Yannick Saouter Claude Berrou Fast soft-output Viterbi decoding for duo-binary turbo codes. 885-888 2002 ISCAS (1) http://doi.ieeecomputersociety.org/10.1109/ISCAS.2002.1009983 db/conf/iscas/iscas2002-1.html#SaouterB02