Parallel maximum a posteriori detectors with forward and reverse viterbi operators having different convergence lengths on a sampled data sequence

Abstract

A soft decision value output detector includes a plurality of maximum a posteriori (MAP) detectors. The MAP detectors are configured to simultaneously generate state metrics for portions of a sampled data sequence, and to generate soft decision values based on the generated state metrics. Each of the MAP detectors includes a first MAP unit that generates state metrics by a reverse iteration using first and second reverse Viterbi operators and a forward iteration using a first forward Viterbi operator through portions of the sampled data sequence, and a second MAP unit that generates state metrics by a reverse iteration using third and fourth reverse Viterbi operators and a forward iteration using a second forward Viterbi operator through portions of the sampled data sequence. The first forward Viterbi operator has a different convergence length than the first and second reverse Viterbi operators, and the second forward Viterbi operator has a different convergence length than the third and fourth reverse Viterbi operators. The first and second forward Viterbi operators may have twice the convergence length of first through fourth reverse Viterbi operators.