[time-nuts] GPS Outage..

Bob Camp kb8tq at n1k.org
Sat Feb 27 07:51:13 EST 2016


Hi

> On Feb 26, 2016, at 8:01 PM, Majdi S. Abbas <msa at latt.net> wrote:
> 
> On Fri, Feb 26, 2016 at 05:56:59PM -0500, Bob Camp wrote:
>> 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,
> 
> 	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.

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


> 
> 	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
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