MPH, A-VSB offer broadcasters mobile DTV opportunities

Two mobile DTV systems with ATSC backwards compatibility made a splash at NAB2007.

Broadcasters, who might have felt that the latest distribution platform for television content was passing them by, had reason to be hopeful thanks to two mobile DTV developments at NAB2007 in Las Vegas last month.

If nothing else, NAB2007 established that broadcasters have an opportunity to exert greater control over their own programming and the advertising revenue associated with it when it comes to mobile TV. And they can do so without the requirement of partnering with another gatekeeper, a cell phone service provider

At NAB2007, two competitive mobile DTV transmission systems — one from Harris and LG Electronics and the other from Samsung and Rohde & Schwarz — took center stage in the ATSC-sponsored DTV Hot Spot and on the streets of Las Vegas in specially equipped buses. Both systems are ATSC backwards compatible, and both would allow broadcasters to begin transmitting to an audience on the go without having to replace their existing DTV transmission infrastructure.

Harris and LG Electronics (Zenith) unveiled their new MPH (which stands for mobile, pedestrian, handheld) in-band mobile DTV system, and demonstrated its ability to deliver programming to a bus traveling at highways speeds and even under an overpass more akin to a tunnel than a bridge. Two mobile MPG streams were transmitted simultaneously together with normal DTV programming from Sinclair Broadcast Group's local CW affiliate KVCW-DT. While the conventional DTV receiver failed shortly after the bus was in motion, the MPH channels — one transmitted at 557Kb/s and the other at 299Kb/s — remained intact.

Following up on its CES debut in January, Advanced-VSB (A-VSB) also made its presence felt in a big way at NAB2007. From the ATSC Hot Spot and in a bus on the street of Las Vegas , Samsung and Rohde & Schwarz demonstrated the in-band ATSC backwards compatible transmission system.

While A-VSB is designed to be transmitted from a broadcaster's conventional DTV transmitter, Rohde & Schwarz also demonstrated A-VSB transmission as part of SFN. Three transmission sites made up the network. One was a 10-watt transmitter and antenna in the ATSC Hot Spot. The other two were 100-watt SFN transmission sites, one atop the Stratosphere and a second atop the Paris Hotel. The demo was intended to show that broadcasters could optionally enhance their mobile DTV service with a private SFN deployment.

The A-VSB demonstration at NAB2007 highlighted the system's ability to use half-rate FEC coding, which provides transmission sufficiently robust enough to allow reception in a vehicle traveling at highway speeds. At CES in January, the A-VSB demonstration used quarter-rate coding, offering twice the forward error correction protection as half-rate for reception on high-speed vehicles like bullet trains. Rohde & Schwarz will make A-VSB SDKs, which include an A-VSB modulator, multiplexer and receiver chip, available in the third quarter of the year.