Symbol Reliability Estimation Using the Bidirectional Viterbi Decoding Algorithm

Abstract

In this paper, we first review the Soft-BIVA based on the bidirectional Viterbi algorithm (BIVA). Next, we apply the Soft-BIVA to QLI codes under the assumption that a Scarce State Transition Viterbi decoder is used. Then the symbol reliability values are derived by applying the Soft-BIVA to the main decoder. Moreover, it is shown that in the case of QLI codes, the symbol reliability is also obtained using bidirectional syndrome decoding in the syndrome trellis.