Visible light communication
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It has been suggested that this article or section be merged into Free-space optical communication#Visible light communication . (Discuss) Proposed since January 2011. |
Visible light communication (VLC) is a data communications medium using visible light between 400 THz (780 nm) and 800 THz (375 nm). Visible light is not injurious to vision.
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. Low rate data transmissions at 1 kilometre (0.6 mi) and 2 kilometres (1.2 mi) were demonstrated.[1][2] RONJA achieves full Ethernet speed (10 Mbit/s) over the same distance thanks to larger optics and more powerful LED.
Specially designed electronic devices generally containing a photodiode receive signals from such light sources,[1] although in some cases a cell phone camera or a digital camera will be sufficient.[3] 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 sensor may provide either a multi-channel communication (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, car headlights/taillights, etc.[4]) are used everywhere.[3]
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[edit] History
The history of Visible Light Communications (VLC) dates back to 1880 when Scotsman Alexander Graham Bell demonstrated the Photophone which transmitted speech on modulated sunlight over several hundred meters. It is interesting to note that this actually pre-dates the transmission of speech via radio.
More recently the Nakagawa Laboratory, in Keio University, Japan began work in 2003 using LEDs to transmit data by visible light. Since then there have been numerous research activities focussed on VLC. The notable research activities being Smart Lighting Engineering Centre, Omega Project, ByteLight, Inc.D-Light Project, UC-Light Centre and work at Oxford University.
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 IEEE Wireless Personal Area Networks working group (802.15).
In December 2010 St. Cloud, Minnesota was the first to commercially deploy this technology.[6]
In July 2011 a live demonstration of high definition video being transmitted from a standard LED lamp was show at TED Global.
[edit] See also
- Free space optics
- IrDA — Same principle as VLC but uses infrared light instead of visible light
[edit] References
- ^ a b c "Image Sensor Communication". VLC Consortium. http://www.vlcc.net/modules/pico2/index.php?content_id=28.[dead link]
- ^ "Lighthouse Sub Project". VLC Consortium. http://www.vlcc.net/modules/pico3/index.php?content_id=7.[dead link]
- ^ a b "About Visible Light Communication". VLC Consortium. http://www.vlcc.net/modules/pico2/index.php?content_id=1.[dead link]
- ^ "Intelligent Transport System – Visible Light Communication". VLC Consortium. http://www.vlcc.net/modules/pico2/index.php?content_id=4.[dead link]
- ^ "500 Megabits/Second with White LED Light" (Press release). Siemens. Jan 18, 2010. http://w1.siemens.com/innovation/en/news_events/ct_pressreleases/e_research_news/2010/e_22_resnews_1002_1.htm.
- ^ "St. Cloud first to sign on for new technology" (Press release). St.Cloud Times. Nov 19, 2010. http://www.sctimes.com/apps/pbcs.dll/article?AID=2011101070009.[dead link]
[edit] External links
- IEEE 802.15 WPAN Task Group 7 (TG7) Visible Light Communication
