Re: [802.3_EPOC] Exclusion Sub-band Question
All
I have been thinking about this email thread and I'm beginning to question
why we should have any exclusions except where there are clearly
frequencies tied to carriers "in the closed coax network" (think pilot
tones or STB carriers). Included below is a URL put up by the FCC showing
quite nicely the licensed and allocated frequency spectrum which is
"outside" of the coax that cable operators currently operate in "inside"
the coax.
http://reboot.fcc.gov/spectrumdashboard/searchSpectrum.seam
Once you have seen the dashboard above, depending on an individual cable
system or even part of a cable system, you should recognize the possible
severity of the "swiss cheese problem" tied to exclusion bands.
Please understand some of these licensed services are omni directional
while others are very direction (think cellular versus air nav such as
ILS). I would argue if you were going to do exclusion based on what gets
into a closed network (coax) then you would have to look at large frequency
bands which might have to excluded.
Having maintained cable networks where we kept off air television channels
on channel in the cable in the face of very high power transmitters I know
as an absolute I can keep a "closed network" closed. So I would argue
nothing should be excluded except where the operators have internal
frequencies in the coax which control amplifier pilot carriers or STB and
cannot be simply changed or changed out.
Any exterior signal (out to in) affecting part of the cable spectrum or
vice versa (in to out) should be fixed. Part 76 of the FCC Rules clearly
states the required correction. If there is a question as to whether the
FCC field intensity spec is too lenient, then they or even the SCTE should
investigate it and establish the correct criteria.
In the case of internal carriers that need to be excluded, then the model
should be to bracket the frequency in question plus a guardband above and
below.
My thoughts on the topic...
Tom
On Wed, Nov 28, 2012 at 12:48 PM, Victor Blake
<victorblake@xxxxxxxxxxxxxxx>wrote:
> Hi Hal,****
>
> ** **
>
> Sorry, I wasn’t trying to be sarcastic, but on reading my email, I can see
> I probably was. ****
>
> ** **
>
> On topic -- Because some of the RF apps (cellular, ISM, unlicensed
> wireless mics for example) use sub-bands, the potential exclusions are very
> small (<< 1MHz). But I don’t think it is practical or reasonable to
> micromanage that small.****
>
> ** **
>
> So I think exclusion is one aspect of what is needed. To address problems
> smaller than the elected exclusion (1 or 2Mhz appears to be the choice), I
> still think the system has to be able to back out the order of modulation
> in a time period which is not “real-time” but frequently (period = 180
> seconds perhaps).****
>
> ** **
>
> The combination of these two methods is better than “all exclusion” (aka
> engineered) or all dynamic (aka reactive).****
>
> ** **
>
> -Victor****
>
> ** **
>
> *From:* Hal Roberts [mailto:Hal.Roberts@xxxxxxxxx]
> *Sent:* Wednesday, November 28, 2012 11:28 AM
>
> *To:* STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx
> *Subject:* Re: [802.3_EPOC] Exclusion Sub-band Question****
>
> ** **
>
> When I said ‘fit’ I meant fit without undue waste. I agree the 2MHz on
> 1MHz spacing can cover everything.****
>
> ** **
>
> *From:* Victor Blake [mailto:victorblake@xxxxxxxxxxxxxxx<victorblake@xxxxxxxxxxxxxxx>]
>
> *Sent:* Wednesday, November 28, 2012 10:14 AM
> *To:* Hal Roberts; STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx
> *Subject:* RE: [802.3_EPOC] Exclusion Sub-band Question****
>
> ** **
>
> All-****
>
> ** **
>
> Exclusions will always fit no matter what the minimum exclusion size is,
> the real question is how much are you excluding that you don’t need to and
> therefore the wasted band-width? I suppose that’s the same as asking,
> what’s the minimum spectrum that would need to be excluded due to
> regulatory reasons or defensively to avoid ingress interference. ****
>
> ** **
>
> -Victor****
>
> ** **
>
> *From:* Hal Roberts [mailto:Hal.Roberts@xxxxxxxxx <Hal.Roberts@xxxxxxxxx>]
>
> *Sent:* Wednesday, November 28, 2012 11:04 AM
> *To:* STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx
> *Subject:* Re: [802.3_EPOC] Exclusion Sub-band Question****
>
> ** **
>
> Leo,****
>
> ** **
>
> I didn’t know the adaptive bit loading per subcarrier had already been
> decided upon. I agree that is a better method, if available.****
>
> ** **
>
> However now the question degenerates to the minimum size of exclusion
> zones. Already an example of a 1.75 MHz exclusion has been raised, are
> there other examples that don’t fit neatly into 2MHz chunks?****
>
> ** **
>
> Hal****
>
> ** **
>
> *From:* Leo Montreuil [mailto:leo.montreuil@xxxxxxxxxxxx<leo.montreuil@xxxxxxxxxxxx>]
>
> *Sent:* Wednesday, November 28, 2012 9:59 AM
> *To:* Hal Roberts; STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx
> *Subject:* RE: [802.3_EPOC] Exclusion Sub-band Question****
>
> ** **
>
> Hal,****
>
> The exclusion band is a tool for the operator to specify bands to avoid.
> For example: SC-QAM DOCSIS, set-top out of band channel, pilots, etc.****
>
> ** **
>
> For plant ingress and CSO/CTB, the adaptive bit loading per subcarriers
> will address these problem with a finer granularity. We envision the EPoC
> CLT will send probes downstream (like MoCA) and collect the MER per
> subcarrier from the CNU and adaptively adjust the bit loading per
> subcarriers. This is better than excluding these bands.****
>
> ** **
>
> The exclusion bands are to tell the CLT and CNU to never probe and use a
> given spectrum.****
>
> ** **
>
> Thanks****
>
> Leo****
>
> ** **
>
> *From:* Hal Roberts [mailto:Hal.Roberts@xxxxxxxxx <Hal.Roberts@xxxxxxxxx>]
>
> *Sent:* Wednesday, November 28, 2012 10:40 AM
> *To:* STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx
> *Subject:* Re: [802.3_EPOC] Exclusion Sub-band Question****
>
> ** **
>
> Unless Method 2 is a lot more complex, it would seem to be the way to go.
> Being stuck with 2MHz exclusion sub bands may be too restrictive.****
>
> ** **
>
> To mitigate narrowband spurs or CSO/CTB peaks, the use of a 2MHz exclusion
> may be too wasteful of sub-carriers. All that may be needed for this
> purpose is to exclude a few sub-carriers. ****
>
> ** **
>
> BTW, is this downstream only or upstream as well? The flexibility is
> needed more in the upstream than downstream (at least with upstream in the
> <85MHz region).****
>
> ** **
>
> *From:* Salinger, Jorge [mailto:Jorge_Salinger@xxxxxxxxxxxxxxxxx]
> *Sent:* Wednesday, November 28, 2012 7:40 AM
> *To:* STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx
> *Subject:* Re: [802.3_EPOC] Exclusion Sub-band Question****
>
> ** **
>
> Steve,
> Marek,
>
> Thanks for the summaries and thoughts.
>
> As an operator, I think that the second option would be preferable since
> it provides almost complete configuration flexibility. However, today we
> are bound to 6 or 8 MHz channel plans with center frequencies following 1
> of 3 frequency plans, so method #1 may not be too bad. I think it is
> probably more about the minimum exclusion zone (which if I understand
> correctly it would be 2 MHz in method #1 versus 1 sub-carrier in method #2)
> than about the way to describe it.
>
> But, I wonder about the implementation complexity of method #2.
>
> And, as an alternative to the lack of granularity of method #1, and the
> extreme granularity of method #2, could there be a method #3 that allows
> for the exclusion of individual sub-carriers somehow?
>
> Also, could we have vendors' opinions on the implementation complexity of
> method #2 versus method #1?
>
> Thanks!
> Jorge
>
> ****
>
> *From*: Marek Hajduczenia [mailto:marek.hajduczenia@xxxxxx<marek.hajduczenia@xxxxxx>]
>
> *Sent*: Wednesday, November 28, 2012 03:19 AM
> *To*: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx <STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>
>
> *Subject*: Re: [802.3_EPOC] Exclusion Sub-band Question
> ****
>
> Steve, ****
>
> ** **
>
> Very good summary of the discussion. ****
>
> ** **
>
> In my mind, both options are very similar, with the only two differences
> being the granularity of exclusion bands requested (fixed for method #1,
> arbitrary in method #2) and complexity of configuration (in method #1, we
> would list bands to be excluded, in method #2, we would list start/stop
> frequencies for exclusion bands). ****
>
> ** **
>
> If full flexibility is really what we are after, I’d go with method #2,
> even though it might generate a bit more management traffic to configure
> CNU. However, it is more future proof and could save us the headache of
> working with different grids and granularities of channels. ****
>
> ** **
>
> Marek****
>
> ** **
>
> *From:* Shellhammer, Steve [mailto:sshellha@xxxxxxxxxxxxxxxx<sshellha@xxxxxxxxxxxxxxxx>]
>
> *Sent:* Tuesday, November 27, 2012 23:36
> *To:* STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx
> *Subject:* [802.3_EPOC] Exclusion Sub-band Question****
>
> ** **
>
> EPoC TF,****
>
> ** **
>
> On today’s RF Spectrum Ad Hoc call we discussed the
> Exclusion Sub-band Rules. There are two approaches that we discussed and
> it was suggested that it would be good to get feedback from the larger
> group, including the MSOs, on this topic. Here is a description of the two
> approaches that have been proposed. If you have technical opinions on the
> advantages/disadvantages of the two approaches or you have a preference for
> one method, we would like to hear from you.****
>
> ** **
>
> *Method #1*
>
> **· **Exclusion sub-bands are multiples of 2 MHz (e.g. 2, 4, 6,
> etc.) and are on a 1 MHz grid.****
>
> **· **In this case one could configure 36 MHz exclusion sub-band
> on the lower channel edge and 36 MHz exclusion sub-band on the upper
> channel edge and get 120 MHz channel. Then one could include a 2 MHz
> sub-band within the 120MHz to make room for a cable plant pilot.****
>
> ** **
>
> *Method #2*
>
> **· **Exclusion sub-bands are specified with a start and stop
> index.****
>
> **· **In this case one could configure a 31 MHz exclusion
> sub-band on the lower channel edge and a 22.5 MHz exclusion sub-band on the
> upper channel edge. Then one could also include a 1.75 MHz exclusion
> sub-band within the channel to make room for a cable plant pilot.****
>
> ** **
>
> *Personal Opinion*
>
> **· **In my opinion, Method #1 is potentially less complex to
> implement.****
>
> **· **In my opinion, Method #2 provides more flexibility than
> Method #2****
>
> **· **This seems to be a trade-off between complexity and
> flexibility****
>
> ** **
>
> Comments?****
>
> ** **
>
> Steve****
>
> ** **
>
> ** **
> ------------------------------
>
> <="" p="">****
>
> ** **
> ------------------------------
>
> <="" p=""> ****
>
> ** **
> ------------------------------
>
> <="" p=""> ****
>
> ** **
> ------------------------------
>
> <="" p=""> ****
>
> ** **
> ------------------------------
>
> ** **
> ------------------------------
>
> ------------------------------
>
>
________________________________________________________________________
To unsubscribe from the STDS-802-3-EPOC list, click the following link:
https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-EPOC&A=1