Turbo-codes and layered video for adaptive QoS and improved service in the DVB-S system

The MPEG-2 standard describes several options to split the video stream into sub-streams conveying information at different detail level. This fact can be exploited to generate a low quality stream with all that is necessary for a basic service, while all other sub-streams carry "detail" information to improve the quality of the reconstructed signal. In a mixed network environment, this can be exploited to allow the stream to be decoded by different terminals. Another use is to provide flexibility in tough transmission systems where either traffic or noise can give rise to severe impairments. Spatial scalability is used in a radio transmission system targeted at DVB-S (digital video broadcasting by satellite) to investigate the eventual gains. It is shown that, for a given target rate, differentiated coding can be exploited to achieve decodability and good quality at a channel SNR much lower than that of single layer streams