[opendtv] Re: (No Date: Tue, 28 Sep 2004 10:30:37 -0400

  • From: Bob Miller <bob@xxxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Sat, 09 Oct 2004 01:57:34 -0400

Manfredi, Albert E wrote:

>Bob Miller wrote:
>
>  
>
>>If Germany and the UK chose a lower data rate for
>>a more robust reception fine. They can with COFDM.
>>But they could have chosen a higher data rate with
>>COFDM than the 19.34 Mbps of 8-VSB and still be more
>>robust than 8-VSB as was demonstrated in Congress in
>>2000
>>    
>>
>
>I see I didn't address this particular comment directly
>as it deserves to be (or maybe not).
>
>At the ~19 Mb/s level, in 6 MHz, and with the severe
>Brazil E profile, the new 8-VSB receivers were capable
>of solid reception with 25 dB of C/N (actually 24.8 dB
>for the Linx receiver, and I didn't see anything as
>precisely stated for the LG). To respond to Mark
>Aitken's concern, yes, this includes symbol sync. Not
>just tracking a signal, but reaquiring.
>
>According to ETSI EN 300 744, the Rayleigh fading
>performance of COFDM at this bit rate is 21.7 dB of
>C/N. But the Rayleigh profile in that document isn't
>Brazil E. The CRC testing reported in 2003 claimed
>that at the time of the test, the COFDM receiver
>managed to receive two 0 dB signals (one 0 dB echo)
>with 31 dB of C/N. And this is not Brazil E either.
>I would expect that COFDM receiver to be of 2002
>vintage.
>
>Going just on this information alone, therefore,
>one has to conclude that what you saw in 2000 is
>irrelevant to this discussion. But more to the
>point, it leaves open the question of how these
>systems compare today. It's entirely possible,
>even likely, that today 8-VSB beats COFDM in certain
>indoor scenarios, and doubtless vice versa, at the
>~19 Mb/s level in 6 MHz (3.3 b/s/Hz).
>
>I'd guess that COFDMS will beat any of these new
>ATSC receivers with dynamic echo, e.g. people
>walking around smartly especially in the signal path,
>but it's very possible that 8-VSB beats COFDM where
>the signal is weak and dynamic echo not too severe.
>It's an intriguing question which you dismiss in
>a most unconvincing manner.
>
>So yes, you can tune COFDM for even higher spectral
>efficiency, but you'll make it more vulnerable than
>8-VSB if you do this. I don't see where E8-VSB
>would allow for more spectral efficiency, because
>it looks like the 2/3 trellis is the weakest one
>permitted. You'd have to either go to 16-VSB and
>fuss with adding trellis coding, or you'd have to
>allow for something like 3/4 or 5/6 rate trellis,
>to get anything better than 19.39 Mb/s for a
>terrestrial n-VSB system. Where we are today,
>that would make no sense at all.
>
>Bert
>  
>
 From what I have seen of 8-VSB and COFDM lately (5th gen)  it would 
make very good sense to switch to COFDM ASAP. There is simply NO comparison.
 
 
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