Patent ID: 6510538
Filing Date: 2003-01-21
Classification: H03M

Abstract:
A method of decoding data which has been convolution encoded,the data consisting of consecutive groups of bits, each group (Gt) comprising n bits whose values depend on the particular state change (St) of the data encoder which occurs at a particular time (t), the particular state change (St) being one of a set of possible state changes (Sj) which the data encoder could have undergone at that particular time (t), the method of decoding data comprising, for the group (Gt) of n bits received at the particular time (t): a) making comparisons between the n bits of the group (Gt) and each possible permutation (Pi) of n bits, and for each comparison, calculating a numerical value for the error metric (Mti) between the group (Gt) and the permutation (Pi); and b) consulting a pre-calculated look-up table (Tt) which contains the set of possible state changes (Sj), and which indicates for each of these state changes (Sj) a particular one of the said permutations (Pi) associated with that state change (Sj), and assigning to each state change (Sj) in the look-up table (Tt) the metric (Mti) calculated in step a) for the permutation (Pi) associated with that state change (Sj); and c) using the metric values assigned to the set of possible state changes (Sj) to update the cumulative metric used to decode the convolution encoded data.