[time-nuts] Time in a cave

[Tucek, Joseph]

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.

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?).

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