[opendtv] Re: NAB Showcases Mobile DTV
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: "opendtv@xxxxxxxxxxxxx" <opendtv@xxxxxxxxxxxxx>
- Date: Fri, 26 Mar 2010 20:49:51 -0500
Tom Barry wrote:
> I'm not sure what everybody means by "monitoring the entire
> stream" and why it's bad. I thought the equalizer chips
> potentially could use a lot of power, and that's what I was
> worried about. And decoding the video potentially can use a
> fair amount of CPU power. But just demuxing a transport
> stream is a fairly light weight task easily done in software
> even on 10 year old PC's. I don't see the worry there compared
> with the other.
I keep seeing announcements of new chips for mobile TV in handsets, which now
list all of the standards, including DVB-H and ATSC M/H. So evidently, the
power draw problem of ATSC M/H is not a big hurdle. I don't have time now to
try to ferret out these announcements. Maybe manana.
It's possible that some of these announcements included the pwer requirement,
and that this can then be compared with cell 3G phones' requirements.
In general, though, these different schemes do either one of two things to save
power. Either they use a narrow RF channel, or they use a wide one only part of
the time.
The Japanese system ISDB-T assigns, IIRC, 1/13th of the COFDM subcarriers to
mobile service. DVB-H and ATSC M/H instead allow the systems to stay on in
short bursts only, using the entire channel bandwidth. W-CDMA is similar, in
that it too uses a wide RF channel but compensates by allowing the receiver to
sleep between chip arrival times, once it's synched up.
Bert
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