A Viterbi equalizer for equalization of a data signal transmitted via a channel that is subject to interference has at least one add-compare-select unit (ACS), which carries out an ACS operation for each channel state in a time step k. Furthermore, the equalizer has a unit for calculating metric increments in advance and for storing the metric increments. The calculation unit calculates in advance the metric increments relating to all the transitions from a state which can be predetermined in the time step k to the states which can be reached by the transitions in the time step k+1. The metric increments are retained in an output memory such that they can be called up for utilization in the ACS unit.