Unequal Error Protection Using Maximum A-Posteriori Probability (MAP) Algorithm, Soft Output Viterbi (SOVA) Algorithm and Modified SOVA

Turbo decoder uses any one of the decoding algorithm of maximum a-posteriori probability algorithm (MAP) or Soft Output Viterbi Algorithm (SOVA). The traditional turbo code system use equal error protection (EEP). In many applications all the information don´t need equal importance. So we need a new method unequal error protection (UEP). By doing so the important message is more protected than the other message bits. In this paper BER performance of UEP in fading channel is analyzed. BER performance substantially improved for the important class messages in UEP. In MAP the important class of message gained 0.4 dB over EEP. In SOVA and modified SOVA the important class of message gained 0.6 dB and 0.8 dB over EEP respectively. Modified SOVA produces a gain of 0.4 dB compared to MAP.