[opendtv] Re: IEEE Ericsson article on use of LTE for TV

  • From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
  • To: "opendtv@xxxxxxxxxxxxx" <opendtv@xxxxxxxxxxxxx>
  • Date: Tue, 19 Jun 2012 18:22:15 -0500

Craig Birkmaier wrote:

> The following paper provides some useful information about how the
> Broadcast LTE infrastructure might be implemented.

http://world2011.itu.int/sites/default/files/pdf/TS07%20-%20Huschke_Presentation.pdf

The important number, to use as comparison, is b/s/Hz.

To reach 2.5 b/s/Hz indoors, Slide 9 shows, the cell spacing has to be about 1 
Km (5/8 mi.). To reach 2.5 b/s/Hz outdoors in a car, they say, about 2.5 Km 
(1.6 mi.). They use a 5 MHz channel to get these numbers, because you can 
probably eek out something slightly better more at higher channel widths.

And larger cells drop that spectral efficiency considerably. So for example, if 
you want to deploy a less dense cell structure in the exurbs, with 4 Km (2.5 
mi.) spacing, you can barely get indoor reception at all. And dor this, you 
have to lower the spectral efficiency to 0.25 b/s/Hz. Or you can allow outdoor 
reception at 1.4 b/s/Hz, with that 2.5 mile spacing.

So in order to serve mobile devices, even just outdoors, spectral efficiency 
suffers a lot. Even with a dense cell infrastructure (I consider even 2.5 mile 
spacing to be very dense).

> This looks like it would be more than adequate to support all existing
> broadcast TV services in most U.S. markets, and a LARGE number of new
> mobile channels.

Well, let's see. Let's forget indoor reception. Let's use 2.5 mile spacing of 
cells throughout the market, so at least we can achieve 1.4 b/s/Hz with 
*outdoor* reception. To provide coverage to a 40 mile radius (hardly 
exaggerated), this broadcast-only LTE network would need 804 LTE TV towers.

As far as spectrum required, the 12 multiplexes now in DC have a capacity of 
233 Mb/s over 72 MHz of spectrum. For equal capacity with this 2.5 mile spacing 
LTE cell network, you would need 166 MHz of broadcast spectrum. Quite a bit 
more than 72, eh?

Now, no doubt, the resulting infrastructure will create easier in-vehicle 
reception than ATSC 1.0. But these are the comparisons to make. And as the 
developments go up, or even tall buildings where there weren't any before, the 
cell structure has to be adjusted.

I question this approach, UNLESS this network is going to be 2-way. And if it 
is going to be 2-way, I ask, why would the cellcos be willing to allow access 
from their phones?

Bert

 
 
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