Soft-decision-based node synchronization for Viterbi decoders

Optimum decision methods are employed to discriminate between in-sync and out-of-sync operations in Viterbi decoders when the received data sequence is given in analog form (soft decisions). The exact solution to this discrimination problem, however, appears too complex in many practical cases. A suboptimum algorithm is then proposed that can be implemented as a hardware device, external to the decoder. This algorithm is recognized as a modified version of an earlier technique known as the “reencoding method”. Analysis and simulations indicate that the modification produces remarkably good results not only in comparison with the reencoding method but also with previous techniques discussed in literature