A class of methods for soft-decision decoding of linear blockcodes, referred to as reconfigurable trellis (RT) decoding, ispresented. In RT decoding a reduced trellis (or tree) search isfacilitated by carrying out the search on a reconfigured trellis (ortree) that corresponds to an equivalent code. The equivalent code isformed by reordering the received symbols according to theirreliabilities. Consequently, the trellis reconfiguration is determined`on-the-fly', but only a small portion of the trellis needs to beconstructed, as guided by the reduced search. The search efficiencyimproves for channels where the soft-decisions provide a good indicationof which symbols are in error. For example, using the M algorithm on anerasure channel, only a single survivor (i.e. M=1) is sufficient toattain maximum-likelihood decoding of maximum-distance codes. For moretypical channels, we present simulation results and a detailedassessment of the number of metric and binary-vector operations for theM algorithm
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