[Mobile China] with the development of communication technology, our signal transmission speed is faster and faster. At present, mobile phone Kwai 5G is gradually supporting the speed of mobile Internet access. It goes without saying that 5g is fast. Many small partners may have experienced it. However, in addition to the mobile network, the home network is also a common place for us to surf the Internet. With WiFi, we can surf the Internet steadily and at high speed at home. Whether in bed, on the sofa, on the balcony or on the toilet, we always connect to WiFi in various ways. Even when our home is disconnected, we can rub the WiFi of the next house and collect the wool of our neighbor Lao Wang. However, when it comes to WiFi, many people still think that it is not fast enough to use mobile phones to connect WiFi at home. The next big game still needs to wait for about half an hour. At this time, a small partner may have played all the games. If I tell you, there’s a technology that’s 100 times faster than WiFi, do you believe it? Are you interested? Will you use it in your life? < / P > < p > this is lifi. You heard it correctly. Its name is similar to WiFi. The full name of lifi is “light fidelity”, which is a new wireless transmission technology that uses visible light spectrum (such as light emitted by light bulb) for data transmission. At present, the transmission speed of visible light can reach tens or even hundreds of megabytes per second, which is 100 times that of WiFi. In the future, the transmission speed of visible light may exceed that of optical fiber. In addition, it’s safer and more energy efficient than WiFi. < / P > < p > in December 2019, oppo applied to the State Intellectual Property Office for a patent for the design of smart phones, which was published only recently. The patent relates to a smart phone that can support lifi communication technology, which has a rectangular area on the back of the phone for placing lifi devices. This patent mainly describes the appearance design of oppo mobile phone, so there is little mention on how the mobile phone applies lifi technology. However, three days after filing the design patent, oppo also applied for the corresponding utility model patent. < / P > < p > this patent entitled “lifi device and its projection system” mainly discusses how oppo uses lifi technology in mobile devices. This lifi device, which is installed in oppo smart phone, is composed of shell, printed circuit board and lifi module for signal receiving. Lifi not only provides much higher transmission speed than WiFi, but also has lower latency (like 5g), and it can also support high frame rate transmission of high resolution images, such as large video and audio files. This accurately describes how the lifi technology works, and the document is now included in the WIPO database to protect this groundbreaking innovation globally. < p > < p > head Haas, the German physicist pioneer, is the inventor of lifi technology. Haas and his team demonstrated lifi for the first time in 2011. Lifi technology takes LED lamp as carrier, and uses electric signal to control led to send out high-speed flashing signal which can’t be seen by naked eye to transmit information. The system made of this technology can cover the range of indoor lighting. The computer does not need wire connection. As long as the light is turned on indoors, WiFi is not needed. < / P > < p > as long as it does not affect the normal lighting, the LED lamp modulates the information through the modulator in the chip, then carries the digital signal to the lamp, and uses the led to send out the fast light pulse to transmit the information. At the receiving end, the photoelectric converter is used to receive the visible light containing information and convert it into electrical signal. Then, filtering, shaping and amplification are carried out, and the corresponding analog information is demodulated. < / P > < p > If bidirectional transmission (i.e. downlink and uplink) or multi-channel transmission is required, spectrum division or multi-channel sampling modulation is required, and synchronous identification signal and synchronous detection signal are added. It is completely feasible for lifi to transmit information wirelessly by using fast light pulses. As long as the information is encoded in light according to different rates, for example, led on indicates 1 and off means 0, information can be transmitted through fast switch. Due to the luminous intensity of LED, the human eye will not notice the rapid change of light. < / P > < p > although we use WiFi a lot, this technology also has some disadvantages, such as the power consumption of router antenna pole in WiFi communication. As LED lights have been widely used, lifi should be more energy-saving and efficient. Regional limitations may also be a problem with WiFi. For example, in an airplane, there is no WiFi signal, not even a mobile network. Therefore, the value of lifi is reflected in such areas. < / P > < p > in addition, security and privacy are issues of wide concern. Because radio waves can penetrate walls, they are easy to be intercepted by criminals and steal personal information. Lifi can solve these problems. First of all, the transmission speed of lifi is very fast. At present, its speed has exceeded 10Gbps, which is 100 times faster than the current WiFi network. In the future, this speed may even exceed 15gbps through adaptive LEDs and systems. < / P > < p > in addition, lifi can also be used in high-density environments, so that more people can use the lifi network. This technology can even enable underwater communication, which is the main reason why the U.S. Navy has shown interest in this new technology, which they hope to use to improve submarine communication. Lifi also has an additional advantage, because light can’t penetrate the wall, so as long as we close the curtain in the room and keep the LED light out of the room, our personal information will not be intercepted and leaked by criminals. Because it uses light to transmit signals, it is also very friendly to the human body. < / P > < p > today, there are still some people who are very sensitive to WiFi’s radio waves, and even people are controversial about the harm of WiFi. Using lifi will not cause such problems. However, the main drawback of lifi is that it only has a 10 meter range, while WiFi has a 32 meter range. In addition, lifi is only suitable for unidirectional downlink transmission, and bidirectional transmission is still a difficult problem for this technology. < / P > < p > due to the above characteristics of lifi technology, it may not completely replace WiFi, but it may become an important supplement to WiFi. The security of lifi technology can make it applied in many places where WiFi cannot be deployed or is inconvenient to deploy, such as hospitals, mines or airplanes. Meanwhile, due to the privacy of lifi technology, it can also provide support for confidential meetings or military affairs.