[opendtv] FCC Broadcasters Forum Yields No Magic Spectrum Solution
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: "opendtv@xxxxxxxxxxxxx" <opendtv@xxxxxxxxxxxxx>
- Date: Thu, 1 Jul 2010 18:54:32 -0500
Doug Lung's take on the 25 June presentation.
I'll partially disagree about the "cellular TV" conclusions, that there are no
substantial savings possible, only because I finally figured out what the
disconnect was. Arguing with Craig about spectrum efficiency for years has
finally given me a sound bite. To achieve meaningful savings in spectrum, you
need two things: (1) regional or national broadcasters, and (2) an RF scheme
that supports SFNs with towers very far apart.
DVB-T does not qualify, because even with a very wasteful GI of 1/4, covering
large regions would take too many towers and create too many opportunities for
self-interference zones. DVB-T2 is a better bet. It can be used essentially to
deploy many big sticks, AND on these big sticks can be on the same frequencies.
Now we're talking savings.
Honestly, in all the years people have been throwing out the idea that "SFNs"
would be the silver bullet, it never dawned on me that the "regional
broadcasting" ingredient was deliberately being left out. Apparently, it is. It
should have been mentioned last Friday.
Also, I have an idea for Ch 2-6. Use them for connecting PCs to TVs indoors,
wirelessly. Make a low power ASTC transmitter for PCs, and give instant access
to web browsing on DTVs. If noise drowns out the signal quickly, all the better
for the next household or next apartment.
Bert
-------------------------------
http://www.tvtechnology.com/article/102898
FCC Broadcasters Forum Yields No Magic Spectrum Solution
by Doug Lung, 07.01.2010.
The FCC Broadcast Engineers Forum held last Friday consisted of some of the
most experienced and skilled broadcast engineers in the country, although as
each panel gave its report, it became clear that there was no way to eliminate
all TV channels above channel 30 without a serious impact on TV broadcasting.
For non-technical readers, it is important to note that the channels the FCC is
proposing to eliminate are not the channel numbers you see on your TV set or
program guide but rather the channels the station is actually transmitting on.
For example, in Los Angeles KNBC, virtual channel 4 transmits on channel 36 and
KCBS, virtual channel 2 transmits on channel 43. Both would lose the RF channel
they use to transmit their signal over the air, although they may be able find
a new channel and build a new transmission facility on another channel to
continue to provide free over-the-air TV.
"Cellularization" of broadcasting would provide little if any new spectrum and
be technically difficult and expensive. Changing stations' channels to more
efficiently use the spectrum-"re-packing", even if protected coverage areas are
reduced, will yield little extra spectrum. More stations will have to use VHF
channels, and beyond some limited relief from power increases, there is no
magic solution to making VHF as effective in reaching smaller antennas as UHF.
The VHF reception panel suggested the best use for the low-VHF spectrum might
be as a "technological innovation" band in areas that would not impact the few
remaining low VHF DTV stations. The panel on compression explained that
combining two or more stations on one channel will work only if one or both of
the stations are willing to make compromises in HD quality, multicast
offerings, mobile DTV capability-or all of the above. MPEG-4 promises better
compression efficiency, but it could take 13 years to replace all the MPEG-2 TV
sets and converter boxes now in use.
One of the interesting things I noticed during the forum question and answer
periods at the end of each panel discussion was that there was little if any
argument on the purely technical points made by the panel. If there was a point
of disagreement, it was that the panels treated the National Broadband Plan
recommendations to clear 120 MHz of the broadcast spectrum as if it would
result in all broadcasters being forced to share spectrum or reduce coverage.
Evan Kwerel, acting FCC Wireless Bureau Chief Economist said this would impact
only 4th or 5th tier stations running mostly reruns, some in black and white,
and not networks. This implies the reward would either be great enough or the
penalty and costs high enough that many TV stations would voluntarily give up
their channels.
I'm encouraged by the format the FCC used in the forum. The depth of material
assembled by the panels in less than a day is amazing, although perhaps not
surprising due to the caliber of panel participants. Julius Knapp did an
excellent job as moderator and even managed to end the forum early. This work
cannot be ignored as the FCC decides how to achieve its wireless broadband
spectrum goals. If they do and focus solely on dollars as the measure of public
benefit, the record will show the resulting fiasco and public outrage cannot be
blamed on the broadcast engineering community. Unfortunately, viewers tended to
blame broadcasters for the loss of analog TV even though that was mandated by
Congress and the FCC. Of course most broadcasters were happy to stop
maintaining and supporting the equipment to transmit on two channels.
Now that the President has supported taking TV broadcast spectrum for broadband
(voluntarily, of course), there is little doubt this will impact all but the
smallest stations and perhaps those on low VHF channels. The video and
presentations presented in this forum are the best way for TV engineers to get
an understanding of the implications of taking away TV channels above 30 so
they can explain it to non-technical management. The FCC has made a video of
the approximately two and one half hour FCC Broadcast Engineering Forum
available at Reboot.FCC.gov/video-archives. Individual panel presentations are
available as PowerPoint files on the FCC Broadcast Engineering Forum page.
To encourage you to download the presentations and, if possible view the video,
I'll provide some short summaries of each panel's presentation:
Andy Setos from Fox Broadcasting delivered the Advanced Compression
Technologies presentation. He showed that demands for broadcast bandwidth are
still increasing-licensees are still migrating to HD and at some point won't be
able to depend on SD material being available. Forcing stations to share
channels will require picking winners and losers. This is the point that Evan
Kwerel strongly disagreed with-the losers will pay less. In addition to Andy
Setos from Fox, the panel included NBC's Glenn Reitmeier, David Converse from
ABC, and Greg Coppa from CBS. These are people that know from practical
experience what the limits are on quality and what viewers and advertisers
want. Cox, ION, and Capital Broadcasting also had one of their top engineers on
the panel, providing more real world experience. See the Agenda and Forum
Participants for a complete list.
The Cellularization of Broadcast Architecture and Distributed Antennas Systems
panel included Merrill Weiss, who I would call the "father" of distributed
transmission for ATSC due to his work on the ATSC standard and his work with
the FCC to make it available to broadcasters; and Dennis Wallace, who I think
it is safe to say has done the most ATSC fixed, DTS and mobile DTV field
measurements of anyone in the country.. Harris Corp., Sinclair, Sprint, CTB
Networks, and Motorola had an engineer on the panel. Bob Seidel from CBS was on
the panel and delivered its presentation. The presentation shows, step by step,
why going to a cellularized broadcast network will provide little or no
additional spectrum and will not work to provide stronger signals at the edge
of a station's contour because of interference to adjacent markets. The
presentation includes some very interesting maps showing the number of channels
that can be received in locations around the country. The maps show there are
many counties in the U.S. where viewers can receive more than 28 channels
over-the-air and some in California and around Chicago, and many throughout the
northeast where viewers can now receive more than 37 channels. It will be very
difficult to find spectrum below channel 31 for all TV stations, even if some
share channels.
The VHF Reception panel included Victor Tawil from the Association for Maximum
Service Television (MSTV), Jeff Johnson from Gannett, and a trio of broadcast
consulting engineers-Greg Best, Charles Cooper and Ross Heide. Dave Young from
Antennas Direct and Will Belt from the Consumer Electronics Association
provided expertise on receive antennas while Kerry Cozad from Dielectric
covered transmitting antennas. The panel's presentation provided a short lesson
on antenna theory, then addressed practical issues. The problems with VHF DTV
reception have been widely reported and I won't repeat them here. Refer to the
panel's presentation for one of the best summaries I've seen of the issue. The
"Final Thoughts" slide sums things up nicely: "Improvement in VHF reception is
difficult and limited by the laws of physics; RF environment; practical
limitation of transmitting and receiving equipment design."
The last panel to present covered the methodology for repacking. This group had
to look at ways of moving all of those stations above channel 30. Panelists
included Bill Meintel, who worked with the FCC in writing the software it used
to determine coverage, interference and DTV Tables of Allotments, Bruce Franca,
an engineer in the FCC's Office of Engineering and Technology before MSTV, and
Dr. Byron St. Clair, who most consider the father of translators and LPTV. They
were assisted by the top engineers from Univision, PBS. Gray Television Group
and Lin Broadcasting. Broadcast engineer Joe Snelson represented the Society of
Broadcast Engineers. Mel Frerking from AT&T provided the wireless carriers'
perspective.
The Repacking panel looked at the analysis in OBI Technical Paper No. 3 -
Options for Broadcast Spectrum and outlined the short-comings and flaws in the
analysis. The panel presented an industry study showing that if full power,
land mobile, Class A and border stations are protected, 366 stations will not
have a channel in 40 percent of the markets. Note that this doesn't mean that
only 366 stations would have to share a channel, but rather it means a total of
732 stations would not have their own channel because those 366 stations
without a channel would need another station to share with. Slide 12 in the
presentation shows a map indicating areas where ALL stations must share a
channel. They include western Washington, northern California, east central
Florida, much of the Washington DC to Hartford corridor and much of the
northeast border of the U.S. with Canada. Even Maine is impacted! One point the
panel emphasized is that the FCC has to be very careful in relaxing
interference requirements because interference ratio differences as small as 1
dB can make the difference between a watchable and unwatchable picture.
The presentations provide an excellent reality check for the OBI Technical
Paper No. 3 - Options for Broadcast Spectrum, which I described as "biased,
incomplete and in some ways, inaccurate" in a June 18 RF Report article.
----------------------------------------------------------------------
You can UNSUBSCRIBE from the OpenDTV list in two ways:
- Using the UNSUBSCRIBE command in your user configuration settings at
FreeLists.org
- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word
unsubscribe in the subject line.
Other related posts:
