[opendtv] Re: The "real" problem with OFDM in the U.S.

  • From: Craig Birkmaier <craig@xxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Thu, 17 Mar 2005 08:55:58 -0500

At 5:41 PM -0500 3/16/05, Manfredi, Albert E wrote:
>Craig Birkmaier wrote:
>>  No, Bert, this is not true. Ubiquitous coverage
>>  comes from the delivery of the INTENDED signals
>>  for the market in which the viewer lives,
>Sorry, Craig, but RF propagation is what it is. Pattern
>overlap is also used in the French DTT scheme, to assure
>ubiquitous coverage. You simply cannot design a
>practical system with sharp coverage contours, no matter
>how much you would want to have this be the case.

You are still missing the point Bert.

Yes overlaps are a necessity; this is especially true for SFNs where 
there are multiple synchronized transmitters.  But overlaps between 
markets SHOULD be avoided or at least minimized. It is absurd that 
Cliff lives near Philly but he is able to receive the Baltimore DTT 
stations easily, while having great difficulty receiving the stations 
from his market.

>This is true at any scale you care to examine. With big
>sticks, small sticks, cell phone towers, or IEEE 802.11
>microsticks in hot spots.

Apples and oranges. Transmission "networks" take advantage of the 
ability to overlap coverage to IMPROVE service. The overlapping 
coverage of the Big TV sticks degrades service and severely limits 
spectal efficiency.

>You're just repeating dogma here. Give me any coverage
>contour you care to hypothesize that does NOT include
>overlap, and I'll show you holes in coverage, and a
>house planted right in that hole that won't have a
>usable signal (in populated parts of the world).

You are the one who is repeating dogma, because of your dog headed 
stubbornness regarding the use of big high powered sticks. The 
evidence is overwhelmingly against your position.

>>  > Where does someone who lives in Aberdeen, Havre de
>>  > Grace, or even Elkton MD get his TV signal from, Craig?
>>  > Why should a Baltimore or Philadelphia station owner
>>  > NOT want to cover those communities?
>>  According to the market coverage maps the answer is
>>  Baltimore.
>Thank you. Now, if you were to deploy small sticks in an
>SFN for Baltimore TV stations, to achieve your desired
>super-sharp contours, just exactly how many towers do
>you expect you would need to cover a 50-60 mile radius
>with the kind of sharp coverage contours you want?

Probably four synchronized mains around the core Baltimore market, 
and a handful of translator/gap fillers in the population pockets 
that are at the edges of the coverage area. And these more distant 
sub-markets would ALSO have provisioning for additional channels to 
meet their local needs.

>If you still don't believe this, say so, and I will copy
>the table for you to see. I'm trying to force you to see
>reality here, Craig.

Thanks for the reality check Bert.

It confirms what I have been saying all along. Each market is unique 
and the design of the networks should be optimized for the market 

>All of which suggests that OTA stations want to achieve the
>widest possible coverage, *even* for their cable carriage
>negotiations. So I ask you again: what are the practical
>ways of achieving this? Not practiced marketese answers
>here, not rehearsed dogma, but real-world.

Define the markets and sub-markets, then design a transmission 
network to provide a uniform RF level over the designated market 
area, assuring a reliable multi0channel service using simple antennas.

>That's the crux of my diagreement! It's not unique at all.
>Up and down the East and West Coasts, Gulf Coast, that's
>the RULE. There are no unpopulated areas between markets

As usual you argue around the point. If you look at the FCC coverage 
maps you will see that there are only a few areas (such as the one in 
which you live) where two large markets have significant overlap. Yes 
there is overlap between markets in rural areas, and there are all 
kinds of deals to determine how people in these netherworlds get 
service. In the vast majority of cases, the cable system that 
provides service in any area will ONLY deliver stations form ONE 
market, even if they can pull in signals from adjacent markets.

Again, based on what I wrote above, with properly designed 
transmission networks you designate the market to which every 
population pocket belongs, then you build the network to provide 
reliable service.

>And once again, even in other parts of the world, ubiquitous
>coverage is required. Check out the map of the French DTT
>coverage. It tries to be uniform. There is no wilderness
>there, Craig. Overlapping patterns of translators.
>Overlapping patterns of big sticks. Overlapping patterns
>of individual small-scale two or three-tower SFNs. What's
>the difference? It's a matter of tradeoffs ALWAYS.

They are able to do this by using networks of low powered 
transmitters. That's the difference Bert.

>Ubiquitous coverage means overlapping patterns. Big sticks,
>with occasional assistance from gap fillers, are a
>reasonable approach, when the markets are huge.

I have consistently acknowledged this Bert. But market size is only 
one factor. The distance to adjacent markets is equally important. 
You can use big sticks and gap fillers to cover the HUGE Salt Lake 
City market, But you CANNOT use the same approach to cover the HUGE 
LA market, without interfering with the San Diego and Bakersfield 

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