Electronic Design

The Cell Phone—Now That's Entertainment

With music, games, and now video populating today's cell phones, who has time to talk?

There was a time when children could convince their parents they needed a cell phone because wherever they were, they would always be just a phone call away. It's hard for a teenager to use that excuse now.

Today's cell phones are as much portable entertainment devices as they are phones. So many models boast MP3 players, games, cameras, and even video, some experts say we soon will spend as much as 80% of the time using our phones for entertainment.

This isn't necessarily a bad thing. It makes some sense to combine applications, especially popular items like MP3 players, with cell phones. One thing's for sure, though. Whether we want it or not, we're going to get it anyway.

Audio already is well entrenched in cell phones from Motorola, Nokia, Samsung, and other companies. Most contain an MP3 player with flash memory and can store from about 50 to 100 songs. Hard-drive models can store thousands of songs. Most of these music cell phones get their downloads from their PC.

Now, Sprint Nextel offers songs for sale directly online. At $1.99 per song, this is expensive music, given Apple's iTunes $0.99 price. But some users want the convenience of getting their music here and now. Since MP3 players and music are such hot markets, this will continue to be a valuable niche for cell phones. Perhaps the biggest development would be an Apple iPod cell phone. With Apple's continued consumer leanings, don't be surprised.

As for games, most cell phones come with a few, but they're simple and boring, and not many people play them. More interesting games, however, could attract more attention, especially from the younger market. Yet because of the small screens and limited controls, cell phones are far from the ideal platform. Expect the market to turn to more exotic games, though, as video arrives with bigger and higher-resolution screens. PCbased games don't translate well to phones, so look for a new market involving video games optimized for small color screens and limited control options.

The ultimate entertainment media is still video. While almost everyone will tell you it's silly to contemplate TV on a cell phone, that's exactly where we're headed. With its limited resolution and download speeds that force video into a slower 12- to 15-frame-per-second (fps) mode, the small screen makes for crummy video.

Just as consumers were upset with snowy and distorted pictures on their TV sets, they will be just as picky with bad video on a cell phone. Noise, dropped connections, and a poor user experience will put consumers off more than anything—anything except, perhaps, worse program and content selection.

With regular TV as bad as it is, do we really want to carry that around with us everywhere? Virtually every survey of cell-phone owners reveals that subscribers don't really want or care about cell-phone video.

But what do consumers know? Nearly every cell-phone operator, handset manufacturer, and chip company, as well as gobs of service and content providers, are hell-bent to build and develop this market. Cell-phone TV is on the way, big time. Maybe we'll learn to like it. One potentially exciting example is the N92 video phone from Nokia (Fig. 1).

While most of the industry's attention is focused on video today, all sorts of other things are going on with cell phones (see "Next-Generation Cell Phones," p. 44). Yet the biggest challenge is putting video into a handset.

There are two basic ways to deliver video to a handset— through established networks with 2.5G or 3G technology, or by transmitting it on a separate broadcast channel. We've already got limited versions of network-delivered video. In fact, some cellular operators offer it in two flavors— downloads for later viewing and streaming video.

The downloads let viewers store short clips in flash memory for viewing at a more convenient time. These include music videos, short segments from network TV shows, and sports clips. Expect more download-specific varieties soon. As for streaming video, viewers can watch in real time. It takes more on-the-air time, so it uses more minutes, making it potentially the bigger money maker for cellular operators.

Users also will be able to stream video to their cell phone via the Internet with a Slingbox. With this device, users can take TV from off the air or cable and send it over a broadband connection to a laptop or cell phone with Internet access. People desperate for TV will love this interim option until the arrival of real mobile TV.

While you'll continue to see new video offerings from the big cell operators, this mode isn't the future of cellphone TV. If too many subscribers decide to use video at the same time, the downloads and streaming video will quickly overwhelm the capacity of the network, 3G or not. In fact, streaming video could easily bring any cell network to its knees with too many connections.The solution? Establish a new broadcast TV network for cell phones.

Before we get into building a new network, let's discuss why we can't. The first question that comes to mind is why we can't just put a regular TV tuner in a cell phone and watch the available on-the-air channels. Tiny single-chip NTSC tuners have been available and affordable for years. They have three flaws, though.

First, they boost power consumption. Second, they require an impractical antenna. On the low VHF bands where most TV channels are available, antennas must be at least several feet long for good reception. No one will want that on a cell phone. FM radios in cell phones now use the headset cable as the antenna. Maybe this will work for a TV cell phone.

The third and most important flaw is that the newer ATSC digital high-definition system will replace the NTSC video broadcast system in 2009, and ATSC wasn't designed for mobile units. Its complexity and power consumption don't make it a practical alternative. Instead, multiple efforts are attempting to build a broadcast system for videoenabled cell phones. Two competing systems have been developed, and projects are under way to build them out.

The first " competing" system is Modeo. A subsidiary of Crown Castle International Corp., Modeo LLC owns, operates, and deploys over 10,000 cell sites in the U.S. and other countries. Modeo also is the name of the video service expected later this year. The company will develop its own unique programming and content that best fits the small screen and the battery limitations of handsets. Programs will be a mix of news, weather, sports, music, and short clips. The offerings also will include multiple music channels and podcasts. Modeo uses the well-established Digital Video Broadcast-Handset (DVB-H) standard. DVB-H is a mobile version of the DVB-Terrestrial standard developed by the European Telecommunications Standards Institute (ETSI). The standard (EN302 034) defines a digital mobile TV method that can be used in cell phones, PDAs, laptops, and even special handheld or vehicle-installed consumer TVs.

This broadcast system can use any available spectrum, most of which will fall in the 400-MHz to 2-GHz range. Frequencies below 700 MHz are generally preferred, since they produce the most reliable reception. Yet the Modeo system uses a 5-MHz segment of spectrum at 1.67 GHz, which was previously used for weather balloons. Crown Castle bought it at an FCC auction several years ago, and it's now available nationwide. Services using only one continuous piece of spectrum are called single-frequency networks (SFNs), as opposed to the usual paired spectrum (for frequency duplexing) employed in most cellular networks.

Modeo develops video content, stores it on a server, and then distributes it to the company's stations nationwide via a satellite system (Fig. 2). Each local area station has its own tall transmission tower, which is similar to other radio and TV broadcast towers. The individual towers are expected to cover a radius of up to 20 miles. However, each installation will be different, depending on terrain and other factors. In some cases, multiple local stations or repeaters may be needed to get reliable coverage over the desired area. The transmit sites use kilowatt-level transmitters to emit the signal out to handhelds using the DVB-H protocol.

The handsets are also connected to their native cellular provider using a 2.5G or 3G network. While the DVB-H broadcast doesn't need the cellular network to function, an uplink would make consumer response and feedback possible. A two-way connection can even make the video interactive. Besides, there must be a tie-in to a cellular carrier just to get the receiver chips inside the handsets, which are almost always specified and/or subsidized by the carrier that sells them. The cellular operators also probably will handle billing, which they're already equipped to do.

The primary DVB-H requirement was a system that can reliably receive a 15-Mbit/s data stream in 8 MHz of bandwidth. However, the standard also can accommodate versions in 5-, 6-, and 7-MHz bandwidths at lower rates. Also, DVB-H addresses the power-consumption problem many portable devices face through a feature called time slicing.

While the transmitter transmits continuously, the receiver gets bursts of data. The tuner's front end only turns on when it expects to gets its data. The single high-speed data stream is divided up into multiple time-multiplexed " channels." With 10 channels, a receiver need only be on for about one-tenth of the time. With the receiver off 90% of the time, great power savings accrue. DVBH handhelds should provide a viewing time of two-and-a-half to three hours.

DVB-H's real success is its use of the robust and flexible orthogonal frequency-division multiplexing (OFDM). Few other access and modulation methods provide better performance under the severe conditions a mobile handset experiences. Multipath is a given, as is higherthan-usual levels of manmade noise. Add to that the Doppler effects present when a handset or other receiver is in motion. Indoor reception is expected, too.

The DVB-H standard features three modes of OFDM—2K, 4K, and 8K. These figures represent the number of OFDM carriers. The 2K and 8K formats are common in DVB-T, while the 4K mode is new for DVB-H. Carrier modulation may be quadrature phase-shift keying (QPSK), 16QAM (quadrature amplitude multiplication), or 64QAM. The broadcaster selects the exact mode and modulation method for the spectrum and desired coverage. The receivers adapt themselves to the received signal.

DVB-H also offers multiprotocol encapsulation with forward error correction (MPE-FEC). The video data comes as IP datagrams that are encapsulated in MPE packets or sections. Each has a 12-byte header, the data payload, plus a 32-bit CRC. The video IP datagrams comprise the compressed video.

DVB-H is designed to use the MPEG-2 compression scheme. However, most new systems are expected to use the MPEG-4 Part 10 standard, which is the ITU's H.264 compression method and codec definition. Audio-compression formats such as Microsoft Windows Media Audio (WMA), MP3, and AAC are also supported.

Multiple data streams of video data are then time-multiplexed before transmission. The number of time slots or channels depends on the selected number of OFDM carriers and the final peak data speed. DVB-H is expected to support up to 10 video channels. The actual rate of each will be in the 100- to 300-kbit/s range. Because of the timeslicing feature, channel change time is expected to take 1 to 2 seconds, which is a bit slower than the average channel-surfing experience. A GPS-based clock at the transmitter will control the time slicing and demultiplexing.

Most DVB-H handsets will use LCD color screens in the 2- to 2.5-in. diagonal size with a 320- by 240-pixel quartervideo-graphics-array (QVGA) and up to 256k colors. Frame rate will be 30 fps for the highest quality, but 15 fps may be used in some cases.

Modeo LLC heavily tested the system in Pittsburgh last year. It's expected to go into operation later this year in selected U.S. cities, including New York City. A rollout to 30 major markets is planned for 2007. Check out the new Mobile DTV Alliance, which is the industry forum supporting and promoting DVBH in the U.S., at www.mdtvalliance.org.

MediaFLO is the invention of CDMA cell-phone pioneer Qualcomm.FLO stands for forward link only, which implies a broadcast or multicast mode. It resembles Modeo and DVB-H, with a similar distribution system (Fig. 2, again). And, MediaFLO uses a 6-MHz chunk of spectrum from 716 to 722 MHz (formerly UHF TV channel 55), recently acquired by Qualcomm. It's available nationwide.

MediaFLO's air interface, also OFDM, can support a very fast data rate because of the wider 6-MHz channel. Qualcomm states a maximum of about 2 bits/s/Hz up to 12 Mbits/s. As a result, MediaFLO can provide up to 20 video channels and 10 audio channels. Again, the bit stream is divided for flexibility to fit local situations. Compression is MPEG 4.

Like DVB-H, MediaFLO was designed with serious power efficiency for a maximum viewing time of several hours. Two or three transmitters about 50 km apart can cover an entire area. A 15-fps frame rate on a quarter-commonintermediate-format (QCIF) screen is the standard. But 30 fps on a QVGA screen also is possible. MediaFLO will work with cdma2000 networks owned by Sprint Nextel and Verizon using 1xRTT EV-DO. The FLO Forum (www. floforum.org), which supports MediaFLO, maintains the air interface specification.

Modeo and MediaFLO are expected to be the two competing mobile TV systems in the U.S. Look for greater availability of both in 2007. Subscription rates are expected to range from $10 to $15 per month. Cingular and T-Mobile will no doubt partner with Modeo and use DVB-H, while Verizon and Sprint Nextel will adopt MediaFLO, though the final arrangements are still under wraps.

DVB-H will dominate Europe. It's already operational in some countries. Japan has developed a digital system called integrated services digital broadcast-terrestrial (ISDB-T) that's expected to be operational this year. Korea uses a system called digital media broadcast (DMB), which is available now. Both are quite different from the U.S. systems.

Dozens of products already address this vast new market (see the table), with chips once again forming the heart of all designs. But most of these chips are special processors, and they need the right software to work.

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