Two-step trellis decoding of partial unit memory convolutional codes

We present a new soft-decision decoding method for high-rate convolutional codes. The decoding method is especially well-suited for PUM convolutional codes. The method exploits the linearity of the parallel transitions in the trellis associated with PUM codes. We provide bounds on the number of operations per decoded bit, and show that this number is dependent on the weight hierarchy of the linear block code associated with the parallel transitions. The complexity of the new decoding method for PUM codes is compared to the complexity of Viterbi decoding of comparable punctured convolutional codes. Examples from a special class of PUM codes show that the new decoding method compares favorably to Viterbi decoding of punctured codes.