Using wi-fi for bomb and gun detection.

[just Warren]

Interesting.

But what about metal sided briefcases and suitcases?

And if wi-fi can do this, since it is now everywhere, will we see it deployed on city streets?

[MechAg94]

So it wasn't clear if this detection happened when you walked through something or just out in the open.  And would it be difference frequencies than tradtional wifi or interfere with existing signals?  I guess it is new. 

[230RN]

UHF (and higher) and even lower-frequency VHF signals get absorbed and reflected a lot.*  I can tell on my OTA (over the air) telly when my neighbor opens his door, which, like mine, is metal-clad.  On some weak stations, I can tear up the signals just by raising my arms  while sitting on the couch.  And if the pine trees outside get wet by either rain or snow, or are just blowing around, it will upset the OTA signals.

Even at 88.1MHz, my favorite radio station at the low end of the FM broadcast band, I can sometimes detect my movements around the house.

So while I'm not surprised in principle, I have to hand it to them for standardizing methods for detection by using these reflections, et cetera.  (In other words, I wish I'd thought of it.)

Terry

*Remember, all electromagnetic signals are line-of-sight unless reflected or refracted.