Researchers eliminate need for external power in Wi-Fi connectivity system


August 5, 2014

Researchers have developed a wireless system that directly powers Wi-Fi connections using RF backscatter

Researchers have developed a wireless system that directly powers Wi-Fi connections using RF backscatter

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One of the advantages of the "connected world" is that myriad different devices can interact with each other over Wi-Fi to exchange data, control equipment, and generally lay the foundations of the Internet of Things of the not-too-distant future. Unfortunately, on the downside, all of the Wi-Fi connections need power to operate, and this severely restricts the pervasiveness of this technology. However, researchers at the University of Washington have developed a system that they say eliminates the need for power supplies for these connections by using what is known as radio frequency (RF) backscatter technology.

The researchers claim that their prototype technology uses radio signals as a source of power and incorporates this in existing Wi-Fi infrastructure to deliver connections to the internet for devices. The power is sourced via RF Wi-Fi backscatter that exists as reflected energy whenever a wireless router or other radio frequency device transmits (similar to the technology found in RF ID tags, where the circuit remains dormant until radio signals on the device’s antenna create an induced voltage in the circuit to power the device).

In effect, the system scavenges power from the wireless transmitting devices around it to power battery-free devices and connect them to the Internet. Previous technological challenges in providing such Wi-Fi connectivity was that even low-power Wi-Fi consumes three to four times more power than can generally be wrought from Wi-Fi backscatter signals.

To solve this problem, the team claims to have developed its own RF tag prototypes that have ultra-low power consumption. With in-built antennas and circuits that are able to communicate with Wi-Fi-enabled devices such as laptops or smartphones, the team says that they are able to maintain this connection with minimal power.

"If [the] 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."

In essence, to save power and maximize efficiency, the UW team's tags operate by receiving Wi-Fi signals transmitted between the router and a connected device, such as a laptop. By either reflecting or not reflecting the Wi-Fi router transmitted RF energy, the tags then encode data accordingly, to minutely change the wireless signal. Other Wi-Fi-enabled devices then detect these minute changes and receive data 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?" co-author and UW associate professor Joshua Smith said. "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."

The UW team’s work is premised upon previous investigations on ambient backscatter that demonstrated how low-energy requirement devices such as wearable technology could be powered by scavenging energy from the all-pervasive radio signals from TV transmitters, radio towers, and other RF sources that exist all around us. According to the UW engineers, this research enhances that capability to connect individual devices to the internet, which the team claims was not possible previously.

According to the UW team, the Wi-Fi backscatter tag it has developed has achieved a data communication rate of 1 kbps with a Wi-Fi device about 2 m (6.5 ft) distant. The researchers assert that they will attempt to increase the range tenfold and plan to launch a company based on their proprietary technology, with patents being filed to protect their intellectual property.

The team intends to publish the results at the SIGCOMM (Special Interest Group on Data Communication) annual conference this month in Chicago.

The short video below shows the technology being demonstrated in the lab.

Source: University of Washington

About the Author
Colin Jeffrey Colin discovered technology at an early age, pulling apart clocks, radios, and the family TV. Despite his father's remonstrations that he never put anything back together, Colin went on to become an electronics engineer. Later he decided to get a degree in anthropology, and used that to do all manner of interesting things masquerading as work. Even later he took up sculpting, moved to the coast, and never learned to surf. All articles by Colin Jeffrey

What would this be useful for? The only things I can that I would want to connect to the internet or exchange data with, would also have a power supply of either battery or AC / DC. This would be useful for exchanging data with say a rock or a tree, but I don't see how that would be beneficial. Joking aside, I wonder if these could be daisy chained as a way to extend existing wireless infrastructure.

All that said, reducing the power requirements of WIFI is great. And if they can get the range up about 100 times and speeds up about 1,000,000 times, I suppose we can find some interesting uses for it.

Matt Sanders

this is the kind of invention where you don't realize it's a billion dollar idea until many other pieces of the internet of things standardization puzzle comes together.

after that falls into place, many useful puzzle parts, each in their own right worth millions/billions to the overall project of scaling up our world into a giant heaven/hell of information based monitoring devices.

this rf reflector simply holds out the possibility for eliminating the need for as much power storage capacity to run a connected device. ultimately , the device will still need a battery to run it's own electronics, but those require ultra low power and thus a far smaller more effiient battery.

by making things smaller, you make their production scale exponenentially. so by LOWERING POWER REQUIREMENTS YOU ARE SCALING UP .

do not forget that nature's primary design for her evolved systems over billions of years is always to lower power requirements. always. never forget. the future of technology is about lower power requirements.

this device might not seem useful now, but the likelihood is that it eventually will find itself a place to be commercially useful where devices needing small batteries can be upgraded to need even smaller batteries.

(ultimately this is premised on the idea that the cost of the rf reflector, and the circuitry that runs the reflector AND the cost of operating that circuitry is precisely what the inventors claim----lower in terms of energy than of constructing and operating a conventional wifi emitter.)

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