Implementation of error decoders for A-VSB systems with additional use of transport stream information as forward error correction

In the last years several standards had been discussed in order to provide an opportunity for a robust reception of video streams in portable, handheld products. With regard to a backward compatible system, the advanced VSB (A-VSB) standard is presented. One feature of A-VSB is the increasing performance of forward error correction. The additional redundancy information is placed in the adaptation field of the transport stream, which is being ignored by a legacy receiver. Due to this complex transmission technology, the receiver should optimize the performance of its error decoders. The use of optimum decoding with soft-output Viterbi algorithm is essential and offers the possibility of exchanging the belief information between serial concatenated convolutional decoders. Furthermore, this implementation provides a way to adapt Viterbi distances of periodically appearing information in the transport stream which are predictable and can be used as additional forward error correction. This is what will also be described in this paper.