Visible light communication

Visible light communication (VLC) is a data communications variant which uses visible light between 400 and 800 THz (780–375 nm). VLC is a subset of optical wireless communications technologies.

Visible light is only a small portion of the electromagnetic spectrum.

The technology uses fluorescent lamps (ordinary lamps, not special communications devices) to transmit signals at 10 kbit/s, or LEDs for up to 500 Mbit/s over short distances. Systems such as RONJA can transmit at full Ethernet speed (10 Mbit/s) over distances of 1–2 kilometres (0.6–1.2 mi).

Specially designed electronic devices generally containing a photodiode receive signals from light sources,[1] although in some cases a cell phone camera or a digital camera will be sufficient.[2] The image sensor used in these devices is in fact an array of photodiodes (pixels) and in some applications its use may be preferred over a single photodiode. Such a sensor may provide either multi-channel (down to 1 pixel = 1 channel) or a spatial awareness of multiple light sources.[1]

VLC can be used as a communications medium for ubiquitous computing, because light-producing devices (such as indoor/outdoor lamps, TVs, traffic signs, commercial displays and car headlights/taillights[3]) are used everywhere.[2]

History

The history of visible light communications (VLC) dates back to the 1880s in Washington, D.C. when the Scottish-born scientist Alexander Graham Bell invented the photophone, which transmitted speech on modulated sunlight over several hundred meters. This pre-dates the transmission of speech by radio.

More recent work began in 2003 at Nakagawa Laboratory, in Keio University, Japan, using LEDs to transmit data by visible light. Since then there have been numerous research activities focussed on VLC.

In 2006, researchers from CICTR at Penn State proposed a combination of power line communication (PLC) and white light LED to provide broadband access for indoor applications.[4] This research suggested that VLC could be deployed as a perfect last-mile solution in the future.

In January 2010 a team of researchers from Siemens and Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute in Berlin demonstrated transmission at 500 Mbit/s with a white LED over a distance of 5 metres (16 ft), and 100 Mbit/s over longer distance using five LEDs.[5]

The VLC standardization process is conducted within the IEEE 802.15.7 working group.

In December 2010 St. Cloud, Minnesota, signed a contract with LVX Minnesota and became the first to commercially deploy this technology.[6]

In July 2011 a presentation at TED Global.[7] gave a live demonstration of high-definition video being transmitted from a standard LED lamp, and proposed the term Li-Fi to refer to a subset of VLC technology.

Recently, VLC-based indoor positioning systems have become an attractive topic. ABI research forecasts that it could be a key solution to unlocking the $5 billion "indoor location market".[8] Publications have been coming from Nakagawa Laboratory,[9] ByteLight filed a patent[10] on a light positioning system using LED digital pulse recognition in March 2012.[11][12] COWA at Penn State[13][14] and other researchers around the world.[15][16]

Another recent application is in the world of toys, thanks to cost-efficient and low-complexity implementation, which only requires one microcontroller and one LED as optical front-end.[17]

VLCs can be used for providing security.[18][19] They are especially useful in body sensor networks and personal area networks.

Recently Organic LEDs (OLED) have been used as optical transceivers to build up VLC communication links up to 10 Mbit/s.[20]

In October 2014, Axrtek launched a commercial bidirectional RGB LED VLC system called MOMO that transmits down and up at speeds of 300 Mbit/s and with a range of 25 feet.[21]

In May 2015, Philips collaborated with supermarket company Carrefour to deliver VLC location-based services to shoppers' smartphones in a hypermarket in Lille, France.[22] In June 2015, two Chinese companies, Kuang-Chi and Ping An Bank, partnered to introduce a payment card that communicates information through a unique visible light.[23] In March 2017, Philips set up the first VLC location-based services to shoppers' smartphones in Germany. The installation was presented at EuroShop in Düsseldorf (March 5 – 9 th). As first supermarket in Germany an Edeka supermarket in Düsseldorf-Bilk is using the system, which offers a 30 centimeter positioning accuracy can be achieved, which meets the special demands in food retail.[24][25] Indoor positioning systems based on VLC[26] can be used in places such as hospitals, eldercare homes, warehouses, and large, open offices to locate people and control indoor robotic vehicles.

There is wireless network that for data transmission uses visible light, and does not use intensity modulation of optical sources. The idea is to use vibration generator instead of optical sources for data transmission.[27]

Colour shift keying

Color shift keying (CSK), outlined in IEEE 802.15.7, is an intensity modulation based modulation scheme for VLC. CSK is intensity-based, as the modulated signal takes on an instantaneous color equal to the physical sum of three (red/green/blue) LED instantaneous intensities. This modulated signal jumps instantaneously, from symbol to symbol, across different visible colors; hence, CSK can be construed as a form of frequency shifting. However, this instantaneous variation in the transmitted color is not to be humanly perceptible, because of the limited temporal sensitivity in the human vision — the "critical flicker fusion threshold" (CFF) and the "critical color fusion threshold" (CCF), both of which cannot resolve temporal changes shorter than 0.01 second. The LEDs’ transmissions are, therefore, preset to time-average (over the CFF and the CCF) to a specific time-constant color. Humans can thus perceive only this preset color that seems constant over time, but cannot perceive the instantaneous color that varies rapidly in time. In other words, CSK transmission maintains a constant time-averaged luminous flux, even as its symbol sequence varies rapidly in chromaticity.[28]

gollark: Mostly okay. Though as of now I'm kind of bored and putting off maths homework.
gollark: Hi, since I happen to be here, I guess.
gollark: I mean, if we're registering opinions on school now, I don't like it much.
gollark: Er. Is this a general thing, or what?
gollark: At least on mine, which is "seventh generation" or something.

See also

References
  1. "Image Sensor Communication". VLC Consortium.
  2. "About Visible Light Communication". VLC Consortium. Archived from the original on December 3, 2009.
  3. "Intelligent Transport System – Visible Light Communication". VLC Consortium. Archived from the original on January 28, 2010.
  4. M. Kavehrad, P. Amirshahi, "Hybrid MV-LV Power Lines and White Light Emitting Diodes for Triple-Play Broadband Access Communications," IEC Comprehensive Report on Achieving the Triple Play: Technologies and Business Models for Success, ISBN 1-931695-51-2, pp. 167-178, January 2006. See publication here Archived 2016-03-04 at the Wayback Machine
  5. "500 Megabits/Second with White LED Light" (Press release). Siemens. January 18, 2010. Archived from the original on September 29, 2012. Retrieved June 21, 2012.
  6. "St. Cloud first to sign on for new technology" (Press release). St. Cloud Times. Nov 19, 2010.
  7. "Wireless data from every light bulb".
  8. "LED and Visible Light Communications Could be Key to Unlocking $5 Billion Indoor Location Market". www.abiresearch.com.
  9. Yoshino, M.; Haruyama, S.; Nakagawa, M.; , "High-accuracy positioning system using visible LED lights and image sensor," Radio and Wireless Symposium, 2008 IEEE , vol., no., pp.439-442, 22-24 Jan. 2008.
  10. "Light positioning system using digital pulse recognition".
  11. Yoshino, Masaki; Haruyama, Shinichiro; Nakagawa, Masao (1 January 2008). "High-accuracy positioning system using visible LED lights and image sensor". 2008 IEEE Radio and Wireless Symposium. pp. 439–442. doi:10.1109/RWS.2008.4463523. ISBN 978-1-4244-1462-8 – via IEEE Xplore.
  12. S. Horikawa, T. Komine, S. Haruyama and M. Nakagawa,”Pervasive Visible Light Positioning System using White LED Lighting”, IEICE, CAS2003-142,2003.
  13. Zhang, W.; Kavehrad, M. (2012). "A 2-D indoor localization system based on visible light LED". 2012 IEEE Photonics Society Summer Topical Meeting Series. pp. 80–81. doi:10.1109/PHOSST.2012.6280711. ISBN 978-1-4577-1527-3.
  14. Lee, Yong Up; Kavehrad, Mohsen (2012). "Long-range indoor hybrid localization system design with visible light communications and wireless network". 2012 IEEE Photonics Society Summer Topical Meeting Series. pp. 82–83. doi:10.1109/PHOSST.2012.6280712. ISBN 978-1-4577-1527-3.
  15. Panta, K.; Armstrong, J. (2012). "Indoor localisation using white LEDs". Electronics Letters. 48 (4): 228. doi:10.1049/el.2011.3759.
  16. Kim, Hyun-Seung; Kim, Deok-Rae; Yang, Se-Hoon; Son, Yong-Hwan; Han, Sang-Kook (2011). "Indoor positioning system based on carrier allocation visible light communication". 2011 International Quantum Electronics Conference (IQEC) and Conference on Lasers and Electro-Optics (CLEO) Pacific Rim incorporating the Australasian Conference on Optics, Lasers and Spectroscopy and the Australian Conference on Optical Fibre Technology. pp. 787–789. doi:10.1109/IQEC-CLEO.2011.6193741. ISBN 978-0-9775657-8-8.
  17. Giustiniano, Domenico; Tippenhauer, Nils Ole; Mangold, Stefan (2012). "Low-complexity Visible Light Networking with LED-to-LED communication". 2012 IFIP Wireless Days. pp. 1–8. doi:10.1109/WD.2012.6402861. ISBN 978-1-4673-4404-3.
  18. Xin Huang; Bangdao Chen; A.W. Roscoe; , "Multi−Channel Key Distribution Protocols Using Visible Light Communications in Body Sensor Networks", Computer Science Student Conference 2012, (pp. 15), Nov. 2012., See publication here
  19. Huang, X.; Guo, S.; Chen, B.; Roscoe, A. W. (2012). Bootstrapping body sensor networks using human controlled LED-camera channels. pp. 433–438. ISBN 978-1-4673-5325-0.
  20. Haigh, Paul Anthony; Bausi, Francesco; Ghassemlooy, Zabih; Papakonstantinou, Ioannis; Le Minh, Hoa; Fléchon, Charlotte; Cacialli, Franco (2014). "Visible light communications: Real time 10 Mb/S link with a low bandwidth polymer light-emitting diode". Optics Express. 22 (3): 2830–8. Bibcode:2014OExpr..22.2830H. doi:10.1364/OE.22.002830. PMID 24663574.
  21. Axrtek MOMO Axrtek, Inc.
  22. "Where are the discounts? Carrefour's LED supermarket lighting from Philips will guide you" (Press release). Philips. May 21, 2015.
  23. Chen, Guojing (June 28, 2015). "Commercial banks eye mobile payment innovations". China Economic Net. Archived from the original on October 3, 2018.
  24. "Two more indoor positioning projects sprout in European supermarkets". www.ledsmagazine.com. 2017-03-08.
  25. "Favendo collaborates with Philips Lighting" (PDF).
  26. "Visible Light Communication". www.ntu.edu.sg. Retrieved 2015-12-24.
  27. Bodrenko, A.I. (2017). "New Wireless Technology Not Covered by the Existing IEEE Standards of 2017". International Research Journal (published 2018) (4 (70)). doi:10.23670/IRJ.2018.70.022.
  28. Aziz, Amena Ejaz; Wong, Kainam Thomas; Chen, Jung-Chieh (2017). "Color-Shift Keying—How itItsargest Obtainable "Minimum Distance" Depends on its Preset Operating Chromaticity and Constellation Size". Journal of Lightwave Technology. 35 (13): 2724–2733. Bibcode:2017JLwT...35.2724A. doi:10.1109/JLT.2017.2693363.

Further reading
  • David G. Aviv (2006): Laser Space Communications, ARTECH HOUSE. ISBN 1-59693-028-4.
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