Recursive calculation circuit for path metric values in Viterbi decoder, has two's complement arithmetic circuit for performing compare operations

摘要

A branch metric unit (BMU) circuit calculates branch metric values, which are normalized so that one of the branch metric values is set to zero. An add-compare-select unit (ACSU) updates the path metric values using ACS operations and the calculated branch metric values. At least the part of the circuit (ACSU) that performs ACS operates using the branch metric value normalized to zero has a two's complement arithmetic circuit (21,23) for compare operations. An Independent claim is included for a method of recursively calculating path metric values.