Concatenated coding scheme employing soft decision for outer codes-DSD (double soft decision) concatenated coding system

A novel concatenated coding scheme employing soft decision decoding for not only inner codes but also outer codes is proposed. In this scheme, likelihood information from an inner Viterbi decoder is used to decode outer codes. `Path memory final bits 1 to 0 ratio´ for likelihood information is proposed, and it it shown that this method is most reliable and requires simple hardware. It is clarified by computer simulation that the proposed DSD scheme improves that Pe to 1/3 of the conventional one by employing outer soft decision Viterbi decoding and outer soft decision Reed-Solomon codes. A soft decision coding gain of 0.5 dB is obtained by using the DSD scheme in various environments such as additive white Gaussian noise channels, co-channel interference channels, and Rician fading channels