Re: [STDS-802-3-EPOC] MMP Ad Hoc Slides for Tomorrow
I have some questions about the definitions below.
1) What is meant by the term "code word" in the MCS definition? Does this refer to a FEC code word? The 65b code word which we have adopted? Or something else?
2) The last phrase "Multiple code words may have the same MCS" implies that multiple code words may not have the same MCS. This seems contrary to my (admittedly limited) understanding of MCS, I would expect all codes words in an MCS profile to have the exact same QAM modulation and FEC. Yes different profiles may have different MCS but in one profile all sub-carriers are equal.
Note: At some point before I can vote in favor of any MCS plan someone must explain to this ol' optics dude how sub-carriers operating at the average QAM level but below their optimal QAM level as defined by their SNR can carry data without excessive BER.
3) In the bit loading definition why do we say "typically all subcarrier shared the same coding rate"? Does this mean that the combination of QAM modulation and FEC result in the same rate for all sub-carriers? This does not make any sense to me as I would expect the FEC to apply to all sub-carriers. How can each sub-carrier have the same rate if running at different QAM modulation level?
I will beg forgiveness for OFDM "newbie" questions in advance.
Best Regards,
Duane
FutureWei Technologies Inc.
duane.remein@xxxxxxxxxx
Director, Access R&D
919 418 4741
Raleigh, NC
From: Solomon, Joe [mailto:Joe_Solomon@xxxxxxxxxxxxxxxxx]
Sent: Thursday, May 02, 2013 10:34 AM
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx
Subject: Re: [STDS-802-3-EPOC] MMP Ad Hoc Slides for Tomorrow
Thank you very much, Andrea, for this contribution. I have been trying to consolidate different proposals and definitions that have been presented, and apologize for leaving out some of these very important details.
I have updated slides 17 and 18 based on your feedback.
Joe
From: Garavaglia, Andrea [mailto:andreag@xxxxxxxxxxxxxxxx]
Sent: Thursday, May 02, 2013 1:43 AM
To: Solomon, Joe; STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx
Subject: RE: MMP Ad Hoc Slides for Tomorrow
Hi Joe,
Thanks for sharing - I am not able to attend tonight, here one suggestion to further refine the text of straw poll #1, which is about capturing the definitions - the suggestion is based on the document from Rob, Hesham and me, which was agreed some time back and include such definitions already (attached). I do not think we need to make step back and reinvent the wheel, we can simply formalize those via a straw poll if that creates better clarity - I tried to enhance the current text, which in my opinion was missing some key points, I hope this is acceptable.
A Modulation profile based on Modulation and Coding Scheme (MCS) will be called MCS Modulation Profile
* An MCS Modulation Profile applies the same QAM modulation and coding rate to all the subcarrier carrying an individual code word, by defining the MCS for each code word, based on the average channel characteristics. Multiple code words may have the same MCS.
Modulation Profile based on Bit Loading scheme will be called a Bit-Loaded Modulation Profile.
* A Bit-Loaded Modulation Profile applies a QAM modulation order for each subcarrier, based on the subcarrier's narrowband channel characteristics. Each subcarrier may have a different QAM modulation order and typically all subcarrier shared the same coding rate.
Note that for bit-loading, it may turn better to define QAM modulation for (small) group of subcarriers - the configuration of the group size can leverage the trade-off between overhead and performance and the case of each subcarrier can still be included as sub-case in which the group is only one subcarrier. Maybe these can be part of further refinement in a second stage, but at least it would seem to me that subcarriers close by are likely to end up using the same QAM as they have very close channel characteristics, so some optimization of the overhead should be possible.
Thanks,
Andrea
From: Solomon, Joe [mailto:Joe_Solomon@xxxxxxxxxxxxxxxxx]
Sent: Thursday, May 02, 2013 00:55
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>
Subject: [STDS-802-3-EPOC] MMP Ad Hoc Slides for Tomorrow
Have taken another pass at the straw polls to attempt to clarify. Have also added a couple slides.
We will discuss and rework on the ad hoc call tomorrow. Hope you can make it.
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Topic: 802.3bn MMP Ad-hoc
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Joe Solomon
Comcast - T & P Access Technology
303-242-7037
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