REDUCED-TREE-BASED SOFT DECODING FOR BLOCK-CODED MODULATION

It is shown that soft maximum-likelihood decoding for block-coded modu lation (BCM) can be performed using the code tree. It is easy to gener ate the code tree for any type of block code, linear as well as nonlin ear. A reduce tree is obtained from the code tree. The trellis for a b lock code can be obtained from the reduced tree. Using this structure to perform computations in parallel, a scheme is proposed for the impl ementation of the soft decoder. Back tracking, necessary in a soft dec oder using the Viterbi algorithm on a trellis, is eliminated.