Use it or lose it

For decades, broadcasters have been blessed with free access to some of the most desirable spectrum in the RF bands. But, because of the technical realities broadcasters encountered when they first constructed transmission facilities on this “beach-front property,” they have used this spectrum inefficiently. The market-based approach to broadcasting and the potential for interference between stations operating on the same channel in adjacent markets (or on adjacent channels in the same market) has left much of the spectrum assigned to TV and radio broadcasting (at least half the spectrum in any market) unused to prevent interference.

The use of high-powered “big sticks” by TV broadcasters to cover large geographic areas makes this problem worse. For example, the rules for digital TV allotments specify minimum spectrum separations between co-channel stations ranging from 196.3 to 273.6 kilometers, and separations of 110 kilometers between adjacent-channel stations that are not colocated or in close proximity.

The decision to continue with this approach to TV broadcasting as the industry makes the transition to digital may now be coming back to haunt TV broadcasters.

The HDTV Trojan horse

For decades, other industries have coveted the spectrum occupied by TV broadcasters, partly because of the desirable propagation characteristics in these bands, and partly because of the general scarcity of spectrum resources. Advances in transmission technology have made it possible to develop services in higher-frequency bands, but the demand for spectrum to support new services, including wireless telephony and broadband data services, has had broadcasters on the defensive for decades.

In the mid-‘80s, the FCC proposed that land-mobile telephony be allowed to share some of the frequencies assigned to broadcasters. In markets where a channel was unused because of potential interference with other broadcasters, the proposal would have allowed land mobile to operate low-power, two-way radio services. Broadcasters needed an excuse to prevent this erosion of their “property rights.”

The genesis of the current transition to digital broadcasting is rooted in the perceived need to prevent other industries from sharing the TV bands. In 1987, TV broadcasters went to the FCC with a bold request. They suggested that it would be inappropriate to allow land mobile to share the TV bands because broadcasters would need this unused spectrum to offer a new service — HDTV. Each station would require a second 6MHz channel to carry an analog augmentation signal with the added information needed to upgrade NTSC broadcasts to HDTV. The FCC postponed the decision to allow frequency sharing while it investigated the broadcasters' request. As they say, the rest is history.

Thanks to the broadcasters' HDTV Trojan horse strategy, nobody knows for certain when broadcasters will return the frequencies assigned to analog NTSC broadcasts to the government for other uses. When the FCC authorized DTV broadcasts in 1997, it set a date of Jan. 1, 2007, for the return of the analog channels. Within months, broadcasters had used their considerable influence in Washington to render that date meaningless. Congress amended the 1997 Balanced Budget Act with a provision requiring 85 percent of the homes in a market to be capable of receiving all of the DTV broadcasts in their market before the FCC could shut down analog service. Currently, less than 5 percent of U.S. homes have receivers that can pick up all these DTV broadcasts.

By any measure, the Trojan horse strategy has been a success. But pressure has been mounting to move the transition along, and now there are noises coming out of the nation's capitol for imposing a new deadline. Meanwhile, the runaway success of a new unlicensed wireless data service is changing the competitive landscape again. Wireless Fidelity, or Wi-Fi, is making it possible for people to create small, low-power networks to deliver broadband data to portable and mobile devices.

In May, the FCC dropped another bombshell on broadcasters, announcing its intention to allow the unlicensed use of the TV bands for two types of data services. The first is a duplication of the Wi-Fi service that is currently using spectrum in the 2.5GHz band. In addition, the FCC would allow any wireless-Internet service providers (WISPs) to deliver broadband data services to consumers using low-power, point-to-point transmitters.

To do this, those who would share the TV frequencies must develop smart radio technologies that would detect the channels TV broadcasters are not using. This would protect current TV broadcasts and allow the FCC to assign new TV channels in the future. The technology to do this is already proven.

Now, broadcasters are going to have to prove that the unlicensed use of “their” spectrum will cause irreparable harm. Will broadcasters be able to stop this new attempt at frequency sharing as they did in 1987, when HDTV was used as a tactic to block the land-mobile proposal?

As long as broadcasters continue pushing to maintain the status quo of big, high-power transmitters, the spectrum will be used inefficiently. But it may be impossible to prevent the sharing of the underused spectrum for unlicensed, low-power services. To make matters worse, only a small percentage of U.S. homes actually use the free-to-air television broadcast service; 85 percent of U.S. homes subscribe to a multichannel cable or DBS service. The FCC has opened another inquiry to determine just how many people still rely on NTSC broadcasts, and members of Congress are talking about subsidies for the holdouts so that it can recover the analog channels in this decade.

Between a rock and a hard place

There is little doubt that broadcasters will try to use their waning power in Washington to block the latest FCC overture to enable frequency sharing.

Already, the NAB is suggesting that the FCC delay the proposed sharing until broadcasters complete their DTV transition. During the transition, the new DTV service occupies many channels. Unfortunately, as these channels move to full power levels, broadcasters may become their own worst enemy. There are many indications that interference between analog and digital broadcasts will be significantly greater than the industry projected when the FCC assigned these channels. It is going to be difficult to prove that unlicensed transmitters operating at low power levels on unused channels are going to create a bigger problem. It is beginning to look as if broadcasters may need to learn how to share.

But there may be a way out of this ugly mess — single-frequency networks (SFN). These could change the competitive dynamic in this spectrum war. They could allow broadcasters to deliver a competitive multichannel service in every market simply by using the TV spectrum efficiently.

So, perhaps a new strategy is necessary. Instead of falling back on the old reliable interference canard, it may be time to go on the offensive. With SFNs, broadcasters could return to their roots — free TV — offering SDTV, HDTV and data broadcasts, and enough channels in the free and clear to compete effectively with cable and DBS. This might give viewers compelling reasons to put up an antenna again.

For more information on this subject, see FCC Proposes Rules to Facilitate Wireless Broadband Services Using Vacant TV Channels, located at

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

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