sensors in a low-resolution camera and other devices.
University of Washington engineers have developed a story technology
that works on the Wi-Fi router -- a way to obtain ubiquitous but untapped energy
in indoor environments -- to power devices.
The Power Over Wi-Fi (PoWiFi) system is one of the most innovative
and game-changing technologies of the season, based on Popular
Science, which included it in the magazine's annual "Best of What's
New" awards announced Wednesday.
The technology attracted attention earlier in 2010 when researchers
published an online paper showing how they harvested energy from Wi-
Fi signals to power a straightforward temperature sensor, a low-resolution
grayscale camera and a charger for a Jawbone activity tracking
bracelet.
The last paper is going to be presented the following month at the Association for
Computing Machinery's CoNEXT 2015 conference in Heidelberg,
Germany, on emerging networking experiments and technologies.
"For the first time we've shown that you should use Wi-Fi devices to
power the sensors in cameras and other devices," said lead author
Vamsi Talla, a UW electrical engineering doctoral student. "We also
made a system that can co-exist as a Wi-Fi router and an electric
source -- it doesn't degrade the caliber of your Wi-Fi signals while
it's powering devices."
PoWiFi may help enable development of the Internet of Things, where
small computing sensors are embedded in everyday objects like cell
phones, coffee makers, washing machines, air conditioners, mobile
devices, allowing those devices to "talk" to each other. But one major
challenge is how to energize those low-power sensors and actuators
without having to plug them into a power source as they become
smaller and more numerous.
The team of UW computer science and electrical engineers found that
the peak energy found in untapped, ambient Wi-Fi signals often
came near meeting the operating requirements for some low-power
devices. But since the signals are sent intermittently, energy "leaked"
out of the system during silent periods.
The team fixed that problem by optimizing a hub to send
superfluous "power packets" on Wi-Fi channels not currently used --
essentially beefing up the Wi-Fi signal for power delivery -- without
affecting the quality and speed of data transmission. The team also
developed sensors that may be integrated in devices to harvest the
power.
Inside their proof-of-concept experiments, the team demonstrated that the
PoWiFi system could wirelessly power a grayscale, low-power
Omnivision VGA camera from 17 feet away, and can store enough
energy to recapture a picture every 35 minutes.
Additionally it re-charged the battery of a Jawbone Up24 wearable fitness
tracker from zero to 41 percent in 2.5 hours.
The researchers also tested the PoWiFi system in six homes. Users
typically didn't notice deterioration in website loading or video
streaming experiences, showing the technology could successfully deliver
power via Wi-Fi in real-world conditions without degrading network
performance.
Although initial experiments harvested relatively small amounts of
power, the UW team believes there's chance for make the PoWiFi
system more effective and robust.
"As time goes on, PoWi-Fi could leverage technology power scaling to
further improve the efficiency of the device allow operation at larger
distances and power numerous more sensors and applications," said
co-author Shyam Gollakota, assistant professor of computer science
and engineering.
The research is funded by the National Science Foundation, Qualcomm
and the UW.
Co-authors include UW electrical engineering doctoral students Bryce
Kellogg and Saman Naderiparizi, research associate Benjamin
Ransford and associate professor of computer science & engineering
and of electrical engineering Joshua Smith.
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