| 摘要 |
This invention generally relates to methods, apparatus and computer program code for decoding signals, and more particularly to trellis-based decoding using a variant of a BCJR procedure. A trellis decoder for decoding symbols of a received signal, said symbol comprising a sequence defined by transitions between states of a trellis, the trellis decoder comprising: means for performing a forward recursion through said trellis to determine a first set of probabilities (alpha(X<SUB>t</SUB>)) each defining a probability of a said trellis state (X<SUB>t</SUB>) responsive to one or more current or earlier received signal values (y<SUB>1:t</SUB>); means for providing a second set of (beta(X<SUB>t</SUB>)) probabilities each defining a probability of one or more received signal values (Y<SUB>t+1:T</SUB>) given an earlier said trellis state (X<SUB>t</SUB>); means to decode said received signal to determine probabilities (p(b<SUB>t</SUB>|y<SUB>1:T</SUB>)) for symbols of a corresponding transmitted sequence of symbols from said first and second sets of probabilities; and wherein said decoder further comprises: means to select states for determining said first set of probabilities responsive to one or more received signal values later than a said trellis state defining a probability in said first set.
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