Hi Yaakov, unfortunately I was not able to attend the meeting. Comparing the definitions provisionally agreed in ITU-T and currently included in the G.pactiming-bis draft (the definitions are copied below) with the concepts you have discussed it seems that
Phase Synchonization (ITU-T) = aligned phase (TICTOC)
Time Synchronization (ITU-T) = labeled time + calibrated time (TICTOC)
Phase Synchronization - The term phase synchronization implies that all
associated nodes have access to reference timing signals whose significant
events occur at the same instant (within the relevant phase accuracy
requirement). In other words the term phase synchronization refers to the
process of aligning clocks with respect to phase (phase alignment).
Note: phase synchronization includes compensation for delay between the
(common) source and the associated nodes.
Note: this term might also include the notion of frame timing (that is, the
point in time when the timeslot of an outgoing frame is to be generated).
Note: the concept of phase synchronization (phase alignment) should not be
confused with the concept of phase-locking where a fixed phase offset is
allowed to be arbitrary and unknown. Phase alignment implies that this phase
offset is nominally zero. Two signals which are phase-locked are implicitly
frequency synchronized. Phase-alignment and phase-lock both imply that the Time
Error between any pair of associated nodes is bounded.
Figure 1/G.8266 - Phase Synchronization
Time synchronization - Time synchronization is the distribution of a time
reference to the real-time clocks of a telecommunications network. All the
associated nodes have access to information about time (in other words, each
period of the reference timing signal is marked and dated) and share a common
timescale and related epoch (within the relevant time accuracy requirement).
Examples of timescales are:
* UTC
* TAI
* UTC + offset (e.g. local time)
* GPS
* PTP
* Local arbitrary time
Note that distributing time synchronization is one way of achieving phase
synchronization.
Figure 2/G.8266 - Time Synchronization
Best Regards
Stefano
________________________________
From: [email protected] [mailto:[email protected]] On Behalf Of
Yaakov Stein
Sent: lunedì 11 maggio 2009 6.00
To: [email protected]; [email protected]
Subject: Re: [TICTOC] Document with definitions discussed during the lastTICTOC
conference call
Sebastien,
We discussed the definitions section of the requirements document.
I believe that we managed to pin down the concepts of
· frequency
· phase (1 / frequency - e.g. 1 pps, no connection between different
systems)
· aligned phase (phase with zero or known relationship at different
systems)
· labeled (previously called uncalibrated) time (aligned phase events
are labeled, but no link to official time standard, e.g. TDMA systems)
· calibrated time (locked to UTC or national time standard)
We also discussed stability and accuracy (which refer to one of the above)
We looked at the ITU and 1588 definitions where applicable.
Y(J)S
From: [email protected] [mailto:[email protected]] On Behalf Of
[email protected]
Sent: Monday, May 11, 2009 00:23
To: [email protected]
Subject: [TICTOC] Document with definitions discussed during the last TICTOC
conference call
Hello,
Since I was late during the last TICTOC conference call, I was wondering what
was the document that has been discussed during the call containing the
definitions?
Is it the requirements document? A new document? Where does the need for new
definitions come from?
Thanks in advance for the clarifications.
Just a personal opinion regarding possible new definitions in TICTOC: it would
be good as far as possible to align and re-use terms that are already defined
in other groups dealing with synchronization (e.g. NTP, IEEE1588, ITU-T...). It
would avoid confusion in the timing community in general.
Thanks.
Best Regards,
Sébastien JOBERT
R&D engineer, network synchronization
Orange Labs / France Telecom R&D
FT/RD/CORE/MCN/WAN
Tel : +33 2 96 05 20 93 - Mob : +33 6 82 69 00 50
[email protected]
<mailto:[email protected]>
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