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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 ref
by tux1968 10y ago
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
- ccostes 10y agoTheir video from 2013 shows some pretty cool applications of an earlier version of this tech that looks essentially like passive NFC using ambient RF rather than using 802.11. Very cool stuff!
- akovaski 10y agoAs far as I can tell, it seems to work the same way that passive RFID tags work. Pretty neat, I guess.
- mrb 10y agoAlmost. 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.
- lowglow 10y agoDid they just say enabling internet for billions of battery free devices? Is it like a push method? So I guess I could imagine state updates, or task pushes to autonomous agents.
- kens 10y agoI'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 10y agoThe 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.
- roryisok 10y agoWhen will they reevaluate those twelve wing aeroplane designs
- ReverseCold 10y agoWow that's interesting, how did they find "The Thing"?
- toomuchtodo 10y agohttps://en.wikipedia.org/wiki/The_Thing_(listening_device)#Discovery https://en.wikipedia.org/wiki/The_Thing_(listening_device)#D...
- sleepingeights 10y agoPassive RFID is powered by the incoming radio waves that is 1000x stronger than the signal transmission energy from the RFID tag. There is no statement to the power requirement for passive WIFI from an active WIFI power source. The active WIFI transmitter may require outputting radio waves many times more powerful in order to receive a signal transmission from the passive wifi device. edit: For that reason, I'm not that excited about this, and this is likely why it wasn't pursued earlier due to the power requirements of active <-> passive signalling. If it pollutes the EM spectrum with powerful radio waves that are magnitudes more powerful than what we're outputting today, then I hope it gets abandoned. If it's the same power consideration, then it's worth pursuing imo.
- y04nn 10y ago
- y04nn 10y agoIs it the sort of tech used by some devices in the NSA ANT catalog? It is useful for spying because they are undetectable if they are not subjected to a carrier frequency. There was also The Thing[1] [1]https://en.wikipedia.org/wiki/The_Thing_(listening_device) https://en.wikipedia.org/wiki/The_Thing_(listening_device)