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Wireless Communication with the Power of Sunlight

Researcher with smart glass

Sahar Ammar, a Ph.D. student at King Abdullah University of Science and Technology (KAUST), Saudi Arabia, shows an experimental sample of a dual-cell liquid-crystal “smart glass.” A system that encodes sunlight using such glasses could, in the view of the KAUST team, help enable energy-efficient communication between Internet of Things (IoT) devices. [Image: © 2022 KAUST]

Researchers in Saudi Arabia have figured out a way to harness sunlight for wireless communications using a novel “smart”-glass system (IEEE Photonics J., doi: 10.1109/JPHOT.2022.3200833). The device contains an array of dual-cell liquid-crystal shutters, which encodes signals into the light as it passes through.

While the smart-glass system has not yet been built, the team’s proposed design and simulation results demonstrate that, with further development, it may provide a greener alternative to conventional Wi-Fi or cellular data transmission.

Designing a sunlight modulator

Basem Shihada, a computer science professor at King Abdullah University of Science and Technology (KAUST), initially thought about encoding data into an artificial light source. It then dawned on him to try the same thing with sunlight to save energy.

“I was intrigued by the idea of harnessing sunlight for such an unusual purpose as wireless communication applications,” said Sahar Ammar, a Ph.D. candidate co-supervised by Shihada and Mohamed-Slim Alouini, also at KAUST. “So I began to explore the potential of using smart-glass technologies to manipulate the properties of daylight in order to build a green wireless communication solution.”

Ammar and her colleagues designed a dual-cell liquid-crystal shutter by stacking two liquid-crystal cells operating in opposite manners. A sunlight modulator that covers a whole window, for example, might feasibly be built up with an array of duel-cell liquid-crystal shutter pairs. Such a device, according to the study, could offer fast and symmetrical switching times, requiring just 1 W of power to operate, which can be supplied using a small solar panel.

The researchers envision sunlight passing through a window equipped with the array of shutters, which would selectively filter the light in a way that encodes data. The modulated light would then travel to a receiver located indoors that consists of two photodetectors with polarizers.

An energy-efficient solution

Typical wireless communication technologies are based on either radio frequency (RF) or optical transmission. While RF systems suffer from a congested frequency band, optical systems require energy-expensive light sources, such as lasers and LEDs. Using sunlight as information carrier, the researchers hope, would enable energy-efficient wireless communication with an unlicensed, wide optical band.

Mathematical modeling reveals that the smart-glass system could transmit data at a rate of 16 Kbps. Ammar and her colleagues foresee the sunlight modulator being implemented for indoor Internet of Things (IoT) applications in wireless sensor networks, since they require both low data rates and low energy consumption.

“We intend to practically implement the sunlight communication system and further improve its performance in terms of data rates to achieve Mbps and Gbps,” Ammar said.

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