Li-Fi

Li-Fi
Introduced March 2011 (2011-03)
Industry Digital Communication
Connector type Visible light communication
Physical range visible light spectrum, ultraviolet and infrared radiation

Li-Fi (/ˈlaɪfaɪ/; short for light fidelity) is a technology for wireless communication between devices using light to transmit data and position. In its present state only LED lamps can be used for the transmission of visible light.[1] The term was first introduced by Harald Haas during a 2011 TEDGlobal talk in Edinburgh.[2] In technical terms, Li-Fi is a visible light communications system that is capable of transmitting data at high speeds over the visible light spectrum, ultraviolet and infrared radiation.

In terms of its end use the technology is similar to Wi-Fi. The key technical difference is that Wi-Fi uses radio frequency to transmit data. Using light to transmit data allows Li-Fi to offer several advantages like working across higher bandwidth, working in areas susceptible to electromagnetic interference (e.g. aircraft cabins, hospitals) and offering higher transmission speeds.[3] The technology is actively being developed by several organizations across the globe.

Technology details

This optical wireless communications (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.[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 the current to the LEDs off and on at a very high rate,[6] too quick to be noticed by the human eye. Although Li-Fi LEDs would have to be kept on to transmit data, they could be dimmed to below human visibility while still emitting enough light to carry data.[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 is not 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 without causing electromagnetic interference.[8][12][9] Both Wi-Fi and Li-Fi transmit data over the electromagnetic spectrum, but whereas Wi-Fi utilizes radio waves, Li-Fi uses visible light, Ultraviolet and Infrared. 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.[13] The visible light spectrum is 10,000 times larger than the entire radio frequency spectrum.[14] Researchers have reached data rates of over 224 Gbit/s,[15] which was much faster than typical fast broadband in 2013.[16][17] 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.[18]

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.[19][20]

History

Professor Harald Haas coined the term "Li-Fi" at his 2011 TED Global Talk where he introduced the idea of "wireless data from every light".[21] He is a Chair Professor of Mobile Communications at the University of Edinburgh, and the co-founder of pureLiFi along with Dr Mostafa Afgani.[22]

The general term "visible light communication" (VLC), whose history dates back to the 1880s, 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.[23] Haas promoted this technology in his 2011 TED Global talk and helped start a company to market it.[24] PureLiFi, formerly pureVLC, is an original equipment manufacturer (OEM) firm set up to commercialize Li-Fi products for integration with existing LED-lighting systems.[25][26] Oledcomm, French company founded by Pr Suat Topsu from Paris-Saclay University.

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.[27]

A number of companies offer uni-directional VLC products, which is not the same as Li-Fi - a term defined by the IEEE 802.15.7r1 standardization committee.[28]

VLC technology was exhibited in 2012 using Li-Fi.[29] By August 2013, data rates of over 1.6 Gbit/s were demonstrated over a single color LED.[30] In September 2013, a press release said that Li-Fi, or VLC systems in general, do not require line-of-sight conditions.[31] In October 2013, it was reported Chinese manufacturers were working on Li-Fi development kits.[32]

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 (GB/s) but they foresee boosting speeds up to 5 GB/s in the near future.[33] In 2014 a new record was established by Sisoft (a Mexican company) that was able to transfer data at speeds of up to 10 GB/s across a light spectrum emitted by LED lamps.[34]

Recent integrated CMOS optical receivers for Li-Fi systems are implemented with avalanche photodiodes (APDs) which has a low sensitivity.[35] In July 2015, IEEE has operated the APD in Geiger-mode as a single photon avalanche diode (SPAD) to increase the efficiency of energy-usage and makes the receiver more sensitive.[36] This operation could be also performed as quantum-limited sensitivity that makes receivers able to detect weak signals from a far distance.[35]

Standards

Like Wi-Fi, Li-Fi is wireless and uses similar 802.11 protocols, but it uses ultraviolet, infrared and visible light communication (instead of radio frequency waves), which has much bigger bandwidth.

One part of VLC is modeled after communication protocols established by the IEEE 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 optical orthogonal frequency-division multiplexing (O-OFDM) modulation methods which have been optimized for data rates, multiple-access and energy efficiency.[37] 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.

The standard defines three PHY layers with different rates:

  • The PHY 1 was established for outdoor application and works from 11.67 kbit/s to 267.6 kbit/s.
  • The PHY 2 layer permits reaching data rates from 1.25 Mbit/s to 96 Mbit/s.
  • The PHY 3 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.[38]

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.

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.[39][40] 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. The first smartphones using this technology should arrive in 2015. This screen can also receive VLC signals as well as the smartphone camera.[41] The cost of these screens per smartphone is between $2 and $3, much cheaper than most new technology.[42]

Signify lighting company (formerly Philips Lighting) 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.[43]

Home and building automation

It is predicted that future home and building automation will be highly dependent on the Li-Fi technology for being secure and fast. As the light cannot penetrate through walls, the signal cannot be hacked from a remote location.

Applications

Security

In contrast to radio frequency waves used by Wi-Fi, lights cannot penetrate through walls and doors. This makes it more secure and makes it easier to control access to a network.[44] As long as transparent materials like windows are covered, access to a Li-Fi channel is limited to devices inside the room.[45]

Underwater application

Most remotely operated underwater vehicles (ROVs) are controlled by wired connections. The length of their cabling places a hard limit on their operational range, and other potential factors such as the cable's weight and fragility may be restrictive. Since light can travel through water, Li-Fi based communications could offer much greater mobility.[46] Li-Fi's utility is limited by the distance light can penetrate water. Significant amounts of light do not penetrate further than 200 meters. Past 1000 meters, no light penetrates.[47]

Hospital

Many treatments now involve multiple individuals, Li-Fi systems could be a better system to transmit communication about the information of patients.[48] Besides providing a higher speed, light waves also have little effect on medical instruments and human bodies.[49]

Vehicles

Vehicles could communicate with one another via front and back lights to increase road safety. Street lights and traffic signals could also provide information about current road situations.[50]

Industrial automation

Anywhere in industrial areas data has to be transmitted, Li-Fi is capable of replacing slip rings, sliding contacts and short cables, such as Industrial Ethernet. Due to the real time capability of Li-Fi (which is often required for automation processes) it is also an alternative to common industrial Wireless LAN standards.[51]

See also

References

  1. ↑ "Comprehensive Summary of Modulation Techniques for LiFi | LiFi Research". www.lifi.eng.ed.ac.uk. Retrieved 2018-01-16.
  2. ↑ Harald Haas. "Harald Haas: Wireless data from every light bulb". ted.com. Archived from the original on 8 June 2017.
  3. ↑ Tsonev, Dobroslav; Videv, Stefan; Haas, Harald (December 18, 2013). "Light fidelity (Li-Fi): towards all-optical networking". Proc. SPIE. Broadband Access Communication Technologies VIII. Broadband Access Communication Technologies VIII. 9007 (2): 900702. Bibcode:2013SPIE.9007E..02T. CiteSeerX 10.1.1.567.4505. doi:10.1117/12.2044649.
  4. ↑ Sherman, Joshua (30 October 2013). "How LED Light Bulbs could replace Wi-Fi". Digital Trends. Archived from the original on 27 November 2015. Retrieved 29 November 2015.
  5. 1 2 "Global Visible Light Communication (VLC)/Li-Fi Technology Market worth $6,138.02 Million by 2018". MarketsandMarkets. 10 January 2013. Archived from the original on 8 December 2015. Retrieved 29 November 2015.
  6. 1 2 Coetzee, Jacques (13 January 2013). "LiFi beats Wi-Fi with 1Gb wireless speeds over pulsing LEDs". Gearburn. Archived from the original on 5 December 2015. Retrieved 29 November 2015.
  7. 1 2 Condliffe, Jamie (28 July 2011). "Will Li-Fi be the new Wi-Fi?". New Scientist. Archived from the original on 31 May 2015.
  8. 1 2 Li-Fi – Internet at the Speed of Light, by Ian Lim, the gadgeteer, dated 29 August 2011 Archived 1 February 2012 at the Wayback Machine.
  9. 1 2 "Visible-light communication: Tripping the light fantastic: A fast and cheap optical version of Wi-Fi is coming". The Economist. 28 January 2012. Archived from the original on 21 October 2013. Retrieved 22 October 2013.
  10. ↑ "The internet on beams of LED light". The Science Show. 7 December 2013. Archived from the original on 22 July 2017.
  11. ↑ "PureLiFi aims at combating cyber crime". Ads Advance. Archived from the original on 9 October 2017.
  12. ↑ "Li-Fi: A green avatar of Wi-Fi". Livemint. 9 January 2016. Archived from the original on 25 February 2016. Retrieved 24 February 2016.
  13. ↑ "The Future's Bright - The Future's Li-Fi". The Caledonian Mercury. 29 November 2013. Archived from the original on 4 November 2015. Retrieved 29 November 2015.
  14. ↑ Haas, Harald (19 April 2013). "High-speed wireless networking using visible light". SPIE Newsroom. doi:10.1117/2.1201304.004773.
  15. ↑
  16. ↑ Vincent, James (29 October 2013). "Li-Fi revolution: internet connections using light bulbs are 250 times". The Independent. Archived from the original on 1 December 2015. Retrieved 29 November 2015.
  17. ↑ "'LiFi is high speed bi-directional networked and mobile communication of data using light. LiFi comprises of multiple light bulbs that form a wireless network, offering a substantially similar user experience to Wi-Fi except using the light spectrum.Li-fi' via LED light bulb data speed breakthrough". BBC News. 28 October 2013. Archived from the original on 1 January 2016. Retrieved 29 November 2015.
  18. ↑ "pureLiFi to demonstrate first ever Li-Fi system at Mobile World Congress". Virtual-Strategy Magazine. 19 February 2014. Archived from the original on 3 December 2015. Retrieved 29 November 2015.
  19. ↑ Giustiniano, Domenico; Tippenhauer, Nils Ole; Mangold, Stefan. "Low-Complexity Visible Light Networking with LED-to-LED Communication" (PDF). Zurich, Switzerland. Archived (PDF) from the original on 20 June 2015.
  20. ↑ Dietz, Paul; Yerazunis, William; Leigh, Darren (July 2003). "Very Low-Cost Sensing and Communication Using Bidirectional LEDs" (PDF). Archived (PDF) from the original on 1 July 2015.
  21. ↑ "Archived copy". Archived from the original on 2 February 2016. Retrieved 2 February 2016.
  22. ↑ https://www.crunchbase.com/organization/purelifi#/entity Archived 26 August 2016 at the Wayback Machine.
  23. ↑ Povey,, Gordon. "About Visible Light Communications". pureVLC. Archived from the original on 18 August 2013. Retrieved 22 October 2013.
  24. ↑ Haas, Harald (July 2011). "Wireless data from every light bulb". TED Global. Edinburgh, Scotland. Archived from the original on 8 June 2017.
  25. ↑ "pureLiFi Ltd". pureLiFi. Archived from the original on 19 December 2013. Retrieved 22 December 2013.
  26. ↑ "pureVLC Ltd". Enterprise showcase. University of Edinburgh. Archived from the original on 23 October 2013. Retrieved 22 October 2013.
  27. ↑ Povey, Gordon (19 October 2011). "Li-Fi Consortium is Launched". D-Light Project. Archived from the original on 18 August 2013. Retrieved 22 October 2013.
  28. ↑ "Archived copy". Archived from the original on 24 January 2016. Retrieved 2 February 2016.
  29. ↑ Watts, Michael (31 January 2012). "Meet Li-Fi, the LED-based alternative to household Wi-Fi". Wired Magazine. Archived from the original on 25 May 2016.
  30. ↑ pureVLC (6 August 2012). "pureVLC Demonstrates Li-Fi Streaming along with Research Supporting World's Fastest Li-Fi Speeds up to 6 Gbit/s". Press release. Edinburgh. Archived from the original on 23 October 2013. Retrieved 22 October 2013.
  31. ↑ pureVLC (10 September 2013). "pureVLC Demonstrates Li-Fi Using Reflected Light". Edinburgh. Archived from the original on 29 June 2016. Retrieved 17 June 2016.
  32. ↑ Thomson, Iain (18 October 2013). "Forget Wi-Fi, boffins get 150Mbps Li-Fi connection from lightbulbs: Many (Chinese) hands make light work". The Register. Archived from the original on 22 October 2013. Retrieved 22 October 2013.
  33. ↑ Li-Fi internet solution from Russian company attracting foreign clients Archived 22 July 2014 at the Wayback Machine., Russia and India Report, Russia Beyond the Headlines, 1 July 2014
  34. ↑ Vega, Anna (14 July 2014). "Li-fi record data transmission of 10GBps set using LED lights". Engineering and Technology Magazine. Archived from the original on 25 November 2015. Retrieved 29 November 2015.
  35. 1 2 "Highly Sensitive Photon Counting Receivers for Li-Fi Systems - Lifi Research and Development Centre". Lifi Research and Development Centre. 3 July 2015. Archived from the original on 17 November 2016. Retrieved 17 November 2016.
  36. ↑ Chitnis, D.; Collins, S. (1 May 2014). "A SPAD-Based Photon Detecting System for Optical Communications". Journal of Lightwave Technology. 32 (10): 2028–2034. Bibcode:2014JLwT...32.2028.. doi:10.1109/JLT.2014.2316972. ISSN 0733-8724. Archived from the original on 16 October 2017.
  37. ↑ Tsonev, D.; Sinanovic, S.; Haas, Harald (15 September 2013). "Complete Modeling of Nonlinear Distortion in OFDM-Based Optical Wireless Communication". IEEE Journal of Lightwave Technology. 31 (18): 3064–3076. Bibcode:2013JLwT...31.3064T. doi:10.1109/JLT.2013.2278675.
  38. ↑ An IEEE Standard for Visible Light Communications Archived 29 August 2013 at the Wayback Machine. visiblelightcomm.com, dated April 2011. It is superfast modern intelnet technology.
  39. ↑ Breton, Johann (20 December 2013). "Li-Fi Smartphone to be Presented at CES 2014". Digital Versus. Archived from the original on 8 January 2014. Retrieved 16 January 2014.
  40. ↑ Rigg, Jamie (11 January 2014). "Smartphone concept incorporates LiFi sensor for receiving light-based data". Engadget. Archived from the original on 15 January 2014. Retrieved 16 January 2014.
  41. ↑ An Internet of Light: Going Online with LEDs and the First Li-Fi Smartphone Archived 11 January 2014 at the Wayback Machine., Motherboard Beta, Brian Merchant
  42. ↑ Van Camp, Jeffrey (19 January 2014). "Wysips Solar Charging Screen Could Eliminate Chargers and Wi-Fi". Digital Trends. Archived from the original on 7 November 2015. Retrieved 29 November 2015.
  43. ↑ LaMonica, Martin (18 February 2014). "Philips Creates Shopping Assistant with LEDs and Smart Phone". IEEE Spectrum. Archived from the original on 17 October 2017.
  44. ↑ "Li-Fi: Lighting the Future of Wireless Networks". Archived from the original on 18 April 2017. Retrieved 17 April 2017.
  45. ↑ "Applications of Li-Fi - Lifi Research and Development Centre". Lifi Research and Development Centre. Archived from the original on 30 October 2016. Retrieved 15 November 2016.
  46. ↑ "Li – Fi Technology, Implementations and Applications" (PDF). International Research Journal of Engineering and Technology (IRJET). Archived (PDF) from the original on 17 November 2016.
  47. ↑ "Archived copy". Archived from the original on 31 January 2017. Retrieved 4 February 2017.
  48. ↑ "Data Services of Li- Fi in Hospital Management- Communication in Hospitals" (PDF). International Journal of Science and Research (IJSR). Archived (PDF) from the original on 4 September 2014.
  49. ↑ "Get ready for Li-Fi: Ultrafast new technology shown off at tech show". Mail Online. Archived from the original on 17 November 2016. Retrieved 15 November 2016.
  50. ↑ "Applications of Li-Fi - pureLiFi™". pureLiFi™. Archived from the original on 20 November 2016. Retrieved 15 November 2016.
  51. ↑ Happich, Julien. "Fraunhofer IPMS pushes Li-Fi to 12.5Gbit/s for industrial use". European Business Press SA. André Rousselot. Archived from the original on 13 November 2017. Retrieved 13 November 2017.

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