Wi-Fi backscatter tech powers Wi-Fi devices using RF transmissions

The Internet of Things will revolutionize the way we interact with our electronics, providing an unparalleled level of insight and convenience through autonomous data gathering and control. Yet, the biggest detriment to growth is power consumption; all these Wi-Fi connections need power to operate. But now, researchers from the University of Washington have created a system that turns this notion on its head by drawing power directly from radio signals, thus eliminating the need for an external power supply.

The prototype system, called Wi-Fi backscatter, simultaneously connects devices to the Internet while drawing power from the signals used to connect them. This is accomplished using radio frequency (RF) backscatter technology to extract the power that exists as reflected energy each time a wireless router or other RF device broadcasts a signal within the Wi-Fi infrastructure. Similar to the technology found in RF ID tags, the RF Wi-Fi backscatter remains dormant until radio signals on the antenna spark an induced voltage, which generates the power to activate the circuit.

“If Internet of Things devices are going to take off, we must provide connectivity to the potentially billions of battery-free devices that will be embedded in everyday objects,” said Shyam Gollakota, a UW assistant professor of computer science and engineering. “We now have the ability to enable Wi-Fi connectivity for devices while consuming orders of magnitude less power than what Wi-Fi typically requires.”

The UW research builds upon prior studies demonstrating how wearables, or other low-energy devices, can be powered by scavenging energy from TV transmitters, radio towers, or any of the other RF sources around us. What sets UW’s findings apart is the unique method employed for connecting individual devices to the Internet.

Traditionally, the biggest challenge associated with Wi-Fi power transfer was that low-power Wi-Fi consumed anywhere between three to four times as much power as could be produced through Wi-Fi backscatter signals. To overcome this challenge, the University of Washington team crafted unique RF tags with ultra-low power consumptions that are receptive to the Wi-Fi signal moving between a router and connected device. These chips encode data by either reflecting or not reflecting the router’s wireless signal, minutely changing the signal. Wi-Fi-enabled devices detect the slight data variations from the tag.

“You might think, how could this possibly work when you have a low-power device making such a tiny change in the wireless signal? But the point is, if you’re looking for specific patterns, you can find it among all the other Wi-Fi reflections in an environment,” states the study’s co-author, Joshua Smith, a UW associate professor of computer science and electrical engineering. 

Currently, the Wi-Fi backscatter tag is able to achieve a data communication rate of 1 Kbit/s at a distance of up to 6.5 feet (2 meters). However, the team remains hopeful that it will be able to extend this range tenfold. 

Via UW