Mobile DTV News from the Net - Page 5

Piggie · 08-03-2009, 11:34 AM

Quote:

I found the cover of “Making Mobile TV Pay” interesting, as it shows a Japanese iPhone with a Softbank One Segment tuner/battery-pack add on. A similar cell phone/smart phone add-on or back-pack could prove an easy way to get ATSC Mobile DTV in the hands of consumers quickly in the U.S.

We already have Mobile Pay TV.. What the heck was the channel grab in the 50's about about anyway? So the wanted to "own" the public airwaves, now they also want the public airwaves for Pay TV?

I say a huge no.

Flo TV has the old ch55, what else do they want.

At this rate don't fear being taxed to breath, but pay some company to breath.

O-O · 08-04-2009, 08:24 AM

Quote:

Originally Posted by Piggie

We already have Mobile Pay TV.. What the heck was the channel grab in the 50's about about anyway? So the wanted to "own" the public airwaves, now they also want the public airwaves for Pay TV?

I say a huge no.

Flo TV has the old ch55, what else do they want.

At this rate don't fear being taxed to breath, but pay some company to breath.

They probably want to grab as much of the airwaves as they can so "free tv" doesn't become more available. That's just my unknowledgable in the matter, guess though.

O-O · 08-07-2009, 04:24 PM

It's been a another slow week for news on mobile dtv. Just not a lot going on right now I guess. Maybe we'll see some test reports at the end of August??

TonyT · 08-14-2009, 09:00 AM

Any new, news? Anything?

O-O · 08-14-2009, 12:27 PM

Real world Mobile DTV test from TV Technology.

Quote:

REAL WORLD EXAMPLES

How does it work? The DTS demonstration at the 2009 NAB Show I mentioned in June's RF Technology column showed multiple transmitters can improve coverage in urban areas without causing interference.

The main fill-in transmitter was located on top of the Stratosphere Las Vegas Hotel and operated at an ERP of 1,000 watts. It used a 200 watt Rohde and Schwarz transmitter and a simple antenna array composed of two vertically polarized Scala log-periodic antennas with a maximum at 189 degrees.

Offset mechanical beam tilt was used to maximize the signal over the Las Vegas Convention Center area while providing a strong signal down the Strip. The primary transmitter operated at 230 kW ERP from Black Mountain using horizontal polarization only.

From previous articles on DTS, you'll realize this system violated one of my rules for DTS—minimize signal overlap in the area between two transmitters. This system worked because the fill-in transmitter ERP was low and it was vertically polarized.

Timing difference increased in locations further south towards the main transmitter, but its much higher power allowed receivers to treat the weaker Stratosphere signal as noise. Interference was predicted in a weak signal shadowed location west of Black Mountain, but the signals were so weak anyone would require an outdoor antenna to receive KBLR. Due to the use of vertical polarization on the Stratosphere and the angle between the sites, interference was unlikely.

I created the "KBLR-Stratosphere Signal Difference and Delay" map using SPLAT GIMP and some PERL scripts. The difference between the two signals is shown in colors ranging from green (16 dB) to cyan or yellow when the difference is only 2 dB. A gray-scale overlay shows the timing difference between the two transmitters, with the bright areas and narrow bands in the middle showing delay under 10 microseconds and the broader bands representing 20-microsecond steps out to 70 microseconds. This figure is based on a 30-microsecond delay in the signal from the Stratosphere. The PERL scripts can be downloaded from xmtr.com/splat/perl/.

How did it work? No interference was reported. LG supplied a handheld mobile DTV receiver that was used to check the signal throughout the Hilton and Convention Center. In multiple locations in the South Hall meeting area, reception was poor or non-existent until the Stratosphere transmitter was turned on. Without out the Stratosphere transmitter, conventional ATSC reception was impossible in the meeting rooms; the signal couldn't even be detected. With the Stratosphere transmitter, KBLR could be received on a USB tuner with a whip antenna, although it wasn't perfect.

The mobile DTV signal was rock solid on a Pixtree USB receiver. Along the strip, I heard the mobile DTV signal was being received reliably deep in hotels, even at ground level.

DTV Coverage Problems, by Doug Lung

Aaron62 · 08-14-2009, 01:26 PM

Quote:

Originally Posted by O-O

Real world Mobile DTV test from TV Technology.

DTV Coverage Problems, by Doug Lung

Would have been nice to see tests from an actual working transmitter than a test setup like the one in the article. Still worth the read though.

jsmar · 08-23-2009, 02:01 AM

Quote:

Originally Posted by O-O

Yeah I think you're right about that. It's not like atsc-m/h tuners are more going to be more energy efficient. If anything, they may use more power but I'll leave that judgement up to the first reviews whenever that may be.

I don't know anything about FLO TV, but I do know that the ATSC M/H standard contains support for energy efficiency. Basically, a M/H device will be able to turn the receiver on and off between M/H groups, only receiving the groups that it cares about. It will be able to do this because of the following two features of the standard:

1) The ATSC M/H standard contains signaling information so that the receiver can know at what time the next group that it is interested in will be sent. Each frame contains signaling information for the current frame in the first two subframes and then for the last three subframes it switches to "signaling in advance" that the receiver can use to determine when the next group will be transmitted.

2) In order to be able to turn off the receiver and turn it on again the receiver has to be able to reaquire the signal very quickly. The ATSC M/H standard has 6 training sequences that are sent within the data that help to enable that. I've been reading the low level parts of the standard in detail, and it is amazing how much trouble they had to go through to get these sequences, which span many packets, through unmolested to the final transmission stage. Every time I find something that I wonder "why did they do that" I later realize it is because of the training sequences. It's all about the training sequences at the low level

.

CptlA · 08-23-2009, 11:13 AM

Quote:

Originally Posted by jsmar

I don't know anything about FLO TV, but I do know that the ATSC M/H standard contains support for energy efficiency. Basically, a M/H device will be able to turn the receiver on and off between M/H groups, only receiving the groups that it cares about. It will be able to do this because of the following two features of the standard:

1) The ATSC M/H standard contains signaling information so that the receiver can know at what time the next group that it is interested in will be sent. Each frame contains signaling information for the current frame in the first two subframes and then for the last three subframes it switches to "signaling in advance" that the receiver can use to determine when the next group will be transmitted.

2) In order to be able to turn off the receiver and turn it on again the receiver has to be able to reaquire the signal very quickly. The ATSC M/H standard has 6 training sequences that are sent within the data that help to enable that. I've been reading the low level parts of the standard in detail, and it is amazing how much trouble they had to go through to get these sequences, which span many packets, through unmolested to the final transmission stage. Every time I find something that I wonder "why did they do that" I later realize it is because of the training sequences. It's all about the training sequences at the low level

.

Energy efficiency has to be pretty high up there on the priority list for ATSC-M/H if there's even he slightest chance of mobile phones getting those chips. IMHO.

HTNut · 09-22-2009, 06:48 AM

Great article on whether VHF mobile DTV is going to provide good enough reception.

Quote:

TECH SPOTLIGHT
VHF On Handhelds Is Mobile's Top Job
By Jim Barthold
TVNewsCheck, Sep 17 2009, 11:42 AM ET
You can look it up: Higher frequencies with shorter wavelengths are more easily received by smaller antennas.

This means that when TV broadcasters start delivering mobile digital TV, those with UHF channels will find they have an advantage over their VHF rivals when trying to reach cell phones and other handheld devices with tiny antennas.

"VHF is at a disadvantage over UHF, which is all about the laws of physics." says Jay Adrick, vice president of broadcast technology at Harris, which is among the leading transmission companies building products for mobile digital TV. "A handheld device with a built-in antenna or a little pull-out antenna performs much better at higher frequencies than it does at lower frequencies."

In fact, some believe effective mobile broadcasting in the VHF band, especially in the low V band between chs. 2 and 6, may not even be possible.

"Sticking a three-foot antenna onto a three-inch mobile phone [to receive VHF signals] is going to be really tough and it just isn't going to work," says Perry Priestley, vice president of Linear Industries, a mobile transmission equipment vendor.

"Walk anywhere in the country with a good network and your cell phone will work," he says. "Do that with a TV; go down highways, go anywhere outside of a general coverage and you have no coverage, no TV station there."

But others believe that as the transmission and receiver technology evolves, VHF mobile will eventually overcome some its inherent disadvantages and close the gap with the UHF variety.

"You're not going to have a two-foot-tall antenna on a mobile DTV device so it's going to require some further work to get low V," says LG corporate spokesman John Taylor. "Our initial implementation has an antenna that's designed for high V and UHF with a VHF-UHF receiver on the chip."

http://www.tvnewscheck.com/articles/2009/09/17/daily.3/


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