[EFM] Network timing?
I guess this is a question for the service providers out there. Imagining an
EFM ONU supporting bearer emulation (say, in order to provide E1/T1 interfaces
for connection to a legacy PABX), is there any interest in having the OLT
propagate network timing (usually 8kHz, traceable back to some reference) to
the ONUs by some method?
Propagation of network timing is allowed for in the xDSL standards.
Should we require propagation of network timing in EFM it could be propagated
by either the Ethernet symbol rate itself or via some coding method. Some
physical layer schemes (ATM25 comes to mind) use a low spec oscillator for the
line rate and insert special line tokens at 8kHz to allow user side equipment
to recover network timing if required. It would be possible to use one of the
non-data 8B/10B tokens as a timing marker and send at 8kHz, alternatively if
there is an OAM block it could be sent at 8kHz rate.
Matt Beanland, Project Manager/Principal Architect
Telecommunications Research and Development, Fujitsu Australia Ltd
5 Lakeside Drive, Burwood East 3151, Victoria, Australia
e-mail: matthew.beanland@xxxxxxxxxxxxxx Phone: (613) 9845 4313