Monsters university

Researchers Set New Record for Data Transmission Using LED Light


The Internet of Things should have some 20 billion products online by 2020, which means that the radio spectrum used by these products to transmit information wirelessly will become increasingly congested. As more and more internet-connected devices demand a share of the radio spectrum, pressure was exerted on the National Telecommunications and Information Administration at regulate more spectrum for the devices to work.

In the meantime, researchers are experimenting with unregulated frequencies on the electromagnetic spectrum (like those in the visible and infrared light range) to develop new ways of transmitting data wirelessly in an increasingly noisy world.

The latest development in this field comes from the King Abdullah University of Science and Technology in Saudi Arabia, where researchers have successfully created a light bulb able to transmit data more than 20 times faster than before LiFi devices.

Most LiFi visible light communication (VLC) methods use bulbs that transmit data wirelessly using light emitting diodes (LEDs). LiFi is similar to WiFi, but rather than using lower frequencies that are closer to the radio spectrum, LiFi operates in the higher frequencies characteristic of visible, infrared and ultraviolet light.

The electromagnetic spectrum. Image: Wikimedia Commons

LiFi LED devices typically work by combining blue diodes with phosphor which transforms some of that radiation into red and green light, resulting in the desired white light for a bulb or display device.

“VLC using white light generated in this way is limited to around one hundred million bits per second”, noted Boon Ooi, professor of electrical engineering at King Abdullah University of Science and Technology (KAUST).

The reason for this limit in the amount of data that can be transferred is that this process of generating white light is much slower than the speed at which an LED light can be turned on and off. The phosphors used in these devices are a photoluminescent material commonly found in LEDs, but their photoluminescent lifespan is relatively long once activated by a blue diode, so limit the bandwidth of the device to about 12 megahertz (MHz).

The speed at which the light can turn on and off is important as this is the method that LED light uses to communicate. By turning on and off faster than the eye can see, the LED communicates in binary code with a receiver.

As detailed in their recent article for ACS Photonics, KAUST researchers improved this VLC model by using a nanocrystalline structure consisting of lead cesium bromide combined with a conventional phosphorus nitride. When they projected a blue laser on the nanocrystals, it emitted a green light while the nitride emitted a red light. When the green and red lights were combined, they emitted a soft white glow.

As the researchers found, the addition of this nanocrystalline structure reduced the phosphor photoluminescent lifespan from the microsecond range characteristic of traditional LEDs to just seven nanoseconds. This has enabled bandwidth of nearly 500 megahertz and data transmission rates of up to two billion bits per second (2 Gbps), a 20-fold increase over other VLC technologies operating at around 100 million. bits (100 Mbps).

For comparison, most WiFi systems that you will encounter today operate at speeds in the order of a few tens of Mbps.

Not only was this a dramatic improvement in data transmission rates, but the light emitted by the team’s bulb was of a quality comparable to that of other LED lights and was in fact more energy efficient. .

“In this bandwidth-hungry era, consumers will be constantly pushed by VLC systems with higher bit rates,” Ooi said. “We believe that white light generated using solid-state lasers will one day replace white light LED bulbs for energy efficient lighting.