[opendtv] Re: Spectrum is too valuable

  • From: Ron Economos <w6rz@xxxxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Thu, 12 Nov 2015 11:28:50 -0800

Here's a pretty good set of slides on DOCSIS 3.1 migration. Certainly better than reading the PHY specification. :-)

http://www.piedmontscte.org/resources/july2014/D3.1-Overview-JJD-073114.pptx

Ron

On 11/12/2015 11:04 AM, Craig Birkmaier wrote:

And this is also important. If you read the DOCSIS 3.1 standard, you will note
that the **only** way DOCSIS 3.1 can manage ~10 Gb/s per PON is by doing
assuming these two points:

1. That there are no MPEG-2 TS broadcast streams on that PON. All dedicated to
broadband service, like I said.
That is clearly not true. You can dedicate a portion of the 1 GHz available in
the most up to date 1 GHz HFC systems; you do not need the entire GHz. Cox is
deploying DOCSIS 3.1 in many systems next year - these are 1 GHz systems that
will continue to offer linear MPEG-2 TS streams.
2. That the usable spectrum is just about doubled, from ~900 MHz to ~1800 MHz.
Can you point me to a 1.8 GHz HFC system Bert?

Ron may be better equipped to talk about this, but I have heard of no plans for
cable systems to upgrade to 1.8 or 2 GHz systems. Ron noted that DOCSIS 3.1
channels can be set up at many sizes, and that 200 MHz channels may be the
norm. For most cable systems that still offer analog TV, it should be possible
to add two 200 MHz DOCSIS channels if you turn off the analog service. I expect
that will happen long before the cabled systems recover channels now dedicated
to MPEG-2 TS streams.

OFDM is used at much higher frequencies for cellular and other applications, so
I see no reason why DOCSIS 3.1 would not work on a 2 GHz system. But cable
systems are already experiencing emissions problems at 1 GHz, and you must look
at the length and condition of the coax runs from the PONs, and other real
world issues that degrade from the theoretical to the real world.

The numbers I quoted were for ideal 0db conditions.

So, Craig, how many households, at 5 Mb/s, could be fed from a single PON? Or
even at 15 Mb/s? How does that compare with your average of 500 households per
PON today?
I already gave you the numbers at least twice. Under ideal conditions a 500
home PON that uses ONLY DOCSIS 3.1 in a 1 GHz HFC system could provide just
over 11 Mbps to each home.

Regards
Craig




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