In the future, lights in homes, schools and hospitals will be transmitting data, says professor Marcos Katz. By way of a new information transmission technology, LED lamps will relay a network signal in very high speed. Centre for Wireless Communications is a research center in the University of Oulu, which is developing a technology called “light data” and pondering its future applications.
Marcos Katz (pictured left) and doctoral thesis writer Muhammad Saad Saud illustrate the cooperation between light and radio network with test equipment (in the middle). In the test, video is transmitted from a LED lamp wirelessly into a lens acting as a receiver. The lens is connected to a screen which plays the transmitted video. When you place your hand between the lamp and the lens, the video is transmitted by a radio network and plays on.
Data is transmitted wirelessly mainly on radio waves. There are, however, only a limited number of radio frequencies. Especially in big cities there is so much data transmission that radio frequencies are running out.
”There are 10 000 times as many light frequencies than radio frequencies. That is enough for the growing needs of data transmission”, says Marcos Katz, professor of wireless data transmission. With light, data can also move dozens of times faster than on radio waves.
Li-Fi (Light Fidelity) and VLC (Visible Light Communication) are names used for the novel data transmission technology. Li-Fi will not visibly revolutionize data transmission, only technically. “Telecommunications will be integrated in lighting. The infrastructure already exists”, Katz explains.
The technology is based on making LED lamps flicker billions of times per second. With this flickering, the LED transmits a kind of a Morse code, whith travels within visible light. The receiver, a smart phone or such a thing, will interpret the code and display its content on its screen or some other way. That makes a LED lamp both a light source and a router for a network signal.
The receiver must have optics that can read light data. For example, a phone may have several little lenses for this purpose. “A lens is like an optical antenna, which can interpret the data the lamp is sending”, Katz describes. The human eye cannot notice that the light is flickering.
Light and radio need not compete
Data transmission with light is secure. In order to intercept data transmitted by light waves, the light must first be seen. Radio waves travel long distances, therefore intercepting and interference are easier.
Information transmitted via light data does not interfere with other devices. It can therefore be used for example in airplanes, hospitals and factories with radiowave-sensitive electronics. Also, health effects of radio waves are currently not completely clear. According to Katz, light data is a form of “pure technology” compared to traditional data transmission.
Data transmission via light is based on braking light up into code, which the optics of a receiver reads and displays.
Both traditional radio technology and data transmission via light have their advantages. Radio signals are still by far the best way to transmit information especially outside, where radio waves move long distances by way of masts. But inside buildings, Li-Fi may be the quicker and more secure option.
In principle, data transmission by light may decrease energy consumption. Energy efficiency is, however, hard to evaluate, because the faster data transmission we want to achieve, the quicker LED’s must flicker. Therefore, the receiver will need a more complex system, which needs more power.
Moreover, intensity of lighting will affect data transmission speed. Should lights then stay on constantly for transmission to work? “Yes and no. Light must be on, but it can be dimmed. Then transmission will be slower but remain substantial”, Katz explains. Neither does the light source need to be directly visible, as light waves are reflected on walls and only lose a small part of their intensity.
The major challenge with light data, says Katz, is not so much related to technology, but politics. “Radio controls the wireless world”, he says. Katz’s research group does not aim to pit radio and light against each other, but make different technologies cooperate as smoothly as possible. Instead of trying to replace radio, they try to develop a system where Li-Fi and data transmission by radio waves will complement one another.
The research group is developing a system for the future 5G technology, where light data is part of a radio network. A device used this way can automatically select either light or radio waves for data transmission. For example, a phone inside a pocket may use radio waves but switch to light data when taken out. By using both technologies simultaneously data transmission speed can be multiplied.
Light offers opportunities for Oulu
Marcos Katz sees light as potential for Oulu. Oulu has the only university in Finland studying the subject. Li-Fi has not yet fully broken through, but big companies are following the developments closely. “It is good to be a pioneer. There is a rumour that Apple is going to bring this technology to its devices. If that happens, the picture will completely change in one day”, professor Katz points out.
These everyday LED lights bought in a store can already be used for wireless data transmission.
The research project by the CWC center is developing a technology but also thinking about how to apply light data. Katz’s research group is designing light data applications in collaboration with the faculties of Education and Architecture. The researchers will concentrate on the potential of light data especially in schools, hospitals and traffic of the future.
LED lights can be grouped so that they work together like screens. In Katz’s visions, schools of the future will have smart devices wirelessly connected to this kind of lighting. This way LED’s in the ceiling will work interactively in teaching situations. They will give students personal feedback for their answers.
”In the future, lights can direct people the way musical conductors do”, Katz predicts. Hospital walls and ceilings may have LED’s that will indicate which way is safest to exit during a fire.
Light data may have a role in the roads of the future, as well. The signal transmitted by red LED’s may be used in brake lights, for example. The light data they transmit could tell the following car to slow down long before its human driver has reacted to the potential danger.
Katz talks enthusiastically about ”the Internet of all objects”. That means technology which enables all our objects to interact in a smart way. “Communication with light would be the natural way to do it”, says Professor Katz. Time will tell how bright our future with this new technology will be.
Text: Antti Miettinen
Pictures: Juha Sarkkinen
Last updated: 17.10.2016