Wireless Systems Design

TV On The Go Is The New Mobile Experience

Consumers want television on their mobile phones, but only if form factor and power consumption aren’t negatively affected.

As the market awaits the latest 3G phones, it's clear that consumers are eagerly anticipating new mobile-entertainment experiences. Mobile digital-broadcast TV is promising to deliver the big bang that will excite consumers worldwide. It marries two of history's hottest technological innovations: television and wireless telephones. The task that confronts wireless OEMs is to develop TV-enabled handsets that users will like.

Limited offerings of analog broadcast television are now available, but mostly in Japan and Korea. In addition, the U.S. has already seen early trials of DVB-H technology. These early mobile-TV offerings have shown that consumers want high-quality mobile TV. Yet they've also established that analog picture quality simply isn't good enough. A viewer who's watching a 2-in.2 screen may not be able to detect minor losses in video quality. But that viewer certainly will notice the pops and fades and signal drops that are apparently inevitable in mobile analog TV. Consequently, digital-television reception will be essential as OEMs and service providers seek to win the hearts and minds of television viewers on the go. Only with digital TV can reception be bright, clear, and reliable enough to please huge numbers of users.

Most of the capabilities that are needed to reproduce TV picture and sound are already built into 3G handsets. For example, phones based on Texas Instruments' OMAP platform already provide all of the necessary back-end processing, H.264 video decoding, and formatting color display. They also include the user-interface capabilities that are required for digital television. Add an appropriate antenna, tuner, and demodulator/decoder and you quickly have digital television on the wireless handset.

Although these additions aren't simple, they would be readily do-able if consumer preferences weren't paramount considerations. Putting the components together in an appliance that consumers will like presents several significant manufacturing and design challenges. In some cases, the technology needed to meet these challenges isn't yet available to OEMs (FIG. 1).

As has been the case with almost every advance in handsets, limiting power consumption will be the biggest challenge. Wireless OEMs already began to reach beyond simple telephony to add such features as color display, MP3-player capability, video games, and now digital television. In the meantime, consumers have refused to sacrifice talk and standby time even as they clamor for the latest handheld-device innovation.

It's safe to assume that the broad marketplace acceptance of mobile-television technology will depend on the industry's ability to receive, process, and present TV pictures and sound without significantly cutting battery life. Unfortunately, the power consumption of a typical television tuner makes this difficult. In most existing configurations, a tuner consumes 2 to 3 W. It roughly equals the combined power consumption of the other components of a wireless phone. In other words, simply adding a tuner to the phone could reduce battery life by as much as half. Bolting a tuner onto the front of the phone also could cause the device to heat up as it is being used. While this aspect might present some interesting marketing opportunities in cold climates, most consumers would not welcome such a thermal effect.

To overcome these difficulties, mobile-television standards provide for energy reduction within signal transmission and reception. DVB-H, for example, includes a time-slicing scheme. This scheme allows the handset to receive data in bursts. It also can switch off the tuner and demodulator/decoder between bursts. Other standards, such as ISDB-T, truncate video bandwidth. As a result, they limit the amount of data that's required for TV on a handheld device. These schemes can reduce power consumption by as much as a factor of 10. Yet both of them somewhat degrade picture quality. The fact is that displays on wireless handsets are so small and have such low resolutions that the human eye cannot detect such picture-quality reductions.

Advances in semiconductor-process technology promise to further improve the power economy of wireless handsets. By integrating the tuner, demodulator/decoder, and signal processor into a single submicron CMOS device, designers can help to extend wireless battery life. They will effectively reduce overall system power requirements. In addition, submicron CMOS allows the radio-frequency tuner to consume a fraction of the power of conventional tuners. Bringing the tuner on chip with the digital signal processing also allows the tuner to be precisely controlled by the system logic. This feature further extends performance while reducing power. Of course, a well-architected digital-signal-processing system will always consume minimal power in a deep-submicron CMOS process that's been optimized for mobile-device applications.

As digital-television capabilities are integrated into the handheld entertainment center, form factor is another major challenge that must be faced. Consumers have grown accustomed to extremely compact devices that fit easily in a shirt pocket or purse. They are unlikely to accept anything larger. Yet a standard television tuner can be quite large. Plus, a tuner and demodulator/decoder together may require several semiconductor chips.

Mounting all of this hardware on a board would eat up more real estate than a wireless handset designer can spare. Instead, the handset calls for a tuner and demodulator/decoder combination that occupies no more than a few square centimeters of board space. CMOS technology can meet this challenge by providing the necessary integration within acceptable real-estate limits.

Another test will be the task of adding functionality without greatly increasing system cost. A conventional tuner can be quite expensive. But market studies suggest that consumers aren't willing to pay much more for a wireless handset than the prices that they see today. As a result, the additional components that are required for handheld television reception must cost very little compared to their conventional cousins.

Most needed functionality is already built into the phone, which will help OEMs control cost. Semiconductor makers also can do a lot to address cost concerns as they integrate the tuner, demodulator/decoder, and processor. In the race to hold the line on handheld-wireless-system prices while adding television-viewing capabilities, extremely high levels of silicon integration will be critical. Such integration must be based on the most cost-effective process technologies.

The four challenges listed above are the major issues facing handset OEMs. Yet many other variables must be addressed before widespread mobile digital television becomes a reality. As stated, consumers aren't willing to sacrifice basic wireless-telephone functionality to gain non-telephone features. They may want the handheld appliance to double as a game machine, MP3 player, Internet terminal, or digital-television receiver. But they also expect to place and receive telephone calls even as these other, often complex applications operate.

For digital television, this requirement means that audio and video must not interfere with voice and data transmission or reception. Currently, new technologies are enabling digital-broadcast reception independent of the cellular network. As a result, a user can receive television images and sound without degrading wireless-telephone access.

Yet we also know that consumers expect TV picture quality that equals the reception on their living-room sets. With refresh rates of 15 frames per second or less, streaming video simply cannot satisfy this expectation. Emerging digital technologies do enable rates of 20 to 30 frames per second, which are similar to standard television rates. At this level, picture motion will essentially be what consumers are used to seeing (FIG. 2).

In order for mobile television's market growth to quickly reach its full potential, open standards will be essential to OEMs. If proprietary technology cannot accommodate different emerging digital-broadcast standards, it could stand in the way of development for diverse geographic regions. Right now, the standards that will be employed for mobile digital television remain to be finalized. In Japan, ISDB-T is the leading standard. In Europe, DVB-H is under development. Both of these standards are based on orthogonal-frequency-division-multiplexing (OFDM) technology. They include special features to reduce system power.

Last September in the U.S., Crown Castle International—an independent owner and operator of shared wireless infrastructures—revealed that it had purchased broadcast spectrum. The company plans to build its own mobile broadcasting network around the DVB-H standard. It has already tested such a network in Pittsburgh, Penn. With this pioneering effort as a model, chances are that DVB-H—the standard in development in Europe—also will be adopted in the U.S.

Yet engineers and designers must keep in mind that standards remain uncertain. In addition, different standards may entail slightly different design considerations. Similarly, semiconductor makers must be ready with components that are tailored to the various standards.

Consumer expectations also must be taken into account. For instance, one important expectation is programming. Just what will people want to watch on their mobile TVs? Acquiring, packaging, and branding programming will fall to system operators. These tasks may prove to be a considerable gamble. It's very likely that viewing habits for mobile TV will be quite different from those to which we are accustomed. For instance, prime time is traditionally in the evening. However, mobile-TV viewing is more likely to peak during rush hours both in the morning and evening. The TV viewer on the move also is likely to enjoy programming that comes in shorter segments. He or she may be less likely to watch movies or shows that consume long time segments.

Finally, it's extremely significant that most cellular handsets will offer Internet access in the timeframe that mobile TV takes off. For years, the potential for interactive TV has been discussed. But most consumers don't have uplink communication capability integrated into their living-room entertainment centers. The cellular handset, in contrast, will provide the most interactive and ergonomic platform imaginable for interactive TV. The ability to easily and seamlessly move between broadcast content and the Internet is very likely to invite exciting services and marketing potential.

While important challenges remain for all of the participants in mobile digital-television development, there's no doubt that they will be met. Already, technology is moving forward. OEMs are hard at work on preliminary designs that will help the wireless telephone take the next step toward becoming a true handheld multimedia-entertainment center. Meanwhile, operators like Crown Castle are testing the waters of consumer acceptance and demand.

As test markets emerge for digital TV in the U.S., early adopters will soon begin to acquire the new handsets. By 2006, it's expected that new wireless appliances will hit the market in a big way—especially in Japan and Korea. Mobile digital-TV proponents expect that by 2007, the market for this nascent technology will really take off. The challenge will be to turn out handsets and produce programming fast enough to feed the predicted buying frenzy. That's a challenge to which we can all look forward.

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