DTV channels: Time to start over?

July 31st, 2007

Local TV stations will be shifting to different channels, in many cases, because of the transition to digital television. The FCC has spent years trying to painstakingly determine which stations will go where. Now a prominent broadcast technology consultant suggests it’s time to start over.

That daring suggestion, from Charles W. Rhodes of TV Technology, arises from concern that over-the-air digital TV reception is threatened by interference. The arguments are highly technical, but in a nutshell, broadcasters worry that TV signals will go haywire if empty television channels are given over to new uses after the DTV transition is completed.

Last week, industry trade associations warned that DTV converter boxes may be susceptible to interference caused by new technologies that would share the public airwaves with television broadcasts. The FCC is making plans to allow “unlicensed” devices to make use of “white spaces,” portions of the airwaves unoccupied by TV stations in a local area. The blank channels might be used for wireless services, including high-speed internet access.

The National Association of Broadcasters and the Association for Maximum Service Television are “very concerned” that adding personal or portable unlicensed devices to the airwaves “will jeopardize the success of the impending digital television transition,” according to a letter from NAB President David K. Rehr and MSTV President David Donovan to John Kneuer, an assistant commerce secretary. Kneuer is in charge of the National Telecommunications & Information Administration (NTIA), which administers a program that will provide coupons worth $40 toward the cost of a digital-to-analog converter box to consumers that request them.

To be eligible for the coupon program, DTV converter boxes must be performance-certified by NTIA. The federal requirements are based in part on the A/74 receiver performance guidelines published by the Advanced Television Systems Committee (ATSC), a broadcasting standards organization. NAB and MSTV urged NTIA last fall to adopt requirements growing out of the ATSC A/74 guidelines, in some cases exceeding them or adding new requirements. The broadcast lobbying groups are now criticizing A/74’s “interference rejection” standard.

Among the consumer electronics companies planning to market coupon-eligible DTV converter boxes are Thomson/RCA, LG, Samsung and Jasco/GE. After Rhodes wrote that A/74 is “busted,” I asked Thomson for a response.

“Charlie Rhodes likes to complain about everything,” said Thomson spokesman Dave Arland, via email.

Rhodes, former chief scientist of the Advanced Television Test Center, favors “some partitioning of spectrum” to keep unlicensed devices out of the way of TV broadcasts:

This drastic step may be the only way to save terrestrial broadcasting from hopeless interference from unlicensed devices spread across the broadcast spectrum and across the coverage area of DTV stations.

A University of Kansas study concluded that “preliminary experimental results support the claim that properly implemented secondary transmission in the television band is possible without significant impact upon DTV reception.” The report was commissioned by the New America Foundation (NAF), a think tank that advocates spectrum-policy reform.

“Incumbent industry interests have mounted a concerted effort to exclude as many unused and under-utilized channels as possible from productive use by new services and devices,” according to comments NAF filed with the FCC in March.

The prospect that TV broadcasts will be disrupted by unlicensed devices is also disputed by the White Spaces Coalition, a technology-industry group that includes Microsoft, Dell, Intel, Hewlett-Packard, Google, Philips and Earthlink.

Consumers need to be assured that if they buy digital TV converter boxes for their analog TVs, they will be able to actually watch digital channels. Converter boxes are scheduled to reach stores by January, in time for the launch of the DTV coupon program. The FCC and NTIA must provide solid answers to the interference questions without delay.

DTV converters are expected to incorporate many improvements to digital TV receiver technology from the past several years. Here’s a question I hope the experts will address: Could further improvements to TV receivers, along with smart-radio technologies used in unlicensed devices, lead to fewer potential interference problems in the future? (Even if that happens, of course, it may not help consumers who own existing TV sets or converter boxes.)

After its years-long struggle to assign post-transition channels, the FCC probably would not be eager to repack the DTV channel allotments to provide separate spectrum for unlicensed devices. Moreover, spectrum is a multibillion-dollar political battle involving lawmakers, interest groups and lobbyists. In the current environment, rules are seldom changed at the behest of engineers—or the general public, for that matter.

The move toward digital TV began in the 1980s. Since then, technology has only kept moving, and demand is now building for spectrum devoted to new uses. A digital TV dividend of great significance is in the spotlight today as the FCC prepares to announce auction rules for a portion of the public airwaves currently used by local television stations. The prime spectrum to be auctioned, worth perhaps $15 billion or more to the U.S. treasury, is eagerly sought by telecom providers and technology companies.

Over-the-air TV, meanwhile, is nowhere near as important as it was decades ago. If too little spectrum is available to accommodate more unlicensed devices, then perhaps too much spectrum is devoted to TV.

Converter-box performance: Reports raise concerns
Changing channels: FCC releases national DTV list

• Links: TV Technology, Drew Clark, New America Foundation, NAB [pdf]

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