Keeping the 8-VSB faith
Fox and Philips are working on fix; CBS says trouble may be in faulty transmission
By Glen Dickson -- Broadcasting & Cable, 4/9/2000 8:00:00 PM
FOX and Philips think it can be fixed, and CBS thinks it may not be broken.
With the help of two universities, FOX and set-maker Philips Electronics are launching a new research effort that it expects will yield demodulator chips within a year that will adequately receive 8-VSB signals. FOX plans to announce the initiative at the NAB convention in Las Vegas this week.
"Over the course of the next six to twelve months, we hope to see a lot of results that are very promising, culminating in commercial implementations in very short order," says Andrew G. Setos, Fox's point man on DTV. Also working on the project are Cornell University and The Australian National University (ANU).
Meanwhile, also at the NAB, CBS will release results of 8-VSB tests that suggest the reception problems lie in faulty engineering at the station rather than in some flaw inherent in the standard.
The 8-VSB standard has been under growing criticism. Led by the Sinclair Broadcast Group, the critics contend that the signal is too fragile for indoor or portable reception. Some have urged the FCC to replace it with Europe's COFDM standard or to mandate receiver standards that can overcome 8-VSB's problems.
After ignoring the critics for months, the Advanced Television Systems Committee, the U.S.'s digital television standard-setting body, admitted that many of the complaints were valid and formed a task force to consider switching to COFDM.
Despite the criticism, FOX and CBS have been steady supporters of 8-VSB. FOX has been working on 8-VSB's reception problems for two-and-a-half years, says Setos, who adds that the timing of the research announcement is "coincidental" in regards to the ATSC's change in position. He says FOX also supports research into COFDM, but is focusing its efforts on the standard the U.S. has today.
Fox's partnership with Philips is key, says Setos. Color TV took off because RCA owned NBC and made color TV sets. Since that level of vertical integration doesn't exist today, FOX has "created a virtual one" with Philips. FOX will use its 22 owned-and-operated stations, 15 of whom are already broadcasting DTV, to collect extensive "channel characterization" data about the 8-VSB signal.
Through Philips Research USA, its laboratory in Briarcliff Manor, N.Y., Philips will contribute algorithmic and architectural modifications to improve the performance of 8-VSB receivers. The two universities, both of whom have teams of doctorates working on the project, will also contribute channel characterization and receiver improvement technology.
"Fox will help us characterize the transmission channel and capture signals from difficult locations, so we can better develop the architecture and the algorithms to restore corrupted signals in those locations," says Dr. Barry Singer, senior vice president of Philips Research.
The first part of the 8-VSB initiative will focus on indoor DTV reception as well as datacasting to portable devices, such as laptop computers equipped with small antennas and DTV receiver cards. The information gleaned from the project will be commercialized in receiver chips made by Philips Semiconductors, says Singer. "If we do get results, we certainly won't keep them secret," he says.
FOX and Philips won't disclose the terms of their relationship, although Singer allows that Cornell and ANU will be "able to enjoy the fruits of their invention." Setos would only say that the deal was a complex relationship that involved "a lot of intellectual property."
"Fox and News Corp. are not in this for the money," he says. "All we get out of it, quite frankly, are working set-tops and receivers so we can receive digital TV in this country."
CBS tests have focused on what happens to the 8-VSB signal before it leaves the transmission tower. The tests were conducted in Philadelphia at over 100 outdoor sites and some 40 indoor sites during May, June and November 1999, primarily involving kyw-dt.
According to sources who have seen the results, they are good. In outdoor testing, a perfect DTV service was available 99% of the time wherever an even marginal analog NTSC picture was, while, in indoor testing, DTV service was available 94% of the time under the same criteria.
Prior to the test, CBS traced a number of reception defects to discrepancies in the transmission process, among them symbol clock jitter, transmission line problems, noise in the studio-to-transmitter link and PSIP (Program System and Information Protocol) encoding problems. All were corrected before gathering test data.
On the other side of the DTV debate, Sinclair and European standards body Digital Video Broadcasting (DVB) will be conducting an NAB demonstration of COFDM transmission from Sinclair station KVWB-TV Las Vegas.
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