Mobile DTV Speeds Toward Technical Standard

Broadcasters tout potential of new, free delivery path

Development of a new technical standard that would allow digital TV (DTV) stations to broadcast to cellphones and other portable devices is moving at a rapid pace, say broadcasters and technology vendors. In fact, a preliminary “mobile DTV” standard should be in place by month's end.

A “candidate” standard would allow vendors to begin building products with the goal of having mobile DTV handsets and other receive devices at retail for the 2009 holiday shopping season. And that could be a big boost for broadcasters and for mobile TV growth.

The Advanced Television Systems Committee (ATSC), the U.S. digital TV standards body, is currently considering the 800-page draft Mobile and Handheld standard that was submitted in September by an ATSC specialist working group. It should be raised to candidate-standard status in the next few weeks.

“It's one of the best efforts ever in our 25-year history, in terms of the efficiency, the technical breadth and the level of participation across the industry,” says ATSC President Mark Richer. “We are exactly on the schedule that we laid out, and I expect that the Technology and Standards Group will approve the ballots and elevate it to candidate-standard level by the end of this month.”

While minor tweaks are possible before it becomes a final ATSC standard, a candidate standard means that the major technology choices have been made, and vendors can start building devices based on those specifications. “It's a big step,” Richer says.

The draft ATSC-M/H standard is based on the MPH (Mobile Pedestrian Handheld) mobile DTV transmission system jointly developed by consumer electronics giant LG Electronics and transmitter manufacturer Harris Broadcast. It is also now supported by Samsung, which had previously pushed its own mobile DTV system.

By using a new digital exciter that is backward-compatible with the existing 8-VSB (vestigial sideband) transmission system currently used for DTV, MPH allows a mobile DTV stream to be broadcast within a station's digital channel without interfering with existing standard- or high-definition program services. The cost to implement MPH is relatively low, running $250,000 or less per station for the new exciter and supporting encoders and multiplexing gear.

VIDEO: Watch a "road test" of the MPH mobile DTV system from the 2008 NAB Show:

Mobile DTV Road Test from Broadcasting & Cable on Vimeo.

MPH has been tested successfully in the field by members of the Open Mobile Video Coalition (OMVC), a group of more than 800 local stations that has been pushing for a mobile DTV standard since early 2007. Ion Media Networks' WCPX and Fox Television Stations' WPWR in Chicago are currently transmitting mobile DTV signals from atop the Sears Tower using MPH. Ion also has been testing the system in Denver, from KPXC's tower in Fort Lupton north of the city.

All three stations are dedicating about 4 megabits of their 19.4 megabit-per-second (Mbps) DTV pipe to support the delivery of two live mobile TV streams. The Ion stations are broadcasting four standard-definition DTV streams in their remaining bandwidth, while WPWR, a MyNetwork TV affiliate, is transmitting a 720-line progressive HD feed alongside the mobile DTV services. The stations are using equipment from Harris, LG and Zenith to support the tests, and gauging reception with mobile phones, laptops fitted with USB receivers, and screens installed in traveling test vans throughout the downtown area, suburbs and rural regions.

Pat Mullen, VP and general manager of Fox's Chicago duopoly, has been testing the signals with a prototype LG handset. He likes what he sees so far. “You can get on the freeways at 75 mph, or get on a train and go 35 to 40 miles out from the transmitter, and the reception has been remarkable,” he says.


In addition to the MPH transmission system, or “physical layer,” the draft standard for ATSC Mobile-Handheld also includes specifications for how content will be organized—the “management/transport layer”—and for how video, audio and data will be displayed on consumer devices—the “presentation layer.” In doing so, it encompasses existing technologies such as established video and audio compression schemes and mobile-phone control software.

The transport layer is IP-based, the video codec is the MPEG-4 Part-10 (H.264 or MPEG-4 AVC) compression system already used for Web and mobile video, and the audio specification is the HE AAC v2 standard used in Apple's iPods. Application software, such as that used to control the program guide on a mobile handset, will conform to the Open Mobile Alliance Rich Media Environment (OMA RME) specification, which is supported by leading handset manufacturers and mobile systems suppliers.

Using existing technologies for ATSC-M/H both cuts time-to-market and makes the ATSC system interoperable with existing mobile DTV standards such as Europe's DVB-H and Japan's ISDB-T, says Brett Jenkins, director of technology strategy and development for Ion and a member of the ATSC specialist group that drafted the standard.

“We're not reinventing the wheel just to reinvent it,” Jenkins says. “That makes it attractive both from an engineering perspective and a licensing perspective.”

Broadcasters and equipment manufacturers still have work to do. The ATSC and OMVC plan extensive interoperability testing in the coming months to ensure that prototype devices can receive mobile DTV signals, and guarantee that the signals don't interfere with existing DTV services. (So far, there have been “zero problems” with existing receivers, Richer says.)

That could be facilitated by creating one or more “model stations” for mobile DTV, says OMVC Executive Director Anne Schelle, similar to the model HDTV station created at WRC Washington in the early days of DTV. Or there could be “plugfests” where multiple vendors test their gear for compliance.

The OMVC plans consumer trials next year to better inform the business models and programming plans for mobile DTV, once enough prototype handsets with full functionality are available. Mullen believes consumers will naturally gravitate to the local news and sports programming that mobile DTV would provide.

“Imagine Grant Park [in Chicago] on Election Night,” he says. “You had 270,000 people there, with no access to their local TV stations. Now imagine having this device, and how many people would have been watching their local TV stations. Five years down the road, if there's a breaking news story, people are going to be opening their phones and watching.”