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Re: [EFM-P2MP] FW: [EFM] EFM FEC Proposals


Thanks for the comparison slide.  I have the following comments.

1. On the Protection column you say that the S-FEC provides equal protection of all bits.
This is not quite accurate since the CW synchronization bit pattern needed by both the
S-FEC and F-FEC proposals is not, and cannot be, protected by the code.  The F-FEC CW sync
pattern happens to also contain the Ethernet start of frame word so it does double duty
as both  CW sync and frame sync for an FEC enabled receive node and a frame sync for a
non-FEC (legacy) receive node. I do agree that the S-FEC has more freedom to come up with
a reliable tbd sync pattern , on the other hand, the F-FEC proposal describes a sync
pattern and pattern detection method using correlators that seems fairly robust.

2. On the Prior field experience column,  I think that what is proven by G.975 is the
performance of the RS(255,239) code in an optical link.  Since both the S-FEC and F-FEC
use the RS(255,239) code then you could say, to this extent, that both proposed methods
are "field proven".  I agree that the ability of the F-FEC to operate with both FEC
enabled and non-FEC enabled nodes is not field proven, but that's where our job comes in
,i.e., to specify the design so that it will operate in the field.

I'm glad were getting these issues aired and discussed before the meeting.

See you in Vancouver?



Ajay Gummalla wrote:

> Larry and all:
>    I have attached a slide which compares the two proposals.
> I am hoping that this will generate more discussions and help
> us make progress.
> Please take a look at
> for the calculations on efficiency.
> Best Regards,
> Ajay
> > -----Original Message-----
> > From:
> > []On Behalf Of larry
> > rennie
> > Sent: Monday, July 01, 2002 6:31 PM
> > To: stds-802-3-efm
> > Subject: [EFM] EFM FEC Proposals
> >
> >
> >
> > Fellow EFM Task Force Members,
> >
> > At the last EFM meeting in Edinburgh we passed the following FEC motion:
> >
> > 17. Motion to add an FEC option for the 1Gig P2P and P2MP PHY,
> > maintaining backward compatibility with the 1000BASE-X PCS, for the
> > following reasons:
> >     1. Improves reach of a MPN limited link by 50% for links with MPN
> > penalty of about 2dB
> >     2. Permits operation at a SNR lower by 2.5 dB for non-dispersion
> > limited links.
> >
> > Two different FEC implementation proposals will be presented in
> > Vancouver and they are posted under the General Session material on the
> > EFM web site.  One proposal is frame based and the other is stream
> > based.  If you are at all interested in FEC for EFM, I encourage you to
> > please take a look at these two proposals and get your comments and
> > questions back onto the reflector before the meeting.  This will give
> > the presenters and their supporters time to formulate a proper response
> > and will conserve our precious meeting time in Vancouver.
> >
> > Regards,
> >
> > Larry
> >
> >
> >
> >
> >
> >
>   ------------------------------------------------------------------------
>                                       Name: Comparison of FEC proposals.pdf
>    Comparison of FEC proposals.pdf    Type: Portable Document Format (application/pdf)
>                                   Encoding: base64