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Mobile DTV

Mar 1, 2009 12:00 PM, By Jay C. Adrick

The development of ATSC-compatible in-band mobile DTV began more than three years ago with two companies (Samsung and LG Electronics/Zenith) leading the way — each with a different approach. Each company took on transmission partners, and over-the-air demonstrations began in the spring of 2007. The broadcast industry's interest in mobile DTV ignited rapidly and culminated with the formation of the Open Mobile Video Coalition (OMVC), representing more than 20 major broadcast groups.

At the same time, the ATSC moved the standardization of a compatible ATSC mobile DTV system into high gear. When a request for proposals was issued by the ATSC, many companies responded, and various tests were conducted to evaluate systems. This activity concluded with a recommendation to the ATSC's Technology and Standards Group subcommittee on mobile DTV, S-4, to develop a system based on the physical layer of the LG/Zenith/Harris MPH technology.

The road to ATSC Mobile DTV

The ATSC S-4 activity began in May 2007. By August 2008, the four working groups within S-4 had defined the pieces necessary to put together a working mobile DTV system that met the required criteria as defined by the industry. By late November 2008, the ATSC S-4 mobile DTV system was elevated to ATSC Candidate Standard status and assigned the A153 designation. To many, this might sound like a long development process until you compare it with the more than 10 years of activity that led up to the ATSC DTV standard. The ATSC TSG S-4 Working Group, under the leadership of Mark Aitken and the four subgroups, maintained a constant stream of working sessions via telephone conference calls, e-mail and in-person meetings to move the technology forward and get to the Candidate Standard status in just under 18 months.

Figure 1. System architecture with full ATSC M/H
Click to enlarge

Two key annual events drive broadcast industry development. For receiver and consumer products, it's the Consumer Electronics Show in early January. For broadcast equipment, it's the NAB convention in April. In order to show working prototype ATSC Mobile DTV receivers at CES 2009, both receive and transmission technology had to be “reduced to practice” (demonstrate its workability) by mid-November 2008. There was no time to wait for the outcome of balloting with the ATSC TSG if successful demonstrations were to be conducted at CES in January.

LG/Zenith and Harris, along with several partner companies, began product development just after NAB2008. Specifications for the receiver chip sets and the transmission equipment were based on the committee work that was conducted in TSG S-4 with the hope that no major changes would take place. The receive technology is the most sensitive to change as it is reduced to a single ASIC chip. Most of the transmission technology is implemented on software-defined platforms, thus allowing most changes to be made in software code rather than hardware. By mid-October 2008, a plan was in place for a mobile DTV demo that included nine television program streams, two audio-only streams, a data service and a complete electronic program guide service. The mobile DTV service was to be broadcast by two Las Vegas UHF DTV stations.

Receiver chip sets were ready by late October and were integrated into prototype receiving devices. By mid-November, all of the transmission equipment was ready for testing. The CES demonstration system was staged at the Harris facility in Mason, OH. Receiver engineers with prototype receivers and engineers from our ESG partner, Roundbox, converged on the facility to fine-tune and conduct system integration tests for the first implementation of the ATSC A153 Mobile DTV system.

CES 2009 marked the formal introduction of ATSC Mobile DTV. The OMVC conducted a press event and announced that more than 60 U.S. DTV stations committed to launch mobile DTV during 2009. There were a number of prototype receivers shown by LG, Kenwood, Delphi, Visteon and others.

What's next?

So, what's next on the road to mobile DTV? The ATSC, with support from the OMVC, is planning several tests for systems to gain more real-world knowledge of system performance. Distributed transmission technology for mobile DTV has yet to be tested outside of the laboratory. Many believe that distributed transmission systems will enable broadcasters to provide seamless mobile DTV coverage throughout their area of dominant influence. The purpose of the Candidate Standard period is to allow such testing and to verify that the proposed standard performs as anticipated. It is also a time when interested manufacturers can develop prototype products based on the standards documentation, while verifying that the documentation is both correct and sufficient to support product development.