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.
