Passive WiFi could be 10000 times more energy efficient

Researchers at the University of Washington have developed a new type of Wi-Fi, called "passive Wi-Fi". They hope that the new technology will put an end to fast-drained device batteries, which is considered a big downside of the current Wi-Fi technology.

The big advantage of 'Passive Wi-Fi' is that it uses 10,000 times less power than traditional Wi-Fi. It is even more efficient than Bluetooth Low Energy and Zigbee. 'Passive Wi-Fi' consumes only 10-50 microwatts, compared to the state of the art in low power Wi-Fi transmissions today which consume 100s of milliwatts.

The technology is based on a phenomenon known as "backscatter." While most Wi-Fi connections currently require two powered radio signals, the new standard would need only a single powered device, which would generate a single-frequency signal. "Passive" devices could then 'reflect' that tone, while also shifting it to synthesize wireless transmissions.

"We wanted to see if we could achieve wi-fi transmissions using almost no power at all," said co-author Shyam Gollakota, a UW assistant professor of computer science and engineering. "That's basically what Passive Wi-Fi delivers. We can get wi-fi for 10,000 times less power than the best thing that's out there."

"The low power passive device isn't transmitting anything at all. It's creating Wi-Fi packets just by reflection," says Vamsi Talla, another student working on the project. "It's a transmission technique that's ultra low-powered, as opposed to a network device." All the networking, heavy-lifting and power-consuming pieces are done by the one plugged-in devic. The passive devices are only reflecting to generate the wi-fi packets, which is a really energy-efficient way to communicate."

"Our sensors can talk to any router, smartphone, tablet or other electronic device with a wi-fi chipset," said co-author and electrical engineering doctoral student Bryce Kellogg. "The cool thing is that all these devices can decode the wi-fi packets we created using reflections so you don't need specialized equipment."

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