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Li-Fi: A New Paradigm in Wireless Communication

lighting reaches nearly everywhere, so communications can ride along for nearly free.Think of a TV remote in every leD light bulb and you’ll soon realise the possibilities ofcommunications using visible light—also dubbed as li-Fi

Dr Frank Deicke, WAlter kraus, Dr Josef shwartz, rudi Wiedemann

APRIL 2012: Most of us are familiar with Wi-Fi (Wireless Fidelity), which uses 2.4-5GHz RF  to deliver wireless Internetaccess around our homes, schools, offices and in public places. We have become quite dependent upon this nearlyubiquitous service. But like most technologies, it has its limitations.

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

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. In addition, Wi-Fi may not be the most efficient way to provide new desired capabilitiessuch as precision indoor positioning and gesture recognition.

Optical wireless technologies, sometimes called visible light communication (VLC), and more recently referred to as Li-Fi(Light Fidelity), on the other hand, offer an entirely new paradigm in wireless technologies in terms of communicationspeed, f lexibility and usability.

Fig. 1: Li-Fi as a superset of dif ferent optical wirelesstechnologies involving communication, positioning, natural user interfaces and many more

Visible light communications

Many people’s first exposure to optical wireless technology was VLC. This emerging technology offers optical wireless

 

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communca ons y usng v s e g . o ay, s seen as an a erna ve o eren - ase communca on serv ces nwireless personal-area networks. An additional opportunity is arising by using current state-of-the-art LED lightingsolutions for illumination and communication at the same time and with the same module. This can be done due to theability 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 lightingsystems. This will be particularly relevant in indoor ‘smart’ lighting systems, where the light is always ‘on.’ 

Other examples for outdoor use include intelligent traffic systems to exchange data between vehicles, and betweenvehicles and road infrastructure like traffic lights and control units. Alternatively, the LEDs’ primary purpose could be totransmit information while the secondary purpose of illumination would be to alert the user to where the data is beingtransmitted from.

In contrast to infrared, the so-called “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 canbe used for beam guiding, discovery or generating an alarm for misalignment.

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

(a) GigaDock (b) GigaBeam

(c) GigaShower (d) GigaMIMO

Fig. 2: GigaSpeed usage models (Images courtesy: TriLumina Corp.)

One of the biggest attractions of VLC is the energy saving of LED technology. Nineteen per cent of the worldwideelectricity is used for lighting. Thirty billion light bulbs are in use worldwide. Assuming that all the light bulbs are exchangedwith LEDs, one billion barrels of oil could be saved every year, which again translates into energy production of 250nuclear 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 IEEE802.15.7 task group was established by the industry, research institutes and universities in 2008. The final standard wasapproved 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 andon high-speed, short-range M2M and F2M communications to exchange, for example, multimedia data. Data rates aresupported from some 100 kbps up to 100 Mbps using different modulation sc hemes.

Other standardisation groups are working on standardised optical wireless communication (OWC) solutions using visible andinfrared light. The most important groups are IrDA with its new 10 Giga-IR working group, ISO and ICSA.

Li-Fi—the superset of VLC & Co.

VLC represents only a fraction of what appears to be a much larger movement towards optical wireless technologies ingeneral. This larger world has been dubbed ‘Li-Fi’ (Light Fidelity) by people such as Dr Harald Haas of Edinburgh Universityand organisations such as the Li-Fi Consortium.

In that connection, Li-Fi comprises several optical wireless technologies such as optical wireless communication,

navi ation and esture reco nition a lied for natural user interfaces Fi . 1 . Thus it rovides a com letel new set of

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 optical technologies and techniques to offer users add-on as well as complementary functionalities compared to well-known and established RF services. This could reach from a new user experience regarding communication speeds in thegigabit-class to bridge the well-known spec-trum crunch, over to precise indoor positioning or controlling video games,machines or robots with entirely new natural user interfaces. Finally, these and many more could be merged to a full-featured Li-Fi cloud providing wireless services for other future applications as well.

What Li-Fi stands for

Li-Fi comprises a wide range of frequencies and wavelengths, from the infrared through visible and down to the ultravioletspectrum. It includes sub-gigabit and gigabit-class com-munication speeds for short, medium and long ranges, andunidirectional and bidirectional data transfer using line-of-sight or diffuse links, reflec-tions and much more. It is not limitedto LED or laser technologies or to a particular receiving technique. Li-Fi is a framework for all of these providing newcapabilities to current and future services, applications and end users.

Usage models

Within a local Li-Fi cloud several databased services are supported through a heterogeneous communication sys-tem. Inan 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 mobilitytechnologies, and navigation, precision location and gesture recognition technologies.

For giga-speed technologies, the Li-Fi Consortium defined GigaDock, GigaBeam, GigaShower, GigaSpot and GigaMIMOmodels (Fig. 2) to address different user scenarios for wireless indoor and indoor-like data transfers. While GigaDock is awireless docking solution including wireless charging for smartphones tablets or notebooks, with speeds up to 10 Gbps, theGigaBeam 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 transferred from one device to another within four seconds.

GigaShower, GigaSpot and Giga-MIMO are the other models for in-house communication. There a transmitter or receiver ismounted into the ceiling connected to, for example, a media server. On the other side are portable or fixed devices on adesk in an office, in an operating room, in a production hall or at an airport. GigaShower provides unidirectional dataservices via several channels to multiple users with gigabit-class com-munication speed over several metres. This is likewatching TV channels or listening to different radio stations where no uplink channel is needed. In case GigaShower isused to sell books, music or movies, the connected media server can be accessed via Wi-Fi to process payment via amobile device. GigaSpot and GigaMIMO are optical wireless single- and multi-channel HotSpot solutions offering

bidirectional gigabit-class communication in a room, hall or shopping mall for example.

How Li-Fi works

Imagine yourself walking into a mall where GPS signals are unavailable but the mall is equipped with ceiling bulbs thatcreate their own ‘constellation’ of navigation beacons. As the camera of your cellphone automatically receives thesesignals, it switches your navigation software to use this information to guide you to the ATM machine you’re looking for.

You conclude your ATM transaction and notice the GigaSpot sign for instant digital movie downloads. You pick out thatnew Tom Cruise movie using your phone’s payment facility, and then download within a few seconds the high-definitionmovie into the GigaLink flash drive plugged into the USB port of your smartphone.

As you walk away, your phone notifies you that the leather jacket Tom featured in the movie is on sale nearby. You walkover towards the show window and your image comes up on the screen, wearing that coveted jacket. You turn and posewhile the image matches your orientation and body gestures for a ‘digital fitting.’ When you walk into the store, the clerkhands you the actual jacket in exactly your size.

On the verge of a breakthroughFirst applications of Li-Fi have been put to use already, for example, in hospitals where RF  signals are a threat due to

interference problems with medical equipment such as blood pumps and other life supporting instruments. Axiomtek Europepresented such a product at the Embedded World exhibition in Nürn-berg, Germany. The prototype of a mobile phone withan 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 consumermarkets.

The authors are cofounders of the Li-Fi Con-sortium (www.lificonsortium.org)—a non-profit organisation focusing onoptical wireless technologies and fostering the Li-Fi cloud in general 

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Jostin 340 days ago

Waiting for Li-Fi.........Unleash The power of visible light.............Reply 

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