As the society continues to develop high-power LEDs based on solid-state lighting, a bold and innovative approach appears in the minds of some visionary engineers. Their advice is: Why not let the LEDs on/off switch so fast that the human eye can't tell, and use them to transmit data?
This proposal is the theoretical basis of visible light communication (VLC). With enough advanced technology support, each new LED luminaire can also be wired to the backbone network, enabling any device in the room to achieve ubiquitous wireless communication without increasing the already burdensome RF bandwidth burden. Many industries, standards organizations and government agencies that are heavily funded are developing visible light communications. The prospects for visible light communication are very broad, as the traditional lighting market has reached trillions of dollars and the transition to solid-state lighting has begun. According to Strategies Unlimited, the LED lighting market will exceed $1 billion this year and is expected to grow to approximately $7.3 billion by 2014.
Of course, the focus of solid-state lighting is to reduce greenhouse gas emissions, because LED lamps consume much less power than current standard lighting products. But the huge market has inspired almost every major electronic research organization to invest in the development of visible light communication applications.
Most visible light communication applications are not intended to replace other wireless technologies, such as Bluetooth, Wi-Fi, WiMax, and LTE. Applications are targeted at applications where current RF wireless communications cannot be implemented, such as hospitals and aircraft. Radio frequencies can interfere with signals in life-critical devices; robots -- they can navigate using virtual road signs in headlights for information transfer; signage -- provides additional information when the phone camera points at it.
Japan's visible light communication alliance members include Casio, NEC, Matsushita Electric Engineering, Samsung, Sharp, Toshiba and NTT Docomo. The alliance is working to promote the IEEE 802.15 Wireless Personal Area Network Standards Committee to increase the ".7" work, with a view to Visible light communication is upgraded to the same wireless state as RF and IR. The 802.15.7 committee has just approved the current draft version of the wireless VLC standard at the working group level. "But we still have a lot of problems to solve," said Rick Roberts, an Intel laboratory scientist and technical editor of the IEEE 802.15.7 committee.
"The reason for the interest of IEEE is the widespread popularity of LEDs. The current LED technology is mainly used for lighting, but if the wireless market is also developed, we know from the past experience that we need to standardize interoperability." Roberts said, " Our standardization work began in 2008 and is expected to finalize the standard next year."
According to Roberts, the primary task of the 801.15.7 committee is to implement the standards for lighting first and communication second. "Visible light communication is the only 'wireless communication' signal that can be seen with the naked eye, so it can't affect others." He pointed out, "For example, visible light communication is not suitable for remote control because people usually watch TV in dark rooms. You don't want to see the flashing light from the remote control? Communication with LEDs does not cause light to flicker, and visible light communication must adapt to the way people usually use lighting sources, such as light adjustment."
Figure 1: Just as the brake light "tells" the driver to stop, the VLC can send the same message to the engine control unit to avoid collisions.
VLC opens up space for creative applications
Visible light communication is expected to form a series of new applications. Although it can be realized by Wi-Fi or infrared, it is more convenient or safer to realize by visible light. For example, mutual interference with adjacent RF signals may limit the use of Wi-Fi, while visible light is substantially free of interference problems; adjacent beams may pass through as long as their destinations are different. For safety reasons, RF communications such as hospitals and airplanes are prohibited in some places. Visible light communication is an ideal alternative to these applications because LED illumination is already in use, and visible light communication does not interfere with system signals that carry important tasks. At the same time, visible light communication also has the potential for high data capacity.
"Visible light communication can implement various types of new applications," Roberts said. "I especially like smart LED signs that can display ''cho's restaurant'', but if you take out the mobile device and point to this sign You can also download more information - such as the restaurant's address, menus, even coupons, etc. You have to expand your imagination, and there are a lot of new possible applications."
Samsung is experimenting with the use of visible light communication in LED-based backlit LCD flat panel displays so that users can download all information from product information to website addresses. "We believe that LCD backlight communication is one of the best applications for visible light communication, because LCD backlights are turning to LEDs," said Scott Birnbaum, vice president of Samsung's LCD business unit.