Maybe I'm misreading what you're saying, but no matter the cause, it
points out what can and does happen when you put all the mission
critical eggs in one basket.  That we don't have as reliable as
possible a backup system, or why we destroyed the one we had, is mind
boggling.  This is a perfect example of what happens when you have
people who don't understand the problem/s making the wrong final
decisions in spite of having been warned.

It is my belief that if we are to be so reliant on these systems for
so many things, we need to have a functioning backup system in place.

Burt, K6OQK

Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California  U.S.A.
biwa@att.net
www.biwa.cc
K6OQK

Hi

….. ummm ….. errr …..

Cell phones since they first came out have never ever been setup to run on anything other than GPS. Retrofitting them to use something else would take a decade or more. We didn’t “destroy the backup”, there never was one. Pretty much all of our surplus gizmos are cell tower surplus (like 99.99%).

Bob

Hi Burt,
you are more than right, but don't forget the bean counters! they have
power over everything even logical thinking.
73
KJ6UHN
Alex

On 2/26/2016 8:57 AM, Burt I. Weiner wrote:

Bob,

Nope. Cell phones have been using land-lines for ages to sync up. It was
with the CDMA stuff that GPS phase was starting to be used to
coordinate. GSM for instance does not need GPS on the base-stations, it
even goes to lengthy extends to avoid it. CDMA didn't come into much use
over here. GPS wasn't even there when cell phones got started. It is
only lately that GPS have become a more integrated part of the system,
but as GLONASS has become more popular more base-stations support that
too, in order to support AGNSS. Landlines still provide an interesting
backup and big efforts is invested on the sync-networks.

Cheers,
Magnus

On 02/26/2016 11:56 PM, Bob Camp wrote:

On Fri, Feb 26, 2016 at 05:56:59PM -0500, Bob Camp wrote:

Bob,

It depends.  

We're used to thinking of those GPS and oscillator packages

as the only timing for a cell site, but that was not the case until
fairly recently.

In many of those sites, there was also transport gear that

would take line timing from a CO or other site upstream that
typically had diverse reference clocks available.  It might even
have provided a backup BITS T1 as a frequency reference to cell
equipment.

Even without a local transport node, prior to the last few

years (where things seem to be going Ethernet), most cellular equipment
was still taking TDM handoffs, and could revert to taking line timing
off its transport circuits, thereby indirectly getting it from
practically anything upstream if its local reference failed.

Certainly, the surplus device pool is all GPS, but that's

because of the number of additional devices deployed, not necessarily
representative of the full footprint of LORAN and other methods that
used to be available as indirect backup references for the sites.

Of course, that's not going to be an option going forwards.

I, for one, welcome our new Ethernet overlords.

--msa

Hi

So in the context of the original post, exactly how many Loran-C disciplined cell phone systems were there? … errr .. none.

The only systems that use any sort of external disciplining are GPS based.

Self contained or “not disciplined” does not count in this case.

Bob

Hi

Again, the context of the question is an external to the system timing
source. In other words Loran-C or something similar. Even today, the network
sync to the backbone does not come from the GPS. That comes from the
carrier’s data line sync.

Bob

I'd be curious to know how many carriers have a reference source other than GPS for their "data line sync."

A few decades ago when I worked with long haul data circuits for a living the use of in non GPS timing references still seemed fairly common in my view.

Yes I agree that some systems can run from "line timing" but a reference source is still needed some where.
In my experience there was a common assumption made that the carriers had an accurate reference source for the timing that customers would pull "data line sync" from.

Later when I entered the time nuts hobby I saw lots of ex Telecom timing  gear for sale on the usual auction site.

All the best
Mark Spencer

Hi

All CDMA systems are directly locked to GPS time. None of them do the Gold Code
sync based on central office timing. Prior to CDMA, the AMPS system was frequency
domain based not time. Those basestations did not use anything more than an OCXO
to keep them up and running on the wireless side of the system.

Regardless of the ultimate backhaul sync source above the CO, the basestation will keep
talking based on whatever sync pulse it gets on the backhaul link. If the CO goes off and away
network wise, that is only a problem for traffic that leaves the local area. Indeed much of “that stuff”
(Stratum 1,2,3) is based on various timing sources. It also was designed in an era of “top down”
timing. That is a very different approach than the “bottom up” timing of the over the air codes
on CDMA or some (but not all) advanced TDMA systems.

Bob