A novel fast soft-decision decoding algorithm

called variable-threshold Chase algorithm (VTC)

is described.The set of test patterns is first produced by using A

*

algorithm

then is partitioned into the equivalence classes.During the partition

the equivalence class representatives can be generated.A variable threshold is derived for optimality test on a candidate codeword.With set partition and optimality test

a fast soft-decision decoding algorithm is obtained.Simulation results show the advantage of the proposed algorithm over soft-decision decoding algorithms available is much faster decoding speed without loss of decoding performance.