Low-power state-sequential viterbi decoder for CDMA digital cellular applications

摘要

A method, apparatus, and a program storage device useful in performing computations to decode a convolutionally coded sequence without resorting the use of switching elements is disclosed. The method comprises the steps of computing a first branch metric between a first input node and an output node, adding a first input path metric to the first branch metric to produce a first candidate output path metric, computing a second branch metric between a second input node and the output node, adding the second branch metric to a second path metric to derive a second candidate output path metric, and configuring a decision bit based upon the parity of the output state node state and upon whether the first candidate output path metric is greater than the second candidate output path metric. In one embodiment, a comparison between the first and the second candidate output path metrics is compared to the parity of the output node by an exclusive OR gate or a table lookup to determine the decision bit. The invention also is described by an apparatus comprising a means for performing these steps and a program storage device tangibly embodying instructions to perform the steps.