Mobile madness

What is all the fuss about mobile TV? At NAB2006, the topic of mobile video broadcasting created quite a buzz. The NAB Multimedia World Conference included

What is all the fuss about mobile TV? At NAB2006, the topic of mobile video broadcasting created quite a buzz. The NAB Multimedia World Conference included a full day track, the Mobile Video & TV Forum. As this column related last month, the TV industry is finally realizing that mobile TV is a unique market, with unique programming requirements. It's as if the entire concept of broadcasting to small mobile receivers is a 21st century breakthrough. Haven't these people heard of the Sony Watchman?

Portable TVs have been around since the earliest days of NTSC broadcasts. In 1982, Sony introduced the Watchman fd210, with its tiny 2in B&W CRT display. For the past two decades, pocket TVs cost less than $200, often less than $100. Yet these tiny TVs have been an equally tiny niche of the global market for broadcast TV receivers. Apparently, the ability to pull TV pictures out of the air for free has not been all that compelling.

Then again, with multichannel TV services now in more than 80 percent of U.S. homes, one could argue that pulling free TV from the air is not a high priority for consumers, who now spend hundreds, even thousands, of dollars each year for TV entertainment content viewed in homes, cars, and more recently PCs and cell phones.

Considering the low cost and complexity of an analog pocket TV, it seems relevant to ask if there is really a market for mobile TVs. You'll see them occasionally at sporting events, but it is rare to see them dangling from peoples' necks such as the portable music players that have multiplied like rabbits in recent years. Yet the notion of delivering video content to cell phones, PDAs and notebook computers has gained tremendous currency.

To be fair, NTSC never worked well in mobile environments, despite all of the gull wing TV antennas seen on limos. And critics are quick to point out that watching TV while driving, or even walking down the street, can be dangerous, even illegal.

What we're really talking about when we explore mobile broadcasting's potential is supporting true portability for passengers in cars, trains, boats and so on. The obvious appeal is to reach these viewers while they are commuting, traveling and shopping. It is also important to note that these mobile broadcasts may include a variety of services, such as audio and video entertainment, news and information services, and data services that can be pushed to mobile Web browsers.

Monetizing the spectrum

Currency may well be the operative word here. Terrestrial U.S. broadcasters hadn't paid much attention to the mobile market. They focused on the fixed receiver market, where Nielsen measures ratings. Only in recent years has Nielsen begun tracking TV viewing away from home in commercial establishments, such as restaurants and sports bars. And U.S. broadcasters have paid little for the use of a valuable public resource. They've enjoyed the use of a broad swath of beachfront spectrum resources without paying hefty fees for its use.

When broadcasters in the United States developed the ATSC digital television standards, the focus was entirely on HDTV and fixed reception. The standard testing configuration was an outside antenna on a 30ft mast. HDTV was to be a service for fixed receivers (for big-screen TVs). SDTV formats were added to the ATSC standard in 1995, just before Congress authorized the service.

But reception and formats are decoupled in digital television. A digital broadcast can carry anything that can be represented with bits — data, audio, video, still images, Web pages, etc. The ability to receive these bits is entirely dependent on the modulation technology and the transmission infrastructure.

While other areas of the world were developing terrestrial digital broadcast standards with the ability to support mobile reception, U.S. broadcasters optimized the ATSC standard for fixed receivers to carry the maximum bit payload for HDTV. Unless things change, terrestrial broadcasters in the United States will be watching from the sidelines as new competitors use the reclaimed spectrum to develop services targeted at the wireless market, such as cellular telephony, wireless data, audio and video.

But this recovered spectrum doesn't come cheap. The demand for spectrum in the UHF bands is intense, due in large part to the improved propagation characteristics of this band relative to the higher frequencies that have been opened up for mobile telephony. Spectrum auctions in the 700MHz band have produced billions in revenue for politicians, who are constantly looking for new sources of revenue. These billions — and the accrued interest on the spectrum investment — must be recovered by the successful bidders, along with the cost of the transmission infrastructures they build, operating costs and profits.

One of the most significant operating costs for a mobile broadcast system is for the delivered content. The ability to collect fees from consumers (monthly subscriptions or per use charges) is one of the primary reasons that the content conglomerates have little interest in enabling existing terrestrial broadcasters to serve the mobile market with “free” advertiser-supported mobile broadcasts. Broadcasters currently lack the transaction networks and customer support infrastructure needed to offer subscription- and fee-based services.

As things stand today, there are three companies vying to serve the mobile broadcast market, two of which have spent billions for small slices of spectrum in the 700MHz band. As the rest of this band is recovered from terrestrial broadcasters, we may see additional entrants. However, much of this spectrum is likely to be acquired by existing cellular operators to expand the currently overtaxed capacity of their networks.

QUALCOMM is building a national network using 6MHz of spectrum currently occupied by UHF channel 55 in many markets. Its MediaFLO subsidiary will operate the network, partnering with cellular operators across the nation to deliver approximately 20 video channels and 10 audio channels to mobile receivers. The system will typically use a single frequency network with two or three medium-powered (50kW) transmitters per market; gap fillers are planned as the system matures. QUALCOMM demonstrated the MediaFLO technology during NAB2006.

The MediaFLO technology is proprietary; however, it uses the same Orthogonal Frequency Division Multiplexing (OFDM) modulation techniques used by Digital Video Broadcast-Handheld (DVB-H) and Integrated Services Digital Broadcasting-Terrestrial (ISDB-T). DVB-H was developed in Europe, where it is being deployed in several countries. ISDB-T was developed in Japan and was recently selected by the Brazilian government, though it's not final. South Korea is now delivering mobile broadcasts from satellite using the ODFM-based Digital Multimedia Broadcasting (DMB) standard.

In January, Crown Castle Mobile announced a name change to Modeo and plans to build out a national network for mobile broadcasting. Modeo will also use OFDM modulation but will operate at a disadvantage as it owns only 5MHz of spectrum in the 1.67MGHz to 1.675GHz weather-balloon band. The system will use networks of 2kW transmitters to deliver 10 to 12 video channels and 24 audio channels per market.

In June, Aloha Partners announced the formation its HiWire subsidiary, which will use the DVB-H standard for mobile broadcasting. Aloha plans to use 12MHz of spectrum originally purchased for wireless broadband services. As the largest owner of 700MHz spectrum, with 166 licenses in markets with more than 120 million people, including all of California, Nevada and Hawaii and most of Arizona, Arkansas, Ohio, Oklahoma and Tennessee, Aloha may have a competitive advantage in terms of system capacity.

Technology hurdles

Mobile broadcasting faces a number of technical hurdles, primarily related to the receivers that will be used with these services. Current cell phone handsets will need additional demodulators to work with OFDM and larger screens for viewing TV content. Most mobile broadcasts will use QVGA resolution (320 × 240) at 20fps to 30fps.

But the largest hurdle is the increased power requirements for the receiver and display. An additional one to two hours of video viewing during commute time would compete with the battery requirements for cellular telephony and data services. To help minimize power requirements, DVB-H, ISDB-T and MediaFLO technology all use variants of time slicing, so that the tuner is only powered for the portion of time during which the bits of interest are being transmitted.

The interest in mobile broadcasting has not been lost on the ATSC, which is currently evaluating backward compatible technologies for the ATSC standard. At NAB, Rohde & Schwarz and Samsung jointly conducted the first public demonstrations of Advanced-VSB (A-VSB) at the ATSC/NAB DTV Hot Spot. A-VSB was submitted by the proponents to the ATSC in 2005, approved and is currently in standardization process for consideration as an amendment to A/53.

A-VSB is focused at bringing extensibility tools to the 8-VSB physical layer to allow broadcasters new and more reliable terrestrial DTV services in the future, including Supplemental Reference Sequences (SRS) to address the problem of reliable ATSC dynamic reception. A new harmonized method to enable ATSC Single Frequency Networks was also demonstrated based on a new FEC technique (Turbo Stream), which uses Turbo Coding to enable a lower SNR and time diversity to bring new levels of performance in dynamic channels. SRS and SFN Turbo Stream can be used alone or synergistically together. Work is also underway to add time slicing capabilities to enable low-power mobile reception.

Further development and testing are anticipated over the next year, but it is still too early to determine if A-VSB will allow ATSC broadcasters to get into the mobile broadcast game. The “Web links” for this article include an extensive list of articles and white papers with additional information related to mobile broadcasting.

Craig Birkmaier is a technology consultant at Pcube Labs, and he hosts and moderates the OpenDTV forum.

Web links

Digital Video Broadcast-Handheld

Integrated Services Mobile Broadcasting — Terrestrial

Texas Instruments white paper on mobile DTV

Nokia Mobile TV Forum


MediaFLO technology overview