In what could have a big impact on the Internet of Things, researchers at the University of Washington say they've developed the first power over Wi-Fi system that both delivers power and works with existing Wi-Fi chipsets.
Specifically, the researchers say a Wi-Fi router can provide far field wireless power without compromising the network's communications performance. "Building on our design we prototype, for the first time, battery-free temperature and camera sensors that are powered using Wi-Fi chipsets with ranges of 20 and 17 feet, respectively," they wrote in the paper "Powering the Next Billion Devices with Wi-Fi," led by Ph.D candidate Vamsi Talla.
The paper states that while recent efforts in the RFID community have focused on designing efficient 2.4 GHz harvesters, none of them have demonstrated power delivery using signals from existing Wi-Fi devices. To check if it would "just work," they placed a battery-free temperature sensor equipped with 2.4 GHz harvesting hardware 10 feet from their organization's Wi-Fi router. "We found that, over a 24-hour period, the sensor could not reach the minimum voltage of 300 mV to operate the harvesting hardware," they wrote.
But by co-designing harvesting hardware circuits and Wi-Fi router transmissions, they were able to achieve PoWiFi, or power over Wi-Fi. They prototyped their router design using Atheros chipsets.
"We have a huge Wi-Fi infrastructure already in place," Talla told Popular Science. "If we can repurpose existing infrastructure for power delivery as well, then we can actually enable wireless power delivery in homes and offices."
They were able to draw enough power from standard Wi-Fi signals to power a security camera and recharge a fitness tracker to 41 percent of its battery power in 2.5 hours.
To test potential effects on Internet speed, they outfitted six Seattle homes with active PoWiFi routers and asked the users to surf the web as they usually would. Four of six users found no difference, and one found the Internet service actually improved--though the researchers noted that the PoWifi router was a better model than their previous router, according to Popular Science.
Regarding fairness with other Wi-Fi networks, the research paper notes that PoWiFi is compliant with the 802.11 MAC protocol to ensure that active Wi-Fi devices get equal access to the wireless channel.
The researchers also say that there's increasing interest in the Internet of Things, where small computing sensors and mobile devices are embedded in everyday objects. A key issue is how to power these devices as they become smaller and more numerous; plugging them in to provide power is inconvenient and difficult at large scale.
Their work is related to efforts from startups such as San Jose, Calif.-based Energous, which developed WattUp, and Redmond, Wash.-based Ossia, which was named to the FierceWireless "Fierce 15" list last year. Ossia's Cota technology is designed to charge many devices simultaneously, regardless of whether a device is stationary or moving. Designed for an effective radius of 40 feet, a single Cota charging station can charge or power all the battery-operated devices in every room of an average home or office suite.
For more:
- see The Stack article
- check out this abstract
- see this Popular Science article
- see this Slash Gear article
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Ossia - wireless charging - wireless startups - Fierce 15 2014