[opendtv] Re: DTT tuner design
- From: "Dale Kelly" <dalekelly@xxxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Wed, 04 Jul 2007 19:03:47 -0700
Thanks for the update Bert, I'll recalibrate my C/N references. With a good
front end the Gemini should be impressive.
> -----Original Message-----
> From: opendtv-bounce@xxxxxxxxxxxxx
> [mailto:opendtv-bounce@xxxxxxxxxxxxx]On Behalf Of Albert Manfredi
> Sent: Wednesday, July 04, 2007 5:52 PM
> To: opendtv@xxxxxxxxxxxxx
> Subject: [opendtv] Re: DTT tuner design
>
>
> Dale Kelly wrote:
>
> >I misspoke, either modulation system requires increased C/N
> >to handle multipath.
>
> I this strictly true? I don't think so. And I believe that's why
> the Chinese
> standard adopted a training sequence in the GI (same one they use
> in their
> single carrier mode), rather than using the end of the previous
> symbol, as
> standard COFDM does. And that's also my bet for DVB-T2. (Just
> speculation.)
>
> The ideal equalizer should not require a higher C/N to twist multipath
> distortion back into shape.
>
> Here is an example. I'm assuming here that the numbers provided
> are C/(N+I),
> and that when this value is less than 15 dB, what you're actually
> seeing is
> a (C+I)/N that is close to 15 dB.
>
> (I also believe that eventually we'll be seeing (C+I)/N better
> than 15 dB,
> when the combined trellis and R-S FEC schemes are more cleverly
> exploited.)
>
> These are C/N numbers that apply to the Samsung Gemini chip.
>
> No multipath 15.2 dB
> Brazil A 15.0
> Brazil B 17.0
> Brazil C 13.5
> Brazil D 13.8
> Brazil E 19.9
>
> Compare this to the CSA values for 64-QAM and 3/4 FEC (same spectral
> efficiency if GI is 1/16).
>
> No multipath is 18 dB, Ricean is 18.6 dB, and their Rayleigh,
> which is less
> strenuous than Brazil E, is 21.7 dB. (Brazil E has 3 dB echoes, vs two.)
>
> So basically, the planning factors used by the CSA do assume a
> deficit of ~3
> dB or more in C/N margin, compared with a well executed equalizer
> demod. And
> that's reflected in the field strength minima. If good demods are
> used, the
> FCC and CSA planning factors should provide very close to the
> same coverage,
> is my thinking.
>
> Bert
>
> _________________________________________________________________
> http://liveearth.msn.com
>
>
>
> ----------------------------------------------------------------------
> You can UNSUBSCRIBE from the OpenDTV list in two ways:
>
> - Using the UNSUBSCRIBE command in your user configuration
> settings at FreeLists.org
>
> - By sending a message to: opendtv-request@xxxxxxxxxxxxx with the
> word unsubscribe in the subject line.
>
>
----------------------------------------------------------------------
You can UNSUBSCRIBE from the OpenDTV list in two ways:
- Using the UNSUBSCRIBE command in your user configuration settings at
FreeLists.org
- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word
unsubscribe in the subject line.
Other related posts:
