The value of datacasting

November 1, 2004

Radio spectrum is a lot like real estate in that the portion of spectrum controlled by an individual or corporation can be viewed as vacant land. Consider some other similarities:

  1. The amount of footprint permitted on that piece of spectrum determines how large an area can be covered (proximity to population centers).

  2. The amount of permissible bandwidth for use by an owner (how much land is available).

  3. The specific location where the licensee has the rights to use the spectrum (more population equals more potential demand).

  4. Other spectrum available in the same location (more supply equals less demand).

  5. Specific uniqueness of the spectrum (what differentiates the particular portion of spectrum).


For most of its history, the broadcast industry benefited from the fact that it was one of the only media capable of providing adequate and reliable signal coverage over a large area. Beginning in 1955, broadcasters were permitted to use subcarriers for voice and data (also known as the Subsidiary Communications Authority or SCA). Many leased the space to various reading or language services. It was also common to use a subcarrier to provide data returning from the remote control unit at the transmitter site.

In 1993, the Radio Broadcast Data System (RBDS) standard was introduced as a means of using the subcarrier to broadcast specific information that permits a receiver to tune stations based on format and provide traffic, program and emergency broadcast information, as well as other capabilities.

One-way or two-way?

Datacasting real-time information, such as traffic, program or emergency information, is becoming more commonplace.

By definition, datacasting was intended as a means to continually broadcast (or stream) real-time information for a specific audience. In some cases, the data may either be streamed to every subscriber or selectively broadcast to subscribers based on their preferences. There are several good applications for one-way datacasting, particularly as a means to send real-time information such as news, traffic, weather, stock info and music titles.

Other less obvious applications include program-associated data (PAD), differential signals for precision GPS, time-shifting, telematics, commerce, subscription, supplemental audio, messaging, electronic program guide and Emergency Alert System information. Of course, some of these applications are currently enabled with the stations' RBDS capabilities. Given the nature of datacasting, having two-way capability may not be a necessity, but it could provide certain interactive capabilities more in line with a traditional Internet connection.

In the past 10 to 20 years, several platforms that permit the broadcast of data to the general public have emerged.

Without a doubt, the Internet is the largest and most economical medium for the real-time broadcast of data. While many would argue that this means of transport is limited because of the need to have a PC connected to the Internet, the reality is that the Internet is commonly available through devices such as the new generation of wireless mobile telephones and PDAs.

Verizon has begun an initiative to provide fiber to every home and business it serves, called FTTP or fiber to the premise. Of course, the realization of this will take several years and a huge financial commitment, but in the end they will be capable of providing more content than any currently available medium. And, let's not forget satellite radio. This service has more than adequate bandwidth to handle any type of datacasting application, including video. XM, for example, recently announced that it will provide a weather service aimed primarily at the aviation industry. It will broadcast high-resolution graphical weather products, as well as other aviation-specific flight information. The service was recently certified by the FAA for use in commercial aircraft.

Compared to other wireless services broadcasters, such as wireless telephone and satellite radio, terrestrial broadcasters have a significant disadvantage. Wireless telephone carriers have been aggressive with the deployment on current-generation technologies such as GSM (also called 2.5G) and are actively making key markets ready for the expected next-generation of service called 3G, which promises a seamless moderate speed (as much as 128kb/s) mobile data connection. Satellite radio, through a combination of direct satellite broadcast and local repeaters, provides a completely national footprint.

Once again broadcasters have limitations in terms of bandwidth and, more notably, what is available for datacasting. This lack of bandwidth translates to relatively low data rates, which may not be a problem when it comes to broadcasting most text information; however, supporting large data streams such as graphical information or multiple data streams may be nearly impossible. The IBOC system claims to be able to operate at a total data rate of 150kb/s in hybrid mode; this would leave about 54kb/s available for data services. The rate would increase at least two-fold if operated in the full digital mode. This data rate would certainly support most types of datacasting applications.


In established radio markets there are usually several stations capable of covering the same signal coverage to that market. The question is, will there be enough datacasting opportunities to go around? Currently the answer is no, however, as new applications are developed and accepted by the general public there could be some opportunity. It is more likely that the most mainstream applications will use alternative platforms that can reach the highest amount of people before considering terrestrial broadcasting. Consider the economic advantages of using a single platform that can reach most of the U.S. population, rather than entering into agreements with a large number of individual stations to cover roughly the same amount of population. There is also the issue of the cost of managing a large number of stations.

Terrestrial broadcasting doesn't contain any particularly unique qualities. Sure, some stations cover a market better than another due to license class, location or engineering, but in general they all do the same thing and there are about 13,486 stations licensed in the United States.

McNamara is president of Applied Wireless, Elkins Park, PA.