Iterative Decoding vs. Viterbi Decoding: A Comarison

Abstract- Decoding algorithms employed in wireless
communication use either hard decision decoding or soft decision
decoding. Quantization is use in soft decision e.g. in Viterbi
decoding. Similarly in iterative decoders (Turbo Codes) either
serially concatenated or parallely concatenated decoders with
interleavers use soft-input soft-output (SISO) and additive loglikelihood
version (L-SISO) algorithms, to compute a posteriori
probability (APP). Even though soft decision is more powerful
than hard decision decoders, many systems can not use soft
decision algorithms, e.g. in GSM. In GSM channel decoding is
used after de-interleaving. So, if one were to use iterative
decoding, one is constrained to hard decision decoders. We
propose the uses of soft decision iterative decoders (Turbo codes)
in place of hard decision data (i.e. data in binary format). We
compare the performance of hard decision Viterbi decoding with
iterative decoders.