A low complexity soft-output Viterbi decoder architecture

A means to adapt the classical architecture of a Viterbi decoder to make it able to provide soft (weighted) decisions is presented. After a theoretical justification of the proposed method, based on Battail or Hagenauer-Hoeher algorithms, the new architecture is detailed. It leads to a real-time circuit, the size of which is roughly twice the size of the classical Viterbi decoder. In order to appreciate the quality of the weighting method, an application to the decoding of concatenated convolutional codes, with the proposed soft-output decoder as the inner decoder, is examined