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Technology Stocks : C-Cube -- Ignore unavailable to you. Want to Upgrade?

To: Don Dorsey who wrote (42470)	6/29/1999 5:35:00 PM
From: John Rieman	Read Replies (2) \| Respond to of 50808

8-VSB vs. COFDM........................... tvbroadcast.com DVB Shuttles Mobile Test Of COFDM By Adam Wisniewski (June 25, 1999) Those NAB attendees who were savvy enough to avoid long lines for the LVCC/Sands shuttles by congregating at the small, blue DVB sign were given a mobile reception demonstration of the rival to the ATSC's 8-VSB DTV transmission format while zipping around the back roads of Las Vegas. The mobile COFDM (Coded Orthogonal Frequency Divisional Multiplex) test was sponsored by the Digital Video Broadcasting Project (DVB), a group of over 200 broadcasters, manufacturers, network operators, and regulatory bodies in over 30 countries worldwide. DVB had a subtle, but noticeable presence at NAB between the bus and its identification tags on products at members' booths--including Dolby, OpenTV, and Snell & Wilcox. The DVB consortium publically stated that the demonstration was mainly for the benefit of those international NAB attendees whose countries had not chosen a transmission standard for digital television so that they could see COFDM in action. An added bonus, certainly, was the exposure of COFDM, Europe's in-use terrestrial transmission standard, on the ATSC's home turf at a time when the 8-VSB standard has faced some strong criticism from a vocal minority of broadcasters. While the transmission debate continues between terrestrial broadcasters, DVB has made inroads with American satellite broadcasters, notably EchoStar, whom DVB engineering coordinator Peter MacAvock called "a DVB broadcaster." DVB set up a broadcast site on top of the Stratosphere tower about 1.1 miles NNW of the LVCC. They were only permitted to use a 100 W of transmitter power, via a Rohde & Schwarz transmitter, because of the close proximity to public areas. Two SD feeds were coded at 4 Mb to make up an approximate 8.2 Mb stream which was transmitted at 1 kW ERP in 16-QAM in a 6MHz channel. The bus was outfitted with a small, omnidirectional, stub COFDM antenna, and the signal was decoded by a Nokia Mediamaster set-top box and displayed on Sharp LCD screens in the PAL format. During the approximately 20 minute trip, a DVB representative on-board switched between between both channels several times. There was also a 13-inch Sony monitor displaying the RF signal of a local Las Vegas station for comparison. According to Manfred Kuhn, a broadcast-area project manager for Deutsche Telekom Berkom who led trips in the bus, the signal reception was "very good" with the exception of dropouts at the Tropicana on the strip. He also noted that signal loss manifested itself both in macroblocking and in the frozen pictures of the "cliff effect." Audio was not a part of the demonstration. While many riders were interested in viewing the tests, the lack of a full-bandwith 19.4 Mb signal meant for some that the test was little more than a experiment and not a true comparison to "real-world" 8-VSB, though it was reported that limited full-bandwidth tests were made separately. MacAvock countered the statement, saying that since mobile 8-VSB testing is currently impossible, it is difficult to say that there could be a true comparison between the two at all. He also added that the tests were very well received by both the U.S. and international broadcast communities. Several Television Broadcast staff members rode the DVB shuttle bus at different times during the show. On this reporter's trip from the LVCC to the Sands, signal quality was quite good with just a little macroblocking and no evidence of the cliff effect, though the use of the LCD monitors obscured some faults in the video and did not always provide accurate color representation. But compared with the signal being shown on the small Sony monitor, it was clear that mobile digital transmission, despite any faults, was a definite cut above analog.