
Wireless devices go battery-free with new communication technique - Irene
http://www.washington.edu/news/2013/08/13/wireless-devices-go-battery-free-with-new-communication-technique/
======
beambot
Backscatter is (indeed) phenomenally interesting. We used it to build "cyborg"
dragonflies [1] and to build battery-free tags capable of transmitting video
and audio [2]. We've demonstrated fully-passive tags (at 915MHz UHF) capable
of 100Mbps communications. Using ambient signals as the carrier is a pretty
cool extension.

[1] [http://www.wired.com/wiredscience/2013/06/dragonfly-
backpack...](http://www.wired.com/wiredscience/2013/06/dragonfly-backpack-
neuron/)

[2]
[http://www.travisdeyle.com/publications/pdf/2013_rfid_rich_m...](http://www.travisdeyle.com/publications/pdf/2013_rfid_rich_media_tags.pdf)

~~~
Stwerp
It seems like this would work over extremely short distances since the carrier
signals at tags A and B are basically the same.

If ambient backscatter is going to be implemented over a larger area, the
multipath or modulation of the carrier seems like it will be problematic.

Also: From measurements we have seen, the ambient RF power levels vary
_drastically_ with location from TV transmitters.

~~~
beambot
I believe you re:ambient signals (or rather, no reason to disbelieve you).

For those who are unfamiliar with backscatter modulation / passive UHF RFID...
most systems are forward-link limited: the limitation on range is dictated by
the ability to harvest enough energy to powerup the tag.

At a fundamental level, backscatter modulation is little more than a reflector
that modulates its radar cross section. You could imagine building massive
spinning reflectors to serve the same purpose at very low datarates. As for
conventional tags, I've seen read ranges on the order of 30-100 meters using
directional antennas.

You can build systems that are limited by receiver sensitivity, eg. by using
different RX-TX antennas or by using a battery (not for transmission, but for
_very_ low power load-modulating the antenna). This is a classic radar problem
-- but you can get pretty substantial ranges.

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ChuckMcM
This is very cool. There was an interesting project at a former employer which
used ambient light to power conference room schedule displays, attached to the
outside of conference rooms.

Something like that with e-ink would be even nicer (you can save up energy for
changing things rather than keeping an LCD on)

There was also some interesting robotics work out of Mark Tilden's lab called
BEAM which was primarily solar powered things but it would be really cool to
do those things with backscatter powered energy harvesting devices.

~~~
hedgehog
Radish?
[https://developers.google.com/gdata/articles/radish](https://developers.google.com/gdata/articles/radish)

~~~
capex
Radish is cool. Is there an open source or commercial implementation of the
idea elsewhere?

~~~
hedgehog
Not that I'm aware of but it would be quite useful. Components are getting
better so you might design it differently these days.

------
jacquesm
[http://www.spybusters.com/Great_Seal_Bug.html](http://www.spybusters.com/Great_Seal_Bug.html)

------
JoeAltmaier
What kind of havoc does backscatter/reflection wreak on normal tv/radio
signals? Do I want this noise in my house?

~~~
skrebbel
My mom would ask: "Does it give me cancer?" (she has the same doubts about
microwave ovens)

Does anyone know, with certainty, what to answer to that?

~~~
pedalpete
Well, I don't know your Mom, but the answer is 'yes, but 0.0001% less risk
than either the sun or time'.

Of course, I'm going by the moto here that 93% of statistics are made up on
the spot.

~~~
corin_
To be slightly pedantic, 0.0001% less risk than the sun is actually a fair bit
of risk. 0.0001% of the sun's risk is not much risk.

------
Stwerp
For anyone else interested, the full paper is available here:

[http://conferences.sigcomm.org/sigcomm/2013/papers/sigcomm/p...](http://conferences.sigcomm.org/sigcomm/2013/papers/sigcomm/p39.pdf)

------
dlhavema
duplicate:
[http://news.ycombinator.com/item?id=6004470](http://news.ycombinator.com/item?id=6004470)

------
rentzsch
Am I the only concerned that once a few billion of these energy parasites are
deployed everyone will have to have to use more energy to broadcast the same
signal the same distance?

~~~
csmatt
Does the increase in radio receivers require an increase in the energy to
broadcast to the same area?

~~~
acjohnson55
Nope. If it were inductive or capacitive transmission, this would be the case,
but for far-field radiation, it's generally not.

------
eksith
I did an experiment a while ago on whether I could use a crystal radio to
light up an LED. Short answer, yes. Long answer, only in very short pulses and
that still required a fairly strong AM signal. I guess, this absorbs
frequencies of a much wider range.

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Lagged2Death
There was a time when battery-less electronics might have excited me, but
these days dis-connectable batteries/power supplies and real, hardware off
switches seem like important, useful features for just about anything.

~~~
zhemao
Just put a Faraday cage around it by wrapping it in tin foil. </sarcasm>

~~~
noonespecial
I know, its a joke, but just the other day, I was thinking about faraday cages
and how maybe it wouldn't be terrible to have one around the house and if I
could pull it off with tin foil...

I was seriously considering tin foil to stop snooping from government rays.
What. A. World.

~~~
adestefan
I live in a house with aluminum siding and foil wrapped sheathing.

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frozenport
Will this destroy signal integrity for everybody in the vicinity?

~~~
jpmattia
It's roughly as small of a perturbation to the radiation field as, say, a
tinfoil hat.

------
leishulang
also harnessing the power from sound:
[http://www.instructables.com/id/Harnessing-sound-
power/](http://www.instructables.com/id/Harnessing-sound-power/)

When lose an item in house, shout loudly and it will appear on radar ;)

------
revelation
This would be awesome for home automation devices (sensors, actuators and
stuff). It's a pain to have a battery for each little button and sensor.

------
aroman
As a human this fascinates and excites me because of the possibilities for
innovation.

As a hacker this fascinates and excites me because of the potential for abuse
and, well, hacking.

This is really cool stuff. I can't wait to see what is built with this
technology and how it will get broken.

~~~
twinge
Indeed. This reminds me of "Larson Localizers" [1] from Vernor Vinge's "A
Deepness in the Sky":

    
    
      "Among the unsuspecting, they are an espionage miracle.
       Abused, they lead to ubiquitous law enforcement, and a
       quick end to civilization."
    

1:
[http://en.wikipedia.org/wiki/A_Deepness_in_the_Sky#Localizer...](http://en.wikipedia.org/wiki/A_Deepness_in_the_Sky#Localizers)

------
arjn
This is a very interesting development. Kudos to the UW folks for this great
piece of research.

Few questions :-

\- Would there be a problem if the devices were inside an enclosed/shielded
area (I assume there would be) ?

\- Isn't the data rate dependent on the kind of ambient wavelengths available
?

------
neya
Isn't this something like what Tesla proposed earlier? Can someone elaborate
how this is different from Tesla's proposition?

Thanks!

------
knieveltech
Would anyone be willing to explain the proposed benefits of an "Internet of
Things"?

~~~
samatman
Logistics is a multi trillion dollar industry. I doubt there's a larger sector
of the economy than moving things around.

~~~
marshray
Yeah, let's kill it off!

------
benjaminva
From my first read it seems that I will not be able to pay with my
"backscsatter creditcard" in a Faraday cage or anywhere, where background
radiation is strongly shielded. But from a general stand point, I really like
the idea.

------
s_q_b
I remember, as a small child, building a powerless radio that vibrated the
speaker using the strength of the radio transmission itself. Is ambient
backscatter is the same thing, except across much wider frequencies ranges?

~~~
jzelinskie
You're talking about Crystal Radios[0], right?

[0]
[https://en.wikipedia.org/wiki/Crystal_radio](https://en.wikipedia.org/wiki/Crystal_radio)

~~~
s_q_b
:) Yes, I am. It was part of an electronics kit my father bought for me. I
remember carefully placing the pieces between spring-end contacts to construct
the basic circuits.

Building electronics from scratch is very satisfying. I think I may get into
DIY drones soon to scratch that itch.

------
j45
This needs to be in any 2013 year in review article. The implications for this
with existing and new technologies is unique and doesn't happen often enough,
presuming my understanding is correct :)

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csmatt
There are those times when the device you're powering isn't supposed to be
visible and would benefit greatly by the reduction in size from shucking the
battery.

------
gcb0
wouldn't deploying this in big numbers work against the solution itself? you
would have so much noise in the existing signals that the main signal, as well
as the bounced signals, would be useless?

Also, can we just say this is a cat's whisker receiver[1] that instead of
powering a speaker/headphone powers another transmitter?

[1]
[http://en.wikipedia.org/wiki/Crystal_radio](http://en.wikipedia.org/wiki/Crystal_radio)

~~~
beambot
This is the same principle as long-range UHF RFID tags. There is a
communications protocol (Gen2) that deals with collision detection and
multiple access to allow for hundreds (thousands?) of tags in the same space.
Part of the protocol involves a tunable value for "the probability that an
individual tag should respond."

------
gavinlynch
Obligatory Tesla Post.

~~~
marshray
Yeah, I hear The Hyperloop pods have been designed to fit the Model S.

~~~
gavinlynch
Nikola Tesla... Wireless transfer of energ...--nevermind.

~~~
marshray
;-)

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nkorth
I was just reading the Wikipedia article about crystal radios yesterday. Does
this have anything to do with them?

------
leeoniya
i imagine the signal would have to be reflected in a highly directional manner
or at very close distances. it's cool nevertheless, but i think storing some
solar power in a capacitor/coil would produce more powerful rf communication
bursts at least for outdoors applications.

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ck2
Hmm, imagine a massive array of those like solar panels that work at night.

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dhughes
This reminds me of a spark-gap transmitter but without the spark.

------
zw123456
This non-sense has been posted a number of times and concluded that it is RFID
redux.

