Patent ID: 6257756
Filing Date: 2001-07-10
Classification: H03M

Abstract:
A method for implementing Viterbi butterflies with the steps of adding, comparing, and selecting, characterized in that the step of comparing is anticipated before the steps of selecting and adding and that:in said step of comparing, a first path metric P (2i, j-1), a second path metric P (2i+1, j-1) and a branch metric+B (i, j) are related to a sign vector {SP, SB, S.DELTA.} and components SP, SB, S.DELTA. of said sign vector {SP, SB, S.DELTA.} are related to a binary decision vector {D (i, j), D (i+N/2, j)} having first component D (i, j) and second component D (i+N/2, j);in said step of selecting, a first intermediate path metric P (i, j) is selected from P (2i, j-1) and P (2i+1, j-1) according to D (i, j), a second intermediate path metric P (i+N/2, j) is selected from P (2i, j-1) and P (2i+1, j-1) according to D (i+N/2, j), a first intermediate branch metric B1 (i, j) is selected from +B (i, j) and an inversion-B (i, j) of +B (i, j), and a second intermediate branch metric B2 (i, j) is selected from +B (i, j) and -B (i, j);in said step of adding, P (i, j) and B1 (i, j) are added to third path metric P (i, j)=P (i, j) +B1 (i, j), and P (i+N/2, j) and B2 (i, j) are added to fourth path metric P (i+N/2, j)=P (i+N/2, j) +B2 (i, j).