Fudan University studies visible light communication "Li-Fi"
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Click on the LED light to get online without Wi-Fi signal, and click on the LED light to get online. Yesterday, the School of Computer Science and Technology of Fudan University reported good news, an international frontier communication technology that uses the visible light transmission network signal in the house to be successfully realized in the laboratory. The researchers connected the network signal to a 1W LED bead. The four computers under the light can access the Internet. The maximum speed is 3.25G and the average Internet speed is 150M. It is the fastest lighting Internet in the world. Next month, 10 prototypes will be unveiled at the 2013 Shanghai Industry Fair.
Visible light communication is called Li-Fi
All along, a shiny light bulb was painted on the head of a person, symbolizing the inspiration of an inventor, but the German physicist Harald Haas lit up the whimsy by the light bulb itself: Relying on a small light, the invisible network signal becomes a visible network signal. Haas and his team at the University of Edinburgh in the UK have invented a patented technology that uses flashing lights to transmit digital information. This process is called visible light communication (VLC), which is often called Li-Fi. In order to show that it can bring revolutionary changes to the wireless network transmission technology represented by Wi-Fi.
How far is this unimaginable network technology from us? The answer is: very close, it is coming to us from the Fudan University laboratory step by step. Xue Xiangyang, a professor at the School of Computer Science and Technology of Fudan University, told reporters that the current radio signal transmission equipment has many limitations. They are rare, expensive, but not efficient. For example, mobile phones, millions of base stations around the world help them enhance their signals, but most of them Energy is consumed in cooling, and the efficiency is only 5. In contrast, the bulbs used in the world are inexhaustible, especially in domestic LED light sources are replacing traditional incandescent lamps on a large scale. Simply add a microchip to any humble LED bulb to turn the bulb into a wireless network transmitter.
Visible and safe communication of visible light communication Since last year, the Shanghai Municipal Science and Technology Commission has deployed this internationally advanced wireless communication technology in universities and research institutes throughout the city. The research and application of key technologies for visible light communication undertaken by Fudan University have made important progress: In the laboratory environment, the visible light is used to transmit the network signal, and the realization can be one for four, that is, one small light is illuminated, and four computers can simultaneously access the Internet and transmit the network signal at the same time. Professor Chi Nan, a researcher, pointed out that light, like radio waves, is a kind of electromagnetic wave, and the basic principle of transmitting network signals is consistent. In the research, the ordinary LED bulb is equipped with a microchip, which can control it to flash millions of times per second. It lights up to indicate 1 and extinguishes to represent 0. Since the frequency is too fast, the human eye can not detect it at all, but the photosensitive sensor can Received these changes. In this way, the binary data is quickly encoded into a light signal and transmitted efficiently. The computer under the light reads the Morse code in the light through a special set of receiving devices.
Where there is light, there is a network signal. Turn off the lights, no network. Chi Nan told reporters that compared with existing Wi-Fi, the future visible light communication is safe and economical. Wi-Fi relies on invisible radio wave transmission, the power of the device is getting larger and larger, and the local electromagnetic radiation is bound to increase; the wireless signal passes through the wall and the network information is not safe. These security risks are swept away in visible light communication. Moreover, the spectrum is 10,000 times larger than the radio spectrum, meaning more bandwidth and higher speeds, and the network setup requires almost no new infrastructure.
Li-Fi technology also has its limitations. Of course, as a new network technology and products still in the laboratory, its future potential should not be overestimated. Because a series of key technology products, from lighting communication control to chip design and manufacturing, are all done by researchers. To truly enter the home like Wi-Fi, it needs a series of industrial development, and it is still very long. The way to go. Chi Nan believes that Li-Fi technology itself has its limitations, for example, if the lights are blocked, the network signal will be cut off and so on. Therefore, it is not a competitor to Wi-Fi, but a complement to each other that helps to free up the spectrum space. In the future, whether it can produce killer-style applications, but also rely on people's unlimited imagination: cars rely on LED lights to talk, passengers in the aircraft cabin use the overhead LED reading lights to access the Internet 
