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Re: [8023-10GEPON] [CHANNEL_LINK] New Excel spreadhseet available ...

Dear Tatsuta-san,
please find my comments inline in green ...
Best wishes

Marek Hajduczenia (141238)
NOKIA SIEMENS Networks S.A., Portugal - R
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Dear Marek,

Thank you for the answers.
I understand some of them, but I still have some questions.
See blow.
By the way, if I do not mention anything, I basically refer to sheet "T-10GPX30.1570" in 10GEPON-D.0.4_with_examples.xls.


From: TATSUTA [mailto:tatsuta@ANSL.NTT.CO.JP]
Sent: quarta-feira, 2 de Maio de 2007 6:49
To: STDS-802-3-10GEPON@listserv.ieee.org
Subject: Re: [8023-10GEPON] [CHANNEL_LINK] New Excel spreadhseet available ...

Dear Marek,

In my slide, I have some questions.
1. Is "Pc" a value of cell "S34"?
[Marek Hajduczenia] Cell S34 is empty in the quoted vecrion of the spreadsheet. Do You refer to some other version of the spreadhseet?
[Marek Hajduczenia] If I am not mistaken, cell S34 in 10GEPON-D.0.4_with_examples.xls which You referred to is the value of PCross_Central, - the Pc, which is defined as the correction factor due to penalty interactions, is indeed represented by this particular column rather than a single cell. At the maximum transmission distance of n km, You could say that Your Pc is defined by S34.
I understand it.
I have to explain the reason why I mentioned S34. I checked sheet "T-10GPX30.1570" and I thought a target length of PX30 was 20km, so I referred to S34. I understand which cell we refer to is depending on maximum transmission distance.
[Marek Hajduczenia]  Indeed, we treated the 30 type systems as having the maximum reach of 20 km. You may however have 10 km reach with double the subscriber count ... it is up to You how You want to use the budget - we want to define only the budget and not the way to use it. If You happen to have a dense customer base, You may want to fan out 5 km PON with 128 subscribers using the 30 class...
[Marek Hajduczenia] Besides, I believe that the 30 class systems should not be refered to by the number 30 since everyone gets the idea they are supposed to cover 30 km ... what about using something like E instead of 30 to indicate Extended CHIL ? Anything is better than another confusing number which will be misinterpretaed 6 months after the standard is approved and everyone forgets what the 30 was about .

2. Which cell is representing item "M"?
[Marek Hajduczenia] in current version http://www.ieee802.org/3/av/public/tools/10GEPON-D.0.7h.xls of the spreadhseet has cell B45 which represents the Budget_margin
[Marek Hajduczenia] This one I believe was answered. In 10GEPON-D.0.4_with_examples.xls which You referred to, which value was represented in cell L6, though in the end we decided to do a more detailed budget overview and organize the spreadhseet, thus version D.0.7 was born, along with all the subversions.
I see. However, I still have a comment.
I think a power budget is ChIL + penalties + Margin.
However, "L6", which represents "Margin", is derived from Power budget - ChIL - (SRS+SBS), so it does not include the other penalties .
I think that an equation of "L6" should be L6=(C8-T4)-L7-L8-L9-L3*P5-V34.
[Marek Hajduczenia] You are right about the definition of the power budget. It looks reasonable. Please have a look at the latest version of the spreadsheet and compare the current power margin estimation ...  

3. "LP Pen central" (cell "V34") looks like representing all of penalties. Is my understanding right?
[Marek Hajduczenia] See comment to point 1.
[Marek Hajduczenia] It would seem so - though beware that the value does not include the attenuation as well as any non-linear penalties which are calculated in a separate spreadhseet and inserted into this one.
Thank you.
One comment. I think the attenuation is not a penalty.
[Marek Hajduczenia] Point taken. I was looking at the wrong cell :-) 
4. "LP Pen central" is including cell "L34" which is "P_DJ central". The white paper does not notify it. If question no.3 is yes, do we need to include "P_DJ central" in "LP Pen central"?
[Marek Hajduczenia] See comment to point 1.
[Marek Hajduczenia] I believe so - I think that this particular question would be better answer by the original authors of the spreadhseet - some of the relations between the individual variables were modified with time and are not often reflected in the quoted white paper.
I see.

A following comment relates to your file.
5. Cell "B42" in file "10GEPON-D[1].0.7" is specified as other_penalties which represents other system penalties. However a value is derived from cell "L7" in file "10GEPON-D[1].0.4_with_examples", which represents Connections etc. I think this value should be included in ChIL and a penalty should come from cell "V34".
[Marek Hajduczenia] In http://www.ieee802.org/3/av/public/tools/10GEPON-D.0.7h.xls, the cell other_penalties (B42) is a total of the non-linear penalties (B21) and fibre plant penatlies (B22), whic includes splices, connectors etc. Cell B41 (fibre_loss) includes pure fibre loss only, assuming there are no connectors, PSC etc. and the channel is ideal.
[Marek Hajduczenia] As far as I understand the question, what You're saying Tatsuta-san is that we should take the splices, connectors etc. and include them in the CHIL and take the system penalties as the maximum value calculated in cell V34. Please note however that the said system penalty value You refer that is column V is not used in any calculations apart from charting ... It is hard for me to say whether we should therefore use this value or not. 
Umm..... a little complicated.
Is not A value of "V34" used for anything except for making the chart?
[Marek Hajduczenia] As far as I can say .... no. In terms of calculations, we take the difference between the Tx power and Rx sensitivity, substract the fibre loss, PSC loss and additional channel loss (splitters etc.) and what's left is what goes for penatlies and power margins. I am not aware how precisely one can model the RIN penalities etc. That would have to be explored in depth but I would say those values are pessimistic at best. That is at least the impression I get from the white paper and discussions with Piers and Pete ... In other words, in the spreadsheet we estimate the maximum value of the penalities we can tolerate in the system and do not try to estimate their values per say ... I hope that is clear right now.
I thought this sheet was used for calculating a power penalty as well as calculating a ChIL
[Marek Hajduczenia] Indeed it is. It just gives You the upper bound on how much penalty You can tolerate in the system ... As I said before, the formulas governing calculation of individual penalities are approximated at best so do not count on really precise modelling. Matlab would have to be used to calculate them precisely.  
If you are right, how can we calculate the penalties?
[Marek Hajduczenia] By calculate You mean take a formula and plugin in some numbers and get a result. You can estimate their values in the extended tables (lines 15 - 34 in D.0.4) but I am not sure about their precision level ... Piers would have to answer that but from what I gather from the white paper, the modelling is simplified to be used in Excel. You might need to use Matlab models to produce more precise results.  

Sincerely yours,
Tsutomu TATSUTA