[opendtv] Re: TI Exec: Open Standards Crucial for Mobile TV
- From: "John Shutt" <shuttj@xxxxxxxxx>
- To: "OpenDTV" <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 29 Mar 2005 21:05:19 -0500
Bert,
The correct terms are 1/2 rate and 1/4 rate, not 1/2 additional FEC.
http://www.atsc.org/standards/a_53c_amend-1_corr-1.pdf
As you correctly state, at 1/2 rate, for 542 Kbps, you get 18.1 Mbps in the
main stream. You removed 1.3 Mbps from the main stream to get 542 Kbps in
the robust stream. lose 2 bits to gain 1 bit.
For 1/4 rate it's even worse. To achieve 542 Kbps robust, you get 16.9 Mbps
main stream. You removed 2.5 Mbps from the main stream to get 542 Kbps for
the robust stream. You lose 4.5 bits to gain 1 bit.
As I understand it, with DVB-H, as implemented within a 6 MHz DVB-T stream
(as opposed to a
dedicated 5 MHz DVB-H carrier as Crown Castle is planning in the US), the
DVB-H data is time sliced within the DVB-T bitesream, and is a straight
one-for-one bit usage. The DVB-H data includes additional FEC, so for your
542 Kbps you may need to use 25% more bitrate for the additional FEC data.
So you lose 677 Kbps from the main stream for a single DVB-H payload of 542
Kbps.
http://webapp.etsi.org/exchangefolder/en_302304v010101p.pdf
http://www.dvb.org/documents/DVB-H_Outline.pdf
And I hate to point this out, but E-VSB may not even work very well. E-VSB
was designed to improve reception, but not to increase battery life of a
portable device. DVB-H is first and foremost a standard to save battery
power.
John
----- Original Message -----
From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
To: "OpenDTV (E-mail)" <opendtv@xxxxxxxxxxxxx>
Sent: Tuesday, March 29, 2005 6:33 PM
Subject: [opendtv] Re: TI Exec: Open Standards Crucial for Mobile TV
>
> 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
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