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UW engineers achieve Wi-Fi at 10,000 times lower power

washington.edu

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Re: UW engineers achieve Wi-Fi at 10,000 times lower power

#21

Post by kens »

tux1968 wrote: post #6

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 fr…

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

Re: UW engineers achieve Wi-Fi at 10,000 times lower power

#22

Post by 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 (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(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 (http://passivewifi.cs.washington.edu/]

Re: UW engineers achieve Wi-Fi at 10,000 times lower power

#23

Post by stephengillie »

sgentle wrote: post #22

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 indi…

PoWIFI

Re: UW engineers achieve Wi-Fi at 10,000 times lower power

#24

Post by PhasmaFelis »

Scaevolus wrote: post #9

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.

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.

Re: UW engineers achieve Wi-Fi at 10,000 times lower power

#25

Post by mkagenius »

ajhc112 wrote: post #12

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

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

Re: UW engineers achieve Wi-Fi at 10,000 times lower power

#27

Post by mrb »

akovaski wrote: post #17
tux1968 wrote: post #6

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 fr…

As far as I can tell, it seems to work the same way that passive RFID tags work. Pretty neat, I guess.

Almost. Technically it's the same as active (not passive) RFID tags: both reflect RF signals, and both need a source of battery power is needed to open and close the antenna circuit.

Passive RFIDs harvest power from the RF signals.

Re: UW engineers achieve Wi-Fi at 10,000 times lower power

#28

Post by toomuchtodo »

kens wrote: post #21
tux1968 wrote: post #6

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 fr…

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

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://en.wikipedia.org/wiki/The_Thing_(listening_device)

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

Re: UW engineers achieve Wi-Fi at 10,000 times lower power

#30

Post by ClassyJacket »

paulddraper wrote: post #3
Namrog84 wrote: post #2

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

You won't be downloading OS images very well, but it's still a lot. That's two HD videos simultaneously, with some to spare.

5Mbps is an interesting definition of HD...
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