Forgot your password?
typodupeerror
Power Wireless Networking

Harvesting Wi-Fi Backscatter To Power Internet of Things Sensors 138

Posted by Unknown Lamer
from the energy-everywhere dept.
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.
This discussion has been archived. No new comments can be posted.

Harvesting Wi-Fi Backscatter To Power Internet of Things Sensors

Comments Filter:
  • Sponsors (Score:5, Funny)

    by penguinoid (724646) <spambait001@yahoo.com> on Tuesday August 05, 2014 @12:06AM (#47604683) Homepage Journal

    And now a word from our sponsors, the NSA. Oops, I mean look a distraction.

    • Re:Sponsors (Score:5, Interesting)

      by viperidaenz (2515578) on Tuesday August 05, 2014 @12:28AM (#47604745)

      That's actually how the NSA snoop on monitor cables.

      They attach a device that looks like an EMI suppression choke that taps in to the red wire on a VGA cable. They use a microwave transmitter/receiver and the amount of RF it reflects back is based on the signal on the wire.
      Doesn't need batteries and doesn't transmit any thing so you can't detect it.

      The only difference here is the use of WiFi as the RF source.
      I don't see how they can patent something that's been done since at least 2008 by the NSA. It's the same idea except ".... over WiFi". Like all those "... on a computer" patents...

      It's described here
      http://en.wikipedia.org/wiki/N... [wikipedia.org]
      Item 35, RAGEMASTER

      • by bonehead (6382)

        Like all those "... on a computer" patents...

        And then those were all copycatted by "on the Internet" patents.

        Which, in turn, are now being copycatted by "in the cloud" patents.

        Everyone on the planet can see the absurdity of it except for a very select few morons. Unfortunately, it's those select few morons that we hire to work in the Patent Office.....

        There was a time in my life when I believed certain things but was afraid to mention them, lest I be branded paranoid. Two decades having gone by now, it turns out I was actually unrealistically optimi

        • They sure as hell know. But they also know the value of job security.

          • by bonehead (6382)

            Given our success in the "War on ...",

            Given our success in the "War on Drugs", we should declare war on prosperity.

            Given our success in the "War on Terror", we should declare war on freedom.

            Seems like the only thing we accomplish when we declare "War on" something is to ensure that it will propagate and grow. /me declares "War on Giant Piles of Cash in my Bank Account".

            (Oh, wait, I already won that war decisively. It was a scorched earth sort of thing. Recovery won't be possible within 10 lifetimes....)

            • by Zanadou (1043400)

              You forgot one:

              "Given our success in the "War on Child Pornography", we should declare war on rational thinking."

              • by MitchDev (2526834)

                You forgot one:

                "Given our success in the "War on Child Pornography", we should declare war on rational thinking."

                Religion would sue you for patent infringement...

            • by ultranova (717540)

              Given our success in the "War on Drugs", we should declare war on prosperity.

              Unfortuntely, that was one war the Powers That Be actually wanted to win, rather than keep going in perpetuity, so they did. After all, prosperous people are hard to control, since they can afford to think beyond mere survival.

      • Re:Sponsors (Score:5, Interesting)

        by SuricouRaven (1897204) on Tuesday August 05, 2014 @04:27AM (#47605331)

        Further than that. The Great Seal bug - widely considered one of the most audaciously planted listening devices of all - operated on the same idea. It used vibration - ie, sound - to mechanically modulate a reflected radio signal. No electronic components required at all.

      • by Goody (23843)

        That's actually how the NSA snoop on monitor cables.

        They attach a device that looks like an EMI suppression choke that taps in to the red wire on a VGA cable.

        What if all the wires in your VGA cable are gray?

      • by RevWaldo (1186281)

        COTTONMOUTH: (see image at right) A family of modified USB and Ethernet connectors that can be used to install Trojan horse software and work as wireless bridges, providing covert remote access to the target machine.[18] COTTONMOUTH-I is a USB plug that uses TRINITY as digital core and HOWLERMONKEY as RF transceiver. Cost in 2008 was slightly above $1M for 50 units.

        So AudioQuest has been working with the NSA this whole time?

        .

      • by dnavid (2842431)

        That's actually how the NSA snoop on monitor cables.

        They attach a device that looks like an EMI suppression choke that taps in to the red wire on a VGA cable. They use a microwave transmitter/receiver and the amount of RF it reflects back is based on the signal on the wire. Doesn't need batteries and doesn't transmit any thing so you can't detect it.

        The only difference here is the use of WiFi as the RF source. I don't see how they can patent something that's been done since at least 2008 by the NSA. It's the same idea except ".... over WiFi". Like all those "... on a computer" patents...

        The "only" difference is a substantial difference. First, they do not need a high-powered signal illuminator to energize them. That's significant because that's the entire point of the invention: that it can self-power without a dedicated power source. The NSA systems (at least the published ones so far) use (relatively) powerful illuminators to energize and operate the reflectors. Second, by designing devices that can use the extremely small energy harvested by Wifi backscatter *and* use the same backs

        • So kind of like RFID with a little less power.

          The idea is still the same
          The theory is still the same
          The power level has been dropped

          It's like saying a 5mcd red LED is the same invention as a 10,000mcd red LED.
          The theory is the same, the idea is the same, they chemicals and manufacturing process have been tweaked a bit to make it 1000's of times more efficient.

          • by dnavid (2842431)

            So kind of like RFID with a little less power.

            The idea is still the same The theory is still the same The power level has been dropped

            It's like saying a 5mcd red LED is the same invention as a 10,000mcd red LED. The theory is the same, the idea is the same, they chemicals and manufacturing process have been tweaked a bit to make it 1000's of times more efficient.

            The difference is the modulating mechanics appear different: the Wifi system described is an ambient backscatter system while the NSA catalog describes the system as a retroreflector: retroreflectors are designed to reflect signals back to the sender with minimal scattering: inducing a modulation on the return wave creates an information signal. Backscatters work by absorbing or reflecting incident signals; the absorption of the signals generates a distinguishing pattern from the reflective signal taking a

    • Re:Sponsors (Score:5, Insightful)

      by TubeSteak (669689) on Tuesday August 05, 2014 @12:34AM (#47604765) Journal

      If they're talking about launching this commercially, it means the Alphabet Agencies have been doing it for years now.

    • Re:Sponsors (Score:4, Insightful)

      by Dutch Gun (899105) on Tuesday August 05, 2014 @12:42AM (#47604803)

      Internet of things, huh? I think I'll wait a generation or two until they hammer out the worst of the security issues. One of the latest missteps was caused by a smart bulb that embedded the encryption key in the firmware [smh.com.au]. Oops. Yeah, no one would think to look there, right? There's likely going to be an entire generation of devices that will have the same sort of flaws that early wireless routers had - essentially, the result of average programmers (i.e. non-cryptographic experts) trying to invent cryptographic solutions.

    • by MitchDev (2526834)

      Everytine I see story like this, about the "Internet of THings" constantly spying on us, I throw up at how sad humanity has gotten that they think this is a good idea...

    • Do you want a Samsung Android backdoor in your refrigerator, your gym shoes, your thermostat, your clothes hamper?

      What the fuck people? Seriously. This is fake convenience, pushed to micro-monitize every minor detail of your lives - bad enough.

      That entails micro-monitoring of where you are walking, how much milk you drink, what you say when you can't find something in the bathroom, how long you pant after taking out the garbage, how many times you have to say goodnight to your kids before they sleep, how m

  • by Anonymous Coward

    I can't believe they're actually advocating for RF pollution as a way to power things.

    • That, and it would reduce the WiFi range of the device it's pulling energy from. Back scatter my ass, it's parasitic loss of an RF signal regardless.

      • by Anonymous Coward
        Because the signal that ounce off your wristwatch is really what give you that 11th bar of signal strength.
        • by skids (119237) on Tuesday August 05, 2014 @12:46AM (#47604819) Homepage

          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.

          • by AmiMoJo (196126) *

            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.

            • by drinkypoo (153816)

              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.

              We're also going to have to mandate some way to get their cellphone signals out of the house for that. At the point when it's all IP (all the way down) then that will be a reasonable idea.

              • Can't you just stick an antenna on the roof (or in the attic, if you didn't include the attic cavity in the faraday cage)?

                It seems like a stucco (metal lath) house with a standing-seam metal roof and metallic-tinted windows, with those things electrically connected together, would work... is there anything else that would need to be done? (In particular, is it important to stop signals from leaking out the bottom? And what about grounding?)

                • by drinkypoo (153816)

                  Can't you just stick an antenna on the roof (or in the attic, if you didn't include the attic cavity in the faraday cage)?

                  At minimum you need two antennae, one on the inside to pick up your signal and one on the outside to send it on (and vice versa). And you're going to need the external to be omnidirectional, so that it doesn't have to be fiddled with when new cell sites come up, and the interior to have a sort of cone-shaped coverage pattern to cover the house beneath it. Then you'll need to poke a new hole in your roof to pass the antenna lead, which should be as short as possible. Not using an amplifier (etc) will attenua

                  • Yeah, I think I implicitly assumed the antenna would be hooked to some device to receive the signal. (I also glossed over the whole "cell phone" part, and was thinking of my HDHomeRun.)

                    As you know, if it were all just IP, then you'd just have one IP-based connection to worry about.

                    I must be living in the future, because my cellphone already uses VoIP over WiFi at home (and VoIP over 3G/4G when I'm out -- it's nice that cheap (almost)-data-only plans finally exist). : )

                    • by drinkypoo (153816)

                      I must be living in the future, because my cellphone already uses VoIP over WiFi at home (and VoIP over 3G/4G when I'm out -- it's nice that cheap (almost)-data-only plans finally exist). : )

                      Yes, that's a big help. It won't help people on pay-as-you-go plans and whatnot, because that breaks the whole pricing model, but the Future Is Here(tm) for some customers, at least.

                    • It won't help people on pay-as-you-go plans and whatnot, because that breaks the whole pricing model

                      Why wouldn't it? You can do per-megabyte pricing just as well as per-minute pricing, I think.

                      Besides, monthly no-contract plans are good and cheap enough anyway: my veritable-firehose-of-data (5GB of 4G, then unlimited 3G) is $30/month from T-Mobile, and I hear you can get even better deals from companies like Republic Wireless or FreedomPop (I need to evaluate these and see about switching).

            • We should be mandating that new houses are basically Faraday cages

              We should be mandating that new houses are priced out of the market for first time home buyers. Seriously, people 35 and younger purchasing a home is at an all time low since 2004. And it's not the material that's the most expensive, it's the labor. So while I share the frustration of regulating and curtailing RF pollution, mandating a solution such as this isn't going work; at least not this this current economy.

            • Some people like to get wifi outside as well you know.
      • Sounds great where do I get one? I've got about 3000 wifi access points coming into my apartment I'd like to degrade...

        Seriously though, I can see how if you live in the country this maybe requires you to pump additional power into your wifi device. But in any city, wifi range is MUCH bigger than apartment size, and it's a non-issue.

      • by Kythe (4779)
        I don't think so. This isn't like siphoning energy from the E-field around a power line (which actually does result in loss of power): electromagnetic signals are radiated away and go to heating the environment if they're not received.
  • by Anonymous Coward

    Powered by radio waves.

  • What was old... (Score:3, Interesting)

    by Anonymous Coward on Tuesday August 05, 2014 @12:25AM (#47604739)

    ...is new again:

    http://en.wikipedia.org/wiki/The_Great_Seal_bug

    Nice to see the idea being put to a less nefarious use. :)

    • by freeze128 (544774)
      If your smartwatch has to be the size of the great seal, then I think they need to re-think this technology.
    • I think you are being overly optimistic if you think that this technology would not be used to spy on people.

  • iFind (Score:2, Insightful)

    by enoz (1181117)

    This sounds just what iFind [slashdot.org] was promising before they were suspended from kickstarter [slashdot.org]

    • Re:iFind (Score:5, Interesting)

      by ljw1004 (764174) on Tuesday August 05, 2014 @02:08AM (#47605029)

      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.

      • Re:iFind (Score:5, Insightful)

        by MattskEE (925706) on Tuesday August 05, 2014 @03:31AM (#47605221)

        It only works because it has a very low bitrate of 1kbps:

        The UW’s Wi-Fi backscatter tag has communicated with a Wi-Fi device at rates of 1 kilobit per second with about 2 meters between the devices.

        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 [washington.edu] that fails to address the one metric which would allow them to make such a claim.

  • They're talking about very short ranges, like under 2 meters. This may not be too useful.

    What we need in wireless power is for the inductive charging pad industry to get their act together. There are at least three competing standards (QI, PMA, and WiPower/Rezence), so they're not widely used. Last February, the PMA and WiPower groups agreed to develop multi-mode charging pads that will power both PMA and Rezence devices. Then there are some Samsung devices that will charge from either a Qi or a Rezence

  • by AYeomans (322504) <ajv@@@yeomans...org...uk> on Tuesday August 05, 2014 @02:13AM (#47605047)

    ... 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.

    • That's my thought. Although this device takes no internal power to cause the back scatter effect, how useful can it be if whatever data is to be collected is likely provided by something that needs a power source to begin with. If its just a static device, then its not much more that a longer range RFID. If it is active, it needs power.
      • by MattskEE (925706)

        Although this device takes no internal power to cause the back scatter effect

        That's incorrect, a switch always requires energy to change state, as well as a usually very small amount of power to maintain at least one of the two states. Quite a bit of a CPU's power dissipation comes from the energy consumed by CMOS switches switching from a one state to another.

        It may well be that this is more power efficient than other methods of transmitting information but that has yet to be backed up by theory or demons

        • We are not talking about a switch or a cpu. We are talking about a reflector, of sorts, which can be detected based on the effect it has on external signal fields. And, also, I said no 'internal power', thus any power required being supplied externally. A CPU would be the case of the active component, not a passive one.
          • by MattskEE (925706)

            Yes and if you read their paper an RF switch is used to adjust the terminating impedance of this antenna which perturbs the reflectivity. That RF switch will consume a finite energy and power. It is an active component and not a passive component. A passive component would not accomplish the modulation.

            I think it sounds reasonable that a reflector like this might be able to use less energy per bit than a conventional high-efficiency transmitter, since the RF power is being provided elsewhere, this is eff

  • Wonderful (Score:5, Interesting)

    by sjames (1099) on Tuesday August 05, 2014 @02:16AM (#47605059) Homepage

    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.

    • by AmiMoJo (196126) *

      Why would anyone buy such a device? They would quickly become like those black boxes insurance companies offer to install in your car to "lower premiums for good drivers". They are too stupid to realize that you need to put your foot down a bit when your car only has a 1.0 litre engine, so report that you are accelerating excessively hard. Once people realize they they get rid of them, and the same will happen to any device or app that tries to screw the user.

      Also, what kind of crappy spam filter lets ads f

      • by tibit (1762298)

        The black boxes measure physical acceleration. Sure, they can log the throttle angle, but those two things aren't in a linear relationship, and you can't infer much from the throttle angle other than determining what the driver was trying to do at the time of the crash (WOT, idle, in-between). At the very least the acceleration is a function of RPM and mass air flow. How the latter relates to throttle angle is very engine dependent.

      • by sjames (1099)

        Not sure why anyone would own such a device, but nest sells and the WD 'personal cloud' sells. Also, if this is a tiny device powered by random RF, you might not know you own such a thing. It might be inside the insulated coffee mug you bought.

        As for the spam filter, if it's sent to your work email, it doesn't have to actually get through to give your homophobic employer the wrong idea.

    • by geekoid (135745)

      " Too bad your watch tattled that you just paused in front of a 'bookstore' that sells gay porn."
      And that would be bad.. why?

      ". 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."
      Why is it reporting to me employer, exactly? My phone doesn't report to my employer when it know I stop in front of a store.

      I rarely see any spam anymore, so I'm not sure why it would increase.

      Here, have some more straws to grasp:
      htt [pbase.com]

  • Won't this just put a greater load on the Wifi transmitters, or dampen the signal ?
    • by fleebait (1432569)

      Won't this just put a greater load on the Wifi transmitters, or dampen the signal ?

      It will take about as much power as a mirror does sucking the power out of a light bulb.

      • by Kythe (4779)
        Exactly. It's like saying a telescope sucks power out of whatever it looks at. Electromagnetic radiation doesn't work that way.
  • Can you ...

    ...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 â" all without requiring batteries.

    All to well, I'm afraid. What I can't imagine is what the hell I or anybody else would want that? I'm not much of a Luddite, but being constantly online is just not part of my lifestyle, and seeing the quality of the online natterdom, I feel no attraction at all, on the contrary. It's just like having a million TV channels, all of them showing Big Brother and Coronation Street and nothing else, 24/7.

    • by geekoid (135745)

      Do you realize you said the internet equivalent of:
      "Noone in New York drove, there was too much traffic" - PJ Fry

  • by cascadingstylesheet (140919) on Tuesday August 05, 2014 @05:50AM (#47605517)

    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!

    • by geekoid (135745)

      It's no more stupid then the phrase 'Cascading Style Sheet'
      It's about what you are used to.

  • But having a way to cheaply power and connect these devices to the Internet has kept this from taking off.

    Of course it has nothing to do with cost, uselessness, or invasion of privacy. People are just waiting for this technology in Bumfuck Nowhere like they've been waiting for "home automation" all these years.

    *LMAO*

    • People are just waiting for this technology in Bumfuck Nowhere like they've been waiting for "home automation" all these years.

      I've been waiting for "home automation" for years, and by that I mean digital control of my electrical outlets. I even have some X10 equipment that I've been using every day for more than a decade. I only have it because I got it during their $10 for a four-pack promotion, around the turn of the millenium. I've never bought any at the regular price.

      Having just now looked at their web site for the first time in 6 or 8 years, I see they finally got a web designer who wasn't an SEO spam specialists crossed

  • ... where you can't take the batteries out of things to keep the from spying on you.

  • "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 &#226;&#8364;" all without requiring batteries."

    Because I certainly don't feel comforted by it.....
  • Inforwars called. They said all of ya are at the wrong website.
  • Take a look at how RFID chips have worked since day one [washington.edu] - they use the incident RF to power the chip that then back-modulates the transmitted signal. In other words, the RFID tag actively modulates the load impedance it places on the antenna causing changes in the radar cross-section of the tag. The tag transceiver sees these variations in cross section as data from the tag.

    • by bobbied (2522392)

      RF-ID tags take pretty high field strengths to charge up before they can interact with the near field. This means you have to get the reader within about 2 wavelengths of the transmitter and provide pretty high field strengths for the tag to work. There are tags that work a greater distances, but they too require high field strengths to "charge" or carry batteries. Either way RF-ID tags require field strengths that require tens of watts and directional antennas to produce, even over short distances.

      Commer

      • by Muad'Dave (255648)

        I never said it was efficient, just not novel. I understand the RFID technology pretty well - we did have tags that would read from 10m or so with about 4W EIRP (1W power + 6dBi antenna). The other thing that you run into is that no one wants a tag with an antenna anywhere near the length required to be efficient. A 1/2 wavelength dipole at 915MHz is still 16cm overall.

        If this were developed years ago and if you were to rely on transmitters outside the home, they'd use the pager transmitters at 450/460 MHz

        • by bobbied (2522392)

          Still the problem remains that WiFi is pretty much limited to really low field strengths compared to what your RFID tags required. WiFi operates on FCC Part 15 rules, which usually means 1/2 watt ERP into an isotropic radiator. There is a reason WiFi is not generally useful beyond about 100 yards, unless you have ideal (unobstructed line of sight) conditions. The power received is in the micro watts.

          • by Muad'Dave (255648)

            I absolutely agree - that's why I opined that harvesting power form other, higher power external sources might be more effective.

            I've done a fair bit of weak signal work on the 30m band. I once transmitted with 100mW of power using the WSPR mode [princeton.edu] from Richmond Va and a station in New Zealand received and correctly decoded it. That's a lot of km/W ! Here's a map [wsprnet.org] of current activity.

            • by bobbied (2522392)

              I forget what they call the award, but the ARRL offers some kind of certificate for people making verified contacts on very low power over very long distances. Sounds like you might qualify.

              • by Muad'Dave (255648)

                There are QRP versions [arrl.org] of the regular DXCC/VUCC awards for working 100 countries on HF or 100 grid squares on VHF+. I usually run 100W or so, so the vast majority of my QSOs don't count. It's been hard enough getting 200 DXCC entities using 100W and a multiband dipole.

      • by geekoid (135745)

        The means you would increase the power on your wifi to charge your devices.
        It's inefficient, bot OTOH, no wires.

        • by bobbied (2522392)

          The means you would increase the power on your wifi to charge your devices. It's inefficient, bot OTOH, no wires.

          Not without running into the FCC part 15 limits which govern the field strengths of WiFi devices. And I'll warn you, for your own safety, please don't mess with WiFi amps and/or directional antennas. Apart from being illegal (in the USA anyway) they are DANGEROUS if you don't understand what's going on and how this kind of thing can harm animals (including humans).

          Personally, I have a Ham radio license which gives me authorization to use 802.11g spectrum at much higher powers than Part 15 users, but to g

  • Gathering power from RF is not new. This might be a novel way to implement it, but it will have the same issues.

    1) No free ride. Taking RF and turning it into electricity means less range for the RF.
    2) You are still paying for power. No it's just a lot less efficient.

    There is a reason the radio industry has worked hard to stop RF power light bulbs. Because the broadcaster would be paying for your electricity.

  • "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..."

    My friends don't need to know about my wrist's daily life. Adding sensors for heart rate, glucose level, and so on would make me even less inclined to want my wrist to be ratting me out constantly to Facebook.

    Call me a curmudgeon, but I see all this wearable tech crap as a passing fad at best, and more likely just

  • 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

    This must be an early April fools joke.

    . 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

    Who thinks it is a good idea for sensors monitoring "structural safety" to be harvesting energy from WiFi signals?

    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.

    Unless your using resistive heating (most wasteful way to heat a home imaginable) no complex array of sensors is going to conserve anything worth measuring compared with a simple PID loop and properly sized forced air system.

  • 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.

    Even if it doesn't require batteries, why would I want to have an online profile updated with what I've shat today?

1 + 1 = 3, for large values of 1.

Working...