Use of the list Viterbi algorithm to compute the distance spectrum of trellis codes and ISI channels

We propose to compute the distance spectrum of arbitrary trellis codes (including convolutional codes, trellis-coded modulation, continuous phase modulation, etc.) and intersymbol-interference (ISI) channels by means of a modified list Viterbi algorithm (LVA). This search procedure is (i) computationally efficient, (ii) is applicable to linear as well as nonlinear codes, (iii) can be applied to arbitrary distance measures, (iv) can be used for MLSE as well as RSSE or related techniques, and (v) guarantees that an ordered list of the N nearest error paths is produced. A sample results illustrates the distance spectra of linear ISI channels, both for MLSE and ideal RSSE receivers.