[opendtv] Re: Fw: Re: Post on alt.tv.tech.hdtv of interest today

  • From: Craig Birkmaier <craig@xxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Mon, 11 Apr 2005 22:16:46 -0400

At 11:28 AM -0400 4/11/05, Manfredi, Albert E wrote:
>By the way, just as a point of comparison, I read an
>article in EE Times not long ago that said that to cover
>the area or NYC completely, with Wi-Fi signals, would take
>"tens of thousands" of access points. And similarly,
>Verizon uses "about 1000" cell towers to cover NYC.
>
>So this is the tradeoff to consider.

You need to be careful when citing numbers like this. The number of 
cellular cells in a network in a densely populated market has less to 
do with coverage than capacity. As demand to access the network 
increases, you need more cells to handle the load. This requires a 
combination of more frequencies and/or improved spectral reuse - 
closer spacing of cells on the same frequency, or reuse of 
frequencies in "protected spectrum." What I mean by this is that you 
may be able to put a cell in train or subway station in New York (i.e 
an area that is protected from outside signals by terrain or building 
blocking).

In a city like New York you need a thousand cells to handle the load, 
and this give you the advantage of putting those cells everywhere, 
including areas that are typically difficult to serve with 
transceivers on towers or buildings.

None of this is relevant to a terrestrial DTV transmission 
infrastructure. The only capacity limit is how many people CHOOSE to 
RECEIVE the service. Economics may dictate that you use many 
repeaters in a city like New York, in order to provide reliable 
service in challenging RF environments. What I am talking about is 
the economics of reaching additional consumers. IN the boonies a 
repeater may only reach a few thousand people; in Grand Central 
Station you may be able to reach a few hundred thousand in the course 
of a day.

>
>>  While TV and driving do not mix well, there is no reason
>>  to limit the transmission system to fixed receivers. We
>>  do not do this today with NTSC.
>
>Not sure what you're saying here. NTSC in moving vehicles
>is awful. Possible, but awful. Even if DTT in moving
>vehicles were not possible, we wouldn't have given up much
>compared with analog TV. And I'm not saying ATSC in moving
>vehicles isn't possible.

NTSC on a portable TV in a van at a tailgate party, or a Watchman in 
a football stadium, is commonplace. These are portable, not mobile 
applications. But we should not use NTSC as the standard for 
comparison. We did demos of MOBILE COFDM in Las Vegas about five 
years ago. We should be expecting much more out of a modern digital 
transmission infrastructure.

Regards
Craig
 
 
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