On 15 Dec, 2012, at 22:38 , Hal Murray <hmur...@megapathdsl.net> wrote:

> 
>> GSM cell sites in the US have GPS because it is required to support E911
>> positioning.  I'm not sure if it is used for anything other than this, but
>> it doesn't have to be. 
> 
> So it's cheaper to install and maintain GPS rather than make one measurement 
> and tell the setup where it is?

E911 requires the carrier to be able to figure out where the handsets
are.  I think GPS is used as a common timing reference so they can
triangulate to locate the phone using time-of-arrival measurements
of the handset's transmissions made at several cell towers.

GSM/UMTS carriers do it this way, at least.  CDMA2000 carriers instead
rely on the handsets to make the time-of-arrival measurements, both
of signals from cell towers and of GPS signals the handset can hear.

Dennis Ferguson
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Reply via email to