Re: [802.3_EPOC] Questions on varanese_01_0912.pdf
Thank you Andrea,
Please see inline
Marek
From: Marek Hajduczenia [mailto:marek.hajduczenia@xxxxxx]
Sent: Friday, September 28, 2012 10:29
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx
Subject: [802.3_EPOC] Questions on varanese_01_0912.pdf
Dear colleagues,
Here are some questions on the varanese_01_0912.pdf presentation which did
not get sufficient time for discussion. I?d appreciate if they were answered
via reflector so that everybody benefits from these clarifications:
- How many taps have been examined in total in this study? I do not
care much about names, types but rather to see what the sample size we are
looking at and whether it is representative of a large network as a whole
rather than a single CMT port or not.
[AG] I think it is mentioned in the slides, we have 140 subscriber (CNU)
ports for the model, we considered all of them in the analysis. As you can
see from the curves, since this is a model and small variability have not
been included, SNR curves overlap when users are attached to same last
splitter ? in reality, the CDF is more continuous like shown in the measured
valued, rather than step-wise. Does that answer your question?
[mh0928] This begs a question then. Is this a number of CNUs that you?d
consider typical? What I am trying to understand whether the scenario that
was presented is the worst-case, best case or average (what can be expected
in majority of deployments)? Would it be possible for an operator to use
more tailored service groups to optimize them for SNR performance and to
avoid complicating the design of devices, allowing for more optimized
performance, rather than complicating the design of active devices?
- What is the most probably SNR distribution for a much smaller
population of CNUs connects to a single CLT port? I assume that you will see
some difference in SNR but it is not very likely to be as high as it was
presented at the meeting for the whole measured population of taps and
ports.
[AG] That may be the case, depends on how the few users are distributed in
the plant. However, the question is whether this would be representative of
a realistic plant ? measurements are over population of ~240 modems, so it
seemed to us that 140 (already smaller) was in the correct ballpark. Do you
see any use case for much smaller plants, we could include in the analysis?
[mh0928] This is something that operators should speak to. However, when I
look at the OLT driven deployment model with several CLTs deployed in field,
I?d not expect each CLT to be connected to 150+ CNUs. That would easily
reach thousands of CNUs visible to a single OLT, which brings the available
bandwidth down drastically, while burning a lot of bandwidth on scheduling
overhead. I?d like to understand the trade-off here, that is all.
Please consider presenting more focused study for the next meeting, focusing
on a number of drop sections to show what is expected to be seen on a single
CLT port. While I am not against adaptive loading on per CLT port, I do not
believe that this contribution has sufficient footing to justify adaptive
loading on per CNU basis.
[AG] What we shown is one CLT port and 140 CNU ports attached for the
modeled plant ? for measured values, each plant is one node and ~240 CM all
attached to the same coax distribution tree (Comcast may provide more
clarifications in case) ? we can make it more clear and improve in the next
steps.
Regards
Marek Hajduczenia, PhD
ZTE Portugal
Technology Strategy Department
Edifício Amoreiras Plaza,
Rua Carlos Alberto da Mota Pinto, nr. 9 - 6 A,
1070-374 Lisbon, Portugal
Office: +351 213 700 090
Fax: + 351 213 813 349
Mobile: +351 961 121 851 (Portugal)
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