[opendtv] Re: Seeing Ghosts on a Single Frequency Network

  • From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
  • To: "opendtv@xxxxxxxxxxxxx" <opendtv@xxxxxxxxxxxxx>
  • Date: Thu, 10 Feb 2011 16:00:49 -0600

John Shutt wrote:

[SFNs are a kludge]

> They're only a kludge when used with a single carrier system that is
> ill-equipped to handle them. A kludge is ATSC-MH.

I disagree, John. SFNs are always a kludge.

COFDM was designed to make reception easier in multipath environments. SFNs 
were an afterthought. Sort of, "Hey, if reception is easier with multipath, why 
don't we try this?" And they created a scheme with egregious amounts of 
multipath.

And most of the proponents, from day 1, totally forgot the price you pay to 
implement the afterthought. Instead, they latched onto the notion that "COFDM 
was designed for SFNs." But it wasn't.

All you have to do is read ETSI EN 300 744. Even COFDM struggles dealing with 
more and more multipath energy. That's why the receivers are desensitized when 
facing difficult environments.

Bert
 
 
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