[opendtv] Re: Interview: ARE MANY TRANSMITTERS BETTER THAN ONE?
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 18 Sep 2007 11:12:48 -0400
Craig Birkmaier wrote:
> I think it should be noted, however, that Merrill also had a
> hand in the decision to reject the COFDM system, when it was
> evaluated by the Advisory committee. He developed the economic
> model for deployment of COFDM, which was one of the major
> reports used to eliminate it from consideration. The report
> noted that it would be prohibitively expensive to deploy COFDM
> SFNs in the U.S. because of the telco tariffs on the data
> lines needed to deliver synchronized feeds to multiple
> transmitters.
I'm not sure where you're going with this. It sounds like in terms of
the SFN argument alone, it's six of one and half a dozen of the other.
The cost of deploying SFNs is a wash, if you assume synchronization to
be required in both cases.
Are you saying that he should have included the example of passively
synchronized, small area SFNs, with either two towers or one big stick
and a few much smaller ones?
> This effectively forced COFDM to be compared with ATSC using
> only single high powered transmitters. In this comparison, many
> of the advantages of the COFDM approach are lost.
Which is exactly the right analysis. The passively synchronized, small
area SFNs, for which COFDM would have the clear advantage, require
dialing down spectral efficiency, and are not very effective in covering
huge OTA markets. As we have in the US. So it is very appropriate, IMO,
to consider whether the benefits outweight the liabilities.
Now that synchronization is more practical, using GPS rather than
perfectly measured transmission lines, more useful SFNs can be installed
in both systems. Which makes the two more similar, and further pushes
into the past all the silly debates about COFDM vs 8-VSB.
Bert
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