Re: [802.3_EPOC] another argument for MCS
So this is interesting. Extending return to 65 or 88 or higher MHz means
ingress can come from low band VHF channels, air navigational frequencies,
safety radios and a host of others that the industry has managed to impact
over the years. Of course this also applies to high band VHF, LTE, DF, ILS
and depending on frequency, VorTac's and other over the air services which
are generally handled with low power receivers. Some of these "interferers"
are not narrow band (ie 50 Khz versus 6 MHz). The worst case condition is
not whether we null sub-channels for ingress interference but how we impact
over the air services like air-nav by egress issues. The CableLabs guys
should be able to add more to this because of cable impact on LTE
complaints, which in the face of other types of carriers are "narrow band."
The FCC has shut down channels in cable networks that affected over the air
service and particularly safety related, so if we end up in those areas with
impact, the FCC will impose the best known and certain impact control:
"nulling of carriers" by shutting them down. J
Unfortunately, as a very general RF rule is, ingress also means egress. In
my view the channel model will need to state ingress tolerance but may also
need to establish egress tolerance because of the potential power required
to transmit in the downstream and the upstream. The FCC didn't necessarily
identify tolerances for EPoC carriers when the Part 76 rules were written
which now may have to transmit is excess of 65 dBmV in a network and
particularly a drop system.
From: Victor Blake [mailto:victorblake@xxxxxxxxxxxxxxx]
Sent: Thursday, October 11, 2012 1:35 PM
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_EPOC] another argument for MCS
Identify well known ingressors. There are a lot of them besides cellular and
satellite (unlicensed wran, wireless microphones, etc.).
-Victor
From: Marek Hajduczenia [mailto:marek.hajduczenia@xxxxxx]
Sent: Thursday, October 11, 2012 1:16 PM
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_EPOC] another argument for MCS
I was going to ask whether the next step would be also protecting against
GPS signaling as well as satellite radio and such . it seems to me that it
is the problem which has been solved in the past, as Rich points out.
Marek
From: Rich Prodan [mailto:rprodan@xxxxxxxxxxxx]
Sent: Thursday, October 11, 2012 13:12
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_EPOC] another argument for MCS
On the other hand, it is easier to avoid LTE interference by carrier nulling
the small amount of spectrum impacted. This is also why premium services
today are not placed in the 88 to 108 MHz FM band on many systems.
From: Tom Williams [mailto:T.Williams@xxxxxxxxxxxxx]
Sent: Thursday, October 11, 2012 10:58 AM
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_EPOC] another argument for MCS
All-
Here is a another good reason to use different MCS'es: some homes will have
LTE interference and will need a more powerful (and less efficient) FEC to
overcome the ingressing interference.
Again, it makes little sense to force everybody to the lowest common
denominator when the lowest comment denominator is low and the spread is
high.
I personally think a big value of multiple MCS'es may be 1-1.8GHz downstream
band. At these frequencies, the attenuation differences will be huge due to
different cable lengths between the subscriber right off the node and
subscriber at the end of the line. Once attenuation gets too high, S/N
falls.
Tom Williams
Cablelabs
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