Become a fan of Slashdot on Facebook

 


Forgot your password?
Close
typodupeerror
×
Wireless Networking Communications Power

Wireless Devices Go Battery-Free With New Communication Technique 111

Posted by Soulskill from the harvesting-energy-from-the-ether dept.
melios sends this quote from an University of Washington news release: "[E]ngineers have created a new wireless communication system that allows devices to interact with each other without relying on batteries or wires for power. The new communication technique, which the researchers call 'ambient backscatter,' takes advantage of the TV and cellular transmissions that already surround us around the clock. Two devices communicate with each other by reflecting the existing signals to exchange information. The researchers built small, battery-free devices with antennas that can detect, harness and reflect a TV signal, which then is picked up by other similar devices."

This discussion has been archived. No new comments can be posted.

Wireless Devices Go Battery-Free With New Communication Technique More

Wireless Devices Go Battery-Free With New Communication Technique

Comments Filter:

  • New??? (Score:3)

    by acariquara ( 753971 ) on Wednesday August 14, 2013 @06:02PM (#44569319) Journal

    http://en.wikipedia.org/wiki/Crystal_radio [wikipedia.org]

    • Re:New??? (Score:5, Informative)

      by bobbied ( 2522392 ) on Wednesday August 14, 2013 @06:19PM (#44569461)
      Not exactly the same thing, but receiving RF without power has been done for about as long as RF has been received... Actually... Exactly as long as RF has been received. Crystal Radios where how this whole "Let's communicate by radio waves" thing got started...

    • Re:New??? (Score:5, Insightful)

      by mcl630 ( 1839996 ) on Wednesday August 14, 2013 @06:21PM (#44569479)

      Not quite the same. Crystal radios can't transmit information, only receive it, while this can both transmit and received. In the sense that they're powered only by the RF received, they are similar.

  • ....small.....

  • tinfoil hat: check
    shielded paint: check
    wide range radio scrambler: check

  • The Technology is Not New (Score:5, Informative)

    by bobbied ( 2522392 ) on Wednesday August 14, 2013 @06:15PM (#44569421)

    This is not new technology.

    Toll Tags and other RF-ID devices have been using "back scatter" techniques to capture energy to transmit with for decades. The reader device provides RF energy that is captured by the tag charging up a capacitor enough to send a short burst of data back to the reader. I saw this being done during a Job interview in Dallas sometime in the 90's and was impressed with the idea. I was even more impressed that it worked well enough to actually be in use on various tolling systems. Still remember the test rig they had with the tags mounted to the ceiling fan blades as being decidedly low tech, but wonderfully effective.

    The application might be a bit different, but the technology is NOT new.

    • Re: (Score:2)

      by cusco ( 717999 )
      Key card readers have been using this since the 1980s for access control systems. The big new thing here is that new electronics can be so low-power that they're able to use the ambient background radiation of modern civilization rather than a dedicated reader. If this works reliably it's going to be huge in the access control, alarm system, building automation, and remote sensor industries.

      • Actually, Key Card systems are not quite the same as what I described for the toll tags. Many of those systems actually require close coupling with the reader to get the data off them and are not really storing the energy transferred for later use. The card is magnetically coupled to the reader and the data on the card clocked out though the same link. The readers and the cards are much simpler (and thus cheaper) but is decidedly not the same thing,

        Of course the principle of getting power without having

        • Re:The Technology is Not New (Score:5, Informative)

          by adolf ( 21054 ) <flodadolf@gmail.com> on Wednesday August 14, 2013 @07:51PM (#44570139) Journal

          Actually, passive key cards do store the energy for later use.

          "Later" happens to be measured in microseconds or so, but it's still later (much, much later in computer terms).

          First, the antenna inside of the card is used with a rectifier and a capacitor to make DC voltage to power an IC from the RF energy radiated by the card reader. Once the voltage is high enough (which cannot occur instantaneously), that IC then uses the energy stored in its capacitor to send its ID string over the same antenna that was part of a power supply a brief moment earlier.

          And like anything else RF, distance is largely a function of radiated power and receiver sensitivity. Cards and readers generally only work within a few inches merely because that was one of the design parameters, not because that is the maximum attainable using the technique:

          Improve the performance of the card (more capacitance combined with a beefier RF section), and/or increase the sensitivity of the reader (using a higher-gain antenna and/or lower-noise electronics), and functional operating distance is increased accordingly.

          • near field is induction, far field is radio (Score:4, Informative)

            by raymorris ( 2726007 ) on Wednesday August 14, 2013 @11:03PM (#44571009) Journal

            Interesting comments. You mentioned RF power functions. The main function for radio, also called far field, is that power drops with the square of distance.

              I'd like to point out card readers do not work using radio waves, not like these devices do. At distances less than about 1 wavelength, the primary effect is what's called "near field", commonly referred to as induction. This is the same way transformers work. Near field power drops at distance to the SIXTH power. That means that while it's very strong within a few millimeters, it basically dissapears within a few centimeters or meters.

            The new devices are using RADIO energy from arbitrary far away sources. Card readers use near field induction, a completely different mechanism.

            • Re: (Score:2, Informative)

              by adolf ( 21054 )

              I'd like to point out that the frequencies involved are most certainly RF.

              Inductive coupling is a cute efficiency trick, but it's not necessary -- even in existing systems.

              (And if inductive coupling were really the primary means of communication, we'd be calling the radiating elements "inductors" instead of "antennas." I mean: It's not as if these two concepts are not well-understood, even if they are often related.)

              Meanwhile, I do not understand your millimeter boojigity as it relates to common practice:

              • As I mentioned, near field predominates up to about one wavelength, and basically goes away at around four X wavelength. For reference, commercial AM radio in the US is about 1/2 meter wave, commercial FM is about 1/2 centimeter.

                So if your key used a wavelength similar to AM radio, the near field would be detectable up to about two meters. In your experiment , you found that it's detectable up to about that distance. It may use a frequency slightly lower than AM radio, meaning a slightly longer wavelength.

            • Re: (Score:2)

              by cusco ( 717999 )
              You're thinking of the credit card readers, which do use near-field induction. I was talking about proximity card readers, such as are used in access control systems. The most common format, the HID Wigand standard cards, use a 125 kHz RF field to power the card, which may function from as much as five meters away. There are other formats that use other frequencies.

              • > The most common format, the HID Wigand standard cards, use a 125 kHz RF field to power the card, which may function from as much as five meters away.

                Pulling out our handy calculator, we find that the wavelength way down there at 125 Khz is 2400 meters.
                That means the near field at such a low frequency is dominant to about 2400 meters away. It means a quarter wave radio antenna would be 600 meters long.
                Do you think you have a 60 meter antenna in that PROXIMITY card, to pick up RADIATED signals, or o you

                • Re: (Score:2)

                  by cusco ( 717999 )
                  Interesting. Cards have an antenna that is 1 - 2 1/2 meters long (older cards have the longer antennas, I assume because they need more power). Depending on the reader they will function anywhere from 1 mm to 5 m away. I have heard of custom readers that will work from further, but have never worked with one. Looks like we're both wrong, I guess.

              • Re: (Score:2)

                by chihowa ( 366380 )

                As he said above, "At distances less than about 1 wavelength, the primary effect is what's called "near field", commonly referred to as induction."

                At 125 kHz, one wavelength is 2.4 km. Even at 13.56 Mhz (also used in proximity readers), one wavelength is 22 m. Even the reactive nearfield region for these frequencies is 380 m and 3.6 m, respectively. The range at which the cards work has more to do with the emitted power of the base station than near- or far- field effects.

      • Re: (Score:1)

        by gwjgwj ( 727408 )
        The problem is, that the background radiation level can also fall down when all the electronics reduces the power consumption.

    • Re: (Score:1)

      by Anonymous Coward

      Who said it is new technology? That is your words.

      It is a new technique under the backscatter methodology for re-using existing energy sources.
      It is completely different to the method used by RFID, but they both use the similar parent technique of using backscatter, that is the only relation they have.

      Regardless, it will allow for some more interesting technology as the research improves. (as well as easy spying tools)

      • First thought that came to me was using the unique blend from my device picture of the backscatter surround and yours to create a snapshot 'fingerprint' that could be used as key and seed for a one-time pad to use for secure comms. No two people at a given time will have the same, if the resolution is fine enough.

      • Re:The Technology is Not New (Score:4, Interesting)

        by bobbied ( 2522392 ) on Wednesday August 14, 2013 @07:32PM (#44570035)

        Why does it matter where the "backscatter" energy comes from? It doesn't matter if the energy is "ambient" or specifically supplied it comes though the RF fields it is receiving. The device I described didn't care where the energy came from, it just took energy it found and charged up something so it could use it later. This "new" device is no different in principle, and certainly not that different in application to what I saw nearly 20 years ago now.

        Heck, I remember back in the 80's listening to my EE power systems instructor showing us how you could get "free" power from the utility companies with a sufficient sized coil of wire and then calculating the amount of wire you would need. This is exactly the same physics (albeit at 60 Cycles and not RF so the wire you need is less) he was discussing way back then. This is NOT a new idea. The application is not new either...

        Spying equipment has used backscatter power for even longer than toll tags. In one cold war situation, the US embassy was built by local contractors and riddled with passively powered listening devices. They where literally put everywhere. The Embassy was finished and occupied when the adversary decided it was time to crack up the RF and "power up" the microphones. The RF exposure in the building was pretty bad from then on and additional Faraday shielding was subsequently added to secure the building (at least until another one could be built).

        I suppose it might seem new, being repackaged and smaller than before... But those toll tags where not much bigger than a credit card...

        • Re:The Technology is Not New (Score:4, Insightful)

          by Sockatume ( 732728 ) on Thursday August 15, 2013 @02:37AM (#44571667)

          It matters because it's interesting and implies new applications. Why is it that every time there's a new idea presented on Slashdot, the slightest connection to existing technology makes it completely worthless?

          • Like I said.. This is not new technology... It's not based on anything recently "discovered" in science nor is it a measurable step forward in features.

          • Why is it that every time there's a new idea presented on Slashdot, the slightest connection to existing technology makes it completely worthless?

            For some people, it's easier to tear down another person's idea or accomplishment than to accomplish something great themselves. It's really like saying, "I could've done that... but I didn't... 'cause it's dumb."

    • Re: (Score:2)

      by jon3k ( 691256 )
      Ambient backscatter. Ambient is the keyword here.

    • But RFID tags dont transmit anything.

      They modulate the load seen by the tag readers antenna by modulating the power drawn from the tag antenna by short circuiting it.

      • Re: (Score:2)

        by tlhIngan ( 30335 )

        They modulate the load seen by the tag readers antenna by modulating the power drawn from the tag antenna by short circuiting it.

        It is a form of transmission, still, even though it's not actively broadcasting.

        What you need ot know is that wireless power has been with us for a long time now - basically since the late 1800s. We've been putting energy in the air since then. Of course, it's what Tesla was experimenting with, except his system was trying to boost efficiency as wireless power transmission is stil

    • It's not very widely useful either. They mention getting the things to work at 6.5 miles from a television tower. That's great if you happen to be that close to a megawatt transmitter. Not so great everywhere else. Their effective (one device to another) is also very limited, because transmitter power is super low. It's limited to less than what you receive off the transmitter, which is not much. At a mile from a TV tower, you've got a few milliwatts to work with at most.

      It's impressive that they go

    • What's new is that the UW technology does not depend on having a powered RF transmitter built into the reader. In fact, both the transmitter and the reader are both completely unpowered.

  • The researchers tested the ambient backscatter technique with credit card-sized prototype devices placed within several feet of each other.

    Not very far.

    • Re: (Score:1)

      by Anonymous Coward

      Not very far.

      Not likely to get much father either. This is a near field communication trick. The examples in the video have the antennas closer than the antenna length. Just use a wire instead.

      • Re: (Score:1)

        by adolf ( 21054 )

        Not likely to get much father either. This is a near field communication trick. The examples in the video have the antennas closer than the antenna length. Just use a wire instead.

        This. Someone please mod AC parent up for this glaringly-obvious observation.

    • From the paper:

      For a target BER [bit error rate] of 10^-2, the receiver can receive at a rate of 1 kbps at distances up to 2.5 feet in outdoor locations and up to 1.5 feet in indoor locations.

      Range is improved a little with slower bit-rates, or in the presence of stronger ambient RF.

  • Does this mean that if you live in the middle of nowhere, your TV remote will mysteriously fail to work? Great.

  • it is new... in a way. (Score:3, Informative)

    by jhfry ( 829244 ) on Wednesday August 14, 2013 @06:26PM (#44569527)

    Sure backscatter has been done... But it always used known frequencies as the signal source. This will pick up any ambient ref noise and use it to generate a new signal.

    Essentially, you could embed a transmitter anywhere without concern for a power source (assuming there are other transmitters around).

    • Re:it is new... in a way. (Score:5, Interesting)

      by ls671 ( 1122017 ) on Wednesday August 14, 2013 @06:45PM (#44569687) Homepage

      Peer to peer analogy? If not enough people seed with devices hooked up to power sources, the system will fail.

      Also, I remember that they caught a guy hijacking power from high power lines without touching the wires. He was doing it simply by induction and the power line was close to his barn. The electricity company noticed a power leak and this let to an investigation resulting in him being convicted even if he never touched the wires.

      Now, how will the tv and radio stations react when they notice their signal get weaker because a bunch of devices draw power from their signal?

      • Re: (Score:1)

        by Anonymous Coward

        Nope. Inductive coupling occurs at low frequencies and short distances, neither of which is the case for TV or cellular signals.

        • Re: (Score:3)

          by ls671 ( 1122017 )

          It doesn't matter. The only difference is how the tv or radio station will notice signal weakening compared to the electricity company.

          Electricity company:
          Voltage will go down as amperage will go up.

          For TV stations they transmit at a constant power rate so they will notice signal weakening by taking test at various distance from the transmitting antenna.

          The energy one device "steal" is not available for the device behind it so there is a limit to how many device a transmitter can sustain.

          Proof? If what I s

          • You still don't understand RP propagation. Having an antenna receive a signal does not diminish the strength of the signal behind it any more than a metal light pole diminishes it. Both will cause a slight disturbance in the transmitted signal, but the rest of the signal will still continue past it. You can't calculate how many devices are receiving an RF signal by measuring field strength at a fixed distance.

            Think of throwing a pebble into a pond and watching the waves travel outward. If you put a s

          • Re: (Score:2)

            by PhilHibbs ( 4537 )

            congratulations! You have just defined an infinite energy supply. Set up a transmitter with a number of devices large enough to produce more energy then it took to power the transmitter.

            That would involve more devices than would fit into a spherical shell at any given distance from the transmitter. So yes, there is an upper limit before you start to hit serious signal degradation, but when that upper limit is billions of devices per transmitter, it is not worth worrying about. That little bit of signal that my RF device used was probably going to be absorbed by the steel frame of the building next to me anyway.

          • Re: (Score:2)

            by AmiMoJo ( 196126 ) *

            The problem is detecting such a small device. Unless it draws a very large amount of energy it would be impossible to pick out from someone who just moved some furniture in their house.

  • This is not a new idea, just ask the KGB : (Score:2, Interesting)

    by Anonymous Coward

    http://en.wikipedia.org/wiki/Thing_(listening_device)

  • I've got no objection to such research scientifically speaking. However, I am staunchly against any form of computation or communication that someone else can simply pull the plug on. Switch off the microwave carrier signals and these systems are dead. Wouldn't that be scary as hell to rely on? Before I used such tech I'd want it made legal to generate my own background radiation at home. That's currently illegal by the way.

    Before you say it, yes, as a BBS owner I was against the Internet too, in principal. Not the communication, but the ability to spy on, censor, and pull the plug at will. I use todays technology with gritting teeth because although I have the expertise required to beam my data at high speed between my friends and family nation wide wirelessly with commodity radio gear, use of such systems in that manner are forbidden by the FCC, so I must use the principally corrupt systems.

    I remain firmly convinced that large blocks of the air waves, perhaps even in the cellular bands, should belong to the people and if so instead of paying out the ass to support evil "data plans" we'd all be using a decentralized encrypted anonymized high speed hybrid line of sight / self organizing mesh network. You would pay for the hardware once, maintain it, and that's it. Ask a HAMOp about their packet radio "data plans"... If not so restricted by the FCC (and yes some oversight is needed, but not to this degree), we could have cut the cables. Omnivore, Carnivore, ECHELON, and PRISM illustrates why we don't have such technology in place. Before you argue against the feasibility, I would ask if you've actually tried it? If not, then make sure you're not on any (n+2)G network then make a free "long distance" cellular call and tell someone who cares.

    • Re:Scientifically, fine, but not good in principal (Score:4, Informative)

      by Anonymous Coward on Wednesday August 14, 2013 @07:53PM (#44570161)

      I've got no objection to such research scientifically speaking. However, I am staunchly against any form of computation or communication that someone else can simply pull the plug on. Switch off the microwave carrier signals and these systems are dead. Wouldn't that be scary as hell to rely on?

      There's degrees of reliance. For a TV remote or PAN application, not scary at all. For a mobile phone that one's life might depend on, somewhat scary.

      Before I used such tech I'd want it made legal to generate my own background radiation at home. That's currently illegal by the way.

      Sorry, but we have these little thing called the ISM bands, perhaps you've heard of them. (There's one at 2.4GHz, WiFi and bluetooth use it.) You're perfectly allowed to generate RF in these band. You're also allowed to generate unlicensed emissions in many other bands, subject to strict power limits that will still likely be enough (at short ranges) for these devices to work. (I agree with you, at least on a broad view, about what's wrong with the FCC and our current spectrum ownership policies, but you don't help things by overstating the restrictions....)

      I'm not saying the eventual commercial implementation of this idea won't be intentionally crippled to rely on frequencies that are more tightly controlled, precisely to provide an off switch, but until/unless they are, your wholesale indictment of the tech is premature. The natural choice for this tech, outside monopolistic/control-freak pressures, is to have it use several options including one of the heavily-used ISM bands, because there's a lot of available energy in them, and (unlike, say, broadcast TV frequencies) they're used even out in the country. (Mobile phone networks are another obvious choice, with better rural penetration than TV, but there's still sufficiently remote places with almost no mobile phone signal, and people in thes places still run WiFi APs connected to their landline internet.)

      Also, learn the difference between principle and principal. Botching it as you did makes you look like a moron.

      • You are allowed to generate RF at 2.4 GHz, but at a limited power. In the Netherlands you are allowed to put 20 mA into an antenna, more would require a license. In the USA this is a lot higher.
        If you choose to dismantle a microwave oven and turn the magnetron radio emitter on without shielding there will probably be consequences, aside from the severe burns if you leave it on to long. And a microwave is in the 2.4 GHz band, so according to you "You're perfectly allowed to generate RF in these band."
        I h

  • Ubiquitous grid-free digital networking, like grid-free power, are really the holy grail.

    A lot of the worst problems we face on this planet could be solved with these two technologies if they are allowed to come to fruition.

    Institutional poverty, corporate/government tyranny, state-sponsored terrorism and other seemingly intractable problems might really be dealt with if we could have these two things.

    • Ubiquitous grid-free digital networking, like grid-free power, are really the holy grail.

      A lot of the worst problems we face on this planet could be solved with these two technologies if they are allowed to come to fruition.

      Institutional poverty, corporate/government tyranny, state-sponsored terrorism and other seemingly intractable problems might really be dealt with if we could have these two things.

      Long before there were corporations and governments, there was the strong preying on the weak. Sure these two technologies may stop the tyranny that you are concernned about, but tyranny existed before the modern forms of government and will continue after them. After all, corporations and governments are only as good or evil as the people behind them and these technologies don't do anything to change that.

      • Long before there were corporations and governments, there was the strong preying on the weak. Sure these two technologies may stop the tyranny that you are concernned about, but tyranny existed before the modern forms of government and will continue after them. After all, corporations and governments are only as good or evil as the people behind them and these technologies don't do anything to change that.

        You're probably right. But it's in our nature to try. And that is a wonderful thing.

  • ... But we do know it was us that scorched the sky. At the time, they were dependent on solar power. It was believed they would be unable to survive without an energy source as abundant as the sun.

    So much for that bright idea.

  • The day would arrive when some one will be unable to establish or maintain a dial 911 to save lives --- merely because they are surrounded by a Virtual Tuned Faraday Cage of these parasitic signal sucking devices.

    This is an idea that is so bad in principle that it is embarrassing that it has not been laughed out of the room.

    It is an example of what I call predatory engineering, the phenomenon where someone's "bright idea" trumps common sense and consideration for others. Yes, there are moral threads that we

    • Finally, somebody finds something that TV broadcasts are useful for, and all people do is whine.

      Fuck 911, we have 112. It never works anyway.

    • Re: (Score:2)

      by cusco ( 717999 )
      Do you not understand how radio transmissions work? Apparently not. When you turn your radio on to hear the news you are not removing ANY of the signal available for anyone else who might want to listen in. If your radio stays turned off that signal is just not used. If everyone in the practical receiving area turns their radio on at the same time the transmitter doesn't have to output more power, nor do any of the receivers notice that there are other receivers using signal. Your radio receives exactl
  • Somebody, please, think of the children!

  • NSA (Score:1)

    by koan ( 80826 )

    Already did it.

  • Wouldn't these things mess up the reception?

Slashdot Top Deals

You know you've landed gear-up when it takes full power to taxi.

Close