[opendtv] SFNs waste frequency spectrum
- From: "Allen Le Roy Limberg" <allimberg@xxxxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Thu, 8 Jul 2010 16:20:57 -0400
SFNs are wasteful of spectrum, severely reducing the amount of payload that
can be transmitted compared to using repeaters on different channels,
supposing one wishes to avoid spectrum nulls in regions where coverage areas
overlap. This is very evident with 8VSB, where spectrum nulls are best
avoided by staggering the transmission times of the various transmitters.
But it is also the case with COFDM, where the coding to overcome spectrum
nulls is the mechanism that reduces the amount of payload that can be
transmitted.
A regional broadcast system would preferably employ frequency diversity, so
signals from two RF channels could be combined during parallel digital
processing of the two channels in the receiver. This would provide better
reception in regions where coverage areas overlap, without requiring
spatial-diversity antennas.
Al
----- Original Message -----
From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
To: <opendtv@xxxxxxxxxxxxx>
Sent: Thursday, July 08, 2010 3:52 PM
Subject: [opendtv] Re: BIA/Kelsey raises TV station revenue outlook for 2010
> Craig Birkmaier wrote:
>
> > This has always been one of the major strengths of broadcast TV
> > (a.k.a. "the election channel"), BECAUSE of the market based
> > infrastructure. A regional broadcast infrastructure such as that
> > which Bert is advocating for cannot provide the targeting or the
> > local access that politicians crave, especially in Congressional
> > elections, where it is possible to advertise only in markets within
> > a Congressional district.
>
> Yes, I wouldn't mind at least some regional networks at all. But that's
not the point here.
>
> If the goal is to save on OTA TV spectrum, and the technique proposed is
"cellular TV," THEN what I advocate is the truth. The truth behind "cellular
TV" for spectrum savings is that in addition to SFNs, you ALSO need to
deploy regional TV networks. Or there will be no spectrum savings to speak
of. No matter what your modulation technique is.
>
> If the goal is to provide "local TV," as the FCC claims in the next
breath, THEN what I advocate is (again) the truth. The truth of "local TV"
is that it requires single-market broadcasters, or even LPTV broadcasters
for smaller areas of coverage within a single market, and that spectrum
savings will certainly not be achieved by SFNs. As a matter a fact, a strong
case can be made that what you need in such cases is a modulation scheme
with the lowest possible peak to average power ratio (PAPR), to allow the
closest possible spacing of co-channel signal coverage. And power levels
commensurate with the area to be covered.
>
> As always, the answer depends on the requirements. And answers that are
not compatible with requirements, perhaps motivated by ulterior motives or
just by "innocence," are not valid or credible.
>
> Bert
>
>
> ----------------------------------------------------------------------
> You can UNSUBSCRIBE from the OpenDTV list in two ways:
>
> - Using the UNSUBSCRIBE command in your user configuration settings at
FreeLists.org
>
> - By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word
unsubscribe in the subject line.
>
----------------------------------------------------------------------
You can UNSUBSCRIBE from the OpenDTV list in two ways:
- Using the UNSUBSCRIBE command in your user configuration settings at
FreeLists.org
- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word
unsubscribe in the subject line.
Other related posts:
