[opendtv] Re: Perspective
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Tue, 12 Feb 2008 12:28:40 -0500
At 10:40 AM -0500 2/12/08, Manfredi, Albert E wrote:
It could be, but reception would most likely suffer, because of terrain
blockage. Meaning, towers that are "too far apart" yet unblocked from
each other could very easily interfere. And such problems are even more
likely given the 1/32 guard interval used for the 16-QAM transmitters in
the UK. Far from ideal for SFNs.
Reception would improve, not to mention the ability to deliver
significantly more programs to this region in the same spectrum.
The current use of translators means that they must use the terrain
blockage to prevent interference both from the same channel and from
co channels. I'm not certain how many channels are represented in the
Ofcom map, but it is obvious that there is much checker-boarding of
frequencies to get the fine level of coverage now achieved with the
PAL translator infrastructure.
With an SFN, EACH site could deliver ALL of the available channels to
everyone in the region. In reality they would probably retire many of
the sites as they would no longer be needed. And due to the additive
nature of signals from the multiple sites, reception would improve in
what are now marginal areas.
It's a great tradeoff for easier reception and low power transmitters. I
showed you where the Raiway network in Italy does exactly the same
thing. Low power translators everywhere. So this should come as no
surprise.
It was THE ONLY way to achieve the >95% coverage guaranteed by the
government using analog PAL transmission techniques.
This Ofcom map suggests that they are simply going to switch the
existing infrastructure to digital transmission. An easy and
effective way out to support the CURRENT number of channels in this
region (I'm talking about 8MHz transmission channels, not the number
of programs in each multiplex).
With the inevitable clash over more frequencies for another HD
multiplex, the obvious solution will be to transform the existing
infrastructure into an SFN. And this is EXACTLY what the DTG is going
to be forced to do to since it appears that Ofcom is not going to
give them more spectrum.
Still, it's good to have PERSPECTIVE when we make our facile
comparisoons, eh?
There's nothing noteworthy in your perspective. Just more "analog thinking."
The density of translators in this UK region pales when compared to
the state of Utah, with about 600 translators.
In talking about the U.S. markets, I have mostly focused on the
problems associated with a big stick infrastructure. While
translators help to extend the reach of the big sticks, with better
spectral efficiency because of their low power and terrain blockage,
even here SFNs can improve reception and deliver more bits in the
same spectrum.
Which from your perspective must seem absurd.
Regards
Craig
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