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As Submitted by Zenith Electronics Corporation
1/21/00
VSB DIGITAL TV TECHNOLOGY
OUTSHINES COFDM IN LABORATORY EVALUATION
Three years after FCC adoption, the digital television (DTV)
transmission system called VSB continues to gain momentum, with more
than 60 percent of U.S. households now in range of DTV signals. That
momentum for the VSB standard also was exemplifed by literally dozens of
next-generation DTV receivers shown at the International Consumer
Electronics Show in January 2000 by Thomson, Philips, Sony, Zenith and
others??- further weakening a challenge from Sinclair Broadcasting.
In an apparent attempt to delay its investments in making the
transition to digital broadcasting, Sinclair has petitioned the FCC to
consider giving broadcasters the option of using the European
transmission system, called COFDM. The Consumer Electronics Association
and its members have countered, urging the FCC to reject this 11th-hour
Sinclair delay tactic.
For its part, the developer of the VSB (vestigial sideband) system,
Zenith Electronics Corporation, showcased the strength of the standard
at the CES with a compelling comparison of VSB and COFDM receivers.
Zenith turned a private suite in the Las Vegas Hilton into a working
laboratory, complete with racks of equipment and multiple HDTV receivers
and displays. There, broadcasters, government officials, chip makers and
fellow equipment manufacturers saw first-hand the superiority of the
U.S. VSB standard over COFDM and performance improvements found in
current- and next-generation VSB receivers.
Underscoring VSB's superior DTV signal coverage and rejection of
"impulsive noise" were a series of evaluations in which multiple ghosts
and other real-world impairments were introduced into VSB and COFDM
modulated signals and, as a reference, into NTSC signals.
Results show, for example, that in Baltimore, Md. (where Sinclair
conducted DTV demonstrations last summer), COFDM would reduce signal
coverage area by 12 percent compared with VSB, according to Joseph
Flaherty, CBS senior vice president. That represents more than 700,000
television households, which significantly dwarfs the small number
potentially affected viewers relying on indoor antenna reception in
certain urban settings.
Richard Lewis, Zenith senior VP, technology and research, explained
that results also show that impulsive noise -- electrical interference
caused by hair dryers, vacuum cleaners, automobile ignitions, electrical
power lines, etc. -- severely limits COFDM's usefulness, particularly on
VHF channels. User experience in Europe has exposed this problem, he
said.
In addition, using some of the same equipment and testing procedures
that the FCC Advisory Committee on Advanced Television Service used to
evaluate DTV systems, Zenith showed how VSB receivers cancel multiple
ghosts -- comparing today's superior performance to the poorly
performing receivers hand-picked by Sinclair for its attempt in
Baltimore to discredit the ATSC DTV standard.
"8-VSB continues to outperform COFDM," Lewis concluded, referring to
VSB's superior coverage area and impulsive noise performance. "Plus, new
data show that current and next-generation VSB receivers offer
comparable ghost performance to COFDM in 'concrete canyon' urban
environments and indoor reception, and superior VSB ghost rejection for
the majority of viewers."
JANUARY 2000
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