VITERBI DECODER

摘要

PURPOSE: A viterbi decoder is provided to speed up the modem by using a CSA and a 5-bit incrementer for adding a present BM value and a past accumulated PM value. CONSTITUTION: A branch metric units(BM) are constituted with 3-bit CSA. A path metric memory units(PMM) stores a hamming distance value accumulated up to the present state for ACS operations for next states. An adder compare select units(ACS) is constituted with a comparator having a CSA and a 5-bit incrementer for adding an output of the units(BM) and a previously accumulated PM value stored in the units(PMM) and uses a metric rescaling mode for the least PM in each node. A trace back units(TBM) decodes path information in a radix-4 mode.