Re: [8023-10GEPON] [FEC Superating] - kickoff preso
I'm neither a FEC expert nor a PCS expert, so I have what may look like
a simple question:
Why can we not combine the PCS overhead (64B/66B =3%) and FEC overhead
(~7%), so that the combined overhead is less than the sum of the two.
Regards,
Thomas Schrans, Ph.D.
Design Engineering Manager
Optical Communication Products, Inc.
-----Original Message-----
From: EffenbergerFrank 73695 [mailto:feffenberger@HUAWEI.COM]
Sent: Wednesday, February 07, 2007 11:35 PM
To: STDS-802-3-10GEPON@listserv.ieee.org
Subject: Re: [8023-10GEPON] [FEC Superating] - kickoff preso
The actual rate is the repeating fraction. But, it is not a problem to
have a rate that is not expressible in a short fraction. However, a
round number has a 'prettiness factor.'
What is important that the rates have a reasonably simple ratio.
Frank E.
----- Original Message -----
From: glen kramer <glen.kramer@TEKNOVUS.COM>
Date: Tuesday, February 6, 2007 5:16 pm
Subject: Re: [8023-10GEPON] [FEC Superating] - kickoff preso
> Frank,
>
> > Just as a for-example, the 11.049 GHz happens to be 15/14ths of
> 10.3125.
>
> I calculate that 15/14ths of 10.3125 is equal
> 11.049107142857142857142857142857...
>
> Is this a problem? Should super-rating employ additional rate
> adaptationmechanism to make it a "nice" number?
>
> For example, inserting one extra block every 1875 blocks will
> bring the
> rate up to 11.055.
>
>
> Glen
>
>
>
>
> > -----Original Message-----
> > From: Jeff Mandin [Jeff_Mandin@PMC-SIERRA.COM]
> > Sent: Tuesday, February 06, 2007 1:41 AM
> > To: STDS-802-3-10GEPON@LISTSERV.IEEE.ORG
> > Subject: Re: [8023-10GEPON] [FEC Superating] - kickoff preso
> >
> > Frank,
> >
> > I think you might be conflating the loop timing issue with some
> other> issue raised earlier.
> >
> > The point I intended to raise about loop timing is that the upstream
> > frequency of 1.25 GHz is fixed already, and in the asymmetric 10/1
> case
> > the ONU needs to derive the upstream clock from the downstream
> signal.Of
> > course how easy or difficult it is to do that depends both on the
> > dividability of the downstream frequency by 1.25 Ghz and also
> on the
> > jitter of the downstream signal.
> >
> > 11.25 Ghz (rather than 11.049 GHz) would be fine. Can XFI/SPI
> components
> > go that fast?
> >
> > - Jeff
> >
> > -----Original Message-----
> > From: Frank Effenberger [feffenberger@HUAWEI.COM]
> > Sent: Monday, February 05, 2007 6:02 PM
> > To: STDS-802-3-10GEPON@listserv.ieee.org
> > Subject: Re: [8023-10GEPON] [FEC Superating] - kickoff preso
> >
> > All,
> >
> > I don't think that clock management is so strong an advantage
> for one
> > scheme over the other. In all the cases, in all the technologies,
> there
> > are a set of frequencies that are phase-locked to each other.
> Dividers
> > and PLLs do a fine job of inter-converting them. One is not much
> harder
> > than the other, unless we choose a poor frequency for the
> super-rating.
> > We should be more careful!
> >
> > Just as a for-example, the 11.049 GHz happens to be 15/14ths of
> 10.3125.
> > Those are reasonably small clock dividers, and not a big problem to
> > implement. Note that this division builds on top of the 33/32nds
> clock
> > ratio of 64b66b. If we go with super-rating, then I see no
> reason to
> > maintain the redundant framing bit. Rather, I think we would
> look for
> a
> > clock relationship from the FEC super-rate directly to the 10G base
> rate.
> >
> > In any case, I will add the item to the list, for completeness sake.
> >
> > Regards,
> > Frank E.
> >
> >
> >
> >
> > -----Original Message-----
> > From: Jeff Mandin [Jeff_Mandin@PMC-SIERRA.COM]
> > Sent: Monday, February 05, 2007 9:19 AM
> > To: STDS-802-3-10GEPON@LISTSERV.IEEE.ORG
> > Subject: Re: [8023-10GEPON] [FEC Superating] - kickoff preso
> >
> > Frank hi,
> >
> > Loop-timing for the asymmetric 10/1 case would appear to be another
> "pro"
> > for the subrating scheme.
> >
> > The ONU can - perhaps - use the recovered 10.3125 clock to
> derive one
> of
> > 312.5 Mhz (divide by 33), and then use a PLL to generate the
> upstreamrate
> > (multiply by 4). With 11.1 Gb/s XSBI this would probably be
> much more
> > difficult.
> >
> > - Jeff
> >
> > -----Original Message-----
> > From: Frank Effenberger [feffenberger@HUAWEI.COM]
> > Sent: Wednesday, January 31, 2007 10:32 PM
> > To: STDS-802-3-10GEPON@LISTSERV.IEEE.ORG
> > Subject: [8023-10GEPON] [FEC Superating] - kickoff preso
> >
> > Dear All,
> >
> > I have put together the following presentation on the issue of
> FEC and
> > line-rate vs. MAC-rate modification. I tried to include in these
> slides
> > all the arguments I have heard favoring one method or the other.
> If I
> > have forgotten your favorite, you can shoot an Email to me, and I'll
> add
> > it to the list.
> >
> > You may also note that the last slide, entitled "Reaching a
> decision"is
> > blank. I don't know a truly objective way to solve this
> problem... It
> > seems to me that when you stack up the pros and cons, these two
> schemes
> > are pretty equal.
> >
> > One last thought: The one 'hard' (objective) con for the super-
> rating> scheme is the loss of 0.3 dB of sensitivity. The one
> 'hard' con for
> the
> > sub-rating scheme is the loss of bandwidth (7% lost). How can
> we put
> > these two items
> > on a common comparative base? Usually, the common denominator in
> these
> > situations is cost, so...
> > What is the relative system cost increase due to 0.3dB optical loss?
> > What is the relative system cost increase due to a 7% capacity loss?
> > If someone wants to hazard an answer to these questions, please do.
> >
> > Regards,
> > Frank E.
>