
WiFi Backscatter – Connecting RF-Powered Devices to the Internet (2014) [video] - Gys
http://iotwifi.cs.washington.edu/
======
imdsm
Looks like a great proof of concept, but I wonder whether the off-the-shelf
WiFi devices will need to support some sort of protocol to enable this to
work? I didn't see anything in the video about how they specifically integrate
with WiFi, but I'm assuming there will need to be some sort of broadcast and
then response read. Either way, very interesting project from both a software
and electronics point of view.

~~~
crsp
There's a company in Montreal commercializing this technology,
www.wavelite.net, maybe they can answer your questions!

~~~
baharp
This particular work, requires forcing transmission of CTS-to- self to avoid
transmission by nearby stations. The effect of the tag on the signal strength/
CSI can be measured at software level. Both enforcing the CT-to-Self and
measuring the impact on CSI should be doable in software level and on the off
the shelf APs. The downside of this method is low range, and low data rates,
at Wavelite, we are leveraging the same backscattering concept, where we use
off the shelf routers with no software modification, and using a separate
device (a cellphone or laptop or router)as the receiver. Here is a link to a
demo video:
[https://drive.google.com/file/d/1wprRR7LhPNwy07JjDlB0Hv804D7...](https://drive.google.com/file/d/1wprRR7LhPNwy07JjDlB0Hv804D7tLoMW/view)

------
ktpsns
This is interesting. I wonder whether in the domestic apartment, the wifi
signal carries most energy density (Watt/volume) or whether there are more
fruitful bands to explore, such as

\- 50Hz radiating power cables (especially heavy current like for the oven or
water heater)

\- socket transformators (the old ones, not thinking of switching power
supplies as your smartphone charger has it)

\- cellular networks (especially the waves emitted by mobile phones in the
same room)

In principle, exploiting these signals is like operating solar cells but
optimized for other frequencies in the electro-magnetic spectrum.

~~~
ganzuul
IIRC backscatter works by frequency pulling to a free channel, so for mains
frequency the inductor would have to be huge. DARPA was working on some low
frequency tech which might be of aid though.

~~~
godelmachine
Would you kindly post links towards the DARPA work?

~~~
ganzuul
[https://www.darpa.mil/attachments/AMEBAProposersDay_FINAL.PD...](https://www.darpa.mil/attachments/AMEBAProposersDay_FINAL.PDF)

~~~
godelmachine
Thanks ganzuul

------
godelmachine
Reminded me of this →

[https://news.ycombinator.com/item?id=16883447](https://news.ycombinator.com/item?id=16883447)

and this

[https://news.ycombinator.com/item?id=14611399](https://news.ycombinator.com/item?id=14611399)

------
EgoIncarnate
(2014)

~~~
danielh
Thanks for pointing that out. There is more current work from the same faculty
which shows how far the research has come:

Towards Battery-Free HD Video Streaming
[http://batteryfreevideo.cs.washington.edu/](http://batteryfreevideo.cs.washington.edu/)

Discussion:
[https://news.ycombinator.com/item?id=16881946](https://news.ycombinator.com/item?id=16881946)

------
tenryuu
I thought there was a big part of this article missing. but turns out that the
youtube embed isn't over https so the browser blocked it :/

~~~
isostatic
[https://www.youtube.com/watch?v=snZWgAZqo2c](https://www.youtube.com/watch?v=snZWgAZqo2c)

------
Rjevski
Wouldn’t this only work if the receiver has a low strength from the router,
and so the backscatter device can use its antenna to “reflect” more signal to
the receiver? What happens if the receiver already sees 100% signal strength
from the router?

~~~
baharp
The backscatter node is not necessarily used for hopping purpose, since it is
ultra low power in operation, it can be used for data transmission where life
time is a bottleneck.

------
knowsmorsecode
This isn't backscatter. More like active modulated reflection.

------
techwiz72
The authors of this original paper have been leading this work on backscatter
and even have a long range backscatter system that gives ranges of a
kilometer. They also have a startup commercializing backscatter.

[https://www.jeevawireless.com/](https://www.jeevawireless.com/)

[http://longrange.cs.washington.edu/](http://longrange.cs.washington.edu/)

