A hierarchical digital HDTV transmission scheme for terrestrial broadcasting

The future terrestrial television broadcasting system should support the transmission of a digital HDTV signal with a high spectral efficiency. In addition this system should maintain the graceful degradation as the actual analog systems, and should be compatible with the standard definition-TV (SDTV). The system compatibility can be achieved by using a hierarchical HDTV source-coding scheme that can provide at least two (HDTV, SDTV) or three (HDTV, EDTV, SDTV) hierarchy levels: SDTV image quality will be expected for portable receivers, and HDTV/EDTV image quality will destinate to stationary receivers with roof-top antennas. Taking into account the receivers antenna gains and the different channel conditions, there will be a difference of 25-30 dB between the received powers of the stationary and the portable receivers! Therefore the design of a powerful and a suitable transmission scheme for the future broadcasting of the digital HDTV signal will be a technological challenge. A transmission scheme for broadcasting a hierarchical HDTV signal in an 8 MHz terrestrial channel for stationary and portable receivers, is proposed. The system is based on a concatenated coding scheme, where the inner multilevel coding is combined with multiresolution modulation. The principle of OFDM is used to combat the multipath propagation. This combination will allow one to perform a coherent detection with a simple channel estimation algorithm, to use the available spectrum in an efficient way, to achieve high spectral efficiencies, to assume a graceful degradation, and to maintain the compatibility between the different receivers by providing different receiver complexities depending on the desired image quality