Most phones use assisted mode GPS. In this mode, the phone asks the
network what satellites are visible. The network looks at the cell
tower and sector that the phone is in, then looks up what satellites
should currently be visible to the phone. This information is
transmitted to the phone, which then starts to listen to those
satellites for psuedo range information (the transmitted signal from
the phone). Once the psuedo range information is received, it is sent
back to the position determination engine in the network which
combines this information with cell sector info and other information
to calculate the position of the phone. Once the position calculation
is done, the network either used it directly (e.g. an emergency call)
or sends the position to the phone for use on the phone itself.
A few phones are capable of autonomous GPS, and can do all the
calculations internally, but usually the assisted mode is so much
more accurate and much faster there is rarely a reason to use this mode.
Eric Hildum
eric.hildum@mobileplay.com
On Nov 3, 2005, at 12:13 AM, Shannon Jacobs wrote:
> I'm curious if anyone has details on how this works? I was using
> KDDI for a
> while, and they gave me a GPS-capable phone, which I kept when I
> canceled
> the service, but the GPS doesn't work now. I'm curious if that's
> really a
> fake (non-satellite) GPS based on the locations of their transceivers.
>
>
> This mail was sent to address EricHildum@earthlink.net
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Received on Sat Nov 5 09:14:25 2005