WiFi to LiFi
Lightning-Fast Indoor Data
By Professor Janusz Konrad
When you use your smartphone or tablet for a Skype call or to search the internet at home or at a coffee shop, you usually rely on WiFi. When too many people want to watch their favorite shows at the same time, none of them, can get a steady streaming signal (the dreaded hourglass) since the bandwidth of each WiFi access point is quite narrow. Soon, however, all members of a family may be able to watch different shows on their mobile devices at the same time, each in 4K definition, without any difficulties.
ECE researchers are working to make this vision a reality. With the ongoing LED lighting revolution, not only do they want to deliver energy-efficient and visually-pleasing illumination, but they also want to send data to mobile devices at high rates by means of visible light communication (VLC), often referred to as LiFi (Light Fidelity). Since LED light can be modulated at hundreds of MHz, future light fixtures can serve as data transmitters without bothering our eyes, since humans cannot see light fluctuations above 60 Hz. To achieve this goal, however, several issues need to be resolved. How to reliably send data at high rates using visible-light spectrum? How to steer and focus the light beam on a small area of a mobile receiver? And, finally, how to find where the mobile receivers are? Several of our faculty are working to answer these questions within the Lighting Enabled Systems and Applications (LESA) Engineering Research Center funded by the National Science Foundation.
Professor Thomas Little and his research team work on optical wireless communication and networking using the visible spectrum produced by overhead lighting. These optical networks will bring much needed additional capacity, reduce download delays, and have low installation and maintenance costs. Properties of light allow for short-distance and low-interference communication links yet add significant new capacity between mobile devices and the Internet.
Professor David Bishop’s team is working on steering the light to assure quality illumination and to focus data light beams. Their current research focuses on microelectromechanical systems (MEMS) that allow spatial division multiplexing within solid state lighting. In addition to steering the light, the optical MEMS are capable of focal length variation so the light reflected from the mirror can be shaped (either focused or diffused) dynamically.
Professors Janusz Konrad and Prakash Ishwar, and their students are leveraging light sensors to identify where people are in a room, what they are doing and which way they are facing in order to optimize illumination and to steer data light beams towards mobile devices. They use ultra-low resolution sensors, as low as a single pixel, in order to assure user privacy; that is, to learn what a person is doing without identifying the person.