CODED MODULATION FOR SATELLITE BROADCASTING BASED ON UNCONVENTIONAL PARTITIONINGS

Unequal error protection (UEP) is a very promising coding technique fo r satellite broadcasting, as it gradually reduces the transmission rat e. From the viewpoint of bandwidth efficiency, UEP should be achieved in the context of multilevel coded modulation. However, the convention al mapping between encoded bits and modulation signals, usually realiz ed for multilevel block modulation codes and multistage decoding, is n ot very compatible with UEP coding because of the large number of resu lting nearest neighbor codewords. In this paper, new coded modulation schemes for UEP based on unconventional partitioning are proposed. A l inear operation referred to as interlevel combination is introduced. T his operation generalizes previous partitioning proposed for UEP appli cations and provides additional flexibility with respect to UEP capabi lities. The error performance of the proposed codes are evaluated both by computer simulations and a theoretical analysis. The obtained resu lts show that the proposed codes achieve good tradeoff between the pro portion and the error performance of each error protection level.