US Patent 7558343 Tap-selectable viterbi equalizer

A tap-selectable Viterbi equalizer comprises means for determining at least one symbol from a previous determination assigned to a first state, means for determining a second state of the plurality of states and determining a surviving path metric by comparing path metrics originating from the determined symbol, means for determining the value of a previous symbol with respect to the symbol of the surviving state, and calculating means for generating a reduced trellis by calculating only path metrics for states in which the previous symbol has the determined value.