/. : Feds Have Access To Cellphone Tracking On Request

Steve openmokolists at mysteryvortex.com
Tue Nov 27 04:38:09 CET 2007

I remember discussions of this on usenet many years ago.  (in the AMPS
days)  I seem to remember a company selling software that cellular
companies could run on their switches to triangulate phones.  It was
used to catch cloners and supposedly worked quite well, at least in well
covered areas like major cities.  Ostensibly, it worked by commanding
the phone to switch between several towers and used the fact that the
towers are each comprised of three directional antennas to determine
your location.

I always wondered why we needed fancy phones with extra and costly "GPS"
hardware in them to be able to track emergency calls when this sort of
triangulation should be possible at the base station.  I'm not well
versed in TDMA technology, but I seem to remember that the phone needs
to track round trip time to the tower in order to transmit within its
alloted time slice.  I would think that information could also aid in
location finding if transmitted back to the base station and require no
extra hardware.  Even older phones could transmit time slice delta
information with a firmware update.

A lot of Hams like to hold "fox hunts" where they work together in order
to track down a transmitter.  So there should be quite a few people well
versed in attempting things like this.

A dejanews search reveals the following and a bunch of other interesting
threads: (take a look at the bottom of the thread)


Wolfgang S. Rupprecht wrote:
> "Jeff Andros" <jeff at bigredtj.com> writes:
>> OK, legal matters aside, your network operators ALWAYS know where your
>> phone is: cell towers can triangulate the position of your phone(it's like
>> reverse GPS... multiple receivers on a single source).   
> I wonder how well this works on average.  If this would work well
> enough I don't believe we'd be seeing all the integrated GPS units for
> the claimed purpose of servicing E911.  Those things do add a real
> cost to the phone that cell phone providers are eating.
> If I were to try to mask the location of a cell phone, I'd simply
> stand within a few blocks of a cell tower and put the phone in the
> focus of a deep parabolic dish pointed at the cell tower of interest.
> I'd like to see the neighboring towers pick up a phone that is
> commanded to run at low xmit power with what is effectively a tight
> beam talking to the closest tower.
> But I do agree, hiding one's general location to within a few
> cell-tower radii is not possible.
> -wolfgang

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