04.23.2007 09:00 AM
NAB2007 offers two competing ATSC in-band modulation schemes

RF broadcasters at NAB2007 saw two competing ATSC in-band modulation schemes for sending video to mobile devices using the digital TV spectrum.

Aside from the attention these two DTV delivery systems attracted, the entire NAB exhibit floor was littered with a variety of technologies and systems designed to help stations create, prepare and distribute content to portable devices via MPEG-4 AVC encoding. Various tests also used the DVB-H and MediaFLO delivery systems, which are now deployed in select and increasing markets in the United States by cell phone service operators like AT&T and Verizon Wireless, which deploy MediaFLO, and Modeo (Crown Castle), which deploys the DVB-H standard.

Traditional transmitter manufacturers like Axcera, Harris, Larcan, Rohde & Schwarz and Thomson now support DVB-H and MediaFLO. Harris and Rohde & Schwarz both showed prototype exciter boards for their newly proposed schemes while the others said they'd wait for more testing before committing to support either Advanced-VSB (A-VSB) or Mobile-Pedestrian-Handheld (MPH).

Virtually all of the encoding systems displayed and demonstrated at NAB2007 were working with some form of DVB-H, as this is the more prevalent format, especially in Europe, where it was developed and standardized.

Axcera presented a live demo of the Modeo service at the show. The company broadcast a DVB-H signal from its booth in the Central Hall, using an Axcera base station with an Innovator LX solid-state low-power Digital Video Broadcasting (DVB) transmitter. At the booth, live video was displayed on a Modeo Mobile TV Smartphone. The content came from Modeo's broadcast center in Pittsburgh, PN, via satellite to the exhibit hall.

The two ATSC-compatible systems — A-VSB from Samsung and Rohde & Schwarz, and MPH from Harris and LG Electronics — could allow local stations to get in the mobile TV game without having to rely on outside service providers or telcos to get the signal to subscribers. The systems also provide another potential revenue stream for stations' local content.

The competing, noncompatible technologies were demonstrated in Las Vegas on two respective vans equipped with receiving equipment, a spectrum analyzer and LCD monitors to view the signals. Each van showed DTV signals coming from local Sinclair Broadcast Group stations, with the overall 19.4Mb/s signal being split up into a main channel at 15Mb/s and two sub channels. (In the case of the MPH demo, one stream was sent at about 560kbps, using 2.2Mb/s, called 1/2 rate, and another 2.2Mb/s at about 300kbps, or 1/4 rate.) This was to demonstrate how a station might replicate its traditional DTV channel for larger mobile devices, like a laptop or an in-car video system, and send out a smaller signal for display on a cell phone or handheld player, with its 2in x 3in screen, or to stream pure data.

During live demonstrations, both systems worked well. The demos also illustrated how the main DTV channel break ups and freezes when the van was moving (even when moving very slowly at say a traffic light).

The A-VSB system was also demonstrated using a single frequency network set up with special temporary FCC authority using three separate transit sites around the convention center. This method proved also to work well, except inside a tunnel.

Of course, for the system to be successful, LG Electronics and Samsung would have to build the receiver chips and put them into cell phones for consumers to use. Both companies said they would do so when enough stations adopt a particular method. The companies said they could have products on the market in 2008.

Being backwards compatible with the currently mandated DTV system, neither modulation scheme needs approval from the FCC or the ATSC for deployment. It was suggested that complete ATSC standardization, which has already begun for the A-VSB system, could take more than a year, so broadcasters attending NAB2007 were encouraged not to wait.

Indeed, with MediaFLO and DVB-H services now delivering video to limited subscribers in places like New York and Philadelphia, the opportunity for mobile television is ticking. MediaFLO plans to be in 40 U.S. markets by the end of the year. A-VSB and MPH are seen as ways for local stations to fill in the gap left by national service providers with customized, in-market weather, news and sports content. Which system eventually wins out remains to be seen and a new Open Mobile Video Coalition has been announced to review each in more detail.



Comments
Post New Comment
If you are already a member, or would like to receive email alerts as new comments are
made, please login or register.

Enter the code shown above:

(Note: If you cannot read the numbers in the above
image, reload the page to generate a new one.)

No Comments Found




Wednesday 11:59 PM
Peer Profile: Tomaž Lovsin, STN, Slovenia
“Will there be a shift from coax to fibre? Or a mixture between the two which will require hybrid solutions to be implemented?”


 
Featured Articles
Discover TV Technology