Assuming that you have the same MPEG material being transmit

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server
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Posted: Thu Sep 23, 2004 11:18 am Post subject: Assuming that you have the same MPEG material being transmit

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Paul Keinanen
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Posted: Thu Sep 23, 2004 11:18 am Post subject: Re: Assuming that you have the same MPEG material being tran

On Wed, 22 Sep 2004 18:12:00 -0500, Doug McDonald
<mcdonald@scs.uiuc.edu> wrote:

Quote:

The two systems differ substantially in their intrinsic
required singan to noise ratio. To do a proper comparison,
of course, you have to either pick the DVB-T mode that
is the closest to and just higher in bitrate than ATSC, or
normalize. When you do that, you find that DVB-T needs 3 dB more
power, average. This has never changed from day one, since we are
comparing theoretical mumbers. Both systems come very close to
theory these days. This is of course for Gaussian random noise. For
modern receivers, the noise performance (using this DVB-T mode)
is very similar for all Ricean and reasonable Rayleigh channels,
on average, though special cases can vary.

Measuring the power for complex waveforms such as analog or digital TV
is quite complicated. For analog systems with negative video
modulation, the peak (rated) power is at the synch pulse, while the
active video part is well below this and thus the average power with
live program is quite a few dB below the rated power. On DVB-T COFDM
the spectral density for each of the 2000+ or 6000+ carriers only vary
due to the 16QAM or 64QAM amplitude variation, however, the combined
envelope waveform can have quite huge peaks.

First you have to decide if you are interested in the peak or average
power, since average power is usually a better indication for
co-channel interference, while peak power is usually more interesting
from transmitter design point of view, but this also depends of the
transmitter type.

If you are mostly interested in the transmitter electric bill, you
also have to consider the transmitter efficiency at peak and average
loads etc.

To get meaningful results you would have to operate both digital
systems from the same site for at least a year (to include the
variations in vegetation) with equal service area and then compare the
electric bills.

You also have to ask, does it really make sense to greatly increase
the main transmitter power to serve some problematic receiver
locations or is it better install a small transmitter near these sites
e.g. in a cellular phone tower. At least DVB-T allows placing these
transmitters at the same frequency as the main transmitter and operate
all the transmitters as a single frequency network (SFN). Since no
additional TV channels are required for these additional transmitters,
this simplifies the frequency allocations for a large area.

Paul

SaltiDawg
Guest

Posted: Thu Sep 23, 2004 5:16 pm Post subject: Re: What/who detaches the primary msg and leaves Re: replies

kryppy wrote:

Quote:

It is simply your newserver doesn't have the original message anymore,
or the original was canceled by a spam bot.

I suspect that sometimes, if not most times, it is something other than

that. If I read the newserver at 8:00 AM and a particular thread is not
present, and check the newsgroup an hour later and a new thread starts
off with "Re: Subject" I don't think your explanation holds. Is it
possible that when someone posts a new subject that somehow I wouldn't
receive it because of the specific newserver the OP uses?

Doug McDonald
Guest

Posted: Thu Sep 23, 2004 6:34 pm Post subject: Re: Assuming that you have the same MPEG material being tran

Paul Keinanen wrote:

Quote:

You also have to ask, does it really make sense to greatly increase
the main transmitter power to serve some problematic receiver
locations or is it better install a small transmitter near these sites
e.g. in a cellular phone tower.

The answer to this is CLEAR AND UNEQUIVOCAL: it's better to
use a bigger tower and more powerful transmitter.

This because typically you pick up people by getting rural
and very small town people. The way the US is structured, if
you try increasing audience by translators or lots of
small SFN transmitters, you'd by talking maybe 30 people
per transmitter. You get far more bang for the buck with
a bigger stick and more power. AND ... the absolute cheapest
way to increase converage is to simply use a system that
needs only 1/2 the average power and 1/3 the peak power!

*****************************************************************

Just imagine .... you can get coverage equivalent to
TRIPLING the peak power just by switching from DVB-T
to ATSC!!!!

That's the bottom line ... you have to think about that for
a while: no significant change in the transmitter or tower
or antenna ... just switch to a more efficient system.

That's how you have to think about it.

Doug McDonald

jdd
Guest

Posted: Thu Sep 23, 2004 8:29 pm Post subject: Re: What/who detaches the primary msg and leaves Re: replies

SaltiDawg wrote:

Quote:

kryppy wrote:

It is simply your newserver doesn't have the original message anymore,
or the original was canceled by a spam bot.

I suspect that sometimes, if not most times, it is something other than
that. If I read the newserver at 8:00 AM and a particular thread is not
present, and check the newsgroup an hour later and a new thread starts
off with "Re: Subject" I don't think your explanation holds. Is it
possible that when someone posts a new subject that somehow I wouldn't
receive it because of the specific newserver the OP uses?

may be the thread was started on an other group and follow'ed up (fu2) here

jdd

--
pour m'écrire, aller sur:
http://www.dodin.net
http///valerie.dodin.net
http://www.euro-formation.com/~magicalliance

Bob Miller
Guest

Posted: Thu Sep 23, 2004 9:31 pm Post subject: Re: Assuming that you have the same MPEG material being tran

Doug McDonald wrote:

Quote:

Paul Keinanen wrote:

You also have to ask, does it really make sense to greatly increase
the main transmitter power to serve some problematic receiver
locations or is it better install a small transmitter near these sites
e.g. in a cellular phone tower.

The answer to this is CLEAR AND UNEQUIVOCAL: it's better to
use a bigger tower and more powerful transmitter.

This because typically you pick up people by getting rural
and very small town people. The way the US is structured, if
you try increasing audience by translators or lots of
small SFN transmitters, you'd by talking maybe 30 people
per transmitter. You get far more bang for the buck with
a bigger stick and more power. AND ... the absolute cheapest
way to increase converage is to simply use a system that
needs only 1/2 the average power and 1/3 the peak power!

*****************************************************************

Just imagine .... you can get coverage equivalent to
TRIPLING the peak power just by switching from DVB-T
to ATSC!!!!

That's the bottom line ... you have to think about that for
a while: no significant change in the transmitter or tower
or antenna ... just switch to a more efficient system.

That's how you have to think about it.

Doug McDonald

That however is not how most countries in the world thought about it.
The only countries using 8-VSB are doing so for political purposes. No
country has chosen 8-VSB for technical reasons.

Bob Miller
Guest

Posted: Thu Sep 23, 2004 9:39 pm Post subject: Re: Assuming that you have the same MPEG material being tran

ivan wrote:

Quote:

"Doug McDonald" <mcdonald@scs.uiuc.edu> wrote in message
news:ciumt3$65m$1@news.ks.uiuc.edu...

Paul Keinanen wrote:

You also have to ask, does it really make sense to greatly increase
the main transmitter power to serve some problematic receiver
locations or is it better install a small transmitter near these sites
e.g. in a cellular phone tower.

The answer to this is CLEAR AND UNEQUIVOCAL: it's better to
use a bigger tower and more powerful transmitter.

This because typically you pick up people by getting rural
and very small town people. The way the US is structured, if
you try increasing audience by translators or lots of
small SFN transmitters, you'd by talking maybe 30 people
per transmitter. You get far more bang for the buck with
a bigger stick and more power. AND ... the absolute cheapest
way to increase converage is to simply use a system that
needs only 1/2 the average power and 1/3 the peak power!

*****************************************************************

Just imagine .... you can get coverage equivalent to
TRIPLING the peak power just by switching from DVB-T
to ATSC!!!!

In the area of the UK were I live, there are many thousands of people
receiving reliable reception from a couple of local transmitters pushing out
20w of DVB-T.

The highest power in the UK is 20 kW AFAIK and that on only a few
transmitters. Most are using infinitesimal power levels.

Here is a list of all stations in the UK and their power levels.

http://www.wolfbane.com/ukdtt.htm

The UK is also not able to and is not using any SFN these are all
single stick transmitters. Other countries are using or plan on using
country wide SFN's with much lower power levels than the US.

This includes such large countries as Australia and Russia.

Even in the US such entities as Sirius and XMRadio are using COFDM as
will Crown Castle for their mobile 5MHz DTV venture.

NO one even considers 8-VSB except when pressured and bribed by the US.
Thats the reality.

Albert Manfredi
Guest

Posted: Thu Sep 23, 2004 10:33 pm Post subject: Re: Assuming that you have the same MPEG material being tran

"Bob Miller" wrote:

Quote:

NO one even considers 8-VSB except when pressured and bribed by the
US. Thats the reality.

As you very well know, Bob, realities change as technology and know-how
changes.

The debates about whether to go single-carrier or multi-carrier schemes
(e.g. n-VSB or n-QAM or even CDMA vs COFDM) have raged for a long time,
and in many different venues. This includes xDSL techniques used by the
telephone companies, ultrawide band (UWB) used for PANs, not to mention
wireless LAN standards. So it's not *just* about TV standards. TV
standards are simply one manifestation of the same debate.

If there is any "reality," it is that single carrier schemes have gained
some ground, thanks in part to the improvement in the state of the art
of equalizer designs.

You don't get anything for nothing. The gains in inherent multipath
tolerance you get with multicarrier schemes carry a price tag of greater
power required for the same range of coverage, and a higher
peak-to-average power ratio in the spectrum of the multicarrier system.
The power issue is of course dependent on the spectral efficiency you're
shooting for. So you have to compare apples with apples.

If ways can be found to achieve good multipath tolerance with single
carrier schemes, you can only come out ahead using single carrier
schemes. You'll get more range for the same power and/or more
bits/second for the same RF bandwidth.

There is no such thing as a free lunch. The decision to stick with 8-VSB
can only prove to be more and more advantageous, as time goes by.
Unfortunately, it took a long time to get to where it's really a
feasible scheme.

Bert

Tom Betz
Guest