On 5/12/15 4:00 PM, Tucek, Joseph wrote:
I'm looking for information on non-GPS time sources.
For background, I need to provide PTP to a cluster where we don't have line of sight to
the sky, and are unlikely to get roof-rights without a fight. There are CDMA solutions
that would work (e.g. Endrun Technologies), but I was wondering if there were any other
options. I either need an indoor capable PTP, or an indoor capable PPS. Microsemi
claims to have an indoor capable "GNSS" system, but I've yet to find a sales
rep to talk about it; if anyone has a link to one who can, I'd love to find out the
problems^W^W^W^W talk to them about it.
But the entire cluster is interconnected?
Or do you need some sort of wireless distribution.
For an example of something that almost but doesn't quite work, Beagle Software
has a CDMA NTP server, but they do neither PTP nor PPS in the CDMA version.
Similarly, Meinberg will sell a PTP unit that freeruns (if you override the
config), but they have no solution to discipline via CDMA.
I'm also curious if anyone has any idea about non-GPS time sync after CDMA gets
turned off (can I get time from 4G?).
What about an off the shelf Rb that puts out 1pps or NTP or PTP.
SRS (http://www.thinksrs.com/products/fs725.htm) does 1pps
MicroSemi (aka Symmetricom,HP,Datum, etc.) has all manner of equipment
that has quartz or Rb references and probably any interface you care to
name (for a price).
If you need sync to outside sources periodically, most of these could be
"carried" to somewhere you have sky visibility to get a GPS 1pps, wait
long enough to synchronize it up, then carry it back down and go on
holdover.
My endgame worst case is to just do PPS from a stratum 2 NTP (or even a
freerunning oscillator) and lie to my PTP server; hard sync to UTC is a
secondary concern so long as the cluster agrees with itself. Endrun is looking
pretty good, but I'd really like to have a second option to compare against.
-Joe
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