Adding momentum to the 8-VSB camp, NxtWave Communications Inc. (Langhorne, Pa.), a developer of broadband demodulation chips, showed that it is well on its way to addressing two major issues that COFDM proponents have criticized in 8-VSB demodulation: poor indoor reception of DTV signals, and the lack of support for mobile applications.

NxtWave disclosed its plan for an 8-VSB demodulation chip designed specifically to improve indoor DTV reception. The chip is slated for launch in the fourth quarter of this year.

Regarding support for mobile and portable applications, NxtWave president and chief executive Matt Miller said his company's new intellectual property could make "mobile applications feasible" within the 8-VSB modulation scheme. "But first," he said, "the industry has to build a consensus" on what sort of mobile applications it is looking for. "It's got to be specified," he said. "We can't build a chip in accordance to 60 different broadcasters' applications."

NxtWave also announced that it's planning to introduce the company's first COFDM demodulation chip for Europe's DVB-T market in the third quarter this year. "We don't see the 8-VSB vs. COFDM debate as a religious war. If there is a well-defined standard, we'll make our product for it," said Miller. The forthcoming chip will not, however, be a dual VSB/COFDM chip, according to NxtWave.

Philly field test

CBS had conducted DTV reception tests at 128 outdoor and 42 indoor sites within the coverage area of the CBS-owned television station in Philadelphia.

The majority of the outdoor tests were performed last May and June, while indoor testing started in February this year and continued through March 15, according to CBS.

The 8-VSB demodulation ICs used in the field tests included Zenith's second-generation demodulator, the new-generation NxtWave device and Motorola Inc.'s prototype evaluation receivers.

The company's report concluded that outdoor reception in Philadelphia showed that if a marginal analog NTSC picture was viewable, then a perfect DTV service was available. The field measurements of over 100 sites indicated a 99 percent success rate, the company said. Similarly if a marginal NTSC picture could be received indoors, the DTV service was available 94 percent of the time.

The CBS report noted that Zenith's ProDemodulator, a commercially available product with a proven RF design, was the basis for collecting and analyzing the data. The NxtWave and Motorola units, meanwhile, are evaluation prototypes that "have undergone constant updates" throughout the field test process, according to CBS. The company's report did not single out the performance of any one receiver, due to the CBS policy of not releasing individual manufacturer's data, but it did point out that "NxtWave and Motorola units performed better than the current versions of consumer grade decoders." Further, it said, "Ongoing work by these companies is already demonstrating that previously failed sites are now consistently receivable."

NxtWave's next move

NxtWave, meanwhile, is sharing preliminary results of its enhanced 8-VSB device, designated NXT2002, due for introduction later this year. "We are going to show that we can actually cancel what appears like a delay in 0 dB multipath, when broadcasters install repeaters to fill gaps," said Miller. While COFDM's single-frequency network requires every transmitter in its network to be perfectly synchronized to avoid multipath, VSB has an advantage of not having to deal with timing issues, explained Miller. With 8-VSB local clock recovery, time domain equalization and asynchronous nature will all come into play to make this possible, he said.

To improve indoor DTV reception capability for NXT2002, NxtWave engineers added "enhancements in algorithms, made fairly simple but valuable changes in physical design, and incorporated new features to make the chip more user friendly," said Miller.

While different parties appear to define "portable" and "mobile" differently when referring to possible future applications of DTV broadcasts, NxtWave's Miller said, "Portable means sending programs/data using a full 19.4-megabits/second data rate to a portable device whose antenna isn't moving." Room-to-room applications of a portable TV, or even using a portable TV when one is walking on the street at a relatively low velocity, may fall into this category, he said. In contrast, "Mobile means sending information at less than a full data rate to a device whose antenna is moving when you are using it," Miller said. Sending data to an automobile is one example of a mobile application, he said.

Delivery questions

While stressing that enabling mobile applications within 8-VSB "is feasible," Miller remained skeptical on whether sending information to a handheld device using high-bandwidth capability developed for broadcasting was an efficient use of spectrum. In broadcasting, "You send a large amount of information to everyone at once, because it can be stored or display on a high-resolution screen." But if a handheld device isn't capable of storing or displaying such a big chunk of data, "why use a wideband connection?" he asked.