anyone running GPS clocks in Southeastern Georgia?
tkapela at gmail.com
Sun Jan 23 10:26:06 CST 2011
> What about Modular DOCSIS 3.0 deployments with external timing sources
> between the QAM and CMTS
A CMTS DS payload is formatted as an MPEG TS (it even has PIDs;
however, no PCR). This in turn establishes cadence for associated
downstream devices (eg. they sync to whatever is within allowable
tolerances). Any digital 'baseband' output from a so-called 'modular'
CMTS (one with external QAM modulation) should likewise serve as a
recoverable timing source for the modulator.
Inter-DS cadence is allowably async; the only important coupling here
are these associated US channels available for a given DS.
Unless I've missed something horribly obvious, I can't see where
strict timing is important, nor can I see where inter or intra-system
synchronization would be critical either, save for corner-cases (i.e.
US or DS dynamic channel change, DCC/UDC, etc). Even in these cases,
the modem is more than able to rapidly resynchronize with a
new/differing cadence in both frequency and phase domains.
I guess, in short, don't worry (about this).
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