[opendtv] Re: Specs flap is mobile TVs next test
- From: Tom Barry <trbarry@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Sun, 12 Mar 2006 18:59:36 -0500
The battery power is sort of another interesting issue I had never=20
really considered in depth.
There seems to be some math about how much power it takes to xmit. But=20
what about receiving? Apart from output devices (displays, etc.) is=20
there any theoretical minimum power it takes to drive a receiver? Or=20
decoder?
When I was a kid I built a crystal radio with no power input except that =
furnished by the antenna.
- Tom
Albert Manfredi wrote:
> Tom Barry wrote:
>=20
>=20
>>What confuses me is that the broadcasters, who supposedly
>>detest the interactive mobile guys, do not instead want to
>>use a form of broadcasting that could easily be received on
>>a normal portable phone, without subscription.
>=20
>=20
> I'm not sure what the broadcasters really think. Some people on here ma=
ke it=20
> sound like everyone, including broadcasters, is hell-bent on forcing al=
l=20
> their customers on some sort of subscription scheme. But I'm skeptical =
about=20
> these opinions.
>=20
> Others will use that as another opportunity to complain about the fact =
that=20
> you can't transmit DVB-H along with 8-VSB on the same frequency channel=
,=20
> even though it's far from certain that any broadcaster anywhere in the =
world=20
> would be doing that, or that DVB-H will be the choice for mobile servic=
e to=20
> handhleds in the first place. It looks like DMB-T will be a strong=20
> contender, and of course neither that nor MediaFlo can be transmitted o=
n=20
> DVB-T bands.
>=20
> And also, there's no reason why broadcasters can't also serve interacti=
ve=20
> mobile customers, if they have a mind to. They can always charge for th=
e=20
> interactive aspects. (You pay x if you to send in your vote in that gam=
e=20
> show.)
>=20
>=20
>>My daughters cell phone also happens to have an FM radio for
>>which no special fees are required. That feature just happened
>>to be in her model. While I realize the cell phone providers
>>might not be particularly pleased to provide normal OTA TV
>>reception it seems some cell phone CE manufacturers would be
>>happy to include it if passable reception could be expected.
>=20
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> Passable reception is not the most difficult problem anymore, I don't t=
hink.=20
> The toughest problem will be power requirements for receivers. I mean, =
power=20
> draw at the receiver.
>=20
> The reception problem can be addressed with some simple arithmetic. Onc=
e you=20
> have developed receivers which are sensitive and tolerate echo well, an=
d in=20
> spite of your continued skepticism this has happened to a large degree =
> already (e.g. the Samsung Gemini chip), the other pieces of the recepti=
on=20
> puzzle are signal margin needed and transmitted power available, compar=
ing=20
> analog FM with ATSC.
>=20
> Signal margins for mono FM reception with the best receivers are lower =
than=20
> for 8-VSB, from numbers Audio magazine used to report back when (~12 dB=
C/N=20
> for the best of them IIRC). That lower margin applies for fairly noisy =
> mono-only reception. Might be good enough for cell phones. Who could te=
ll=20
> the difference? So FM might have the edge there, by 3 dB or so.
>=20
> The antenna is very inefficient for VHF or UHF, but UHF would have the =
edge=20
> there. I'm not sure what the cell phone uses as FM antenna. Could it be=
the=20
> cable to an earphone? Anyway, I'd give TV the edge there, for UHF stati=
ons=20
> anyway.
>=20
> Tranmsitted power gives FM the edge. FM transmitters are limited to 50 =
KW=20
> ERP, correct? If you look at the difference in channel width, that 50 K=
W=20
> would equate to 1.8 MW ERP for TV. So here, DTT is at a disadvantage,=20
> especially the DTT transmitters currently at 50 KW or thereabouts. They=
=20
> would be just about out of the question.
>=20
> Then there's the digital cliff. Any analog reception will be easier, no=
=20
> matter which of the currently available digital schemes you can mention=
, in=20
> terms of graceful degradation.
>=20
> So I think all in all, 8-VSB to cell phones is not impossible, except f=
or=20
> the power drain issue. That will be solved in time. Ditto for any other=
=20
> digital transmission to tiny devices, which isn't specifically designed=
for=20
> tiny devices (and doesn't make big tradeoffs to favor tiny device=20
> reception).
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>>I wonder it if would be royalties issue?
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>=20
> The best we have been able to determine on this open forum, royalties f=
or=20
> ATSC receivers amount to $15 total, for MPEG and 8-VSB together. That i=
sn't=20
> much when you look at what these cell phones actually cost to the servi=
ce=20
> provider (not necessarily what the subscribers see as an initial cost t=
o=20
> them, of course).
>=20
> Bert
>=20
> _________________________________________________________________
> Is your PC infected? Get a FREE online computer virus scan from McAfee=AE=
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> Security. http://clinic.mcafee.com/clinic/ibuy/campaign.asp?cid=3D3963
>=20
> =20
> =20
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