What is A-VSB?

The basic technology for ATSC mobile TV was invented by Samsung in 2003. Samsung and Rohde & Schwarz have been developing A-VSB as an open standard in the Advanced TV Systems Committee (ATSC) since

December 2005.During the past two years, A-VSB has been demonstrated publicly at the NAB (National Association of Broadcasters) Show and at CES (Consumer Electronics Show). Feasibility was proven for the first time at NAB 2006, live real time broadcasting to a handheld device was shown at CES 2007, and a distributed Single Frequency Network for mobile TV was demonstrated at NAB 2007.

In July 2007, Samsung Electronics and Rohde & Schwarz proposed A-VSB for an ATSC Mobile/Handheld standard targeted to be completed by February 2009, in time for U.S. transition to all-digital broadcasting.

In 2008, the A-VSB Initiative team members—world leaders in their respective market spaces—have come together to catalyze the commercial success of ATSC Mobile broadcasting by conducting live consumer trials of the complete A-VSB and OMA BCAST end-to-end solution.

How does it work?

The A-VSB physical layer system has three main parts which broadcasters can use to enable new services:

Reference Sequence: Broadcasters can add a Supplementary Reference Sequence (SRS) to the transmitted signal so A-VSB receivers can remain “locked in” to the transmission. This helps maintain reception even with rapidly changing multi-path interference, such as when the receiver is moving. Meanwhile, legacy ATSC receivers ignore the added information, maintaining backward compatibility.

 

Turbo Streams: A-VSB enables broadcast signals to include multiple Turbo streams with additional error correction and time diversity encoding for reception at vehicle speeds and for enhanced receivability when signal strength is week relative to noise. As with the SRS, the Turbo coded data is ignored by legacy receivers, ensuring backward compatibility.

 

 

Single Frequency Network (SFN): A-VSB includes a deterministic data frame, new to the ATSC system, which eases synchronization of transmission towers in an SFN. Use of multiple towers can improve coverage with higher uniform signal strength throughout a service area, even in locations that would normally be shielded by obstacles such as hills or buildings. For consumer acceptance of mobile services, avoiding “dead spots” in coverage is highly desirable.