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May 01, 2023

Researchers devise smart glass windows that can polarize sunlight for wireless data transmission

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Basem Shihada, an associate professor of Computer Science at the King Abdullah University of Sciences and Technology (KAUST), had been exploring data encoding into an artificial light source when he wondered if the same could be done with sunshine.

"I was simply hoping to use a cell phone camera to record a video of the encoded light stream to try to decode the video to retrieve the data; that's when I thought, why not do the same with the sunlight?" Shihada said in a statement. "This would be much easier and can be done over the cell phone camera too. So we began to explore sunlight as an information carrier."

According to his study, "considerable amounts of ambient light remain unexploited and are mainly used for illumination purposes. Such light can be modulated to transmit data offering a complementary solution for wireless communication".

Sunshine streaming through a window could easily be harnessed for wireless data transmission to electronic devices.

Shihada and his team of KAUST researchers immediately got to work and designed a smart glass system (Switchable glass) that can regulate sunlight passing through it. The system would encode data into the light that can be detected and decoded by devices in the room.

Not only is the system innovative, but it also offers a greener mode of communication in comparison to conventional Wi-Fi or cellular data transmission.

The research was published in the IEEE Photonics Journal.

IEEE Photonics Journal (2022)

The devised system comprises two parts - a light modulator that can be embedded in a glass surface and an in-room receiver.

"The modulator is an array of our proposed smart glass elements known as Dual-cell Liquid Crystal Shutters (DLSs)," Osama Amin, a research scientist in Shihada's labs, said. The liquid shutter array would require only one Watt of power to operate, its function being to encode signals into the light as it passes, acting like a filter. The power would be supplied using a small solar panel.

Sahar Ammar, a student in Shihada's team, explained that data is usually encoded by varying the light intensity. "But if the frequency of these intensity changes is too low, it can be detected by the human eye and cause an uncomfortable flicker effect," she said.

Therefore, the DLS is designed in such a way that it can manipulate polarization. "Change in light polarization is imperceptible to the eye, eliminating the flicker problem," Ammar said. "The communication system works by changing the polarization of the incoming sunlight at the modulator side. The receiver can detect this change to decode the transmitted data."

According to the team, the designed setup can transmit data at 16 kilobits per second. "We are now ordering the necessary hardware for a testbed prototype implementation. We would like to increase the data rates from kilobits to mega- and gigabits per second," Shihada added.

Study Abstract:

Solar energy is widely used for electricity generation, heating systems, and indoor environment daytime illumination. Indeed, large amounts of sunlight energy remain insufficiently used. In this work, we aim at employing sunlight energy for data transmission as a green option for wireless communications. Being emitted by an uncontrollable source, taming the sunlight is a challenging task that requires appropriate technologies to manipulate incident light. Liquid crystal devices are switchable glass technologies that have adequate response time and contrast characteristics for such an application. In this regard, we design a novel dual-cell liquid crystal shutter (DLS) by stacking two liquid crystal cells that operate in opposite manners, and we build our sunlight modulator with an array of DLSs. Then, we adopt time division multiplexing and polarization-based modulation to boost the data rate and eliminate the flickering effect. In addition, we provide mathematical modeling of the system and study its performance in terms of communication and energy consumption. Finally, we introduce some numerical results to examine the impact of multiple parameters on the system's performance and compare it with the state-of-the-art, which showed that our system features higher data rates and extended link ranges.