On Wed, May 30, 2001 at 08:34:28AM -0700, Steve Schear wrote:
> At 06:57 AM 5/30/2001 +0000, Dr. Evil wrote:
> >And also, yes, the CIA direction finding stuff apparently wasn't
> >working there. Oh well, starting in October all cellphones will have
> >GPS built in, which will take all the guesswork out.
>
> Which can be easily jammed by a handi-dandi Hyde 'n Seek (tm) GPS
> transmitter fob near your cell phone antenna.
While that is certainly true (and real low power 1574.2 mhz
jammers aren't that hard to make), it is by no means true that most
cellphone location will be done via GPS. Several of the carriers have
filed for use of various differential time of arrival/ angle of arrival
systems which work with current cellphones and do not require upgrades
of customer equipment (thus avoiding the issues involved in ensuring
that enough customers have upgraded handsets to meet FCC penetration
requirements).
Also most of the GPS approaches involve assisted GPS in which
approximate values of range offset and doppler for visible satellites
are sent to the mobile phone to make its acquistion much faster - and
the phone may send back psuedoranges rather than a complete position
solution - the existance of this dialog no doubt means that the switch
would get some indications that the handset was being jammed or its
GPS was for some reason broken. Given consistant reports of jamming
from particular handsets I would imagine the carrier might be induced
to flag them for special attention and track them approximately via
the nearest cell method. In fact jammed handsets would stick out
like sore thumbs and probably ensure special attention...
>
> steve
--
Dave Emery N1PRE, [EMAIL PROTECTED] DIE Consulting, Weston, Mass.
PGP fingerprint = 2047/4D7B08D1 DE 6E E1 CC 1F 1D 96 E2 5D 27 BD B0 24 88 C3 18
