[opendtv] Re: News: TV Braces for the Apple Tablet

  • From: Craig Birkmaier <craig@xxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Thu, 4 Feb 2010 06:37:11 -0500

At 4:42 PM -0500 2/3/10, Albert Manfredi wrote:
You have mentioned this vague ring of towers over and over. The truth is, if the ring of towers is an SFN, that means the towers need to be quite close together so as not to interfere. If they are not, the first and most obvious problem will be that toward the middle of the ring, reception will be TOTALLY hopeless. 

I believe this will depend on the technology implementation.
Secondly, if the towers are low and low power, for example sitting on existing buildings and output of only a few KW ERP apiece, then reception in the more distant parts of the market will be nonexistent. For example, the NYC market is not just Manhattan. It covers at least half way down to Philadelphia, Long Island, up the Hudson toward Albany, etc. You won't get to those parts with your low power low towers unless you establish a lot of other translator sites, or unless you create a much denser mesh of transmitters a la Qualcomm Ch 55 system.
More likely the power levels will be higher than you are stating here. I have seen estimates that range from 10Kw to 50Kw. And yes, it may be necessary to add on channel repeaters in terrain blocked areas.
Thirdly, if these towers in the SFN are close together, and I mean by that a total diameter of maybe 8 miles or so with 5th gen receivers, they won't do much to support any hyperlocal broadcasting when they are used in non-SFN configuration.
You are still stuck in ATSC land. More likely we are talking about the ring having a diameter similar to the interstate highway rings around major cities like I-295 around D.C.
But yes indeed, if you do what they did in Berlin, you will achieve wide area coverage. For that, they used one big stick, 120 KW ERP, and another medium stick, 50 KW ERP, and then with 16-QAM they achieved the same sort of outdoor-antenna coverage of suburbs as we need here. And they achieved indoor reception out to 12-14 miles, much like we also have here. And the contour chart looks very similar to what a big stick would provide (because it is a big stick), meaning that you need to protect that frequency in adjacent markets just as you would for a big stick.
What I think happened is that an engineer explained to you that Manhattan could be covered with this vague low-power ring, and you extrapolated that to mean "the NYC market area." Much like you interpreted the Qualcomm system consiting of 30 towers as being "up and down the East Coast," when in fact it was just between DC and NYC.
In many markets a configuration like Berlin could work. It all depends on the geographic isolation of the market. In the N.E. corridor the markets are too dense and too close together. But these markets have many more viewers, so the revenues exist in these markets to build out a more elaborate network with better spectral reuse.
And again, I did not interpret anything. I merely reported what I was told by a network engineer who was involved with the tests. Even if it did take 30 towers between NY and DC, this would be quite viable economically as there are hundreds of broadcast towers in this corridor now (TV and radio). In fact there are more than 30 TV towers in the DC, Baltimore, Philadelphia and NY markets...FAR MORE. 

Regards
Craig


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