Explore the "past life" of visible light communication LiFi"
time：2017-07-29 11:18:00 browse：5135次
In October 2013, Fudan University received good news, LED visible light communication technology in its computer science and technology laboratory successfully achieved. The researchers will access a network signal 1W LED chip, under the light of the 4 computer to the Internet, the highest rate of up to 3.25G, the average Internet speeds up to 150M, the world's fastest "lights on the internet". For a time, "Fudan University achieve the lighting on the Internet" news spread like wildfire. Subsequently, the news about visible light communication technology came in like a flood, and LiFi had a complete fire.
Visible light communication research has long been open
The concept of visible light communication was not made in 2013. In fact, as early as 2000, Tanaka of Keio University in Japan and Haruyama of SONY Research Institute of computer science put forward an indoor communication system using LED lamp as communication base station for wireless transmission of information. In 2002, Tanaka and Komine et al carried out a detailed analysis of the LED visible light communication system, and in the same year formally proposed a set of data transmission system combining power line carrier communication and LED visible light communication. Time flies, the researchers never give up the research, finally in the October 2008 Tokyo International Electronics Show, Taiyo Yuden Japan company to the world for the first time display in a communication system, white LED at that time, the maximum transmission distance is only 20cm. Although it was quite a short distance, it was indeed a unique innovation technology!
Research on lens switching to domestic visible light communication. In 2006, Peking University proposed the reception scheme of ultra wide viewing angle signal based on wide-angle lens for the first time, and carried out a series of theoretical and experimental work. In 2008, following Japan's first public display of white LED communications systems, Jinan University professor Chen Changying developed the first white LED visible light communications prototype, transmitting distances greater than 2.5 meters. But until 2013, "Fudan University to achieve LED lighting Internet" news crazy transmission network, LED visible light communication is really presented in front of the domestic people.
After Japan and China, European countries have also demonstrated the research of visible light communication. In 2009, the University of Oxford Brien et al use equalization technology to achieve the communication rate of 100 Mbit/s; the following year, they displayed indoor visible light communication system demo, using 16 white LED communication, the real-time broadcasting 4 Hd video. By 2010, researchers at the Fraunhofer Henrich Hertz Institute laboratory in Germany had raised the communication rate to 513 Mbit/s, creating a world record for visible light communications speeds. Visible light communication was not called LiFi at that time, but VLC (Visible Light Communication). Until 2011, Professor Harald, of University of Edinburgh, demonstrated how LED bulbs with signal processing technology could transmit high-definition video onto computers and named visible light communications as LiFi (Light Fidelity). In October 2013, researchers from several universities in the UK refreshed LiFi's communications rate to as high as 10Gb/s.
Visible light communication technology is being commercialized
LED visible light communication is not a "pet" in the laboratory, it has gradually commercialized. In October 2013, PureLiFi, founded by Professor Haas (formerly known as PureVLC), sold the first LiFi equipment to a medical institution in the United States with a value of 5000 euros (RMB 41 thousand yuan). The deal marks the official recognition of LiFi's practical business value.
Recently, at this year's International Consumer Electronics Show (CES), the French company Oledcomm demonstrated mobile devices that enable optical communications. Technology and staff will be converted into a smart phone front camera light sensor, so that the audience witnessed LiFi optical communications technology, transmission rate of about 10Mpbs. The company said it will achieve industrialization of visible light communications next year.
Visible light communication is widely used
Visible light communication has four main application areas are: 1) lighting and communication, information can be broadcast in the indoor environment, and meet the lighting requirements at the same time; 2) visual signal and data transmission, signal lamp mainly through the color change to provide people the signal, and the data communication and signal lamp combination it can provide better security and reliability for traffic management; 3) display and data communication, LED display is usually used to display information, if the relevant information and data is directly transmitted to the user terminal, will provide great convenience, at the train station, the airport has a great application prospect; 4) indoor positioning, visible optical communication can be the location information of the user through the lighting facilities to carry out the transfer, compared with the traditional satellite positioning is more accurate.
Future prospects for visible light communications
The development and promotion of new technologies is not always smooth sailing. Although LiFi has many advantages, it will also face many technical problems. For example: how can the Internet be turned off during daylight hours? Visible light can not penetrate objects. If the lights are blocked, the signal will be cut off. How can we do that? How can the data return be difficult to solve?
These problems are a headache, and researchers are trying to find a solution. Chi Nan, a professor at the school of information science and engineering at Fudan University, said that a new technology has been developed in the world, and the Internet can be realized by turning on the weak current under the condition that the LED light does not emit light. Professor Haas has said that WiFi can be a complementary technology for LiFi, which can be seamlessly switched to radio frequency communication systems when the lights are blocked. In addition, Professor Hou said that two-way transmission of data remains a major problem. Lighting is easy on the computer, but it's not easy to install data on a computer or cell phone.
"There is no dedicated chip set for visible light communications, and the launch and reception system is very large and needs to be perfected," Nan said. We should objectively look at visible light communication technology. LED light is not designed for communication, so the LED lamp has a narrow bandwidth, about 20MHz, and have a strong nonlinear effect. The detector is not designed for visible light, and Blu ray is not the most sensitive frequency band. Therefore, a series of studies should be done on materials, devices, packages, modules and so on. She said, at present in Fudan laboratory, from lighting, communications control to chip design, manufacturing and a series of key technical products, researchers are doing it themselves. The transmitter and receiver used for sending and receiving network signals are two laptops so large that they are clearly not available.
Therefore, the compression and industrialization of related chips are the most difficult problems for lighting people to enter the internet. Late Nan said, chip compression research and development needs a lot of money, in the people already have the premise of WiFi, whether it will spend a lot of money to research and development LiFi chip needed is unknown. But overall, LiFi is undoubtedly the next generation of smart city applications. In the next generation of cities, the smart grid is complete, and smart wires are connected to thousands of homes. Coupled with the compact chip made visible light communications, transmitting and receiving equipment, LED lighting access to the Internet can be universal.
