Viterbi decoder

A Viterbi decoder, comprising:

• a branch metric operation section for calculating branch metrics based on input codes;
• an add-compare-select (ACS) operation section for calculating path metrics of respective states by time-sharing processing based on the branch metrics calculated by the branch metric operation section;
• a path metric permutation section for temporarily delaying the path metrics sequentially calculated by and output from the ACS operation section and permutating the path metrics to have different time series from those of the path metrics output from the ACS operation section;
• and
• a path metric memory for storing path metrics output from the path metric permutation section,
• wherein the path metric permutation section temporarily delays time series of plural pairs of path metrics of upper order states nad path metrics of lower order states calculated by the ACS operation section and permutates the path metrics to obtain time series of plural pairs of path metrics of continuous even number states and path metrics of continuous odd number states.

A Viterbi decoder, comprising:

• a branch metric operation section for calculating branch metrics based on input codes;
• an add-compare-select (ACS) operation section for calculating path metrics of respective states by time-sharing processing based on the branch metrics calculated by the branch metric operation section;
• a path metric permutation section for temporarily delaying the path metrics sequentially calculated by and output from the ACS operation section and permutating the path metrics to have different time series from those of the path metrics output from the ACS operation section;
• and
• a path metric memory for storing path metrics output from the path metric permutation section,
• wherein using the path metric permutation section for temporarily delaying time series of plural pairs of path metrics of upper order states and path metrics of lower order states calculated by the ACS operation section and permutating the path metrics to obtain time series of plural pairs of path metrics of continuous even number states and path metrics of continuous odd number states, four path metrics are updated by two-time readouts and two-time writings with respect to the path metric memory alone.

A Viterbi decoder, comprising:

• a branch metric operation section for calculating branch metrics based on input codes;
• an add-compare-select (ACS) operation section for calculating path metrics of respective states by time-sharing processing based on the branch metrics calculated by the branch metric operation section;
• a path metric permutation section for temporarily delaying the path metrics sequentially calculated by and output from the ACS operation section and permutating the path metrics to have different time series from those of the path metrics output from the ACS operation section;
• a path metric memory for storing path metrics output from the path metric permutation section;
• a path selection signal memory;
• a trace-back operation section,
• wherein the ACS operation section also selects a maximum likelihood path in combination with a path metric at a preceding time point and generates a path selection signal as information of the maximum likelihood path thus selected (a surviving path),
• the path selection signal memory stores the path selection signal,
• the trace-back operation section searches past state transition using a past path selection signal read out from the path selection signal memory and outputs decoded data, and
• the trace-back operation section includes:
• a Viterbi state memory for storing a Viterbi state following the surviving path based on the path selection signal obtained from the path selection signal memory;
• a Viterbi state prediction section for predicting a part of a Viterbi state to be updated next based on contents of the Viterbi state memory;
• and
• a path selection signal memory address calculation section for calculating an address of the path selection signal memory storing the path selection signal based on the part of the Viterbi state predicted by the Viterbi state prediction section.