Basic Parameters of the Specification for the Digital Terrestrial TV Transmission

In the following section, the basic parameters of the specification for the coding and modulation for the terrestrial channel are represented. The first parts of the channel coding, the energy dispersal, the outer and inner coders and the outer interleaver have been adopted from the satellite standard. For the inner interleaver and all parameters associated with the OFDM modulation, the 8K/2K QAM specification [4.7] was available at the end of 1995. It is the result of combining two draft specifications 8K/QAM [4.1, 4.2] and 2K/DAPSK [4.4]. The two drafts differ in the following basic parameters:In 8K/QAM with an FFT length of 8K, the number of carriers is 6785. The active symbol period T_U = 896 μs results in guard intervals △_l = 1/4 T_U, △₂ = 1/8 T_U and △₃ = 1/32 T_U. The carrier modulation defined is QPSK,16 QAM and 64 QAM as well as 16 MR (Multi-Resolution) and 64 MR QAM for hierarchical coding/modulation. The OFDM frame contains 96 symbols including the zero symbol, the CAZAC/M (Constant Amplitude Zero Auto Correlation with M sequences) symbol and the TPS (Transmission Parameter Signalling) symbol. In addition, continual and boosted pilots are inserted.