[opendtv] Re: LPTV Advocates Eye Cellular Alternative
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Mon, 10 Aug 2009 15:39:11 -0400
Bob Miller wrote:
> Tried to get LPTV owners to do this in early 1999. Was told
> by the FCC then that LPTV stations were given a greater
> latitude in what they could do because of what they were.
> However the Sinclair demonstration and resulting political
> turmoil shut that down. Was told that the digital rules for
> LPTV would be written by Christmas 1999 and "see no reason
> that LPTV stations could not be allowed to use an alternate
> modulation".
>
> TODAY LPTV stations in NYC could be cooperating in a multiple
> station offering that would have numbers like the UK and be
> MOBILE at the same time.
C'mon guys, this is the kind of diversion that derails the discussion.
Assuming what that piece was really about WAS use of an SFN, as Craig
surmised, then there's no reason at all to slide back into that old
modulation debate. Unless no one really cares about solutions.
If LPTV stations are constantly strapped for cash, I have to wonder
whether they are truly capable of building out a viable wide area SFN.
But in principle at least, sure. If you can only use very low power,
your only alternative to achieve coverage of a large area is to use a
distributed transmitter scheme. Either translators in a cell-like
structure, or a wide area SFN. But wide area SFNs are not a trivial
exercise, no matter what the modulation scheme.
Now for the real issues involved, which always get lost:
In the UK and elsewhere in Europe, they exclusively use translators for
wide area coverage. And SFNs, if any, are limited to 2 or 3 towers,
closely spaced, to provide easier reception *within* city-sized markets.
*However*, if these SFNs are meant to provide coverage for an entire
city, as in Berlin, the two or three towers are high powered. In Berlin,
between 50 KW ERP and 120 KW ERP per tower. So this is not compatible
with LPTV at all.
Another possibility is the design used in Paris (and Sydney). The SFNs,
in these cases, consist of one big stick and small gap fillers. For
intance, 25 KW ERP from the Eiffel Tower, assisted by three smaller 1 KW
ERP sticks to the N, E, and S.
None of these options is compatible with LPTV stations.
Possibly, DVB-T2, with its much longer GI, could make wide area coverage
SFNs more feasible. But then again, the much longer symbol duration
required would make such an SFN INCOMPATIBLE with mobile service.
There's no free lunch here, guys. So let's not oversimplify matters.
Bert
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