Patent ID: 7000167
Filing Date: 2006-02-14
Classification: H03M

Abstract:
1. A method for decoding Low Density Parity Check (LDPC) codes in a receiver for recovering information from received signals, the method comprising: executing in a decoder of said receiver a sum product algorithm to recover a set of information bits from an LDPC code represented as a bipartite graph of symbol nodes and check nodes, the sum product algorithm being responsive to input log likelihood ratios associated with the symbol nodes; generating a set of forward difference metrics and a set of backward difference metrics in dependence on ratios of logarithmic probabilities each associated with a corresponding symbol node of the LDPC code, updating each metric in the set of forward difference metrics in dependence on an absolute value of the log likelihood ratio associated with the symbol node and the absolute value of a previous metric in the set, updating each metric in the set of backward difference metrics in dependence on the absolute value of the log likelihood ratio associated with the symbol node and the absolute value of the previous metric in the set, and generating log likelihood ratios to be propagated back to each symbol node in dependence on the updated sets of forward and backward difference metrics.