sa=X&ei=Oiq4UujkMcHorQfqgoHIBw&sqi=2&ved=0CAcQ_AUoAQ&biw=1360&bih=666#imgdii=_
3) http://recombu.com/digital/news/china-lifi-kits-150mbps-broadband-speeds-over-led-bulbs_M12309.html
4) http://seminarprojects.com/Thread-ieee-paper-on-5g-technology
5) http://seminarprojects.com/Thread-report-on-li-fi-technology
6) http://www.technewspaper.net/best-five-benefits-of-li-fi-technology/
7) http://www.youtube.com/watch?v=gjqSgsKbagQ
8) http://lificenter.net/solutions/lifi-solutions
9) http://lighting.com/led-lights-lifi/
10) http://www.dvice.com/archives/2012/08/lifi_ten_ways_i.php
11) http://en.wikipedia.org/wiki/Li-Fi
12) www.macmillandictionary.com/buzzword/entries/Li-Fi.html
13) http://www.digplanet.com/wiki/Li-Fi
14) http://www.scribd.com/doc/163399643/Researchpaper-Li-Fi-Light-Fidelity-LED-Based-Alternative
15) http://jonatasmattes.blogspot.in/2013/06/lifi-alternative-to-wifi.html
16) http://www.authorstream.com/Presentation/2anu3-1740372-li-fi-technology/
17) http://www.ted.com/talks/harald_haas_wireless_data_from_every_light_bulb.html
18) http://www.scribd.com/doc/133997630/li-fi
19) http://www.oledcom.com/
20) http://www1.frm.utn.edu.ar/teleinformatica/docs/TechBriefWireless.pdf
21) http://en.wikipedia.org/wiki/Maxwell’s_equations
22) Dr. Y.P.Singh,”Critical Technical Aspect and Extensive Research Study of the Light Fidelity”International Journal of IT, Engineering and Applied Sciences Research(IJIEASR),Volume 2, No. 9, September 2013
23) M. Thanigavel “Li-fi Technology in Wireless Communication”, International Journal of Engineering Research & Technology(IJERT),ISSN: 2278-0181,Vol. 2 Issue 10, October-2013

Visible Light (Lifi) Based Projects

1. Lifi based Blind Indoor Navigation system

Indoor navigation is convenient for everyone, and it is especially indispensable for the visually impaired. We proposed such a navigation system for the visually impaired as shown in Fig. 2 . LED lights emit visible light with location data and a embedded system or smartphone with a visible light receiver receives the data. The embedded system or smartphone calculates the optimal path to a designation and speaks to the visually impaired through a headphone.

2. Lifi based under water communication system

Information is transmitted from one point to another via modulation. Modulation,  forming  the  basis  of  communication,  is  the  process  of transmission  of  low  frequency  data  signal  with  high  frequency  carrier signal. As it could be understood from the description above, we need two signals for modulation process. These are data signal (voice, music, map, video)  to  transmit  and  high  frequency  carrier  signal.  For three reasons modulation is a necessity. First, low frequency data signal has not that much energy to travel far distances. Second, if low frequency data signal were not imposed on carrier signal, in other words if not modulated, the dimension of the antenna would be inefficiently long. It is because the dimension of the antenna is inversely proportional to frequency. Third, data signal bandwidth is  20  Hz-20  KHz  and  assuming  the  frequency  range  of  amplitude modulation is 5-10 KHz, there could be a few stations established. For these causes modulation as basis of communication is a demanding tool needed to be used.   

3.   Lifi based vehicle underground or tunnel  navigation system

The  g o a l   o f   t h i s   p r o j e c t   i s  t o   d e v e l o p   a   s m a l l ,   p o r t a -b l e   y e t   a n   i n t e l l i g e n t   a n d  r e l i a b l e   s y s t e m   f o r   e v e r y -o n e   w h i l e   r o a m i n g   a u t o n -o m o u s l y   i n   i n d o o r   u n i t  l i k e   m a l l .   N o w a d a y s   p l a c -e s   l i k e   m a l l ,   m a r k e t s ,   e t c  c o n s i s t   p o w e r   d r i v e n  LED’s  because  they  are c h e a p   a n d   p o w e r   e f f i c i e n t  a n d   l o n g   l i f e .   I t   s u p p o r t s  f o r   L i - F i   t e c h n o l o g y .   L i -F i   i s   t h e   e m e r g i n g   a r e a   o f  t e c h n o l o g y   i s   a l s o   k n o w n  a s   V i s i b l e   L i g h t   C o m m u -n i c a t i o n s   ( V L C )   . I t   i s   a l s o  k n o w n   a s   w i r e l e s s   o p t i c a l  c o m m u n i c a t i o n .   V i s i b l e  L i g h t   c o m m u n i c a t i o n   i s   a  w i r e l e s s   c o m m u n i c a t i o n  t e c h n o l o g y   t h a t   u s e s   l i g h t  t h a t     i s   v i s i b l e   t o   h u m a n s .  Li - F i   i s   t r a n s m i s s i o n   o f  d a t a   w i r e l e s s l y   t h r o u g h  L E D   l i g h t   t h a t   v a r i e s   i n -t e n s i t y   f a s t e r   t h a n   h u m a n  e y e   c a n   f o l l o w .   W h e n   t h e  p e r s o n   m o v e s   i n   a n   i n -d o o r   u n i t   ,     t h e   L i - F i   e n a -b l e d   d e v i c e s   r e c e i v e s   t h e  i n f o r m a t i o n   a b o u t   t h e  l o c a t i o n   a n d   d i r e c t i o n s . 

T h e   n a v i g a t i o n a l   i n f o r -m a t i o n   c a n   b e   s e e n   o n   a    g r a p h i c a l   L C D   o r   a n y   o t h -e r   d i s p l a y   u n i t

4.   Monitor as transmitter for Data Communication

The project is based on the next gen data transfer technique to enable transmission from the LED monitor to the devices .  The conventional methods of data transfer are via wired, infrared, blue tooth and NFC. These technologies have their own limitations which is the main reason for us to come up with this novice technology.

The principle for communication here is – encoding and decoding data via black and white color display which will flicker at very high speed. Whenever a file needs to be transmitted, it is initially selected. A mini icon of the file will be created at the right side corner of the LCD screen. This image will constantly flicker between white and black colors. The device with sensor should be brought near the mini folder of the LCD screen which will capture the encoded images and display data on hand held device.

5. LIFi Based Preventing Phishing Attacks using One Time  Password and User Machine Identification

Phishing is a type of attack in which cyber criminals tricks the victims  to  steal  their  personal  and  financial  data.  It  has  become  an  organized  criminal  activity.  Spoofed  emails claiming to be from legitimate source are crafted in a way to lead  victims  to  reveal  their  personal,  financial  data  by misdirecting them to the counterfeit website. This  research  paper  presents  a  novel  approach  to  combat  the Phishing  attacks.  An approach  is  proposed  where  user  will retrieve the one time password by LiFi Device LCD screen. After receiving the one time password the application software will create an encrypted token for the user’s computer/device for authentication.  The  encrypted  token  will  be  used  for identification,  any  time  user  wishes  to  access  the  website he/she  must  request  the  new  password.  The  one  time password  as  name  implies  will  expire  after  single  use.  The one  time  password  and  encrypted  token  is  a  smart  way  to tackle this problem.

6. Lifi enabled super market navigation system and discount information based on location

Positioning, also known as localization, is the process of determining the spatial position of an object or person. Accurate positioning is criticalfor numerous applications. The familiar GlobalPositioning System (GPS), originally a U.S. mili-tary system, is now in everyday use around the world, often in new and unexpected ways. Unfor-tunately, GPS is not suitable in many indoor sit-uations. To obtain location information using GPS, a device must be able to receive signals from a number of GPS satellites, and this is

often not possible indoors. Even when GPS posi-tioning is available, it may not be accurate enough for many indoor applications. Despite decades of research into indoor positioning using technologies such as radio systems based on wireless local area networks (LANs), there is still no system that is cheap, accurate, and widely available . The fundamental problem in radio

based systems is multipath propagation. Radio signals may reach a receiver by both direct line of sight and multiple reflected paths. This means that there is no simple and reliable way of deter mining the distance or direction of the transmitter from the received signal. The widespread introduction of white LEDs for illumination provides an unprecedented opportunity for visible light positioning (VLP) to fill this gap, and form the basis for a widely available, economical, and easy-to-use indoor system. Look up in almost any building and you will be able to see multiple light fittings, demon strating that at most indoor locations, a receiver could be designed to receive line-of-sight signals from multiple light sources. The introduction o LED lighting creates a new opportunity for creating an indoor positioning system. This was no possible with conventional lighting, but LEDs have a number of key advantages. First, LEDs can be modulated at much higher frequencies than  conventional  lighting,  so  the  signals required for positioning can readily be transmitted at frequencies that do not cause visible flick-er. Second, although LED lights are initially more expensive, they have a much longer life-time, typically several years. This means that the added cost of constructing lights with the extra functionality required for positioning will be rel-atively smaller, and the benefits longer lasting.

7. VLC based v2v ( Vehicle to vehicle communication )

Vehicular Ad hoc NETworks (VANETs) belong to a subcategory of traditional Mobile Ad hoc NETworks (MANETs). The main feature of VANETs is that mobile nodes are vehicles endowed with sophisticated “on-board” equipments, traveling on constrained paths (i.e., roads and lanes), and communicating each other for message exchange via Vehicle-to-Vehicle (V2V) communication protocols, as well as between vehicles and fixed road-side Access Points (i.e., wireless and cellular network infrastructure), in case of Vehicle-to-Infrastructure (V2I) communications .

Future networked vehicles represent the future convergence of computers, communications infrastructure, and automobiles . Vehicular communication is considered as an enabler for driverless cars of the future. Presently, there is a strong need to enable vehicular communication for applications such as safety messaging, traffic and congestion monitoring and general purpose Internet access.

Visible Lighting Communications (VLC) can provide a valid technology for communication purposes in VANETs. The use of the visible spectrum provides service in densities exceeding femtocells for wireless access. It represents a viable alternative that can achieve high data rates, while also providing                                                                                                                                                          illumination. This configuration minimizes packet collisions due to Line Of Sight (LOS) property of light and promises to alleviate the wireless bottleneck that exists when there is a high density of rich-media devices seeking to receive data from the wired network.Possible applications of VLC impact the quality of life, including control of auto / traffic signaling for safety and enabling communications where high noise interferes with WiFi.

8. Smart LIFI based Car Parking system

smart  parking  information  system  exploiting  visible  light communication (VLC) technology to help drivers getting the real-time parking information as

well  as  direction  guide.  By  providing  accurate  information  on  available  parking  spaces, drivers  save  time  and  fuel  and  increase  efficiency  of  the  parking  process.  Therefore,  the proposed  system  not  only  gives  the  illumination  function  of  LED  but  also  the  function  of communicating  in  the  manner  of  application  based  on  the  VLC.  The  effectiveness  of  the proposed scheme is validated through experiments in an indoor environment. In  modern  life,  the  shopping  complexes  always  attract  people  for  its  good  products  and service. What’s more, shopping complexes have begun providing services much more diverse than  just  pure  selling  and  buying.  Customers  can  use  banking  services,  post  offices,  food courts,  cinemas,  children's  play  areas. 

Hence,  more  shop  manager  prefers  to  invest  much money and time in designing the interior, store location, parking lots and so on to target more customers and increase revenue.  Providing  sufficient  parking  spaces  for  visitors  is  one  of  the  most  important  issues  in developing shopping complexes. Offering safe and conventional parking lots with a sufficient number  of  spaces  is  a  few  of  the  factors  which  can  increase  customer  loyalty  and  attract customers  to  visit  a  shopping  mall  more  frequently.  However,  until  now,  various  parking information  systems  in  our  life  are  based  on  conventional  radio  communication  system, which need specific industry standard

9.   LIFi Based smart Location Aware of Services

Figures 1  show future applications of indoor positioning, which have very different localization and communication requirements. Each figure shows a room of the future, where six light fittings are transmitting signals that can be used for localization. In Fig. 1, the man wearing headphones is listening to recorded information about the artwork in front of him. This is an automated version of the headsets currently provided by museums and other places of interest, which require a number to be entered by the user at each exhibit. In a VLP-based system, a receiver in the headset

would detect the signal from the nearest LED and play the relevant commentary.         

10.           Visible light positioning for asset tracking

very important use of the new sys-tems will be in asset tracking. Figure 2 shows an example of a system being used to track the position of a wheelchair or a portable medical device, an application that is important in hospi-tals. The same concept coul also be used for a host of other purposes such as tracking trolleys in airports or consignments in warehouses. The receiver on the wheelchair detects the identity of the nearest LED and transmits this information using a radio system such as ZigBee or a wire-less LAN to a central computer. The computer maintains a database of the identity of the LEDs and their locations. The receiver needs only to transmit information about its position intermit-tently, so it could be a low-power battery operat-ed  device.  Note  that  in  these  first  two applications, the receiver needs only to deter-mine the ide ntity of the LED, not its position.

11. POSITIONING TECHNIQUES FOR ACCURATE LOCALIZATION mobile   robot navigation

When accurate positioning is required, as in the mobile robot example of Fig. 3, the VLP receiver will use the received signals to determine the relative distance and/or direction of a number of LED transmitters. These measurements will then be combined using classical triangulation (using angle of arrival information) or tril alteration (using path length or time of arrival information) to determine the  position  of  the receiver. We now discuss a range of positioning techniques and their suitability for use with light- ing LEDs.  Many of the indoor positioning systems that are based on radio signals use received signal strength (RSS) to estimate the distance of the receiver from the transmitter. In general, as the distance between transmitter and receiver increases, the power of the received signal falls. However, the effects of objects blocking and reflecting the radio signal mean that the rela- tionship between distance and RSS is unpre- dictable, limiting the accuracy of an RSS  approach in radio-based systems.

11.           An integrated, underwater optical /acoustic  communications system

Communication  underwater  is  severely  limited  when  compared  to  communications  in  air  because  water  is  essentially opaque  to  electromagnetic  radiation  except  in  the  visible  band. Even  in  the  visible  band,  light  penetrates  only  a  few  hundred meters  in  the  clearest  waters  and  much  less  in  waters  made turbid  by  suspended  sediment  or  high  concentrations  of  marine life.  Consequently,  acoustic  techniques  have  been  developed  for

underwater  communication  systems  and  now  represent  a relatively  mature  and  robust  technology.  Acoustic  systems  are capable  of  long  range  communication, but  offer  limited  data  rates and significant latency (due to the speed of sound in water). We  are  developing  an  optical  communication  system  that complements  and  integrates  with  existing  acoustic  systems resulting  in  an  underwater  communications  capability  offering high  data  rates  and  low  latency  when  within  optical  range combined  with  long  range  and  robustness  of  acoustics  when outside  of  optical  range.  Amongst  a  wide  array  of  applications, this  combination  of  capabilities  will  make  it  possible  to  operate self-powered  ROVs  from  support  vessels or platforms without requiring  a  physical  connection  to  the  ROV.  Such  a  capability will help simplify operations and potentially reduce costs through the  use  of  less  capable  surface vessels.   New  deployment strategies  may  offer  game-changing  opportunities  within  all areas  of  undersea  activities.  For  example, rapid event response will  be  enhanced  and  repair  and  maintenance of the emerging ocean observatory infrastructure will become more cost effective. Such  through-water  communications  will  likewise  enable exchange  of  large  data  files  from  fixed  sensors  using  AUVs  (or ROVs)  as  data  mules,  shuttling real-time  video  from  untethered vehicles  for  inspection,  identification, and other related operations.  Interconnectivity  for  dense  arrays  of  underwater sensors  without  the  need  for  expensive  and  difficult  to  install undersea cables is also possible.  An unmanned battery operated vehicle,  dedicated  to  a  subsea node, that can be wirelessly operated though a combination of acoustic and optical communications,  will be an important asset for both scientific exploration and commercial applications.

12.           Visible Light Communication Based Traffic Information Broadcasting Systems

Traffic safety information broadcast from traffic lights using Visible Light Communication (VLC) is a new cost effective technology which can draw attention to drivers to take necessary safety measures. This paper presents a VLC broadcast system considering LED-based traffic lights. It discusses the conceptual methodology for integrating traffic light road side unit (RSUs) with impending intelligent transportation systems (ITS) architecture.

Results from a case study of VLC system for information broadcast are also presented.

Road accidents which cause loss of material and most importantly human lives are becoming severe even with the deployment of many intelligent communication devices on board vehicle and alongside the road. According to world health organization report [1] road crashes are the second leading cause of death globally among young people aged five to 29 and the third leading cause of death among people aged 30 to 44 years. Over 1.2 million people are killed annually because of road accidents. The study predicted that road accidents would become the sixth largest cause of death in the world in 2020 whereas it was the ninth largest cause of death in 1990

13.           Li-Fi wireless optical communication

Visible  Light  Communication  (VLC)  technology,  one  of  the  advanced  optical  wireless  communication technologies,  in  which  light  in  the  visible  region  (375nm-780nm)  is  used  as  a  medium  for  data  transmission  is  more secure and achieves high data rates as compared to conventional wireless technologies like Wi-Fi, Bluetooth, Wi-max etc.,  which  use  radio  waves  for  communication.  While  using  wireless  internet,  when  more  than  one  device  is  tapped into the network, then bandwidth got frustrated at the slow speeds. To overcome the shortage of bandwidth we can use light to transfer the data which can be known as “DATA THROUGH ILLUMINATION”. The idea behind is  that, infra-red remote is slightly modified i.e., LED light bulb that varies in intensity which cannot be followed by the naked eye.  It  is  possible  to  encode  the  data  in  the  light  by  varying  the  light  at  which  the  LEDs  flicker  on  and  off  to  give  different strings of 1s and 0s.While using mixtures of red, green and blue LEDs to alter the light frequency encoding a different data channel. If you can‟t see the light then you cannot access the data so the security would be snapped.

Reference

1.   Advances in Visible Light Communication Technologies

Shinichiro Haruyama

Graduate School of System Design and Management, Keio University,

        2. An integrated, underwater optical /acoustic communications system 

N. Farr, A. Bowen, J. Ware, C. Pontbriand

Applied Ocean Physics and Engineering

M. Tivey

Geology and Geophysics

Woods Hole Oceanographic Institution

3. Jean   Arm strong ,   Y.   Ahm et  Sekerc ioglu ,   and   Adrian   Neild ,   Monash   University

Visible Light Positioning: A Roadmap for International Standardization

4. DESIGN of LASER BASED UNDERWATER COMMUNICATION SYSTEM

 Mustafa YAĞIMLI 

 Electrical and Electronics Engineering Department, Turkish Naval Academy, 

Tuzla, Istanbul

5. Smart Vehicles, Technologies and Main Applications in Vehicular Ad hoc Networks

Anna Maria Vegni¹, Mauro Biagi² and Roberto Cusani²

^[1] University of Roma Tre, Department of Applied Electronics, Rome, Italy

^[2] University of Rome Sapienza, Department of Information Engineering, Electronics and Telecommunications, Rome, Italy

6. Smart Parking Information System Exploiting Visible Light

Communication

Nammoon Kim, Changqiang Jing, Biao Zhou and Youngok Kim

Department of Electronics Engineering, Kwangwoon University, Korea

kimyoungok@kw.ac.kr

7.Visible Light Communication Based Traffic Information

Broadcasting Systems

Navin Kumar