[opendtv] Re: TI Exec: Open Standards Crucial for Mobile TV
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: "OpenDTV (E-mail)" <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 29 Mar 2005 18:33:16 -0500
John Shutt wrote:
> Who is going to take the bitrate hit that E-VSB demands?
> (lose 2 bits for every 1 robust bit transmitted.)
John, do you know how E-VSB as currently defined compares
with DVB-H? I don't. I'd have to dig into this to figure
it out.
Here's the E-VSB side. Maybe you can enlighten us on the
equivalent DVB-T/DVB-H tradeoff?
I'm just picking two values of robust stream, and the
wide stream is supposed to be as robust as it is when
the entire band is wide stream.
For 542 Kb/s robust stream using 1/2 additional FEC,
wide stream (2/3 FEC) is 18.1 Mb/s
For 542 Kb/s robust stream using 1/4 additional FEC,
wide stream (2/3 FEC) is 16.9 Mb/s
For 1.08 Mb/s robust stream using 1/2 additional FEC,
wide stream (2/3 FEC) is 16.9 Mb/s
For 1.03 Mb/s robust stream using 1/4 additional FEC,
wide stream (2/3 FEC) is 14.7 Mb/s
ISDB can assign 1/13th of the COFDM carriers to the
robust stream. So if you start with a 19.7 Mb/s
wide channel, and want to keep its robustness
unchanged, you should be left with 18.1 Mb/s in the
wide stream.
The robust stream's carriers now carry 1.5 Mb/s if
it remains at 3/4 FEC and 64-QAM, which would be
paired down to whatever robustness level you want.
For example, to compare apples with apples, retain
64-QAM but increase the FEC by an additional 1/2
will result in 758 Kb/s in the robust stream.
But the robust stream will lose some more due to
the RS block that needs to be created, so I'm not
sure there's a huge difference here, in terms of
bit rates anyway.
Not that I'm suggesting this should be done. Just
comparing bit rates for fun.
Bert
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