ASTC 8VSB not a bad choice for Canada, as 95% of the househoulds get TV via cable -- where 256 QAM is the standard...

Paul Keinanen wrote:
On Tue, 6 Mar 2007 15:44:15 GMT, "Albert Manfredi"
wrote:

"Bob Miller" wrote:

SFN's and on channel repeaters are very important tools to have
especially where you have "vast land areas" like Australia, Russia and
China.

I don't see why SFNs would be especially important in those countries
with large plains. SFNs are nice as gap fillers in difficult terrain.

I believe on-channel repeaters would be more important as gap fillers
than SFNs. Most people live in cities. Even countries with large plains
have most of their populations in cities. Combinations of SFNs, on
channel repeaters and multiple frequencies used together allow for a far
more efficient network with better reception characteristics for most.
You need the best tools in your bag no matter what the topology to do
the best job. It is important to have the best modulation no matter what
country you are in.

There is no advantage to 8-VSB that would suggest its use in any country
with any topology in the world that I am aware of. Large countries like
the US, China, Australia and Russia have a diverse topology that
incorporates all possibilities except possibly the South Pole's.

You don't say we will pick a DTV modulation because 2/3rds of your
country is a large plain when 99% of your population lives in cities
along the coast with more typical topology. And while 8-VSB would more
nearly resemble DVB-T in the Outback in fixed reception mode most would
and Australia did pick the better modulation, DVB-T because it is better
everywhere, on the plain or in the city.

Australia, a country with lots of plains, is probably the biggest user
of SFNs. Also a country that did the most extensive test of 8-VSB and DVB-T.

http://broadcastengineering.com/RF/b...deploying_dtt/

Bob Miller


Of course if you do not intend to cover the whole area but only cover
selected villages with small repeaters then this might be a good idea,
so you can use the channel in each village a few kilometers away from
each other.

However, with village distance of 10-50 km, you are still going to
have problem due to insufficient guard time. If the villages are in
different valleys and thus sufficient isolation between the
transmitters, this would not be an issue.

Bob, as you well know, this is certainly not the case. Large area SFNs
make little sense, require way too many towers, and if anything, make
reception more troublesome and unpredictable.

The number of towers is not an issue these days, since the cellular
phone service will require quite a lot small towers. Putting SFN
transmitters in 30-90 m high towers would be quite realistic.

When the GSM cellular phone service started in Finland in the early
1990's, each operator started to build their own towers at each
available hill along each main road. Due to environmental concerns,
the phone companies were required by law to lease space for the
antennas to the competitor in each tower, thus reducing the actual
number of towers built. In practice, the phone companies created a
company to manage this tower and equipment room management.

I don't see a problem, why phone companies and broadcasters could not
share the same towers for cellular phone as well as SFN broadcasting.
Due to the low power required by such SFN broadcasting systems, there
would not be much problems to the cellular phone receivers due to
power levels and phase noise generated by the DVB-T transmitters.

Paul

Albert Manfredi wrote:
"Bob Miller" wrote:

SFN's and on channel repeaters are very important tools to have
especially where you have "vast land areas" like Australia, Russia
and China.

It certainly is the case. I did not mention large area SFNs though I
think they are possible.

Both of the above are your words. Did I misinterpret what you wrote?

Yes. You decided that what I wrote was that if you have a country like
Australia you have to want to install a country wide SFN or there is no
need for a modulation that includes tools like SFNs or on channel
repeaters.

I meant that in large countries no matter what you are doing assuming
you want to have the best reception for the most people at the least
cost you need all the tools you can get, you need the best modulation.

It is absurd to suggest that since a country is big and has a large
plain that a substandard garbage modulation like 8-VSB is preferable to
one like DVB-T that has more and better tools.

That argument is absurd in the US as well. To argue, and it is done,
that since the US is large and has a plain that it is best to choose a
substandard garbage modulation like 8-VSB and make the cities, where
most of the population lives, suffer with multipath problems when you
could have chosen DVB-T that would work better both in the plain and in
the city. Forget that DVB-T would also allow mobile and portable reception.

If you expect to cover, uniformly, "vast land areas" such as Australia,
Russia, or China with nationwide SFNs, I call that (a) untenable,
meaning possible but absurd, and (b) large area.

If you don't intend ubiquitous coverage, then of course SFNs are not
hard to install. You can certainly have pockets of coverage, where each
isolated pocket uses the same set of RF frequencies. A no brainer.

On channel repeaters are also a doable do. The CRC demonstrated those
already, also using 8-VSB, in Ottawa. The trick with OCRs is to ensure
that receivers have adequate pre-echo tolerance and to ensure that a
stronger main signal overpowers the OCR signal before echo tolerance
limits of receivers are exceeded. Directional antennas for the OCRs can
help, by reducing areas in which the main signal may appear as a strong
pre-echo with large separation from the repeated signal.

Bert

It is called hiding behind a mountain. Might as well say that 8-VSB can
do on channel repeaters on the far side of the moon. That is repeat a
channel being broadcast in the US on the far side of the moon and call
it an on-channel repeater.

Maybe with 6th gen receivers they can do something that might be useful.
We will see. Problem is it won't work with all previous receivers.

Bob Miller

Paul Keinanen wrote:
On Tue, 06 Mar 2007 18:12:38 GMT, Bob Miller wrote:

Albert Manfredi wrote:
"Bob Miller" wrote:

SFN's and on channel repeaters are very important tools to have
especially where you have "vast land areas" like Australia, Russia and
China.
Bob, as you well know, this is certainly not the case. Large area SFNs
make little sense, require way too many towers, and if anything, make
reception more troublesome and unpredictable.

Bert

It certainly is the case. I did not mention large area SFNs though I
think they are possible.

Certainly they are, however, the design philosophy is closer to a
cellular phone network than a traditional broadcast network.

Due to the guard time issue, you really have to keep the towers short
enough, in order to avoid the situation of having significant amount
of signals (at a specific receiver site) with more propagation delay
that the guard interval will allow.

There are a lot of ways to use an SFN and or on-channel repeaters and
Australia is experimenting with a number.

In Finland, experiments are done with an antenna at the roof of an
apartment building, receiving horizontally polarised DVB-T signals,
which are then retransmitted downwards to other floors using vertical
polarisation (to help in keeping the repeater input-output isolation
at a sufficient level). The top floors may receive the original signal
directly from the main transmitter, while the lower floor only use the
repeated signals. Middle floors receive signals which are a
combination of the direct horizontally polarised signal and the
repeated vertically polarised signal.

Paul

We were planning on using this for a wireless house where the antenna
receives and the signal is rebroadcast to the rest of a single house.
Could be done for a neighborhood. Question we had was could it be such
that the neighborhood could have a single common antenna for all homes
and could this be put up with the rebroadcast without an entity like the
FCC having to even be involved. Old questions from 1998 and 1999.

Bob Miller

Albert Manfredi wrote:
"Paul Keinanen" wrote:

While this power ratio seems to be quite sufficient most of the time,
however, during slow fades caused by abnormal atmospheric refraction
conditions, the signal may vary with more than +/-10 dB, which in
analog reception only may cause some extra noise into the picture and
sound, but in a digital system (DVB-T and the old NICAM sound) going
below the sharp threshold level will make the reception impossible.

Since the analog and digital systems suffer differently during a slow
fade, IMHO, the fade margin for the digital system should be larger
from the beginning, thus running the digital DVB-T service more than
about 10 dB below the analog ERP may reduce the usability of the
system during abnormal atmospheric conditions. It appears that in UK,
they originally started with a much larger ERP difference, but had to
upgrade the digital power to maintain the same service area and
reliability.

I agree completely. It is those fade margins that have to be considered
with digital.

The number of towers is not an issue these days, since the cellular
phone service will require quite a lot small towers. Putting SFN
transmitters in 30-90 m high towers would be quite realistic.

The problems are two:

1. In the US, terrestrial broadcasters don't have tax revenues or
subscription fees to help pay for installing and maintaining a large
number of towers. And also, the majority of households subscribe to
cable or satellite, so broadcasters rely heavily on these other
distribution media. As a result, terrestrial broadcasters tend to be
very parsimonious when it comes to their OTA plants (alas!).

Why do you argue that what is must always be? Broadcasters are in the
fix they are in and pay little attention to and spend little money on
their OTA because they have had to live with NTSC. NTSC has seen its
viewership fade almost from day one because of reception problems both
quality and quantity.

Now US broadcasters are stuck with a modulation that only tries to be as
good quality wise and NTSC. So yes broadcasters will continue their lack
of interest in OTA.

At the same time it is being proven that with the right modulation and
more content OTA can be very strong, grow very fast and compete with
cable and satellite.

What has been is not what could be. There is something called change and
it is possible.

Broadcasters could and would spend lots on their infrastructure if they
had the right tools and did NOT have must carry.

And it would be a terrific investment.

Bob Miller

2. A cellular telephone system is not an SFN, as I'm sure you know.
Multiple cell towers are really nothing more than a network of
translators. If you try to obtain ubiquitous coverage with a wide area
SFN, mutliple towers carefully synchronized, it takes many antennas, and
areas outside the antenna cluster will get very unreliable service. As
weather conditions change, they will cause the signal from different
antennas to interfere in unpredictable ways (exceeding the GI in
unpredictable ways). So in large area SFNs, coverage becomes reliable
only in close proximity to the antennas.

I think the safe way to implement SFNs is to make them small area,
meaning two or three towers, all within the GI, primarily intended to
make urban reception easier. Distant reception is not really helped by
this, compared with a single big stick. If the urban SFN uses only small
towers, distant reception will actually be hurt compared to a big stick.

By the way, The French CSA has a very good document on these topics (en
Francais):

http://www.csa.fr/pdf/Rapport-GT2-As..._de_la_TNT.pdf

Bert

Bob Miller wrote:

There is no advantage to 8-VSB that would suggest its use in any
country
with any topology in the world that I am aware of. Large countries
like
the US, China, Australia and Russia have a diverse topology that
incorporates all possibilities except possibly the South Pole's.

Since large geographical areas are not credibly covered by SFNs, I mean
continuous covereage such as you want up and down the US East and West
coasts, and most European countries, the advantage of 8-VSB is to
provide more coverage for the same power, at the same spectral
efficiency. Or even if you don't believe this, at least it has no
disadvantages, for large area coverage. Even the inadequate 1st
generation 8-VSB receivers demonstrated *at least* equal long range
performance to COFDM, back in 1999.

COFDM has the advantage still of potentially greater echo tolerances,
especially in 8K mode at GI of more than 1/16, so it makes OCRs and SFNs
easier to implement. At some cost to spectral efficiency.

Everything involves tradeoffs.

The mixed SFN used in Sydney, for instance, would be quite feasible to
do with 8-VSB as well. That's the one with the single big stick VHF
supported by two small UHF towers in an "SFN," which is perhaps more
appropriately described as two low power translators.

As receiver technology improves, the differences are becoming less
significant, so all of this will matter even less than now.

Bert

"Bob Miller" wrote:

Why do you argue that what is must always be? Broadcasters are in the
fix they are in and pay little attention to and spend little money on
their OTA because they have had to live with NTSC. NTSC has seen its
viewership fade almost from day one because of reception problems both
quality and quantity.

US broadcasters spend as little as possible on their OTA plant not
because they relied on NTSC in the past, but mostly because they are
relying ever more on cable or satellite distribution. For the extra
spectrum and for the extra revenues.

This will not go away anytime soon. DTT is not going to change that
spectrum availability equation appreciably. So I'll bet you that US
broadcasters will continue to be as frugal as possible with their OTA
plants.

Broadcasters could and would spend lots on their infrastructure if
they had the right tools and did NOT have must carry.

I don't buy it. If "must carry" didn't exist anymore, the broadcasters
that survive would be the ones who use "retransmission consent" today.
Which means, the subscription media WANT their content. So dropping
"must carry" would change today's reality very little. These
broadcasters of desirable content would have no reason to behave very
differently.

If you are placing all your bets for DTT on the roaring success of TV to
handheld devices, (a) even that can is not out of the question with
8-VSB, (b) these specialized channels will be provided separately in the
US and Europe anyway, and (c) that's far from a sure bet.

So again, no big differences caused by DTT modulation schemes.

Bert

On Tue, 6 Mar 2007, Bob Miller wrote:
Australia, a country with lots of plains, is probably the biggest user of
SFNs. Also a country that did the most extensive test of 8-VSB and DVB-T.

Unlike the USA (and, for that matter, Canada), Australia's plains are
largely uninhabited and uninhabitable. Does "Great Victoria Desert",
"Great Sandy Desert", etc. mean anything to you? They make places like
the Mojave Desert and Death Valley look like a child's sandbox.

But don't just take my word for it. You can see how an area is settled by
its lights at night:

http://www.solarviews.com/browse/earth/earthlights.jpg

As this graphically shows, Australia's population centers are concentrated
on its eastern coast, particularly in the more temperate south, with a bit
on the southwest. The interior is largely empty.

Years ago, some woman made a travelogue called "From Alice to Ocean" that
went through the heart of that area. You can probably still find it at a
large enough bookstore. It would be highly instructive for people who
think that Australian conditions are comparable to North American
conditions.

The notion that Australia has anything like "nationwide" TV coverage, much
less such coverage by SFNs, is absurd. As shown above, almost the entire
population of Australia can be covered with a very modest infrastructure.

Europe is the opposite extreme. Most of Europe is a dense megapolis that
can support an equally dense TV infrastructure.

North America is the middle of the two extremes. There is dense megapolis
in the east to the center, but the western area is much less dense yet
equally distributed. There are very few empty areas where it is alright
not to bother with TV coverage until you get up into the far north.

European Russia has about the same densities as western North America, but
Russia doesn't try to provide the same level of TV infrastructure (and I
don't think that anyone here would care to watch Russian TV). Once you
get out of European Russia, civilization hugs the Trans-Siberian Railway.

-- Mark --

http://staff.washington.edu/mrc
Science does not emerge from voting, party politics, or public debate.
Si vis pacem, para bellum.

Albert Manfredi wrote:
Bob Miller wrote:

There is no advantage to 8-VSB that would suggest its use in any country
with any topology in the world that I am aware of. Large countries like
the US, China, Australia and Russia have a diverse topology that
incorporates all possibilities except possibly the South Pole's.

Since large geographical areas are not credibly covered by SFNs, I mean
continuous covereage such as you want up and down the US East and West
coasts, and most European countries, the advantage of 8-VSB is to
provide more coverage for the same power, at the same spectral
efficiency. Or even if you don't believe this, at least it has no
disadvantages, for large area coverage. Even the inadequate 1st
generation 8-VSB receivers demonstrated *at least* equal long range
performance to COFDM, back in 1999.

I do not accept "equal". For one thing the 2000 test had seven far field
sites where COFDM didn't work and where 8-VSB worked in six of the seven
sites. When Sinclair returned to those seven sites with a corrected
transmitter monitor with a correct filter they found that COFDM worked
in all seven locations. So even in the far field COFDM beat 8-VSB.

And in ALL the coverage area from one inch to the far field 8-VSB was
subject to all the problems presented by static and dynamic multipath.
Something they have still to solve. Something that is not a problem with
DVB-T.

Equal does not belong in the same sentence with 8-VSB and DVB-T, ISDB-T
or DMB-TH. It is ridiculous to even suggest they are in the same ball park.

COFDM has the advantage still of potentially greater echo tolerances,
especially in 8K mode at GI of more than 1/16, so it makes OCRs and SFNs
easier to implement. At some cost to spectral efficiency.

Everything involves tradeoffs.

The mixed SFN used in Sydney, for instance, would be quite feasible to
do with 8-VSB as well. That's the one with the single big stick VHF
supported by two small UHF towers in an "SFN," which is perhaps more
appropriately described as two low power translators.

As receiver technology improves, the differences are becoming less
significant, so all of this will matter even less than now.

Less? How much less. 10%, 50%, 75%? Still not enough. There is no reason
to use an inferior product even if the difference is only ONE%. At the
moment the difference between 8-VSB and DVB-T, ISDB-T and DMB-TH is that
they all support many possible business plans, 8-VSB so far supports none.

If the difference between any technology is only .0001% and that causes
one to be successful and the other to fail then that is a significant
difference. If one rocket gets Evil Knievel over the Grand Canyon by a
foot and another gets him one foot short one is a total failure and the
other a success.

And that is not a good "trade off". BTW what are we trading off when we
picked 8-VSB over DVB-T? What did we get in return. Please not the extra
BS coverage.

Bob Miller

Bert

Albert Manfredi wrote:
"Bob Miller" wrote:

Why do you argue that what is must always be? Broadcasters are in the
fix they are in and pay little attention to and spend little money on
their OTA because they have had to live with NTSC. NTSC has seen its
viewership fade almost from day one because of reception problems both
quality and quantity.

US broadcasters spend as little as possible on their OTA plant not
because they relied on NTSC in the past, but mostly because they are
relying ever more on cable or satellite distribution. For the extra
spectrum and for the extra revenues.

This will not go away anytime soon. DTT is not going to change that
spectrum availability equation appreciably. So I'll bet you that US
broadcasters will continue to be as frugal as possible with their OTA
plants.

I agree as long as they have the garbage 8-VSB modulation. In the UK the
price of OTA spectrum is skyrocketing because it has a decent
modulation. In the US the only reason OTA spectrum on channels 2-51 is
must carry rights. There is little value in the OTA spectrum otherwise
with 8-VSB. Want to know the value. Check out the going price for an
LPTV station in Iowa. That is the real value of 8-VSB spectrum.

If you want to know the value of spectrum with COFDM check out the UK or
wait for the auctions of 51, 52, 53, 56, 57, 58 here in the US next
spring. Then you can compare LPTV stations with 8-VSB to COFDM potential
stations.

Remember right now and for the last 9 years US broadcasters could have
use most of their digital spectrum with 8-VSB for almost anything but
didn't. The UK did. Soon new US broadcasters WILL use DTV spectrum with
COFDM for other things. The value of that spectrum will be at least 100
to 1000 times that of any 8-VSB spectrum. The only spectrum that can be
compared however is LPTV stations which do NOT have must carry rights.

Broadcasters could and would spend lots on their infrastructure if
they had the right tools and did NOT have must carry.

I don't buy it. If "must carry" didn't exist anymore, the broadcasters
that survive would be the ones who use "retransmission consent" today.
Which means, the subscription media WANT their content. So dropping
"must carry" would change today's reality very little. These
broadcasters of desirable content would have no reason to behave very
differently.

The "desirable" content will be found on OTA COFDM channels in the not
to distant future because those are the channels that will work
ubiquitously with simple low power receivers and simple antennas.
Broadcasters are already lining up to sell their content to cell
companies and will sell it to new COFDM broadcasters for a while before
content will find its way right to these new broadcaster, Internet
broadcasters.

Content, the best, is going to bypass current broadcasters. It will be
like water trying to find sea level. They are a dam today, a waterfall
tomorrow.


If you are placing all your bets for DTT on the roaring success of TV to
handheld devices, (a) even that can is not out of the question with
8-VSB, (b) these specialized channels will be provided separately in the
US and Europe anyway, and (c) that's far from a sure bet.

So again, no big differences caused by DTT modulation schemes.

All the difference in the world. OTA in the US is dead. OTA is other
countries on a wild ride of rebirth. Once analog is turned off it will
happen here to but above channel 51.

Bob Miller

Bert

"Mark Crispin" wrote in message
...
On Tue, 6 Mar 2007, Bob Miller wrote:
Australia, a country with lots of plains, is probably the biggest user of
SFNs. Also a country that did the most extensive test of 8-VSB and DVB-T.

Unlike the USA (and, for that matter, Canada), Australia's plains are
largely uninhabited and uninhabitable. Does "Great Victoria Desert",
"Great Sandy Desert", etc. mean anything to you? They make places like
the Mojave Desert and Death Valley look like a child's sandbox.

But don't just take my word for it. You can see how an area is settled by
its lights at night:

http://www.solarviews.com/browse/earth/earthlights.jpg

As this graphically shows, Australia's population centers are concentrated
on its eastern coast, particularly in the more temperate south, with a bit
on the southwest. The interior is largely empty.

Years ago, some woman made a travelogue called "From Alice to Ocean" that
went through the heart of that area. You can probably still find it at a
large enough bookstore. It would be highly instructive for people who
think that Australian conditions are comparable to North American
conditions.

The notion that Australia has anything like "nationwide" TV coverage, much
less such coverage by SFNs, is absurd. As shown above, almost the entire
population of Australia can be covered with a very modest infrastructure.

The amount of infrastructure required to bring terrestrial TV coverage to
Australia's 20 million people would not be considered "very modest".