Comprehensive comparison of turbo-code decoders

The decoding of turbo-codes (a novel class of binary parallel concatenated recursive systematic convolutional codes) relies on the application of soft input/soft output decoders. Such decoders can be realized either using maximum-a-posteriori (MAP) symbol estimators or MAP sequence estimators, e.g. the a-priori soft output Viterbi algorithm (APRI-SOVA). The structure of turbo-codes encoders as well as decoders is described. In particular, four different decoder structures suitable for decoding turbo-codes are illustratively described and their error rate performance capabilites compared in both AWGN as well as flat Rayleigh fading channels based on extensive simulation results.