[opendtv] Re: News: LTE Tempts With Advanced Services
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Wed, 6 Jun 2012 17:35:23 -0400
At 4:10 PM -0500 6/5/12, Manfredi, Albert E wrote:
Sorry, but articles like this one keep missing the point. There's no
reason, or excuse, to focus on LTE. The discussion should instead
be, perhaps it's time to stop broadcasting (I'm using the term in
its literal technical sense) and instead start unicasting.
Sorry Bert, but there are several good reasons to BROADCAST using LTE.
1. Compatibility with LTE enabled mobile devices - smart phone and
tablet manufacturers are NOT going to support a broadcast standard
that requires a separate chip and/or more power.
2. Broadcasting works VERY WELL when there are a large number of
people who want the same content. This is ESPECIALLY important for
live programming such as sports.
3. Broadcasters can deliver all kinds of programming to local cache
in both mobile AND fixed receivers. This ALSO takes traffic off of
the unicast pipes.
If you shift to unicast, this immediately imposes a two-way link
requirement for each user device, and THEREFORE the big stick model,
the most efficient configuration for broadcast, becomes unacceptable
and irrelevant.
Broadcasters may ALSO be able to take advantage of the two-way links
in mobile devices to deliver unicast content (or multicast to small
numbers of viewers). For example popular services such as a local
weather forecast could be sent as data at very low bit rates, and
requests could be queued for short periods to create a multicast
group (i.e. one to few).
Why switch to unicast? Because that's the only viable alternative,
when serving mobile devices. It gives the users the much larger
selection of content that they have come to want and it frees them
from a time schedule. Even in-device storage of broadcast content
cannot match the unicast VOD model, for the sheer amount of choice.
Because that the in-device storage depends on the device having to
dedicate all sorts of time to the downloads, *AND* the broadcast
channel limits the variety of downloads the big stick can provide,
on any given day. Whereas unicast makes use of a much, much higher
capacity cabled Internet infrastructure, and the RF link is just
that tiny last mile (or less) interface to the global Internet
infrastructure.
This is absurd. There is tons of time to download the content people
want the most to local cache. It can be done when a program is
broadcast in a scheduled time slot, and again, typically at much
lower bit rates, overnight to the cache in mobile devices.
Here is a good real world example:
We just completed a video of the Hogtown Craft Beer Festival that I
helped put together last April.
The video was shot using the 1080@30P format, and edited in that
format. We then created four different resolution versions - the
resulting file sizes are shown. I believe the compression program
applied the slight cropping, which accounts for the numbers being
lower than the nominal raster for the HD versions; this may be fairly
normal, so as to deal with picture edge/blanking issues. Obviously,
when streaming to computers and mobile devices the formats/numbers
can be arbitrary (as it should be).
360 x 202 - 11.8 MB
480 x 270 - 22.2 MB - http://www.youtube.com/watch?v=y5a8cEGf6Bc
1248 x 702 - 933.4 MB
1888 x 1062 - 2.02 GB
The 720P version is uploading to YouTube now. I'll send the link when
it is finished.
The 22 MB file delivers very good quality on mobile devices. More
important, it is a small fraction of the size of the 720P version,
which itself is half the size of the 1080P format. The important take
away is that you can send 40 files at the quality of the 22 MB file
in the space required for ONE 720P file.
So look at it this way. If you want to see the HD version, watch it
live, or cache it on your PVR when it is broadcast. If, however, you
only need a file sized for your mobile device, a station could
broadcast multiple versions overnight and still have TONS of bits
left to deliver other programs to cache...
Or a station's newscasts, or an electronic version of the local
newspaper, or...
When you wake up your device already has cached content - no need for
a unicast.
Comments like "LTE is much more efficient than 8-VSB" are not only
irrelevant, they are also FALSE. The spectral efficiency of LTE is
always LESS than that of 8T-VSB, even when the cells are extremely
close together. But this doesn't matter, when the link is just a
short range unicast link.
Not false AT ALL. PLEASE no further comments about bits per HZ.
Efficiency can be measured in many ways. What makes the LTE broadcast
system more efficient is that you do not need to send the same bits
to every home in the market. You can checkerboard your cells and
deliver different bits to different neighborhoods based on demand.
And besides all of this, the other point to be made is that the
two-way infrastructure for broadcasters to use is already in place,
and broadcasters and the main networks are already using it. So the
real question is, how do local broadcasters get visibility on this
huge Internet choice, without that visibility being a natural
byproduct of the scant choice available over current broadcast TV
channels? (And of course, one answer will be, they don't get the
same visibility. And many won't survive the switch to unicast.)
The answer is that current broadcasts are optimized for fixed
receivers; mobile devices are essentially SOL. The ability to view
all kinds of content, via Broadcast LTE, on mobile devices is what
the marketplace is looking for; even better if this content is FREE
(ad supported).
Regards
Craig
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