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Science & Technology
THIS HDTV PIONEER SEES A BETTER WAY
As a Massachusetts Institute of Technology professor in the mid-1980s, William F. Schreiber led a crash effort to develop new broadcast technologies. He succeeded so well that his former students are working on two of the five high-definition television proposals now before the Federal Communications Commission. So when Schreiber warns that the drive for all-digital HDTV systems is headed for trouble in field trials next year, his opinion carries some weight. "In a sufficiently realistic test," he insists, "the digital systems will suffer reliability problems." And unless such failures are remedied quickly, they could seriously delay the biggest TV advance in 50 years.
HDTV backers say Schreiber is wrong. But in case he isn't, he's preparing to step into the breach. Though semiretired at age 66, the diminutive electrical engineer has scraped up $150,000 from Scitex Corp., the Israeli maker of publishing systems. On this shoestring budget, he and four student researchers are mounting a belated quest for a new approach--called spread-spectrum technology--to coding signals for transmission. Today's radio and TV stations send high-power signals over narrow frequency bands, or channels--e.g., Channel 7. The FCC and broadcast equipment makers plan to squeeze low-power HDTV digital signals into the empty channels between these existing ones, and that's where Schreiber fears a glitch. He says a digital signal, packed densely with images converted to computer language, can be easily garbled by interference from buildings, storms, or planes, or just the cacophony of other broadcasts.
In theory, at least, spread-spectrum broadcasting should be more reliable. Based on military radio-communications advances, it divides a signal into 1,000 equal pieces distributed throughout a channel. Most interference would affect only a few of these pieces, leaving the overall signal free of snow and ghost images. This approach is so effective for evading radio jamming and eavesdropping that the Pentagon had long barred its commercial use.
BROAD APPEAL. The ban was lifted in 1978, and several companies are now developing spread-spectrum systems for cellular phones. Schreiber's work, which he hopes to complete in a year, would extend the technology to images. His idea is to encode a picture digitally, then broadcast it using conventional analog wave transmission. The TV set would convert the signal back to digital form, producing a superclear picture. If this approach pans out, it might hold down the cost of advanced TVs, which wouldn't need the exotic ghost-cancelation components now envisioned for them.
Spread-spectrum could also mesh with another emerging technology. Last May, the FCC's Advanced TV Advisory Committee decided to study so-called single-frequency networks. Current broadcast transmitters are so powerful that Channel 4's in New York, for instance, must be 155 miles from Channel 4's in any other city or the two will interfere.
Single-frequency systems, which have been demonstrated in Sweden for digital radio, reduce the required separation to just two miles by replacing a high-power antenna with a network of low-power ones. The same channel could be used more than once in the same general area, and the 40 channels that typically go unused might be freed, easing a battle over spectrum space between broadcasters and cellular-phone operators. Schreiber says not all digital HDTV can make the conversion--but spread-spectrum can. The technology "will appeal to everybody," he declares, "regulators, broadcasters, and viewers."
Schreiber has always liked competition. MIT's Advanced Television Research Program, which he launched in 1983 for the broadcast industry, eventually joined the avant-garde MIT Media Laboratory, which was raking in grants from industry and government. By 1988, however, Schreiber and Media Lab Director Nicholas Negroponte were at odds over the lab's open-door policy, which let the Japanese see Schreiber's work. He and his group walked out.
He also has an entrepreneurial streak. Before joining MIT in 1959, he spent six years at movie icon Technicolor Corp., setting up its first electronics research effort. He co-founded two companies while at MIT, including ECRM Inc. A maker of electronic publishing systems, it sells scanning equipment for desktop production.
The professor could be tilting at windmills this time. His band of researchers is competing with AT&T, Zenith Electronics, and General Instrument, all of which sport huge HDTV budgets. Moreover, the FCC quit accepting new systems for testing in June, 1990. That's when Schreiber started his spread-spectrum work, which isn't yet in the prototype stage. The agency has since indicated a clear preference for an all-digital system. "Bill is probably right," says Tony Uyttendaele, director of advanced television systems at Capital Cities/ABC Inc. "But if he can't build it now, the train is moving."
Indeed, the last of the five proposed systems will be tested in September, with field trials expected a few months later. Former FCC Chairman Richard E. Wiley, who heads the committee responsible for HDTV testing, won't rule out reopening the competition, but he adds: "It would be difficult." The three all-digital U.S. finalists have agreed to share technology and royalties if one of them wins. So even if no system is perfect, the FCC could fuse those three into one rather than solicit new proposals.
CLEAR VISION. It's too early to count Schreiber out, however. "He started off as a lone voice on things that are now widely accepted," says Gary J. Tonge, controller of engineering at the Independent Television Commission, a British regulatory body. Five years ago, when U.S. broadcasters proposed tweaking current television to improve picture clarity, Schreiber was one of the few experts to call for a new system--HDTV. And he has long maintained that HDTV would not use more spectrum than conventional TV, a fact broadcasters and the FCC only recently accepted. He thinks spread-spectrum will prove him right a third time: "If things turn out the way I expect, we'll have a system ready when it's needed."
Schreiber has beaten daunting odds before. In 1987, he argued against making an HDTV production system designed by Japanese national broadcaster NHK the U.S. standard. That meant opposing the State Dept., CBS, and PBS executives, yet Schreiber's view won out. "HDTV means money and jobs," he told Congress then. That's still true. And if the all-digital systems run into trouble, he could end up squarely in the picture.Gary McWilliams in Cambridge, Mass.