
Towards Battery-Free HD Video Streaming [video] - InclinedPlane
http://batteryfreevideo.cs.washington.edu/
======
pocketstar
The new batteryless wireless sensors coming out of uw are incredible. Dr.
Smith is leading some great work. My interest started when I heard of the WISP
[0]. The RF power harvesting design is so simple and elegant. It is amazing
what can be done with uW of power!

[0]
[https://sensor.cs.washington.edu/WISP.html](https://sensor.cs.washington.edu/WISP.html)

~~~
rasz
Indeed, its _so amazing_ it has potential of replacing $.2 watch battery some
day.

~~~
edoloughlin
It is amazing. With this approach, you wouldn't have to change the battery
every 10 minutes.

~~~
icoder
Although I don't recognise myself in the style of the comment you're
responding to, I would like to point out a (watch) battery will not die in 10
minutes when drawing microwats only. I think we want to separate low energy
usage, which is a cool feat by itself, and RF harvesting (which goes well with
low energy usage, but so _might_ a small, cheap, battery).

~~~
edoloughlin
I'm not an RF engineer, but the video mentioned that the 'traditional' WiFi
component would draw 1W. I assumed that, if you add a battery, it's to power
this part.

~~~
rasz
No, backscatter is the only legit part of this writeup, everything else is
made up.

"we simulate an ASIC, which achieves 60 fps 720p and 1080p HD video streaming
for 321 µW and 806 µW, respectively" simulate, how convenient!

"Our inter and intra-frame compression algorithms reduces total bandwidth
requirements by up to two orders of magnitude compared to raw video" so they
also invented mpeg4 level of compression 1mW codec.

You might wonder how such an amazing compression codec works? its middle-out.
They transmit "fullhd" by transmitting ~100x50 resolution intra frames ":).
Everything is Simulated, Estimated, Planned, Theorized, Calculated and Faked.
That cool 1080 YT clip of them walking around the corridor just after showing
you face mounted camera models? Never happened, prototype is BW 112×112,
"simulated" again. Their setup can do 1080@60 of a static picture, there is
only enough bandwidth to sustain ~2fps without dropping data. They even
conveniently kept all the calculations ignoring color (3x the data).

Reminds me of energy harvesting wristwatch crowdfunding HN was raving about
few months back, conveniently ignoring particular design including battery
able to power it for couple of years.

------
kristianp
In the video and paper, they don't actually explain what backscatter is in
this context. The wifi signal is what's being "backscattered". Here's some of
the leadup papers about it:

[https://passivewifi.cs.washington.edu/files/passive_wifi.pdf](https://passivewifi.cs.washington.edu/files/passive_wifi.pdf)
[https://homes.cs.washington.edu/~gshyam/Papers/wifibackscatt...](https://homes.cs.washington.edu/~gshyam/Papers/wifibackscatter.pdf)

~~~
lopmotr
Here's a video explaining WiFi backscatter. It really is an amazing concept
even without doing HD video with it. All kinds of devices - I'm imaging home
automation sensors - could become batteryless.

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

~~~
nightcracker
> All kinds of devices - I'm imaging home automation sensors - could become
> batteryless.

That's terrifying.

~~~
therein
You can still use jammers to prevent backscatter from being readable but your
jamming signal will just power the sensor more. :)

------
jv22222
This is the kind of submission that usually never gets anywhere on HN but it's
very good.

Actually, there is a lot of great stuff that gets submitted that never gets
anywhere.

It would be cool if somehow there was a manually edited "great but never got
anywhere" stream for HN.

Edit: Now I've gone and said that, watch this get a 1000 points ;)

~~~
mrep
There have been lots of posts about new technologies that have not panned out
so HN scepticism is to be expected (remember memristors)

~~~
jacobush
I am still hoping for "yet" in the case of memristors.

------
brianshaler
It seems transmitting the raw sensor data would make it tricky to do this
securely. Would it be possible to encrypt the signal with some sort of
hardware cipher?

~~~
CreepGin
They address the security possibilities in the paper:

> Our current implementation does not account for security. However, to secure
> the wireless link between the camera and reader, we can leverage the fact
> that our digital core processes the PWM signal. Each wireless camera can be
> assigned a unique pseudo random security key. Based on this key, the
> camera’s digital core can modulate the width of the PWM-encoded pixel value
> using an XOR gate. The reader, which knows the security key, can map the
> received data to the desired pixel values by performing the analogous
> operation.

~~~
cm2187
XOR encryption with a mostly static image doesn’t seem very secure to me.

~~~
jacobush
If the static image could be somehow "bankswitched", "shifted" or updated... I
am thinking a huge one time pad. The problem is doing it power effeciently of
course.

~~~
cm2187
Thinking about, the main problem will be the penguin problem [1]. Which for a
video is even worse as if a shape is moving, from seeing the pixels that are
changing you can tell most of what is going on.

[1]
[https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation...](https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Electronic_Codebook_\(ECB\))

------
freeflight
Reading that instantly reminded me of the Great Seal bug the Soviets gifted to
US Ambassador W. Averell Harriman in 1945 [0]

I'm not an engineer, but as I understand it the principles at work here are
very similar?

[0]
[https://en.wikipedia.org/wiki/The_Thing_(listening_device)](https://en.wikipedia.org/wiki/The_Thing_\(listening_device\))

~~~
vanderZwan
Tangentially related to that: a Dutch radar company apparently was responsible
for reverse engineering that for the CIA

[https://thecorrespondent.com/3789/operation-easy-chair-or-
ho...](https://thecorrespondent.com/3789/operation-easy-chair-or-how-a-little-
company-in-holland-helped-the-cia-bug-the-russians/116534484-2a3d7f11)

------
hansjorg
This reminds me of Theremin's Great Seal bug that was placed in the US embassy
in Moscow:

[https://en.wikipedia.org/wiki/The_Thing_(listening_device)](https://en.wikipedia.org/wiki/The_Thing_\(listening_device\))

~~~
awelkie
Definitely, this project is basically the Great Seal Bug but for photodiodes.
The authors even mention the Great Seal bug in their paper.

------
_jmar777
This is truly incredible. I've spent the last 4 years neck deep in live video
broadcasting solutions for consumer, commercial, and government use cases, and
this just blew my mind.

------
Spien
This is moving towards A Deepness in the Sky level surveillance tools.

------
Arbalest
My immediate thought is, even easier to install reversing cameras for older
cars. Now my second thought is, spying devices, a wholly more troubling
prospect.

~~~
coatmatter
Maybe I'm just too old-fashioned, but I generally dislike the idea of
reversing cameras. I only reverse if I'm completely sure of my surroundings,
based on turning back and using my eyes as well as the mirrors. Looking
anywhere else tends to feel like a distraction.

Most people drive and reverse way too fast.

------
timeisapear
Worth noting that the pretty HD pictures came from a laptop hooked up to a DAC
converter to simulate an analog HD video camera. The true analog camera shown
on the page had nowhere near HD color resolution (though it could still
recognize faces in a parking lot with 95% accuracy--impressive in itself.)

------
jsolson
I saw the presentation for their paper at NSDI last week. I was (inwardly)
giddy the whole time. They had a _live demo_. It doesn't even resemble
something that could be turned into a real product in the near term. It is,
despite that, comically amazingly cool tech.

------
awelkie
Very cool project.

I wonder if compressed sensing would be useful here. In the paper they
describe this custom (and seemingly ad-hoc) video compression algorithm that
is suitable for the low-power device. Basically, the camera averages blocks of
pixels into "super pixels" all in the analog domain, sends these super pixels
over the wireless link, and then the receiver can request the individual
pixels of any super pixel that seems like it might have changed since the last
frame. But with compressed sensing, can't all of this be done by sending
random linear combinations of all pixel values (like the single pixel camera)?
It seems like then you can avoid the bi-directional link and also get rate
adaptation for free.

~~~
awelkie
Also, in the paper they say they used pulse-width modulation for the
backscatter signal instead of just attaching the sensors directly to the
antenna like the Great Seal Bug because the dynamic range of the photodiodes
is much less than that of a microphone and they wanted to avoid using an
amplifier (section 3.1 in the paper). But the PWM requires power as well.
Would an amplifier that only has to map the range of a photodiode to the range
of a microphone really require that much more power? And if so, are we talking
like twice the power, 10x, 100x?

------
boxcardavin
This is an incredible outcome and really shows how much work these UW grad
students and Dr Smith have been working on low power passive tech. Great
stuff, I wish more people in software were versed in physical tech so they
could create hardware to enable their ideas.

------
iandanforth
Seems like this could be useful for AR. I'm sure adding two front-facing
cameras to the Vive Pro cut into both power and bandwidth budgets. I'd love to
hear from an AR expert on this!

~~~
paulie_a
What is AR?

~~~
NiceGuy_Ty
Augmented Reality (e.g., Pokemon Go)

------
lessclue
Incredible. Since it is analog and unencrypted, it’s wide open to attacks
though, isn’t it?

~~~
pocketstar
what is there to attack? if someone is in range to get the backscattered
signal they can just see what the camera is looking at...its 16ft LOS, for
privacy concerns at such low powers any walls would attenuate the backscatter.

~~~
muizelaar
What about spoofing or jamming the signal?

------
Animats
I'm amazed they can get so much bandwidth out of backscatter. Their previous
work [1] was more like RFID tag bandwidth.

[1]
[http://iotwifi.cs.washington.edu/files/wifiBackscatter.pdf](http://iotwifi.cs.washington.edu/files/wifiBackscatter.pdf)

------
baobrien
I'm really impressed with the bandwidth. Being analog and only having back-
scatter for the modulation, I thought it'd be way worse than current digital
or old analog schemes, but from the paper, they're saying 2.8Mhz worst case
for 720p@10fps, 0.98Mhz on average.

------
xori
Imagine everyone with google glasses broadcasting what they see unencrypted to
people within ~20ft.

Super cool.

~~~
SmellyGeekBoy
Surely everyone within 20ft of them can pretty much see what they see anyway?

~~~
DanAndersen
It'd be useful for going around corners, visibility in parking lots,
situational awareness for teams of military/SWAT in indoor environments, etc.

------
bwang29
480p at 10fps at 16ft is really incredible. That's enough distance to put
cameras all over cars to sense environments around it. My first immediate
thought is to retrofit old cars with lane-changing assist camera with this in
traffic.

~~~
crooked-v
The power requirements of a camera aren't even a tiny amount of the
complication of retrofitting existing cars.

~~~
aetherspawn
Perhaps it is, as cameras require looming and looming requires removing trim
and finicking around which is expensive in man hours. Especially if literally
every car that comes in is different.

Also fat looms the length of a car can still cost hundreds of dollars said and
done.

Cost of installation is greatly reduced if all you need to do is line it up
and rivet it on and there is no need to customise the power system to
different cars (ie 12V, 24V) and loom layouts (ie old looms are crappy, hard
to get apart for splicing, wires are old and might break during retrofit, some
cars have +ive chassis)

------
jayd16
This is pretty interesting and seems transferable to any application where you
have a data source you don't mind pouring energy into as long as that data
source doesn't need dedicated power.

You could apply this to other types of sensors, such as perhaps accelerometers
or microphones. Device locations could be a smart wearable, a surgical
implant, or some kind of hard to reach diagnostic sensor.

I suppose we already use something similar in rfids but I guess the novelty
comes from updating sensor data instead of a ROM. Very cool stuff.

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alkonaut
How does backscattering work in the presence of multiple networks?

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stefanpie
The recived signal at 16 feet looks suprisingly good, you could probably fix
it up with a bit of image processing and neural networks on the receiving end
(eg. Smartphones)

------
jl6
Could this harvesting technique power battery-free AirPods?

~~~
std_throwaway
For transmission of data yes, but you still need "lots" of energy to drive the
loudspeakers.

------
jacquesm
I just spent a lot of time researching energy harvesting (about a two week
project) and I'm extremely impressed by this. To just power a simple sensor
(temp, pressure) and sending out readings is a non-trivial thing to design in
such a way that it works reliably. To do a lot of processing and to power a
hungry sensor such a camera is orders of magnitude more complex.

~~~
rasz
They didnt. They simulated powering 112x112 black&white sensor, the rest is
just props and 'recreations'.

~~~
jacquesm
It says:

"Finally, we design a proof-of-concept prototype with off-the-shelf hardware
components that successfully backscatter 720p HD video at 10 fps up to 16
feet."

Which to me reads they have it working in principle the other design will be
an optimization.

~~~
rasz
So even here it says 720p instead of fullhd :), and when you read the paper
you learn they didnt even do that, they used 100x100 BW camera module in
prototype. 720 transmission was done with a laptop.

------
roywiggins
Quick, someone put a blockchain on it. Battery-free blockchain Internet-of-
Things sounds like a several million dollar ICO to me!

------
MPSimmons
This is a very cool first effort. I don't think it's suitable as a security
system yet, because it seems like it would be so easy to overwhelm the
relevant spectrum. Eventually maybe.

~~~
chime
Depends on the kind of security system. I manage over 150 IP cameras in our
internal facility CCTV system and it is expensive to pull Ethernet cables to
10 different spots near the ceiling in a single production room just 20x30ft.
I would buy these for $300/each if it meant I only need a couple of $500 hubs
at desk level per room.

I'm not worried about sabotage/jamming etc. We are trying to monitor OSHA-
violations, accidents, and quality control. If I didn't have to worry about
power, I would put multiple cameras in every warehouse aisle, loading dock,
and doorway. Local storage is embarrassingly cheap but dragging CAT5/6 all
over, supporting ton of PoE switches, and coordinating with facility staff to
maintain cameras 20ft up the wall is very expensive and time consuming.

I would also buy like 20 of these for my house and live-stream my mini zoo of
prairie dogs, goats, tortoises, and birds.

------
rsingla
This is quite an interesting concept in general, with cool results. Could
there be extensions to other real-time imaging modalities (ultrasound for
example)? Anyone have a hypothesis?

------
foxfired
Somewhat related, a few days ago there was (is) a Kickstarter for a wireless
1080p surveillance camera that last a whole year with a single charge. Eufy

Edit: Added name

~~~
janekm
It does so by using (very low power) motion sensors before turning on the
camera.

~~~
kuschku
combine it with this and you get a 480p 10fps feed while no one’s moving, and
a 1080p 60fps feed whenever motion is detected – the perfect combination.

------
bookofjoe
"Any sufficiently advanced technology is indistinguishable from magic."—Arthur
C. Clarke

------
jtchang
It's crazy what you can do with such little power. Basically these cameras
need no power at all.

------
ww520
This is amazing tech. Kudos for the theoretical foresight and the execution to
make it come to life.

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dingo_bat
I like it. Throw a bunch of these around the city and you have some
interesting applications.

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hnaccy
Technically very interesting but also depressing that the panopticon continues
to improve unabated.

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pishpash
Analog modulation? So interference will easily kill the signal?

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jlebrech
this would be nice for a safety necklace cam.

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free2rhyme214
This is pretty freaking cool.

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fredley
I think your response to this will depend on whether or not you've read Dave
Eggers' _The Circle_ , in which battery-free wireless cameras play a central
role. (Spoiler: it doesn't go well).

Imagine the current state of blanket surveillance, particularly in dense urban
cities like London, but everywhere, invisibly. Cheap, battery-free,
weatherproof cameras are a step towards this.

P.S.: The book isn't great, but it's miles better than the film.

~~~
VMG
The response needs to factor in that this is more or less inevitable. The
solution to potential power abuse must be Sousveillance.

~~~
aerique
Why wouldn't the average government just outlaw Sousveillance / Inverse
surveillance?

~~~
JoeAltmaier
Rules don't help as much in real life as we think. They are imaginary, and
have influence on our behavior only because we let them. If violating a rule
has no consequence or little chance of detection, we can expect large-scale
violation.

Further, if an action satisfies some person ethic but violates a public rule,
many folks will take that action anyway. Violating the speed limit to get a
spouse to medical aid. Violating a confidence to stop injury. Things like
that.

If a rule is counter to human nature (curiosity, personal safety) then it is
likely to be useless.

