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A-VSB and MPH: A Side-by-Side Demo

This morning, I got the chance to view a live demo of two of the three technologies being considered by the ATSC as a mobile digital TV standard -- A-VSB and MPH. The Open Mobile Video Coalition (OMVC) has set up a van in the Central Hall outfitted to recieve two live channel feeds -- one UHF and the other VHF -- to demonstrate how each system performs.

For the demo, I squeezed myself into the backseat of the van, where a monitoring wall was set up behind the driver and passenger seats. The two main video displays depicted a live, MPH-enabled feed from a local UHF channel and another live, A-VSB-enabled feed from a local VHF channel. According to Victor Tawil, senior vice president of technology for MSTV (which is performing the trials of all the potential ATSC technologies on behalf of the OMVC), the two systems are periodically swapped between each channel, so that the UHF channel might be getting an A-VSB feed and the VHF channel the MPH one. This keeps things as objective as possible, and is also the protocol for the actual field trials of the systems.

The OMVC yesterday demoed the third potential mobile DTV standard candidate -- a system developed by Thomson and Micronas. Unfortunately, I wasn't able to see a demo of this system this morning, because the Thomson/Micronas people decided to showcase it at the Thomson booth, so there was an empty rack where the system sat a day before. I'm looking forward to seeing it in action when I visit with Thomson on Thursday.

As for the live video feeds I did see, both seemed to be performing well. Neither videos froze or dropped out at any point while I was viewing them. I noticed the UHF MPH feed looked a bit blurry, which made it harder to see, but Tawil pointed out that the image wasn't being optimized for a mobile screen for the demo. The demo was really meant to showcase the strength of the signal. So in a real case, a viewer would likely be able to see a much better picture, because he or she would be receiving a feed optimized to his or her particular device.

Tawil was not able to reveal much about the data on the recent Independent Demonstration of Viability trials conducted by MSTV on behalf of the OMVC coalition in Las Vegas and San Francisco, but did say his organization had already collected 700 hours of video from the San Francisco trials and another 400 from Las Vegas. "We're really looking to see if there is any failure in the signal, when it fails, and under what conditions," he said. This will allow MSTV/OMVC to better pinpoint the true viability of all three systems.

As for the prelimary data from the trials already available to the public, the OMVC has found that both high VHF and UHF mobile reception works at pedestrian and highway speeds, mobile reception can be achieved from as far as 40 miles from the transmitter and that none of the systems interfere with normal digital broadcasting signals. For me, this begged the question of how the ATSC would really be able to differentiate among the competing systems to determine a final standard. According to Sterling Davis, vice president of engineering at COX Broadcasting, who was on hand for the demonstration, there are differences in the underlying architecture of the A-VSB, MPH and Thomson/Micronas standards. The determining factor would likely be which system shows the most promise for a rapid deployment.

This is definitely not a story that has reached its final conclusion. To be continued...

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