VITERBI DECODING METHOD, VITERBI DECODER, SIGNAL PROCESSING INTEGRATED CIRCUIT, DATA REPRODUCING DEVICE, MAGNETIC DISK DEVICE, AND INFORMATION PROCESSING SYSTEM

摘要

PROBLEM TO BE SOLVED: To simplify ACS operation by omitting comparison operation for state transition where likelihood is apparently reduced and surviving path selection operation. ;SOLUTION: Comparison operation and surviving path selection operation are not performed for branches where the value of a branch metric B is apparently increased by an input (y) (likelihood is reduced) out of the branches entering each state S in a trellis diagram. For example, in the case of a state 0000 at a time (t), when the expected values of the two branches transited to a state 1000 at a time (t-1) are -2 and -3, and are y_t-20, since they are considerably different from an inputted equalization value, the state 1000 apparently exists on an erroneous path. Consequently, the state transition from the state 0000 to the state 0000 is made as a surviving path because the transition from the state 1000 to the state 0000 is an erroneous path in the state transition from the time t-1 to the time (t). Thus, operation is simplified. Then, the number of comparators is reduced to reduce the circuit scale.;COPYRIGHT: (C)1999,JPO