Error correction schemes for digital television broadcasting

All digital television broadcast schemes require some form of forward error correction. Trellis coded modulation and Reed-Solomon (RS) codes are two of the most commonly used error correction strategies. While RS codes have been used for a fairly long time in various applications and are well understood, use of trellis coded modulation has been restricted mostly to telephone modems. We explain the principles of trellis coded modulation and how trellis codes can be chosen as part of the error correction strategy for digital television broadcasting. A variety of coding and interleaving schemes that can be used to obtain the desired performance for compressed TV signal transmission is discussed. The nature of the terrestrial channel and the system performance requirements for a high definition television (HDTV) system are described, including a coding strategy called concatenated coding