[opendtv] Re: Tiny TV could make billions for FCC
- From: Albert Manfredi <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Thu, 24 Dec 2009 13:23:11 -0500
Jeroen Stessen wrote: > Ho ho ho, Merry Christmas to you too, Jeroen. > A SFN proposal for ATSC. > See: > http://www.theregister.co.uk/2009/12/24/ctia_ces_spectrum_plan/ http://files.ctia.org/pdf/filings/CTIA_CEA_White_Paper.pdf > > "The CTIA argues that modern set-top boxes are so armoured > against receiving bounced ghost signals that they can cope > with one coming from a different transmitter. Modern boxes > accept the strongest signal and are capable of disregarding > the others. That assertion is the weak point, but if the > CTIA has its sums right then there's little reason why the > system wouldn't work." First point is, that's not how 8-VSB manages ghost. As the descriptions of the echo cancelling methods explain, and as the measurements from the Canadian CRC have shown very clearly, the echo energy is twisted back into its original phase (or the phase of the strongest path) by the equalizer, so that echo energy is NOT disregraded. Instead, it goes to supplement the energy along the strongest path. The trick was to make any pre-echo look like post-echo, before the signal reaches the equalizer. As far as I could determine, it was Linx that demoed this first (in 2002 in an unintegrated receiver, 2003 in a chip), but it's likely that Zenith and others had been working the same problem the same way. But more to the point is this. US broadcasters cover markets with separate signals. So for instance, broadcasters in Baltimore, washington, and Philadelphia don't transmit the same schedule. Therefore, JUST LIKE in Europe (in practice), the best an SFN can do is cover a given market. Well, what is the radius of a typical US TV market, roughly? Answer: about 60 miles (100 Km) radius, 120 miles diameter. Which means, you will be very hard pressed to be able to locate TV transmitters, be they big sticks or the centers of SFNs, closer together that about 120 miles. Unless you are willing to give up continuous coverage. That is about the same distance between transmitters as what the white paper claims is the limiting factor with big sticks. If you do synchronize multiple markets, that could change. But then you would need many more towers than you need with big sticks or Euro-style single-market SFNs. More like the Qualcomm Ch 55 system. Bert _________________________________________________________________ Your E-mail and More On-the-Go. Get Windows Live Hotmail Free. http://clk.atdmt.com/GBL/go/171222985/direct/01/ ---------------------------------------------------------------------- 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.