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CHAPTER 1 1.1 INTRODUCTION Li-Fi is transmission of data through illumination by taking the fiber out of fiber optics by sending data through a LED light bulb that varies in intensity faster than the human eye can follow. Li-Fi is the term some have used to label the fast and cheap wireless-communic...

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CHAPTER 1 1.1 INTRODUCTION Li-Fi is transmission of data through illumination by taking the fiber out of fiber optics by sending data through a LED light bulb that varies in intensity faster than the human eye can follow. Li-Fi is the term some have used to label the fast and cheap wireless-communication system, which is the optical version of Wi-Fi. The term was first used in this context by Harald Haas in his TED Global talk on Visible Light Communication. ―At the heart of this technology is a new generation of high brightness light-emitting diodes‖, says Harald Haas from the University of Edinburgh, UK.Very simply, if the LED is on, you transmit a digital 1, if it‘s off you transmit a 0.Haas says,―They can be switched on and off very quickly, which gives nice opportunities for transmitted data.‖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 eye cannot notice, so the output appears constant. More sophisticated techniques could dramatically increase VLC data rate. Terms at the University of Oxford and the University of Edingburgh are focusing on parallel data transmission using array of LEDs, where each LED transmits a different data stream. Other group are using mixtures of red, green and blue LEDs to alter the light frequency encoding a different data channel.Li-Fi, as it has been dubbed, has already achieved blisteringly high speed 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. The technology was demonstrated at the 2012 Consumer Electronics Show in Las Vegas using a pair of Casio smart phones to exchange data using light of varying intensity given off from their screens, detectable at a distance of up to ten metres In October 2011 a number of companies and industry groups formed the Li-F 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. The consortium believes it is possible to achieve more than 10Gbps, theoretically allowing a high-definition film to be downloaded in 30 seconds.

Most of us are familiar with Wi-Fi (Wireless Fidelity), which uses 2.4-5GHz RF to deliver wireless Internet access around our homes, schools, offices and in public places. We have become quite dependent upon this nearly ubiquitous service. But like most technologies, it has its

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limitations. While Wi-Fi can cover an entire house, its bandwidth is typically limited to 50-100 megabits per second (Mbps) today using the IEEE802.11n standard. This is a good match to the speed of most current Internet services, but insufficient for moving large data files like HDTV movies, music libraries and video games

Figure 1.1 . Linksys 2.4 Ghz Wireless Router The more we become dependent upon ‗the cloud‘ or our own ‗media servers‘ to store all of our files, including movies, music, pictures and games, the more we will want bandwidth and speed. Therefore RF-based technologies such as today‘s Wi-Fi are not the optimal way.

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CHAPTER 2

2.1 VISIBLE LIGHT COMMUNICATION Many people‘s first exposure to optical wireless technology was VLC. This emerging technology offers optical wireless communications by using visible light. Today, it is seen as an alternative to different RF-based communication services in wireless personal-area networks. An additional opportunity is arising by using current state-of-the-art LED lighting solutions for illumination and communication at the same time and with the same module. This can be done due to the ability to modulate LEDs at speeds far faster than the human eye can detect while still providing artificial lighting. Thus while LEDs will be used for illumination, their secondary duty could be to ‗piggyback‘ data communication onto lighting systems. This will be particularly relevant in indoor ‗smart‘ lighting systems, where the light is always ‗on.‘ In contrast to infrared, the socalled ―what you see is what you send‖ feature can be used to improve the usability of transmitting data at shorter point-to-point distances between different portable or fixed devices. There, illumination can be used for beamguiding, discovery or generating an alarm for misalignment.

Fig 2.1 Electromagnetic spectrum The premise behind VLC is that because lighting is nearly everywhere, communications can ride along for nearly free. Think of a TV remote in every LED light bulb and you‘ll soon realise the possibilities of this technology.

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One of the biggest attractions of VLC is the energy saving of LED technology. Nineteen per cent of the worldwide electricity is used for lighting. Thirty billion light bulbs are in use worldwide. Assuming that all the light bulbs are exchanged with LEDs, one billion barrels of oil could be saved every year, which again translates into energy production of 250 nuclear power plants.

Driven by the progress of LED technology, visible light communication is gaining attention in research and development. The VLC Consortium (VLCC) in Japan was one of the first to introduce this technology. After establishing a VLC interest group within the IEEE 802.15 wireless personal-area networks working group, the IEEE 802.15.7 task group was established by the industry, research institutes and universities in 2008. The final standard was approved in 2011. It specifies VLC comprising mobile-to-mobile

(M2M),

fixed-to-mobile

(F2M)

and

infrastructure-to-mobile

(I2M)

communications. There, the focus is on low-speed, medium-range communications for intelligent traffic systems and on high-speed, short range M2M and F2M communications to exchange, for example, multimedia data. Data rates are supported from some 100 kbps up to 100 Mbps using different modulation schemes. Other standardization groups are working on standardized optical wireless communication (OWC) solutions using visible and infrared light. The most important groups are IrDA with its new 10 Giga-IR working group, ISO and ICSA.

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CHAPTER 3

3.1 LIGHT FIDELITY(Li-Fi) VLC represents only a fraction of what appears to be a much larger movement towards optical wireless technologies in general. This larger word has been dubbed ‗Li-Fi‘ (Light Fidelity) by Dr Harald Haas of Edinburgh University and organisations such as the Li-Fi Consortium.

Figure 3.1“Li Fi”- The Term Coined By Dr Harald Haas 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 highdefinition 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.

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Fig 3.2 Transfer of data through light Within a local Li-Fi cloud several databased services are supported through a heterogeneous communication system. In an initial approach, the Li-Fi Consortium defined different types of technologies to provide secure, reliable and ultra-high-speed wireless communication interfaces. These technologies included giga-speed technologies, optical mobility technologies, and

navigation, precision location and gesture recognition technologies. For giga-speed technologies, the Li-Fi Consortium defined GigaDock, GigaBeam, GigaShower, GigaSpot and GigaMIMO models to address different user scenarios for wireless indoor and indoor-like data transfers. While GigaDock is wireless docking solution including wireless charging for smartphones, tablets or notebooks, with speeds up to 10 Gbps, the GigaBeam model is a point-to-point data link for kiosk applications or portable-to-portable data exchanges. Thus a two-hour full HDTV movie (5 GB)can be

another

within four

transferred

from

one

device to

seconds.GigaShower, GigaSpot and Giga- MIMO are the other

models for in-house communication. There a transmitter or receiver is mounted into the ceiling connected to, for example, a media server. On the other side are portable or fixed devices on a desk in an office, in an operating room, in a production hall or at an airport. GigaShower provides unidirectional data services via several channels to multiple users with gigabit-class communication speed over several metres.

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CHAPTER 4

4.1 WORKING TECHNOLOGY VLC uses visible light between 400 THz (780 nm) and 800 THz (375 nm) as optical carrier for data transmission and illumination. It uses fast pulses of light to transmit information wirelessly. The main components of this communication system are 1) a high brightness white LED, Which acts as a communication source and 2) a silicon photodiode which shows good response to visible wavelength region serving as the receiving element. LED can be switched on and off to generate digital strings of 1s and 0s. Data can be encoded in the light to generate a new data stream by varying the flickering rate of the LED. To be clearer, by modulating the LED light with the data signal, the LED illumination can be used as a communication source. As the flickering rate is so fast, the LED output appears constant to the human eye. A data rate of greater than 100 Mbps is possible by using high speed LEDs with appropriate multiplexing techniques. VLC data rate can be increased by parallel data transmission using LED arrays where each LED transmits a different data stream. There are reasons to prefer LED as the light source in VLC while a lot of other illumination devices like fluorescent lamp, incandescent bulb etc. are available. Very simply, if the LED is on, you transmit a digital 1, if it‘s off you transmit a 0,‖Haas says, ―They can be switched on and off very quickly, which gives nice opportunities for transmitted data.‖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 eye cannot notice, so the output appears constant. More sophisticated techniques could dramatically increase VLC data rate. Terms at the University of Oxford and the University of Edingburgh are focusing on parallel data transmission using array of LEDs, where each LED transmits a different data stream. Other group are using mixtures of red, green and blue LEDs to alter the light frequency encoding a different data channel.Li-Fi, as it has been dubbed, has already achieved blisteringly high speed 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

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white-light LED. The technology was demonstrated at the 2012 Consumer Electronics Show in Las Vegas using a pair of Casio smart phones to exchange data using light of varying intensity given off from their screens, detectable at a distance of up to ten metres.

Figure 5.1 Working of LI-FI So what you require at all are some LEDs and a controller that code data into those LEDs. We have to just 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 International Journal of Applied Engineering Research, ISSN 0973-4562 Vol.7 No.11 (2012)© Research India Publications; http://www.ripublication.com/ijaer.htm each frequency encoding is a different data channel. Such advancements promise a theoretical speed of 10 Gbps –meaning you can download a full high-definition film in just 30 seconds. Simply awesome!

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CHAPTER 5

5.1 COMPARISION BETWEEN LI-FI&WI-FI LI-FI is a term of one used to describe visible light communication technology applied to high speed wireless communication. It acquired this name due to the similarity to WI-FI, only using light instead of radio WI-FI is great for general wireless coverage within buildings, and li-fi is ideal for high density wireless data coverage in confined area and for relieving radio interference issues, so the two technologies can be considered complimentary.

Table 6.1Comparison between current and future wireless technologies

The table also contains the current wireless technologies that can be used for transferring data between devices today, i.e. Wi-Fi, Bluetooth and IrDA. Only Wi-Fi currently offers very high data rates. The IEEE 802.11.n in most implementations provides up to 150Mbit/s (in theory the

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standard can go to 600Mbit/s) although in practice you receive considerably less than this. Note that one out of three of these is an optical technology.

5.2 ISSUES WITH WI-FI USING RADIO WAVES There are four issues with the current wi-fi scenario , which are :-

Fig 6.1 Four aspects of WI-FI 1.>CAPACITY: We transmit wireless data is by using electromagnetic waves -- inparticular, radio waves. Radio waves are scarce, expensive and we only have a certain range of it. Due to this limitation one can’t forever hope to cope with the demand of wireless data transmissions and the number of bytes and data which are transmitted every month.

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2.>EFFICIENCY There are 1.4 million cellular radio masts deployed worldwide. Most of the energy consumed, is not used to transmit the radio waves,but is used to cool the base stations. The efficiency of such a base station is only at about five percent. 3.>AVAILABILITY Availability of radio waves or RW signals causes another concern We have to switch off our mobile devices in aero planes It is not advisable to use mobiles at places like petrochemical plants and petrol pumps 4.>SECURITY The radio waves penetrate through walls. They can be intercepted, and somebody can make use of one‘s network.

5How LI-FI 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.

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CHAPTER 6 6.1 FUTURE PROSPECTS First applications of Li-Fi have been put to use already, for example,in hospitals where RF signal are a threat due to interference problems with medical equipment such as blood pumps and other life supporting instruments. Axiomtek Europe presented such a product at the Embedded World exhibition in Nurnberg, Germany. The prototype of a mobile phone with an incorporated VLC system was presented by Casio at the Consumer Electronics Show in Las Vegas in January this year. In the coming years, we will see more Li-Fi products entering the market, both in the industrial as well as consumer markets.

Fig 7.1 Anticipated uses of VLC Technology

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6.2 APPLICATIONS 6.2.1 Airplanes 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.

Figure 7.3 Use in airlines

6.2.3 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..

Figure 7.4 Use in power plants

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6.2.4 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.

Figure 7.5 Under sea awesomenes

6.2.5 It Could Keep You Informed and Save Lives Say there‘s an earthquake in New Delhi,or a hurricane. Take your pick — it‘s a wacky city. The average Delhiite 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..

Figure 7.6 Use of li fi in traffic control

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CHAPTER 7 7.1 CONCLUSION 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 any 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.

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CHAPTER 8 8.1 REFERENCES

1. www.wikisedia.com 2 www.visiblelightcomm.com/ 3 http://teleinfobd.blogspot.in/2012/01/what-is-lifi.html 4 technopits.blogspot.comtechnology.cgap.org/2012/01/11/a-lifi-world/ 5 www.lificonsortium.org/

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