A hierarchical QAM system allows the transmission of different sources by embedding the relative constellation points. At the transmitter the constellations generated by the different sources are remapped by a grey coder and then combined. At the receiver, the different source data are decoded by using...http://www.google.com.hk/patents/US7079585?utm_source=gb-gplus-share專利 US7079585 - Gray encoding for hierarchical QAM transmission systems
