Generalized viterbi decoding algorithms
AssigneeAT&T Bell Laboratories
InventorsNambirajan Seshardi, Carl-Erik W. Sundberg
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Abstract
A data transmission system and method for processing speech, image and other data disclosed which embodies parallel- and serial-generalized Viterbi decoding algorithms (GVA) that produce a rank ordered list of the L best candidates after a trellis search. Error detection is performed by identifying unreliable sequences through comparison of the likelihood metrics of the two or more most likely sequences. Unreliable sequences are re-estimated using inter-frame redundancy or retransmission.
Claims23
A method of processing a coded information sequence received from a transmitter comprising,
- determining the value for a metric indicative of the relative quality for each of the L (>1) best candidates to be selected as the sequence actually transmitted,
- wherein said candidates each correspond to paths through a trellis structure having a plurality of stages and a plurality of states at each stage,
- wherein each path entering each state at each stage has a partial metric associated with it,
- wherein said determining comprises finding the L paths through said trellis which have the highest sum of partial metrics,
- said determining further comprises recognizing at each stage of the trellis the L paths entering each state that have the highest cumulative metric at that stage, and
- retaining such recognized paths as partial paths leading to the L paths through the trellis having the largest sum of partial metrics.
A method of processing received coded information sequences from a transmitter which received sequences correspond to respective paths through a trellis structure having a plurality of stages and a plurality of states at each stage comprising
- determining the value for a metric indicative of the relative quality for the best candidate to be selected as the sequence actually transmitted, and
- on L-1 subsequent evaluations of said metric for paths traversing the complete trellis associated with said sequences received from said transmitter, determining the metric value for the L-1 next best candidates,
- said subsequent evaluations comprising evaluating metrics for partial paths that remerge for the first time at a stage j of said trellis with the path for the best candidate after having diverged from said path for the best candidate, and retaining the partial paths having the best metric at stage j and discarding all others, and
- at the final stage selecting the path with the second best metric.
Dependencies are inferred from the claim text.