Wi-Fi chip cannibalizes ambient Wi-Fi signals for power

IoT Wi-Fi radios may soon be the size of a grain of rice and transmit messages forever—without maintenance

Wi-Fi chip cannibalizes ambient Wi-Fi signals for power
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Harvesting electromagnetic energy from thin air to develop self-sustaining Internet of Things (IoT) communications may become reality thanks to a new technology called HitchHike. The goal is to reduce the need for continual maintenance of the expected billions of IoT installations. 

Researchers say they’re close to the finish line. Worst case scenario, they say they’ll be able to get Wi-Fi chips to run for 10 years on the same, small battery.

“HitchHike is the first self-sufficient Wi-Fi system that enables data transmission using just micro-watts of energy, almost zero,” claims Pengyu Zhang, a Stanford researcher, in a recent press release from the school.

Existing commodity infrastructure working with a harvesting technique called “backscatter” signals is behind the researchers' work to achieving Wi-Fi efficiency for IoT.

+ Also on Network World: How the Wi-Fi industry is adapting to keep up with the IoT +

Backscattering is the term used for the creation of new signals quaffed from gathered, ambient radio waves, such as existing television. Those radio signals, prevalent anyway, are ingested and converted into new signals. It uses a kind of reflection cannibalization. The energy from the siphoned radio waves powers the new ones.

In this case, the academics’ processor and radio combination equipment piggy-backs on incoming Wi-Fi signals of the kind we all use in laptop and smartphone communications. It then “translates those incoming signals to its own messages and retransmits its own data on a different Wi-Fi channel.”

The HitchHike prototype is about the size of a postage stamp and uses a coin battery. However, the researchers say they will be able to shrink that, and ultimately it will be as small as the proverbial grain of rice.

The scientists say their device has a functioning range of 50 meters and will be able to message at 300 kilobits per second. IoT-oriented messaging often doesn’t need high bandwidth, just frequent sending and receiving functionality of brief commands.

The low power is the real draw

But it’s the low power use that’s really more exciting here. For IoT to really take off, experts say one can’t expect end users to change out batteries annually. An example I’ve used before describing this problem is in the backyard scenario of hundreds of connected plants. Each moisture sensor could be connect to the municipal water district and report on the flora’s aridity. The water company’s algorithms would then deliver a splash as necessary. The logistical problem is the power—the homeowner likely isn’t going to want to spend a Saturday morning changing a hundred batteries or so.

That kind of thing is why there's a race to find low-power chips and, indeed, more efficient battery chemistry and powering techniques.

“HitchHike consumes 10,000 times less current than Wi-Fi radios. It can operate for years on a simple coin battery,” the scientists claim.

The ideas behind backscatter technologies aren’t all new. But the Stanford work is fresh in that it reuses the 802.11b Wi-Fi using “codeword translation”—a way of embedding the IoT information in standard, existing 802.11b packets, allowing any receiver to decode it.

Therefore, it doesn’t need special hardware, including signal generators, as other backscatter systems would, the researchers explain.

“A backscatter system that can be deployed using commodity Wi-Fi radios on access points, smartphones, watches and tablets, does not exist,” the team says in its paper (pdf).

The HitchHike prototype “can be used as is with existing Wi-Fi without modification.”

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Copyright © 2016 IDG Communications, Inc.

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