Patent ID: 7213194
Filing Date: 2007-05-01
Classification: H03M

Abstract:
1. A method of decoding a convolutionally encoded codeword by means of a window sliding over the codeword, which method comprises computation of path metrics simultaneously forwards and backwards in the sliding window, the method further comprising the steps of a) using a four-part sliding window comprising four successive parts; b) computing path metrics in the forward direction in the first part of the four successive parts of the sliding window and storing path metrics in a four-part memory; c) computing path metrics in the backward direction in two other parts of the sliding window in such a way that an input for a computation unit comes from the four-part memory; d) taking the computed metrics to a synthesis unit and computing a decoding result; e) moving the sliding window one part forwards; and f) repeating the preceding steps a) to e); wherein a part of the four-part memory is identified by the mathematical expression “(k div L)”, wherein a location within the four-part memory is identified by the mathematical expression “(k modulo L)”, and the computation unit computes path metrics in the forward direction at each particular time k and stores the path metrics into a memory location (k modulo L) of the memory part (k div L) modulo 4, L being the length of the quarter of the sliding window.