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Mobile TV for the U.S.

Being early to digital TV meant the U.S. was late to mobile TV. But the waiting is soon to end.

9 min read

In June, the vast majority of analog television broadcasting in the United States ended, leaving digital the only game in town. But the digital television standard adopted in 1996, called ATSC (Advanced Television Systems Committee), left out one potential group of consumers: those who want to watch TV on the go—sitting on a train, perhaps, in a stadium or café, or in the back seat of a car on a long trip.

When broadcasters, manufacturers, and the Federal Communications Commission (FCC) settled on the technical standard for U.S. digital TV, they believed they needed the entire bandwidth available—6 megahertz per channel—to transmit razor-sharp high-definition pictures to people’s living rooms. They didn’t think they could shoehorn in other features—such as fixing the problem that causes digital pictures to break up once the receiver starts moving at more than a few kilometers per hour.

Most other countries made the same trade-off [see sidebar "Tuning In to Mobile TV Around the World"]. But Japan and China came late to digital television, by which time advances in chip technology had already made it economically feasible to build receivers that could decode complex signals. So they were able to incorporate mobile reception into their standards from the beginning.

Meanwhile, cellphone operators and Internet television services stepped into the void, offering, in most cases for a fee, a limited number of channels streamed to mobile phones. And the broadcasters were shut out of the mobile television business—until now.

Following a technology development and standardization effort of unprecedented speed, the ATSC standard is expanding to include broadcast television for mobile handheld receivers, or ATSC Mobile DTV. Broadcasters have begun test transmissions; consumer trials are likely to start in early 2010 in Washington, D.C., with mass-market products available later next year.

Broadcasters will be able to provide this ATSC Mobile DTV programming free, supported only by advertising, because the equipment they need is relatively inexpensive and it uses spectrum they already own. Cellphone operators offering similar television service—for example, Qualcomm’s MediaFLO—must buy spectrum from the FCC and build a network of new transmitters developed specifically to deliver multiple channels of small-screen programming to telephone handsets. In part because of the huge costs of doing so, subscription revenues are essential to operating this enterprise.

The process started about three years ago. In April 2006, Samsung Electronics of South Korea and its partner, transmitter manufacturer Rohde & Schwarz Engineering and Sales, in Germany, demonstrated at the trade show of the National Association of Broadcasters (NAB) something called Advanced Vestigial Sideband (A-VSB), a way to adapt the ATSC standard for mobile devices. At an NAB show a year later, LG Electronics, in South Korea, and Harris Corp., in Melbourne, Fla., revealed an alternative mobile technology they named MPH, for ”mobile, portable, handheld.” Thomson and Micronas, French and German companies, respectively, announced that each was also developing similar technology; the two later merged their efforts and jointly developed a prototype. Along the way, at least 10 other companies, including MobiTV, Nokia, Dolby, DTS, and others announced they were developing various pieces of mobile television technology, although they were not designing complete transmission systems.

It looked like yet another standards battle was about to break out in the world of consumer electronics. These confrontations seem to erupt over and over, in which two different companies or industry consortia develop a great new technology but take different and incompatible approaches. Eventually, one technology prevails, and one group of consumers is left with an orphaned system. This happened in videocassette recording; it happened in high-definition blue-laser videodisc; and it happened in audio, when the battle between the Super Audio CD and DVD-Audio sunk both formats.

But it didn’t happen in mobile television. In April of 2007, broadcasters representing more than 280 TV stations reaching 95 million homes joined together in the Open Mobile Video Coalition (OMVC) with the expressed intent of driving the manufacturers toward a single standard, then taking that standard and running with it. The group held a bake-off. That is, they tested the prototypes, cut the field to Samsung and LG, and then pushed those historic rivals to come together.

In May 2008, the two companies did. Samsung and LG announced their intention to merge their proposals and to offer the result to the ATSC as a possible mobile-TV standard. In December 2008 the ATSC published ATSC Mobile DTV as a candidate standard. Such publication is an open invitation for interested companies around the world to start testing the technology and providing feedback. Typically, after six months or more of such evaluation, the standard is made final. Right now, Chicago TV stations WCPX and WPRW, Washington, D.C., station WPXW, and others are broadcasting ATSC Mobile DTV as part of the first field trials of the technology. The coalition has announced it will perform consumer trials in Washington, D.C., and more experimental broadcasts and market tests of consumer equipment will likely take place throughout the rest of 2009 and early 2010, with products expected to appear on retail shelves in 2010.

Plain-vanilla ATSC broadcasting doesn’t stand up to the demands of mobile reception, because of what’s known as the multipath problem. Television transmissions bounce off hills and buildings on the way to the receiver, which as a result picks up multiple signals with a slight delay between them. In the analog world, multipath problems show up as ghosts—the image on the screen is distorted but still watchable. In a digital world the picture breaks up, freezes, or goes to a blue screen. Stationary receivers can cope with multipath interference, to some extent, by analyzing the incoming signals. Because the radio waves are for the most part reflecting off stationary objects, the time delays are consistent, and separating the desired signal from the troublesome echoes is not terribly difficult. However, when the receiver is moving, or objects causing the echo are moving (like people in a crowded café), the echo delay changes constantly, creating a much more complex problem.

Different countries have adopted different solutions. In South Korea and some other countries [see sidebar, "Tuning In to Mobile TV Around the World"], TV broadcasters offer mobile services using a second slice of the spectrum that’s separate from their primary channel. This approach allows the service to be designed in a way that’s optimized for mobility. However, U.S. broadcasters don’t have that luxury. The FCC isn’t likely to provide any more spectrum for television. Each licensed channel occupies 6 MHz, and that’s all it’s going to get. So any enhancements must fit within that allocation. And, of course, they must not hinder the reception of the millions of stationary digital TVs already out there.

The solution is to use a training sequence—that is, a series of pulses encoding a fixed digital pattern that allows mobile receivers to find and lock onto the transmission. This training sequence helps maintain reception even with rapidly changing multipath interference, such as when the signal is reflected from moving objects near the receiver or when the receiver itself is moving around in the vicinity of fixed reflectors. The training sequence is marked as special or reserved data in the digital transmission, so stationary TV receivers can just ignore it.

In addition, the system applies a technique known as turbo coding. Turbo coding, considered an esoteric marvel just a few short years ago, is now commonplace. Turbo codes send digital information multiple times, spread across a short time interval, to give the receiver a better chance to receive it. Half-rate turbo mode sends every bit of data twice, quarter-rate mode sends every bit of data four times, and so on. The turbo-coded data is invisible to existing TVs, maintaining backward compatibility.

At the broadcast station, several digital signals carrying regular programming come together at a multiplexer, which combines them into one output stream. For mobile broadcasting, the turbo-coded mobile programming is added to this output stream at a remultiplexer before finally being turned into an RF waveform and amplified for broadcast.

The new equipment needed to encode and transmit ATSC-M/H signals is expected to cost a modest US $100 000 or less—which is a fraction of the million or so dollars that each of the broadcasters paid to convert their transmission systems from analog to digital.

But there is no free lunch. The mobile data inserted into a transmission uses up part of the broadcaster’s total capacity, which is limited to 19.4 megabits per second in the ATSC system. However, most high-definition (HD) programs aren’t broadcast at the highest available bit rate and therefore don’t take up a full 19.4 Mb/s, so broadcasters often have bandwidth to spare. The way they divide their shares of the spectrum among normal and mobile services will depend on what they think their viewers want to see and how they expect to make money—through more eyeballs for advertisers or by using some of their capacity for additional services, fixed or mobile, paid for by subscribers.

Imagine two broadcasters with different business models. One is an affiliate of a major national network such as Fox Broadcasting Company or NBC, which typically uses most of its assigned 19.4 Mb/s to transmit a single HD program. This affiliate might instead broadcast its HD program with slightly more compression and reserve 3 Mb/s of capacity to carry a program that could be viewed on a small screen—say, that of a mobile phone—at a resolution that doesn’t require as many bits but in that screen size would be just fine. It could be a lower-resolution version of the main HD programming, or it could be something completely different.

The second broadcaster, an independent operator with little or no HD programming to offer, might transmit a single standard-definition program aimed at living-room TVs—for example, a syndicated program that hasn’t been recorded in a high-definition format. That will take up about 4.7 Mb/s (including some ATSC system overhead), leaving 14.7 Mb/s for mobile content. This is enough capacity for many small-screen programs for mobile phones or for several programs for the midsize screens of laptop computers or in the back seats of automobiles.

All of these possibilities are exciting, but broadcasters are in business to make money, and even a modest investment in equipment and bandwidth must be justified on the bottom line. It’s too soon to tell exactly how mobile TV will work as a business in the United States, but at least three opportunities are already obvious.

First, broadcasters could make money the traditional way, by selling advertising. If people can watch TV when they’re on the go, the number of viewers seeing a particular show, and the resulting advertising revenue, should be higher—but only if their viewing is measured. Fortunately, with the appropriate software built into receivers and some form of return path to transmit information to a ratings service—such as an Internet connection from a PC or a callback from a mobile phone—these viewers can be measured very precisely. Broadcasters might even take advantage of an Internet connection to launch interactive advertisements, which may be more effective and therefore more valuable than typical commercials. In fact, the ATSC Mobile DTV standard includes provisions for such interactivity, in case broadcasters and receiver manufacturers choose to implement it.

Second, broadcasters could offer new data services for a transaction fee paid by the advertiser. Such services would likely emphasize information about the viewer’s immediate area, which is almost every localTV station’s strength. For example, restaurant and special-event guides, combined with interactive software and a GPS navigation device, could show where to find the nearest pizza, espresso, or haircut. If the consumer made such a purchase, identifying the source of the referral in some way—for example, with a coupon code or, in a handheld device with Internet connectivity, by information sent automatically to the retailer—the broadcaster could earn a commission. Such schemes would be an attractive addition to the usual system of collecting fixed advertising revenue from the companies listed in these guides.

Finally, broadcasters could eventually charge viewers a subscription fee to receive some premium mobile content, much like what is currently done with cable and satellite programming.

Broadcast mobile TV seems poised to compete with subscription services like MediaFLO, which right now consists of eight national networks. But because viewers want both national and local programming, the two approaches may in fact turn out to be complementary. Consumers equipped with a dual-mode device could get national content from a service like MediaFLO and local content (and perhaps additional national content) from nearby TV stations—the best of both worlds. No mobile carrier, handset maker, or broadcaster has announced specific plans for such a hybrid system, but all these parties are paying attention as approval of the standard appears imminent.

Indeed, the U.S. ATSC Mobile DTV rollout is likely to be remarkably quick. Publication of the candidate standard at the end of last year led to the mobile video coalition’s announcement in January 2009 that new mobile services will be on the air by the end of 2009 from at least 70 stations.

Samsung and LG have worked on this technology from the beginning and dozens of other electronics companies, including those that proposed technology early on as well as those that didn’t, have been involved in the standards-development process. No specific product introductions have been announced, but it’s likely that many of these manufacturers have mobile TV receivers in the pipeline for introduction in 2010.

There is now a real prospect for watching live, local TV broadcasts as well as network programming on portable TVs, laptop computers, mobile phones, and TVs installed in vehicles for the benefit of those in the backseats.

So, in just four short years, a new broadcast technology will have gone from an item on many people’s wish lists to a national standard and into consumers’ hands. And soon people will think of the ability to receive broadcast TV as just another basic feature of a mobile device, as commonplace as a camera or a Web browser.

About the Author

John Godfrey is vice president of government and public affairs for Samsung Information Systems America. He is a member of the Advanced Television Systems Committee Board of Directors and the Consumer Electronics Association Executive Board. He previously worked for Pioneer, Sony Electronics, the Information Technology Industry Council, the National Research Council, and SRI International.

To Probe Further

For information on standards set by the Advanced Television Systems Committee, go to the ATSC Web site.

See the Open Mobile Video Coalition’s Web site for a description of mobile digital television and its importance to broadcasters.

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