07.19.2005 12:00 AM
Brazil Abandons DTV Standard Development
TMCNet.com reported that Brazil was dropping plans to develop its own DTV transmission standard. As you may recall, tests of various DTV transmission standards in Brazil provided fuel for the COFDM (DVB-T) versus ATSC (8VSB) modulation debate. RF samples and multipath profiles collected during these tests continue to be used to evaluate DTV receiver performance.

Brazil Communications Minister Helio Costa said that while Brazil may have the technical resources, it does not "have the conditions" to develop a digital TV standard, according to the TMCNet article.

This means Brazil will choose one of the current DTV standards--DVB-T, ATSC or ISDB--for its DTV standard. In the earlier tests, DVB-T showed promise with its ability to handle multipath and support single-frequency networks. One weakness was sensitivity to impulse noise. ATSC did better in the presence of impulse noise, but at the time did not equal DVB-T in handling multipath and support for single-frequency networks. ISDB, which like DVB-T uses COFDM, but with longer interleaving to better handle impulse noise, seemed to be Brazil's favorite based on its earlier testing.

The world has changed since these original tests. A DVB-T facility can now use DVB-H to transmit programming to mobile handsets as well as larger TV sets. New ATSC chips work better in the presence of multipath and, for a given data rate, work at lower signal to noise ratios than CODFM. While COFDM-based standards were the leaders when it came to single-frequency network applications, ATSC now has a distributed transmission standard and the latest ATSC receiver technology has enough equalizer range to handle signals from multiple transmitters.

"Compared with competing systems from Japan and Europe, the ATSC DTV standard offers the broadest signal coverage area at the highest bit rates," said ATSC Forum chairman Robert Graves in a press release. ATSC presented a seminar in Brazil that described the improvements in ATSC receivers, tests of ATSC distributed transmission systems and enhanced-VSB (E-VSB) technology.

Communications Minister Costa would begin meetings with representatives from ATSC, DVB-T and ISDB standard organizations within the next two months, according to the TMCNet article. It will be interesting to see if these meetings lead to additional terrestrial DTV tests to compare the standards.


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