APPARATUS AND METHOD FOR CALCULATING PATH METRIC DIFFERENCES IN A MAXIMUM LIKELIHOOD DETECTOR OR DECODER

摘要

A calculating apparatus for use in a maximum likelihood detector, the calculating apparatus comprising: receiving means for receiving convolution encoded data which may include added noise; first calculating means for calculating a first component of a first path metric difference between two possible sequences of states corresponding to said convolution encoded data, the two sequences each having a length equal to a constraint length of the convolution encoded data, and the two sequences starting at a same state and ending at a same state, adapted to calculate said first component using said convolution-encoded data and using convolution encoding parameters of said convolution-encoded data, wherein the first component is independent of the two sequences; and second calculating means for calculating a second component of said first path metric difference using said two sequences, wherein the second component is independent of said convolution encoded data; and adding or substracting the first and second components to obtain said first path metric difference. Hence, the amount of processing in high-speed implementations of radix-2n Viterbi detectors or decoders is reduced.