GSM sites do indeed have GPS antennas. But Dennis is correct; all of them
use GPS for E911 compliance, the GSM standard wasn't up to that task so
sites have an outboard box (LMU - Location Messaging Unit) which provides
E911 Location independent of the actual cell site base station.
By the way - that's where most of the surplus Thunderbolts came from - a
particular LMU manufacturer ran up against some patent issues and had to
take a bunch of product off the market.
That said, yes, some, but a very few, GSM BTS's that I'm familiar with use
GPS as a radio timing source.
Unless your 3G UMTS smartphone has an AGPS chip built in and turned on when
you dial 911 the system hands down your call to GSM for the LMU to do it's
thing. Same for 4G LTE, well at this point in the USA anyway, when you make
any voice call from an LTE device it drops the call down onto the 3G or GSM
network. I think Korea has LTE VOIP working maybe?
-Joe
----- Original Message -----
From: "Dennis Ferguson" <dennis.c.fergu...@gmail.com>
To: "Discussion of precise time and frequency measurement"
<time-nuts@febo.com>
Sent: Saturday, December 15, 2012 8:04 PM
Subject: Re: [time-nuts] Cell timing error
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.
In some other parts of the world it has been considered bad taste
to let the operation of telecommunications infrastructure become
dependent on a facility owned by the US military, so the standards
that are popular there often try to avoid that.
Dennis Ferguson
On 15 Dec, 2012, at 18:59 , li...@lazygranch.com wrote:
I can assure you the GSM shacks have GPS timing in them. I can dig up the
photos if you want.
-----Original Message-----
From: "Joseph Orsak" <jor...@nc.rr.com>
Sender: time-nuts-boun...@febo.com
Date: Sat, 15 Dec 2012 18:24:20
To: Discussion of precise time and frequency
measurement<time-nuts@febo.com>
Reply-To: Discussion of precise time and frequency measurement
<time-nuts@febo.com>
Subject: Re: [time-nuts] Cell timing error
AT&T uses UMTS in most areas which is a "self-synchronizing" modulation
scheme. Supposedly one of the selling points is "no dependence on GPS".
All
the extra sync channels and sync messaging is a capacity hog, not a very
spectrally efficient standard in my opinion.
About 85 maximum simultaneous voice calls in a 5Mhz UL / 5 Mhz DL
sector/carrier before it starts to fall apart. A big step backwards from
good old CDMA2000 (also just my opinion).
But hey, you can surf the web while you talk on the same device.
-Joe W4WN
----- Original Message -----
From: "Jim Lux" <jim...@earthlink.net>
To: "Discussion of precise time and frequency measurement"
<time-nuts@febo.com>
Sent: Saturday, December 15, 2012 5:43 PM
Subject: Re: [time-nuts] Cell timing error
On 12/15/12 2:16 PM, Scott McGrath wrote:
In a prior life we had a CDMA timing receiver for NTP which used VZ for
its source
On Dec 15, 2012, at 12:18 PM, Graham / KE9H <time...@austin.rr.com>
wrote:
You should switch to Verizon.
They are inherently accurate to milliseconds.
Sub micro-seconds inside the base stations.
On 12/15/2012 12:51 PM, Greg Troxel wrote:
In central mass, AT&T and tracfone (? carrier) are showing phone
times
very close to 1 min slow. Virgin/sprint is ok. I've never seen
this
before - usually it's a few s slow.
The time *displayed* on the phone might not reflect the time from the
network.
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