Patent ID: 7353450

Claim:
A method of processing encoded data comprising one or more blocks of samples the method comprising the steps of: (a) receiving the encoded data; (b) retrieving a first block of samples from the encoded data and a corresponding set of forward probabilities, wherein the block of samples correspond to states of a merged trellis, wherein the merged trellis provides combined probabilities of transition from one or more states at k−N, N an integer greater than 1, to current states at time k as the set of forward probabilities; and (c) updating the set of forward probabilities of the merged trellis for the current state at time k, based on the block of samples and the corresponding set of forward probabilities; wherein updating the forward probability for a state in step (c) comprises the step of selecting the maximum combined probability for transitions to the current state, given by: A j k =max* i=0, 1, . . . , 7 ( A i k−3 +{tilde over (Γ)} i,j k ) for j=0, 1, . . . , M− 1 where {tilde over (Γ)} i,j k is the combined probability obtained by adding N individual branch metrics from time k−N to time k in an original trellis, and M is the number of states; (d) using the maximum combined probability A j k to calculate one or more log-likelihood values in a maximum a posteriori (MAP) processor for one or more blocks of samples corresponding to the data; and (e) detecting or decoding the encoded data using the one or more log-likelihood values.