New Bit Mapping for Hierarchically Modulated DAB and Terrestrial DMB

Hierarchical modulation is considered for increased data rate in the next-generation DAB (digital audio broadcasting) or T-DMB (Terrestrial digital multimedia broadcasting) system, which supports backward compatibility to the conventional DAB or T-DMB. Since dedicated pilot signal is not available due to the constraint of backward compatibility, decision-directed channel estimation schemes should be employed at the receiver. In this paper, we propose a new bit mapping scheme for hierarchical modulation which guarantees robust channel estimation against decision errors.