[opendtv] Re: From Broadcast Engineering - WRAL tests mobile DTV

  • From: "John Willkie" <johnwillkie@xxxxxxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Fri, 8 Aug 2008 08:44:39 -0700

You want to be confused, and you usually succeed.  Did you miss the part
about "wait until the standard is released" and that you have no way of
determining if the 'test' at WRAL is using anything close to what is the
intended technology?

There have been plenty of public statements made about mobile in the ATSC
environment, and I have to use those items instead of more-recent,
more-accurate (but confidential) information.

And, I forgot about your didtorto lens.  My bad.  I treated you like a
rational individual.  I won't and can't be made to do tit-for-tat with you
on this.

However, let me give you a zinger.  "It ain't about modulation.  Your
failure to adopt DVB-H in favor of DVB-T means you probably won't be able to
play with M/H."  Assuming, for a second, that Viacel is viable and not
merely a pipe dream.

John Willkie

-----Mensaje original-----
De: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx] En
nombre de Bob Miller
Enviado el: Friday, August 08, 2008 3:26 AM
Para: opendtv@xxxxxxxxxxxxx
Asunto: [opendtv] Re: From Broadcast Engineering - WRAL tests mobile DTV

This is getting more confusing. According to John you need 9 mb/s for
two services regardless of whether you are using 1/2 on one and 1/4 on
the other?

The article says they are using a total of 4.5 mb/s with one service
at 1/2 using .6 mb/s and the other service at 1/4 using .3 mb/s. Mark
says the efficiencies are 18% for 1/4 and 36% for 1/2. If .3 mb/s is
18% efficient then 100% is 1.67 mb/s and if .6 mb/s is 36% efficient
then 100% would be 1.67 mb/s for a total of 3.34 mb/s.

3.34 mb/s is 1.16 mb/s shy of 4.5 mb/s and if John is right and you
need 9 mb/s for two services it is 5.66 mb/s shy.

If John is right then for .9 mb/s of programming you need 9 mb/s of
bandwidth.

I don't think I ever thought it would be that bad.

If Tom is right as to the article they needed or at least 4.5 mb/s to
transmit .9 mbps or a 20% total efficiency.

If John is right they would need 9 mb/s for the two services totaling
.9 mb/s for an efficiency of 10%,

What am I getting wrong? What don't I understand? Was I wildly
optimistic last year?

Bob Miller


On Fri, Aug 8, 2008 at 2:10 AM, John Willkie <johnwillkie@xxxxxxxxxxxxx>
wrote:
> You cannot draw conclusions until the standard has been released.
However,
> I believe that public prints have put the o/h at close to 4.5 mb/seconds
for
> one service, and IIRC, 9 for 2 services.  Maybe the term isn't exactly
> services, but I can only refer to things which have been mentioned
publicly.
>
> John Willkie
>
> -----Mensaje original-----
> De: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx] En
> nombre de Bob Miller
> Enviado el: Thursday, August 07, 2008 9:09 AM
> Para: opendtv@xxxxxxxxxxxxx
> Asunto: [opendtv] Re: From Broadcast Engineering - WRAL tests mobile DTV
>
> That is what I would like to know. How far was I off last year when in
> technical ignorance but from a good source I put out numbers on what
> one 8-VSB mobile modulation would cost in bits. What are the numbers?
> What is the overhead and what is the % of bits that are real at what
> robustness levels?
>
> Anybody care to compare to DVB-T or H or CDMB-T or is it a big secret
> because it is so bad.
>
> Bob Miller
>
> On Thu, Aug 7, 2008 at 11:24 AM,  <dan.grimes@xxxxxxxx> wrote:
>>
>> What is the reason for only getting one 600 Kb/s and one 300Kb/s channel
> out
>> of 4.5 Mb/s?  Are the rest of the bits required for overhead or did they
>> just not fill all the M/H channels possible in the 4.5 Mb/s subchannel
>> bandwidth?
>>
>> Dan
>>
>>
>>
>> Tom Barry <trbarry@xxxxxxxxxxx>
>> Sent by: opendtv-bounce@xxxxxxxxxxxxx
>>
>> 08/06/2008 08:41 PM
>>
>> Please respond to
>> opendtv@xxxxxxxxxxxxx
>> To
>> opendtv <opendtv@xxxxxxxxxxxxx>
>> cc
>> Subject
>> [opendtv] From Broadcast Engineering - WRAL tests mobile DTV
>>
>>
>>
>>
>> Supposedly from Broadcast Engineering though I copied it from AVS
>> <http://www.avsforum.com/avs-vb/showthread.php?t=1056025>.  I'm not sure
>>  I understand it correctly but it looks like they got a total of 900
>> kbps  (2 channels, 300+600) after error correction overhead from using a
>> total of 4.5 mbps of the channel bandwidth.
>>
>> - Tom
>>
>> ---------------------------------------------------
>> From Broadcast Engineering - WRAL tests mobile DTV
>> Broadcast Engineering Mobile TV Update
>>
>> WRAL tests mobile DTV
>>
>> Users in Raleigh-Durham reported reliable signal reception in most parts
>> of the station's existing coverage area.
>>
>> WRAL-DT, the CBS affiliate in Raleigh-Durham, NC, owned by Capitol
>> Broadcasting Company (CBC), conducted a series of mobile DTV tests last
>> week using the Mobile-Pedestrian-Handheld (MPH) system promoted by
>> Harris Broadcast and others. Hosted by CBC's New Media Group, the tests
>> featured seven handsets given to station executives living in different
>> parts of the state. Users reported reliable signal reception in most
>> parts of the station's existing coverage area.
>>
>> To kick off the July 21-25 trial, the station hosted a reception last
>> Tuesday in which about 50 participants were driven in a bus around the
>> area with prototype LG Electronics mobile handsets that featured
>> MPH-compatible reception chips inside. Signal reception of two channels
>> (half rate at 600kb/s and one-quarter rate at 300kb/s) using about
>> 4.5Mb/s (including turbo coding) of the station's 19.4Mb/s on-air DTV
>> stream was reportedly strong everywhere they went during the 10-minute
>> ride - even at 70 miles per hour.
>>
>> The goal of the service, according to John Harris, WRAL's director of
>> programming, is to extend the reach of the station's television channel,
>> and make it available everywhere our viewers are. The initial plan is to
>> simulcast the on-air DTV signal. WRAL-TV broadcasts CBS network and its
>> own local programming in the 1080i HDTV format as well as in SD digital.
>>
>> "We're excited about the possibilities," John Harris, WRAL's director of
>> programming, told Broadcast Engineering. "The priority is to offer
>> WRAL's TV signal in another way, in another place. I took one [handset]
>> east of the station and I just kept driving until the signal dropped
>> out. I got pretty far before that happened, so I can see the potential
>> of this service."
>>
>> LG Electronics, Zenith Electronics and Harris, all proponents of the MPH
>> scheme, helped out with the field trials. WRAL-DT uses a Harris Sigma
>> CVD UHF transmitter, with an MPH module, for the weeklong test.
>>
>> In a statement, James F. Goodmon, CEO of CBC, said "mobile DTV
>> broadcasting enables WRAL to better serve our viewers, communities, and
>> advertisers by providing a strong combination of anywhere access,
>> two-way communication, and mobility."
>>
>> In 1996, Harris worked with WRAL-DT as one of the first DTV stations in
>> the country. Two years later, when John Glenn made his historic return
>> to space, Harris worked with WRAL to conduct the first live HDTV
>> broadcast of a space shuttle launch to audiences nationwide. Now, the
>> station is the first to promote mobile DTV service in the state of North
>> Carolina. WRAL predicts that more than 200 million portable devices will
>> be sold in 2008, although few if any will have the necessary MPH
>> reception chips inside.
>>
>> WRAL-TV and Capitol Broadcasting Company are part of the Open Mobile
>> Video Coalition (www.openmobilevideo.com), a nationwide group of
>> broadcasters driving the deployment of mobile digital broadcast
>> television. Commercial deployments are forecast for 2009. The group
>> hopes to have an established standard available to broadcasters by the
>> February 2009 analog shutoff date.
>> --
>> Tom Barry                  trbarry@xxxxxxxxxxx
>>
>>
>>
>>
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