|
Following a field study capping two years of controversy over the digital terrestrial TV transmission standard adopted by the FCC, U.S. broadcasters have affirmed their initial preference for "8-VSB" signal modulation instead of its European rival, "COFDM".
However, the study also called for "urgent" improvement of 8VSB technology. Conducted jointly by the National Association of Broadcasters (NAB) and the Association for Maximum Service Television (MSTV), the tests compared reception of 8-VSB (eight amplitude-level vestigial side band) signals with the reception of signals modulated by COFDM (coded orthogonal frequency-division multiplexing).
At a combined NAB-MSTV winter board meeting in Carlsbad, Calif., with 32 broadcasters represented, 29 votes favored the joint resolution supporting 8-VSB. The three holdouts were Pappas Telecasting, Paxson Communications and Sinclair Broadcasting.
"We conclude that there is insufficient evidence to add COFDM (to ATSC), and we therefore reaffirm our endorsement of the VSB standard," stated the NAB-MSTV joint resolution. "We also conclude that there is an urgent need for swift and dramatic improvement in the performance of the present U.S. digital television system."
The leading U.S. backer of COFDM, Sinclair Broadcasting Group, is challenging the validity of the tests by circulating a letter from a UK manufacturer saying its COFDM receiver was misused.
"That's just sour grapes," said Gary Shapiro, president and CEO of the Consumer Electronics Association, a vocal opponent of Sinclair. "The COFDM issue in America is over, done, dead, gone."
Arguing that 8-VSB reception suffered from urban "multipath" echoes and other reception problems, Sinclair in 1999 had petitioned the FCC to add COFDM to the Advanced Television Systems Committee (ATSC) standard as an alternative to 8-VSB.
The FCC rejected Sinclair's petition, but the debate did not stop. NBC, ABC and other broadcasters did their own reception tests, then informed the FCC last summer that they also distrusted 8-VSB.
Congress warned broadcasters in reply that a delay launching digital TV and returning to analog spectrum by 2006 would be a "deal breaker" endangering the loan of free spectrum for digital TV.
Facing a crisis, NAB and MSTV agreed to conduct scientifically rigorous field tests to settle the question, creating the "VSB/COFDM Project".
"The problem here is maximum coverage area with minimum signal interference," said Matt Miller, president and CEO of NxtWave Communications, which produces 8-VSB and COFDM receiver chipsets. He voiced surprise the COFDM did not out-perform 8-VSB indoors, as expected, but refused to blame the receiver.
Only four COFDM vendors offered to modify their DTV receivers from Europe's 8 MHz channels to America's 6 MHz channels, he said. The team selected the best one, a DTVM200 test and measurement receiver supplied by Broadcast Technology Ltd. in the UK.
The COFDM receiver was tested side-by-side with an 8-VSB receiver at eight sites in Cleveland, Baltimore and Washington, D.C. Reception tests were conducted indoors without a rooftop antenna and outdoors with standard TV antennas at six feet and 30 feet.
"I can't say enough about how hard everyone tried to do a balanced and objective evaluation," Miller said. "We could find no valid technical reason to delay the implementation of digital TV for the two or three years it would take to develop and approve a new transmission standard. The decision was a practical one."
Said Bruce Franca, acting chief of the FCC engineering and technology office, "Sinclair deserves kudos for pushing development of 8-VSB a few years ahead of where it would have been, and for pointing out where 8-VSB still needs to go."
Sinclair's new technology VP, Nat Ostroff, seems resigned to losing the political battle for COFDM, but he's not done campaigning.
"If the industry is going to devote a significant amount of time and resources to improving 8-VSB," Ostroff said, "we welcome it, and we will contribute whatever we can to make that effort a success. It's in our own self interest to have a broadcast standard that works."
|
