The challenges of datacasting

There is a growing demand for educational content delivery systems and local emergency and homeland security alerts, sent and received as digital files
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Like interactive television before it, the prospects for sending secondary data within a station's digital bitstream, or datacasting, were hyped for years as a viable business model that would allow broadcasters to make DTV transmissions as financially successful as their NTSC channel. Unfortunately, like ITV, several factors have led to a series of failed business ventures and wasted resources, namely getting the 8-VSB modulation scheme to work, building out the DTV infrastructure to meet FCC mandates and competition from outside the industry.

Although some of these now defunct services (e.g., Geocast, DTVPlus, iBlast, Spectra Rep and Wavexpress) could have been ahead of their time with consumers, the technology they used, which has since improved, is readily available. Using standard digital RF transmitters, some terrestrial transmission-delivered business-to-business services are online and thriving. File-based push services, such as The Walt Disney Company's Moviebeam, are also surviving, though not thriving. Also notable, WRAL-TV in Raleigh, NC, serves hundreds of subscribers each day with its AccessDTV service to PCs with a receiver card and a small antenna.

The emergence of the Internet has also hurt subscription-based data delivery models. The initial data services that provided news, sports and weather information to subscribers' desktop computers have been usurped to a large degree by free information from stations' Web sites.

In addition, commercial TV networks are concerned about how using 2Mb/s to 4Mb/s of spectrum to send MPEG-2 compressed data might affect the quality of their simultaneously broadcasted HDTV programs.

Finding the right recipe


Figure 1. Datacasting emergency and public safety alerts. Illustration courtesy Harris. Click here to see an enlarged diagram.

Commercial success is possible. Just ask PBS, which understands that with the myriad of channels on the air, distributing standard programming is not its best chance for datacasting success. Most stations are using Trivini Digital's SkyScraper Data Broadcast System to insert data packets into their digital spectrum. PBS' real asset is its broadcast frequency and the cost-effective delivery of educational and public safety and service content. There is a growing demand for educational content delivery systems and local emergency and homeland security alerts, sent, as well as received, as digital files. (See Figure 1.)

Kentucky Educational Television serves PCs and networked servers across the state with a network of transmitters. The network also streams live local government meetings OTA to government employees' PCs, disseminating valuable information cost-effectively. And there's also talk of delivering school curriculum to the home as well.

High-speed competition

Within the commercial segment, there is more activity (and opportunity) than some realize. A company in Maryland called Cident Entertainment is building a datacast network to push cultural programming to dedicated PVRs. The company is leasing spectrum from a local broadcaster in Washington, D.C., and soon will expand into other select markets. This provides a much more cost-effective way for consumers to view native language content while providing broadcasters with new revenue.

For commercial stations, beating the competition is tougher. WKRC-TV, a CBS affiliate in Cincinnati, OH, got its datacasting start with Geocast in 1999, but that service proved short-lived after it could not get access to the types of content consumers wanted. Thus, subscriptions were paltry, and the service was not financially viable to maintain.

In 2001, station management decided to offer high-speed Internet access to underserved rural communities. Chief engineer Hank Hundemmer worked with several software engineers to develop a service called Web-Hopper.com.

Along with a microwave dish on the roof of the station, the service used the telephone line for requests on the front end and about 3Mb/s to 4Mb/s of its over-the-air digital spectrum as the return channel. The remaining 15Mb/s to 16Mb/s was dedicated for the station's local and CBS network HDTV content.

The technology is sound

At its height, using a Thales Broadcast solid-state digital transmitter at full power and an IP encapsulator system from SkyStream, the high-speed Internet service included about 500 subscribers in the rural areas of Kentucky, Indiana and Ohio. However, after about 18 months, local DSL and cable modem service providers came into the market. Hundemmer says it was an uphill battle all the way. The telcos were aggressive in the areas WKRC was trying to serve, and the Web-Hopper.com service was slower and more expensive than DSL. For a TV station, Web-Hopper.com proved too costly, and the station's owner, Clear Channel, shut it down.

While it's clear that the current transmitters and related technology to send IP-encapsulated data transmissions over the air are sound and reliable, early implementations of an ATSC stream were problematic to receive in many urban areas. Improvements in forward error-correction and noise canceling in the enhanced-VSB specification have made a huge difference. Advancements have also been made in creating backchannels for terrestrial broadcasters, which is also key to two-way datacasting success.

Transmitter manufacturer Harris has been involved with datacasting since the late 1990s, supplying systems to Dotcast, Geocast, IBlast and others to build out their datacast services. The company currently works with a number of PBS stations, but no commercial stations. That's because even after years of discussions and trials, there's still no clear business model or killer app for stations to pursue.

The broadcast model

Digital signage is an opportunity broadcasters can and should experiment with in their respective local markets. The ability to send 2Mb/s to 3Mb/s of data (and paid advertisements) over the air to multiple receive sites throughout a city is a viable and cost-effective service for a station already broadcasting in digital.

Axcera, another maker of analog and digital TV transmitters, is working with several PBS stations, including KERA-TV in Dallas, to keep local municipalities informed via terrestrial datacasting. Using a 28kW Innovator solid-state transmitter, data can be inserted into the digital program stream, getting information to users in a timelier manner than the Internet can. Local schools receive the information as data packets overnight, ready for uploading to a LAN in the morning.

Transmitting at less than full power, which many stations have been doing as a way to save on operating costs, has also slowed datacasting's progress. Axcera recently announced it is working with Crown Castle Media to provide a 1.7GHz single-frequency consumer service via multiple transmission sites in and around Pittsburgh to cell phones and other mobile devices. Axcera is supplying 20 digital transmitters based on the European DVB-H transmission system in outdoor enclosures for the Pittsburgh trials.

Michael Grotticelli regularly reports on the professional video and broadcast technology industries.