"Well, if you can propose a simple way
      to pick out a given phone, I'd like
      to hear it."

Sure ...

Step 1: Secure the band (800 or 1800) and modulation
type, or more importantly, *the air-interface type*
that the system is using on the phone you desire access
to.

Step 2: Radiate an RF signal on the "best known server"
in the area that belongs to the system the phone
has been programmed for - modulate this RF signal
with the system parameters set for auto-registration
using the smallest time value (time interal) for
auto-regs that is possible.

Step 3: DF on the registration attepmts that occur.

(Effectively you have erected your own microcell
 with your own control channel parameters.)

The downside is - every other phone that happens
across that simulated, local control channel is
going to attepmt to register as well ...



**** Your better bet is to monitor for all periodic
registration attempts on all systems in that area - some
of those registrations will be workers - perhaps one
(or more) will be from victims buried in rubble ...


   "Otherwise, you're stuck with numbing the receiver
    till all it can pick up"

A wideband noise source on all but one (perhaps locally
generated?) control channel which will force the phone
to seek it out above all others?

... still requires the correct control channel signal
containing all the correct info (sysid's etc) otherwise
the phone is likely to reject it and keep looking for
the 'home' system (highly dependent on phone programming
and air-interface spec at this point).

Jim



----- Original Message -----
From: "David VanHorn" <dvanhorn@CEDAR.NET>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Thursday, September 13, 2001 7:08 PM
Subject: Re: [OT]:cell phone locating


> At 06:54 PM 9/13/01 -0500, Jim wrote:
> >     "the only practical way to identify a
> >      given signal is by listening to it."
> >
> >This was true in the days of analog only 800 MHz
> >cellular - but those days are long gone for the
> >majority of users today ... where today the mode of
> >choice is digital (GREATLY increases the capacity of
> >the fixed infrastructure operator plus a number of
> >benefits such as security and data can be supported
> >as well). Then there is the problem that digital
> >comes in one bascially one of three flavors (given
> >two 800 MHz operators and at least 3 1800 MHz
> >operators that I'm aware of):
> >
> >1) TDMA (IS-136 et al) 2) TDMA (GSM) and 3) CDMA (IS-95 et al)
> >
> >Then there is WCDMA and GPRS just waiting in the wings ...
>
>
> Well, if you can propose a simple way to pick out a given phone, I'd like
> to hear it.
> Otherwise, you're stuck with numbing the receiver till all it can pick up
> is the nearest source.
> A differential FSM is what you end up with.  This is more useful than you
> might think, since it works better the closer you get.
>
> --

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