[time-nuts] Another Trimble Thunderbolt-like GPS?

Dennis Ferguson dennis.c.ferguson at gmail.com
Mon Dec 19 21:48:42 EST 2011


Yes, USA GSM/UMTS operators also use GPS at their base stations.  They may use it
for timing, but I think the primary requirement for it comes from E911 support,
and maybe to provide AGPS and/or clock-setting support for phones.

European and Asian operators often do without it (they typically won't set the
time on your phone either).  I know of more than a few countries which in fact have
national regulatory constraints against relying on GPS for anything important.
The base stations still need a frequency reference, but they can generally get
that by recovering the clock from the transmission circuit which connects the
base station to the rest of the network.

Dennis Ferguson

On 19 Dec, 2011, at 16:22 , lists at lazygranch.com wrote:

> I was inside a AT$T shack about a month ago. They have GPS timing inside.  I took some photographs, so I will dig up later what timing they use. 
> 
> -----Original Message-----
> From: Dennis Ferguson <dennis.c.ferguson at gmail.com>
> Sender: time-nuts-bounces at febo.com
> Date: Mon, 19 Dec 2011 14:00:29 
> To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
> Reply-To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Subject: Re: [time-nuts] Another Trimble Thunderbolt-like GPS?
> 
> 
> On 19 Dec, 2011, at 11:25 , Rob Kimberley wrote:
> 
>> There was a spec issued many years ago to the industry from Lucent I believe
>> to come up with a GPS product for base station requirements. 10 MHz, 1PPS,
>> OCXO, RS-232 port, and a certain holdover spec.  The Thunderbolt was one,
>> Starloc another, NanoSync (from Odetics/Zyfer). There were others.
>> 
>> Rob Kimberley
> 
> I think it was actually Qualcomm.  The requirement for GPS time and 10 microsecond
> time synchronization (which informs the holdover spec) came from Qualcomm's CDMA
> specification and are unique to it.  GSM, UMTS and (I think) LTE base stations can
> get by without GPS at all.
> 
> Dennis Ferguson
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