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

  • From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
  • To: "opendtv@xxxxxxxxxxxxx" <opendtv@xxxxxxxxxxxxx>
  • Date: Fri, 11 Feb 2011 17:02:35 -0600

> As I expressed to Mark Aitken, I think, the article may have
> been interpreted by readers that there's a magic bullet, aka
> COFDM, that would solve the problems. There isn't. COFDM does
> not solve the problem, as proven conclusively by Qualcomm
> MediFLO, and also by the Ibiquity testing of the two-tower
> radio SFN in Baltimore.

I should rephrase that. COFDM does allow the SFN to work, yes, where 8-VSB 
would have been more sketchy. However, you do need that dense mesh of towers if 
you want to cover large areas, as Qualcomm demonstrated. And with just two 
towers, as in the Ibiquity test, it's not at all clear how much you have 
gained, compared with a single tower.

I would like to see that Ibiquity test repeated, using two different 
frequencies from the two radio towers. It's a no brainer that the reception 
would be less problematic, over a much larger area, with no deep fading issues 
at all and no need to time-align the symbol transmissions.

Bert
 
 
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