Patent ID: 6452979
Filing Date: 2002-09-17
Classification: H03M

Abstract:
A method of decoding a received convolutionally coded sequence of signals represented by a trellis of a total block length N, where N is an integer, comprising the steps of:decoding a portion of the trellis using forward recursion, the portion being shorter than the block length N and including a window of length L, L being an integer, and a learning interval, the forward recursion to define a set of forward recursion state metrics for the portion decoded; decoding the portion of the trellis using backward recursion, the backward recursion using only a single optimal state Smax at end of the portion for the backward recursion, where Smax lies with high probability along the optimal-path, state Smax determined from the forward recursion, the backward recursion starting from the single state and moving to the beginning of the window to define a set of backward recursion state metrics within the window; and calculating soft outputs for the window sections using the forward recursion state metrics, the backward recursion state metrics, and branch metrics, and outputting the soft output at each section of the trellis within the window.