
UW engineers achieve Wi-Fi at 10,000 times lower power - jonbaer
http://www.washington.edu/news/2016/02/23/uw-engineers-achieve-wi-fi-at-10000-times-lower-power/
======
tux1968
The low-power devices don't actually generate any signal at all thus don't
have to pay that expensive power cost. Instead a passive antenna is modulated
to reflect or absorb ambient signal, the reflected signal conforms to
traditional 802.11 packets. The ambient signals are created by a relatively
high-powered device that is plugged into wall power.

Here is a 2 minute video showing an early prototype of their work from 2014:

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

~~~
kens
I've looked at the paper [1], but I can't figure out how this is different
from backscattered RFID with 802.11 on top. The paper says RFID requires a
full-duplex radio while the WiFi chipset is orders of magnitude less
expensive. Are they modulating differently or is there some RF magic?

[1]
[http://passivewifi.cs.washington.edu/files/passive_wifi.pdf](http://passivewifi.cs.washington.edu/files/passive_wifi.pdf)

~~~
toomuchtodo
The technology is ~50 years old, and was originally invented by the Soviets to
eavesdrop on the US embassy in Moscow.

[https://youtu.be/mAai6dRAtFo?t=9m35s](https://youtu.be/mAai6dRAtFo?t=9m35s)

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

TL;DR Using a passive antenna to modulate a directed microwave emission.

~~~
ReverseCold
Wow that's interesting, how did they find "The Thing"?

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toomuchtodo
[https://en.wikipedia.org/wiki/The_Thing_(listening_device)#D...](https://en.wikipedia.org/wiki/The_Thing_\(listening_device\)#Discovery)

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ajhc112
This article is a few months old. The technology is now being commercialized
by the same authors, as Jeeva Wireless:
[http://www.jeevawireless.com/](http://www.jeevawireless.com/)

~~~
mkagenius
In case someone is wondering 'Jeeva' (pronounced as Jeev) means living thing
in Hindi.

~~~
hashin
To add, Jeeva means living thing in Malayalam, another language from the south
India. In fact, Jeeva is a common name in Kerala and Tamil Nadu, two states
from the south India.

[1]
[https://en.wikipedia.org/wiki/Malayalam](https://en.wikipedia.org/wiki/Malayalam)

~~~
exhilaration
Very interesting, thanks. I know a South African family of Indian descent with
that last name. They're the only Muslim family I've met with that name so I've
wondered about its roots.

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sgentle
I wonder if you could use this technique to make a completely passive wi-fi
device. Ie, no battery or plug of any kind, just using the power of the wifi
emitter. I guess it would be similar to passive NFC, but at a longer range and
driven by a separate device from the one that does the receiving. Or would the
power requirements be too high?

Edit: I just realised that the earlier prototype video from the comments
indicates that's the goal, but it's not mentioned in this more recent one.
Instead they just talk about higher power efficiency. I wonder if that means
they tried it and it wasn't feasible.

Edit 2: Aha, got it. There are three separate projects:

1\. Ambient Backscatter (2013): no external power, no base station (uses
ambient frequencies like TV), not wifi, low data rate (1Kbps) and short range
(<1 metre) [[http://abc.cs.washington.edu/](http://abc.cs.washington.edu/)]

2\. Wi-Fi Backscatter (2014): no external power, base station, kinda wifi
(encodes data in the CSI/RSSI metadata and presence/absence of packets), low
data rate (1Kbps) and slightly less short range(<3 metres)
[[http://iotwifi.cs.washington.edu/](http://iotwifi.cs.washington.edu/)]

3\. Passive Wi-Fi (2016): low external power, base station, actual wifi
(802.11b packets), high data rate (11Mbps) and long range (<30 metres)
[[http://passivewifi.cs.washington.edu/](http://passivewifi.cs.washington.edu/)]

~~~
ryao
I doubt that a microprocessor will be able to operate solely off ambient RF,
but I could see a low power microprocessor being combined with this and a
betavoltiac for impressively long life. Using this with the new diamond
battery that they have in the labs at the university of Bristol would enable
the creation of wireless devices that last over 5000 years.

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MrBra
I invented a coffee machine which works using 10000 times less power: it works
by deferring the actual coffee making to another machine you plug into another
wall socket.

~~~
HammondSmoking
Your analogy is flawed: let me fix it for you. "I invented a battery powered
coffee machine which works using 10000 times less power: it works by deferring
the actual coffee making to another machine you plug into a wall socket. Now
you can stop worrying about recharging the battery on the first coffee
machine, and still enjoy your coffee just like before!"

With WiFi, the advantage is that battery powered devices like your smartphone
will consume less energy. Sure, your router will draw more power from the wall
socket, but you are effectively reducing power consumption where you actually
are using WiFi the most, mobile devices that run on batteries.

~~~
mirages
Ty for the analogy, wasn't sure if I really figured what they were saying in
the paper

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Namrog84
10,000 times lower power, but achieving speeds up to 11Mbps

Being named passive wifi. Quite neat and could be useful for IoT considering
also approx 100 ft distance

~~~
jasoncchild
100' is a very low distance for real IoT applications I've run across

~~~
ryao
A directional antenna at the active wifi radio would enable longer range. One
interesting application would be the ability to dogleg a wireless connection
between points A and B where there is no LoS to each other, but both have LoS
with point C. It would be a low throughput link, but it would allow for an
awesome implementation of a private two way communications system. I.e.
Several miles without direct LoS between the two end points.

~~~
jasoncchild
This is already a thing, however data rates tend to be slower

~~~
jasoncchild
Yeah but it's easier to pair down the antenna and underpower the radio than to
go the other direction :)

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vmarsy
This is great research!

10,000 times lower power is only for the "passive wifi" devices, but these
passive wifi devices require a "heavy-lifting and power-consuming plugged-in
device" nearby.

Assuming that device consumes no more than a traditional wifi device, then the
overall system would consume:

    
    
        [usual consumption of 1 wifi device] + [# of passive devices] * [usual consumption] / 10000
    

So, if we want to calculate _per passive device_ it would consume around

    
    
        [usual consumption of 1 wifi device] / [# of passive devices]
    
    

In other words, the more of these devices, the better. Too few devices might
not offset the plugged-in device energy cost.

~~~
MayeulC
I am just wondering if the plugged in part needs to transmit at full power all
the time. This could seriously increase the overall energy consumption.

Plus, I have a hard time deciding _what_ it would transmit at full power all
the time...

~~~
PhasmaFelis
I'm not an RF expert, but it sounds like it would be transmitting an empty
carrier wave, not a real signal. Think of it as a big light source and the
passive transmitters as mirrors used to flash signals back and forth with
reflected light.

(Of course you'd _also_ need a traditional wifi router for everything to
connect through, and you might as well build that router into the same shell
as the emitter thing, so it gets confusing. But the basic carrier wave
wouldn't necessarily carry a signal.)

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Scaevolus
It looks like this can only transmit, not actually receive and interpret
data-- and if you listen carefully, this is the kind of applications they're
suggesting.

That's good for sensor nodes reporting status, but not so good for
interactivity.

~~~
PhasmaFelis
I don't think that's right, except in an extremely narrow technical sense.
This specific technology they've developed is only for low-power transmission,
because receiving wifi signals can _already_ be done with little power. Device
manufacturers can pair the new transmitter with any off-the-shelf wifi antenna
for reception.

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Animats
Interesting idea. Things like this generally need a bigger antenna, since
they're getting power from it. It probably means the base station has to run
at high power most of the time, rather than throttling down for short range
transmissions. If it went all the way to full wireless power, like some RFID
tags, it would be more useful.

High data rate capability probably doesn't matter. Anything that's receiving
or sending a substantial amount of data is probably using more power doing
something with it than sending it.

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tonyplee
Love to see someone makes watch/heart rate monitor with this technology that
last months/years or maybe forever with tiny solar panel like what's on solar
calculator.

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amazon_not
It would be great if this could be used in (new) mobile phones and tablets in
a low power mode when you don't need high data rates.

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omegaworks
>Now, paper towels, coffee or sugar can communicate their status using WiFi.

Internet of edibles?

God help us all :)

~~~
azinman2
You say that but if we could easily swallow or "tattoo" cameras/sensors, there
are many medical upsides.

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yuhong
I wonder why there isn't a WEP-like protocol using AES-CCMP. (of course,
without the problems of WEP)

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maranatha84
old news. I guess I remember this news in February here at HN

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sandworm101
This seem another wifi achievement only replicable in a desert environment,
during a solar maximum, on the dark side of the moon, while holding a black
cat.

If you are using a "wifi" antenna then that antenna is going to be picking up
all sorts of little things. Normally these aren't much of an issue, but at
these sensitivities suddenly that phone down the hall, the one not running at
a 10e-3 power setting, is a real issue.

Also, February 2016?

~~~
dang
There's nothing wrong with posting older material to HN if it hasn't had
attention yet. I'm not sure if this story had, though.

The "new" in "Hacker News" is more like a second-hand clothing store in my
neighbourhood that used to be called "New to You".

