[opendtv] Re: Mobile TV: $2 Billion in Ad Buys

John Shutt wrote:

>>> The DVB HM-COFDM demo at the 2000 NAB delivered
>>> 4.5 Mbps of robust mobile data, and about 13.5 Mbps for
>>> the main service, in a 6 MHz channel.
>>
>> But the wide channel did not meet the FCC planning factors,
>> i.e. 15.2 (or thereabouts) dB of C/N for reception. You
>> need to compare apples with apples when making these
>> comparisons, John.
>
> The only thing that the 2000 demo didn't meet was the FCC
> mask.

In order to allow 13.5 Mb/s in the wide channel, when using HM, you need
to transmit the wide channel at 64-QAM, 3/4 FEC, and 1/32 GI. In this
mode, the wide channel's C/N reception margin in a gaussian channel is
either 18.6 or 21 dB of C/N, depending how you transmit the HM.

So, this is nowhere close to the OET-69 value of 15 dB (rounded from the
supposedly actual value of 15.2 dB), assumed in the FCC planning
factors, for ATSC reception margin.

So what you are saying is that when the broadcaster decides to go to HM,
if the wide stream is kept up at 13.5 Mb/s, it's okay to drop a healthy
fraction of the viewers, either letting their screens go dark or
assuring frequent macroblocking and freezing images and sound.

> The robust stream far exceeded any FCC planning factor with a
> Gaussian noise figure of 10 dB, if it really mattered.

The robust stream is not what the FCC planning factors represent. In any
case, I would be far more excited if the 10.47 dB of C/N theoretically
possible with the 19.39 Mb/s stream were better exploited, instead of
drastically reducing the bit rate to achieve that figure.

> Or one could more easily aruge that radios in cars are in such
> high demand, that they are "automatically" included in cars because
> it is expected.
>
> Do you seriously think that if car manufacturers stopped offering
> radios that people would shrug and say "oh well, didn't need the
> thing anyway"?

I think you will find a high correlation between the success of FM radio
and the universal inclusion of FM in all car radios. People started
listening more to FM when the decision to incorporate the FM tuner in
the car was made for them.

Same goes for HD Radio.

The success of radio, once TV was invented and became prevalent, is tied
to the in-car experience, IMO. THEREFORE, it seems obvious to me that
only after car manufactures include HD Radio will people become
interested in the multicast offerings.

Bert
 
 
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