[opendtv] Re: Doug Lung on DOCRs
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: "opendtv@xxxxxxxxxxxxx" <opendtv@xxxxxxxxxxxxx>
- Date: Mon, 2 Aug 2010 16:44:43 -0500
Craig Birkmaier wrote:
> Yes, this will create reception problems for systems that were NOT
> designed to deal with such environments...
Predictable response, and too simplistic to explain anything.
DVB-T has much the same problem. Not as severe, if you use a large enough guard
interval, which eats into spectral efficiency, but still bad enough that
practical implementations are restricted to a small cluster of towers, close
together. Such small clusters do NOT create sharp contour edges.
Or if not this small cluster, then DVB-T can also use low power gap fillers,
with directional antennas, as described for ATSC.
DVB-T2 makes the problem more amenable, mainly because the towers can be spread
far enough apart that the signals from distant towers can truly be assumed to
become fully attenuated. Of course, deploying such nicely spread out SFN means
that any idea of sharp contours goes out the window.
In any event, limiting these SFNs to just one market area invalidates any
claims of saving spectrum. So the whole discussion becomes irrelevant.
And also the idea that SFNs can allow higher signal strength at the edges of
the market is a non-sequitur. Any system that creates higher signal strength at
the edges will result in an increased interference zone at the edges. That
should be obvious. So much of the adjacent market has to be used as an
interfernce zone no matter what.
Bert
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