[time-nuts] GPS Outage..

[Majdi S. Abbas]

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.

	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