Patent ID: 7062701

Claim:
A method for storing path metrics in a Viterbi decoder, the path metrics being determined using a trellis diagram which is allocated to the Viterbi decoder and in which, in each case, two destination states of a specific time step (t+1) form, with two starting states of a preceding time step (t), a butterfly structure by means of which the corresponding two destination states of the specific time step (t+1) are connected to the two starting states of the preceding time step (t) by means of a respective state transition branch, for each time step (t+1), the path metric (γ t+1 ) of each destination state being determined as a function of the path metrics (γ t ) of those starting states of the preceding time step (t) that form a butterfly structure with the respective destination state, for this purpose the path metrics (γ t ) of the corresponding two starting states being read from memory means, the path metric (γ t+1 ) of the respective destination state of the time step (t+1) being determined as a function thereof and the path metric (γ t+1 ) of the respective destination state being stored in the memory means, characterized in that the butterfly structures of the trellis diagram of each time step (t) are combined at least in pairs in such a way that for each butterfly structure pair of a time step (t), the destination states of the two butterfly structures in the trellis diagram at the same time form starting states for two butterfly structures of the subsequent time step (t+1), and characterized in that after the determination of the path metrics of the destination states of the two butterfly structures of a butterfly structure pair, in each case the path metrics of those two destination states of this butterfly structure pair, which at the same time form starting states of a butterfly structure of a subsequent time step (t+1), are stored in the memory means in the form of a common memory word.