Mike S wrote:
On 2/7/2013 2:17 AM, Terje Mathisen wrote:
Most (GSM/3G/4G) cell towers make do with OCXOs/TCXOs, but very good
ones, rated at a few ppb/day in drift rate.
...
The interesting part here is that the actual requirement is for
_frequency_ synchronization, not absolute time sync!
You're probably not familiar with CDMA systems, which absolutely MUST be
synchronized in both time and frequency.
I'm quite familiar with CDMA, I have used Endrun's CDMA reference clock
on a server in Tampa, FL.
I wrote GSM above specifically to avoid having to go into these issues,
besides taken world-wide CDMA is much less common.
http://www.cdg.org/technology/cdma_technology/a_ross/systemtime.asp
Hence the appearance of surplus GPSDOs, like the HP Z3801A, which was
part of a Nortel CDMA BTS.
That is very nice side-effect, yes!
:-)
Terje
--
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"
_______________________________________________
questions mailing list
[email protected]
http://lists.ntp.org/listinfo/questions
