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Harvesting Wi-Fi Backscatter To Power Internet of Things Sensors
vinces99 (2792707) writes "Imagine a world in which your wristwatch or other wearable device communicates directly with your online profiles, storing information about your daily activities where you can best access it – all without requiring batteries. Or, battery-free sensors embedded around your home that could track minute-by-minute temperature changes and send that information to your thermostat to help conserve energy. This not-so-distant 'Internet of Things' reality would extend connectivity to perhaps billions of devices. Sensors could be embedded in everyday objects to help monitor and track everything from the structural safety of bridges to the health of your heart. But having a way to cheaply power and connect these devices to the Internet has kept this from taking off. Now, University of Washington engineers have designed a new communication system that uses radio frequency signals as a power source and reuses existing Wi-Fi infrastructure to provide Internet connectivity to these devices. Called Wi-Fi backscatter, this technology is the first that can connect battery-free devices to Wi-Fi infrastructure. The researchers will publish their results at the Association for Computing Machinery's Special Interest Group on Data Communication's annual conference this month in Chicago. The team also plans to start a company based on the technology.
The Pre-print research paper.
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...is new again:
http://en.wikipedia.org/wiki/The_Great_Seal_bug
Nice to see the idea being put to a less nefarious use. :)
Really the wristwatch is a silly example; there are better ways to harvest energy on a wristwatch than RF leaching. Stationary objects that can't rely on kinetic energy harvesting could utilize this technology, though.
Anyway, they did test for the interference potential of this, and it was indeed very little at the rates/distances acheived.
I think they should see how much they could *increase* the effect of the reflection on WiFi signals. Then they could look to market passive devices that, instead of being purposed for the "internet of things", are purposed to work in cooperation with MIMO/spatial multiplexing to dynamically adapt the RF environment to increase the overall bandwidth of WiFi devices, allowing an access point to turn them on and off until it gets just the right reflections. Then license that to WiFi vendors to sell them lithographed by the thousands into wallpaper or just thrown helter skepter on top of drop ceiling tiles.
Someone had to do it.
no, the intent is not stupid.
It's malicious.
Don't get me wrong, I'd love to have my gadgets talk to each other. But in this day and age, I doubt that I get to choose the topic.
We used to have a Bill of Rights. Now, with the rights gone, all we have left is the bill.
It's very different from iFind...
This paper flat out says that it's impossible to harvest enough energy from RF sources to power any kind of radio transmitter. Instead, it takes advantage of the existing idea that although you can't transmit your own signals, you can at least selectively block or intefere with someone else's RF signals. And the paper's clever invention is to apply this known technique to wifi in particular, so as to work with off-the-shelf wifi routers.
By contrast, iFind claimed it could harvest enough energy from RF to power a bluetooth transmitter.
... when there's much more energy in light or heat?
Solar cells power calculators and garden lights pretty well. Domestic lights put out 5-100 watts of power distributed around a room.
Wifi power levels are much lower - 0.15 watts or so.
Andrew Yeomans
Oh great. You take a walk during lunch because you're concerned about your health. You stop to re-tie your shoe. Too bad your watch tattled that you just paused in front of a 'bookstore' that sells gay porn.
Suddenly you get spammed with offers for gay porn. It's also too bad your employer was exempted from EOE because it's against the corporation's sincerely held religion, so you get fired in the process.
Sadly for you, as you take that long walk back to your parking space you pause a gain (you'll never learn!) next to a fast food joint. By the time you get home you have an e-mail informing you of the increase in your health insurance premium.
The internet of things could be interesting if those things would report to a server that I own and control. Too bad most corporations make internet enabled things report to them so they can sell your personal information to the highest bidder with no questions asked.
It only works because it has a very low bitrate of 1kbps:
Although the authors claim that "The Wi-Fi Backscatter tags do not require any batteries and can harvest energy from ambient RF signals" they make no attempt to back up this claim with measured or estimated energy efficiency of this transmitter. The standard metric for high efficiency transceivers is joules per bit, because low bitrate communication always consumes less energy than high speed, but the only useful way to compare it to another high efficiency transmitter is to see if it can transmit a certain amount of data for less energy.
While I don't expect every paper to address every aspect of a technology, they should not then turn around and make baseless claims like "We believe that this new capability is critical for the commercial adoption of RF-powered Internet of Things." in a length 12 page paper that fails to address the one metric which would allow them to make such a claim.
Tesla had a long-range high-power transmission system up and running. It just wasn't commercially viable - the transmission losses were so huge, you'd have to pump in orders of magnitude more energy than you get out at the other end. There are some impressive photos of him standing by light bulbs in a field, powered by a transmitter many miles away - but not shown is the sizeable power station he had hooked up to run the thing.
Wireless power transmission makes it extremely hard to monitor usage and thus extract payment.
TV companies have found a solution.
I will continue to call the phrase "Internet of Things" stupid, for as long as you continue to hype it.
The battle of pointless endurance is mine!
The "internet of things" is a pure marketing play. It broad brushes a huge spectrum of possible devices even though any single item typically only applies to a small slice of that market. It is too broad and useless when describing anything in particular, but will be used so that every related product can be considered a big freakin deal. Investors... please line up at the door.....
Wifi is already too good in many situations. We should be mandating that new houses are basically Faraday cages to cut down on RF interference from wifi, Bluetooth, energy monitors, smart meters, video senders, wireless headphones and all the other random devices people own these days.
const int one = 65536; (Silvermoon, Texture.cs)
SJW, n: "Someone I don't like, and by the way I'm a fuckwit" - AC
Exactly. It's like saying a telescope sucks power out of whatever it looks at. Electromagnetic radiation doesn't work that way.
Kythe