Hybrid Technique Breaks Backscatter Distance Barrier

Low cost, long range, or low power — when it comes to wireless connectivity, historically you’ve only been able to pick two. But a group at the University of Washington appears to have made a breakthrough in backscatter communications that allows reliable data transfer over 2.8 kilometers using only microwatts, and for pennies apiece.

For those unfamiliar with backscatter, it’s a very cool technology that modulates data onto RF energy incident from some local source, like an FM broadcast station or nearby WiFi router. Since the backscatter device doesn’t need to power local oscillators or other hungry components, it has negligible power requirements. Traditionally, though, that has given backscatter devices a range of a few hundred meters at most. The UW team, led by [Shyamnath Gollokota], describe a new backscatter technique (PDF link) that blows away previous records. By combining the spread-spectrum modulation of LoRa with the switched attenuation of incident RF energy that forms the basis for backscatter, the UW team was able to cover 2800 meters for under 10 microwatts. What’s more, with printable batteries or cheap button cells, the backscatter tags can be made for as little as 10 cents a piece. The possibilities for cheap agricultural sensors, ultracompact and low power wearable sensors, or even just deploy-and-forget IoT devices are endless.

We’ve covered backscatter before, both for agricultural uses and for pirate broadcasting stations. Backscatter also has also seen more cloak and dagger duty.

[via r/AmateurRadio]

31 thoughts on “Hybrid Technique Breaks Backscatter Distance Barrier

    1. And the fact that the source has to be right next to the device to reach the full 2800 m range. That’s mentioned in the article. With the transmitter away at range, they only achieved ~450 meters of range.

      Obviously, because the closer you are the more you can reflect. The reflected power decreases roughly in the inverse square of distance from the source transmitter, such that the transmission from some tower miles and miles away will not give you enough power to transmit more than a few feet.

      1. “we present a design sketch of a LoRa backscatter IC that shows that it costs less than a dime
        at scale and consumes only 9.25 µW of power, which is more than 1000x lower power than LoRa radio chipsets.”

        Even when you need long range you still need way way less power and so get a way way better useful life from a battery. 100+ times longer before changing battery sounds pretty sweet (I say 100 because that 1000 figure is just the final output I assume and not the circuitry).

    1. The actual paper does mention the data rate; Table 1, page 105:3.
      > LoRa Backscatter: 18bps to 37.5 kbps

      Not exactly video-streaming fast, but sufficient to report relatively slow-changing sensor data.

    1. I immediately thought of that issue too.
      But then realized that those wikileaks files (and CIA historical files) showed that the spooks from both the east and west have been using similar trick for a long time already.

      I think I even saw a variation mentioned in a star-trek (STNG?) episode. Which would indicate the idea has been floating around quite a while.

  1. Why is it that when I see this article and the one on micro antenna https://hackaday.com/2017/09/15/piezomagnetic-trick-shrinks-2-5-ghz-antennas/,
    my dinosaur brain thinks of unwanted/unintended interference with random devices.
    “tin foil hat” moment here:
    Did ya ever notice that “runaway acceleration event” only seems to occur in a region with lots of RF devices, i.e. the cliche crowded area with lots of cell phones and other electronics?
    Or is it just that no one reports a runaway vehicle if no one else sees it happen?

  2. Encoding a signal by elective absorption or reflection is not new. One of the power issues can be overcome by raster scanning the area containing your sensor cohort with a beam of EMR. This allows the base station to dictate when data is transmitted from any given sensor and thereby avoid interference. This scanning method has the additional benefit of lowering the total exposure levels for individuals withing the area while allowing for much higher peak levels when the sensor needs it. The scanning is done with a phase array and can be further enhanced by having separate arrays for power and reception.

    1. Because it’s information that may be useful for others? And you should grow up – there’s no reason to call them bastards unless they are indeed born out of wedlock… But even that would be rude.

  3. * Ambient Backscatter [YouTube video plus a UW Web site Link]

    Published on Aug 13, 2013

    Ambient Backscatter transforms existing wireless signals into both a source of power and a communication medium. It enables two battery-free devices to communicate by backscattering existing wireless signals. Backscatter communication is orders of magnitude more power-efficient than traditional radio communication. Further, since it leverages the ambient RF signals that are already around us, it does not require a dedicated power infrastructure as in RFID.

    http://www.washington.edu/news/2013/08/13/wireless-devices-go-battery-free-with-new-communication-technique/

  4. OK… After digging a bit into the background of this from University of Washington – Seattle (see my previous two posts), this looks like nothing more than using ambient RF energy harvesting to power a transmitter or transceiver on a sensor/IoT device. There seems to me a lot of marketing “hype” here in these University of Washington press releases. To me it looks like there’s NOTHING new going on at all.

    1. Yeah, it isn’t as if they did anything really innovative, a cool hack would be using asynchronous logic and then the RF signal provides power and clock signals for the device, but only if the harmonics match the ID code for a particular unit too. :-)

      1. @Dan, I agree. It really doesn’t look like anything “new” from this University of Washington hype unless they’re “hiding” something intelligent in how the power-harvesting devices are run. But I see NOTHING like that going on here with the UW stuff.
        Regards – Me

  5. FWIW – More on this topic:

    * Hybrid Technique Breaks Backscatter Distance Barrier (yes THIS HaD post, included for scrapers)

    19 Sept. 2017

    https://hackaday.com/2017/09/19/hybrid-technique-breaks-backscatter-distance-barrier/

    * UW team shatters long-range communication barrier for devices that consume almost no power

    13 Sept. 2017

    http://www.washington.edu/news/2017/09/13/uw-team-shatters-long-range-communication-barrier-for-devices-that-consume-almost-no-power/

    For more information, contact the research team at:

    longrange@cs.washington.edu

    The long-range backscatter system will be commercialized by Jeeva Wireless, a spin-out company founded by the UW team of computer scientists and electrical engineers, which expects to begin selling it within six months (13 March 2018).

    https://www.jeevawireless.com/

    * Long-Range Backscatter Enabling The Vision of Ubiquitous Connectivity

    http://longrange.cs.washington.edu/

    * LoRa Backscatter: Enabling The Vision of Ubiquitous Connectivity [PDF Paper] September 2017

    http://longrange.cs.washington.edu/files/loRaBackscatter.pdf

    * YouTube: UW team shatters long-range communication barrier for devices that consume almost no power [54sec]

    * Chirp spread spectrum

    https://en.wikipedia.org/wiki/Chirp_spread_spectrum

    * Ambient backscatter – Wikipedia

    https://en.wikipedia.org/wiki/Ambient_backscatter

    * Ambient Backscatter: Wireless Communication Out of Thin Air

    http://abc.cs.washington.edu/files/comm153-liu.pdf

    * Ambient Backscatter [YouTube plus a UW Web site Link]

    Published on Aug 13, 2013

    Ambient Backscatter transforms existing wireless signals into both a source of power and a communication medium. It enables two battery-free devices to communicate by backscattering existing wireless signals. Backscatter communication is orders of magnitude more power-efficient than traditional radio communication. Further, since it leverages the ambient RF signals that are already around us, it does not require a dedicated power infrastructure as in RFID.

    http://www.washington.edu/news/2013/08/13/wireless-devices-go-battery-free-with-new-communication-technique/

    * UW team captures Best Paper at SIGCOMM 2016 for interscatter (WiFi, not LoRa)

    https://news.cs.washington.edu/2016/08/23/uw-team-captures-best-paper-at-sigcomm-2016-for-interscatter/

    http://interscatter.cs.washington.edu/

    http://interscatter.cs.washington.edu/files/interscatter.pdf

  6. I keep seeing the “10 cent price tag” in news articles discussing this technology.
    What is it that costs 10 cents? The PCB on the picture (in the soil on video) looks to cost alot more then 10 cents.

    Also how do each device get assigned a unique ID?

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