| Abstract: | Two alternative modulation schemes of 64-QAM (quadrature amplitude modulation) and 64-DAPSK (differential amplitude and phase shift keying) with a coherent and incoherent demodulation have been proposed for digital terrestrial video broadcasting (DTVB) in combination with the coded orthogonal frequency division multiplexing (COFDM) technique (Schafer 1995, and Engels and Rohling 1995). Additionally, a hierarchical transmission system based on a multi-resolution (MR) 64-QAM is described in Engels and Rohling which extends the service area of a TV programme in decoding a stepwise reduced data rate with increasing transmitter distance (graceful degradation). This procedure corresponds to a decreasing picture quality. In this paper MR concepts for the 64-DAPSK are developed. A performance comparison between the hierarchical transmission systems (MR-64-QAM/OFDM and MR-64-DAPSK/OFDM) is described for the uncoded and coded case |
