From an uncertain timetable for digital broadcasts to continuing problems with digital buildout, copy protection and indoor reception, the broadcast industry and regulators at NAB expressed frustration with the pace of the DTV transition.

Two of five commissioners from the Federal Communications Commission (FCC) and many broadcasters here said hopes of completing the transition by the 2006 deadline are all but dead. Meanwhile, receiver manufacturers struggling to fix the digital TV transmission standard worried that broadcasters aren't moving fast enough to speed the digital switch. And "None of us has a business if they don't," an executive of one chip maker warned.

The most unequivocal assessment here of the state of the U.S. digital transition came from outgoing FCC commissioner Harold Furchtgott-Roth. He reiterated the agency's stance that industry and government should continue to work toward the deadline, but added, "As I've said over the last three years, it ain't going to happen."

FCC chairman Michael Powell, meanwhile, signaled that delay is likely, saying the 2006 deadline contains "the seeds of its own modification." He added that the spectrum auctions shouldn't be driven by budget politics.

Where all this leaves TV stations, consumers and equipment makers remains unclear, observers said. At a time when broadcasters are suffering from declining advertising revenues, many are anxious about the costs of the digital transition and whether they are worth the risk. Some observers here suggested that smaller TV stations might simply return their digital channels until a firm transition schedule emerges.

Among the hurdles faced by smaller-market and public broadcasters, which must meet a federal mandate to begin the move to digital services in 2002, are ordering costly transmitters and other equipment while scheduling deliveries around the receipt of construction and zoning permits. While Federal Communications Commission officials maintained that stations don't need new towers to transmit their signals, broadcasters said tower modifications still require inspection before stations can go on the air, further delaying the transition.

Broadcasters are "in a crunch time," said David Sparano, principal engineer at Harris Corp. He estimated that it would take at least six months to get a station on air in the best-case scenario if it doesn't need to build a new transmission tower. With a tower on the agenda, "It would take 15 months on average, or even several years," as rework is sometimes necessary on a new tower along with reinforcing buildings, Sparano said.

Most here agreed that while technical issues remain, the primary hurdles to the digital transition are political. The FCC, Congress and the Bush administration are eager to move stations off their analog channels so that they can be repackaged and sold at auction. Critics of that approach said consumer demand, not government fiat, should determine the rollout schedule.

Too, broadcasters face an uphill legal battle in convincing the FCC to compel cable operators to carry their digital signals. Broadcasters should be treated the same as any other multichannel service, Furchtgott-Roth said. "Don't look to Washington for special treatment."

To be sure, not all stakeholders in the DTV transition are pessimistic, but many remained concerned that their investment in technology development is at risk. "We're bullish about the transition," said Zenith spokesman John Taylor. "The biggest impediment is content," he added, referring to the relative lack of digital TV programming offered by the networks.

Zenith, along with a handful of other companies, is working on enhancements to the vestigial sideband (8-VSB) modulation scheme for digital TV that could open up new portable and mobile applications as well as improve indoor reception.

The Washington-based Advanced Television Systems Committee (ATSC) has received 10 proposals for potential enhancements to the 8-VSB standard, which survived a recent challenge by backers of an alternative modulation scheme.

Besides Zenith, proposals were submitted by ADC Telecommunications, Broadcom, Conexant Infotainment Systems, Merrill Weiss Group, Patel-Limberg-McDonald, NxtWave Communications, Oren Semiconductor, Philips and Sarnoff Corp.

John Tollefson, head of the ATSC committee considering the improvements, said it could recommend enhancements by January. Implementing changes could take several years, but companies offering proposals said they expect the process to move faster than that.

Among the proposed enhancements are incorporating multiple data rates to the 8-VSB scheme that would strengthen digital TV signals and hence make it easier to receive DTV pictures indoors. Proponents such as Zenith (Lincolnshire, Ill.) and chip maker NxtWave (Langhorne, Pa.) said the enhancements could also pave the way for portable and mobile applications while maintaining backward compatibility to existing digital receivers.

Zenith demonstrated hardware at NAB it calls Enhanced VSB. NxtWave, which has developed three digital TV receiver chips over the last year, said it began work in 1999 to enhance its chip designs for what it calls "robust data" reception.

Like Zenith's Enhanced VSB, NxtWave's hierarchical-VSB architecture forces "no change in table of allocations, no reduction in coverage area and no impairment in reception of existing receivers," said Matt Miller, NxtWave chief executive officer. "We're trading off data rate for reliability."

Under the Enhanced VSB scheme, a mix of 8-VSB and E-VSB streams are sent to receivers. Broadcasters can change the mix, and can also send — via the E-VSB stream — separate data, audio or video programs that are different from a main video program sent in the 8-VSB stream. Zenith's hardware demonstration showed that conventional DTV receivers equipped with only a standard 8-VSB demodulation chip ignored the E-VSB stream and decoded the 8-VSB stream alone.

After ghosts and noise were added to the DTV signals mixed with E-VSB and 8-VSB streams, conventional DTVs went dark. However, a new DTV receiver featuring combo 8-VSB/E-VSB decoders showed robust pictures sent in the E-VSB stream, which carried a different program at a lower bit rate. Further, the new receiver also improved the pictures of the main video program sent in the 8-VSB stream, thanks to training signals the E-VSB stream provided to the equalizer.

Timothy Laud, senior member of the technical staff at Zenith's research and development unit, said the new 8-VSB/E-VSB decoder chip can be designed by adding a few more gates to the current 8-VSB decoder chip architecture.

Laboratory testing of the enhanced-VSB proposals is scheduled to begin in August,with field testing of selected technologies by the end of 2001, the ATSC's Tollefson said.