4 ms·

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-duple

by kens 10y ago

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 10y ago
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.
- roryisok 10y ago
  When will they reevaluate those twelve wing aeroplane designs
- ReverseCold 10y ago
  Wow that's interesting, how did they find "The Thing"?
  - toomuchtodo 10y ago
    https://en.wikipedia.org/wiki/The_Thing_(listening_device)#Discovery https://en.wikipedia.org/wiki/The_Thing_(listening_device)#D...
sleepingeights 10y ago
Passive 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
  The maximum transmitting power is regulated. In the article they state that it can use some kind of crafted wifi packet to be compatible with any existing devices. Edit: After looking at the pater, it seems that I may have misunderstood the article, it needs a plugged RF carrier tone generator at at fixed frequency.
  - plussed_reader 10y ago
    Imagine coming up with the frequency scheme in an apartment situation; if the building were running the network it would be one thing, but I would expect individual units to foster their own connection.
- makomk 10y ago
  Come to think of it, rather than following the usual inverse square law, power should drop off with the fourth power of distance (just like with radar) - there'd be one inverse-square dropoff on the path from active transmitter to transponder, multiplied by a second inverse square loss on the return path. That's got to hurt performance.

by kens 10y ago

toomuchtodo 10y ago

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.

roryisok 10y ago
When will they reevaluate those twelve wing aeroplane designs
ReverseCold 10y ago
Wow that's interesting, how did they find "The Thing"?
- toomuchtodo 10y ago
  https://en.wikipedia.org/wiki/The_Thing_(listening_device)#Discovery https://en.wikipedia.org/wiki/The_Thing_(listening_device)#D...

sleepingeights 10y ago

Passive 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
The maximum transmitting power is regulated. In the article they state that it can use some kind of crafted wifi packet to be compatible with any existing devices. Edit: After looking at the pater, it seems that I may have misunderstood the article, it needs a plugged RF carrier tone generator at at fixed frequency.
- plussed_reader 10y ago
  Imagine coming up with the frequency scheme in an apartment situation; if the building were running the network it would be one thing, but I would expect individual units to foster their own connection.
makomk 10y ago
Come to think of it, rather than following the usual inverse square law, power should drop off with the fourth power of distance (just like with radar) - there'd be one inverse-square dropoff on the path from active transmitter to transponder, multiplied by a second inverse square loss on the return path. That's got to hurt performance.