full-disclosure - Wi-fi. Approaching customers

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From: michael.holstein at csuohio.edu (Michael Holstein)
Subject: Wi-fi. Approaching customers

> I guess you could only meaningfully compare signal strengths as seen at
> different points, as at light speed the delays wouldn't be measurable
> with any sort of accuracy.  (If you could measure the delays you'd be in
> great shape - that was used in WWI to pick out the location of gun
> batteries, just using two mics and very accurate timers.)

This trick is called "timed difference of arrival" and is one of the two 
methods (the other being GPS) to locate cellphones for e911.

Celluar companies have been doing the TDA trick for years to locate 
stolen/cloned phones. With modern DSP equipment and an antenna array 
whereby the elements are seperated by an interval based on wavelength 
(usually 4 antennas) it's not all that difficult.

LoJack also does it this way, although on a much lower frequency.

~Mike.