Researchers promote battery-free Wi-Fi technology

A research team at the University of Washington pushes forward with technology that uses radio frequency for power

The coming Internet of things (IoT) revolution may not run on batteries, but on power plucked from the air, according to researchers at the University of Washington.

More specifically, a university computer science and engineering team will present a paper this month on a technology called Wi-Fi backscatter, a new communication system that uses radio frequency signals as a power source. The communication technology holds the promise of connecting "billions" of devices to the Internet while avoiding the pesky, long-time problem with limited battery power, researchers said.

The technology has the potential to be "a very big deal," said Bryce Kellogg, a doctoral student in electrical engineering and co-author of a paper on Wi-Fi backscatter. "One of the biggest problems with connecting the next billion devices to the internet ... is the nightmare of charging or swapping batteries for all of them."

Traditional Wi-Fi devices are "very power expensive," Kellogg said. But Wi-Fi backscatter could "greatly reduce dependence on batteries and maybe even get rid of them and harvest energy for many devices," he added.

The University of Washington team developed an ultra-low power tag prototype with an antenna and circuitry that can be connected to a variety of electronic devices. The tags can talk to Wi-Fi-enabled laptops or smartphones, while consuming negligible power.

The tags monitor Wi-Fi signals moving between routers and laptops or smartphones. The tags encode data by either reflecting or not reflecting the Wi-Fi router's signals, making a small change in the wireless signal. Wi-Fi enabled laptops and smartphones then detect these small changes and receive data from the tag.

By exchanging data through the Wi-Fi signal changes, devices like smart watches could download email from laptops or smartphones or send information tracking your morning workout back to those larger devices, the researchers said.

The small changes in the Wi-Fi signal can be a useful way to exchange data, said co-author Joshua Smith, a University of Washington professor of computer science and engineering and of electrical engineering. "If you're looking for specific patterns, you can find it among all the other Wi-Fi reflections in an environment," he said by email.

The research team is considering starting a company to commercialize Wi-Fi backscatter, Smith added.

One of the beauties of Wi-Fi backscatter is there isn't much of a limit on the types of devices it could power, Kellogg said.

"Since it is so low power we are definitely not power constrained," he said. "The biggest constraint on size is the antenna, and Wi-Fi antennas can get very small. Your cell phone has multiple of them."

On the other side of the backscatter device chain, Wi-Fi access points can be upgraded to work with the technology through a software update, Kellogg said. "This means we could deploy a set of battery-free sensors or smart IoT devices around your house and then they could communicate with you existing Wi-Fi router," he said. "This approach removes a significant barrier to adoption."

The research team's backscatter tag has communicated with a Wi-Fi device at rates of 1kbps with about two meters between the devices. Researchers plan to extend the range to about 20 meters and have filed patents on the technology.

Grant Gross covers technology and telecom policy in the U.S. government for The IDG News Service. Follow Grant on Twitter at GrantGross. Grant's email address is grant_gross@idg.com.

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Tags wirelessNetworkingconsumer electronicsUniversity of WashingtonWLANs / Wi-Fijoshua smithBryce Kellogg

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Grant Gross

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