FAST CONVERGENCE LDPC DECODING USING BCJR ALGORITHM AT THE CHECK NODES

摘要

Method of decoding LDPC codes such as IRA codes used in the DVB-S2 standard, the code graph comprising first variable nodes (systematic), second variable nodes (parity) having a degree two, and check nodes connected to second variable nodes by a zigzag connectivity, the method comprising a) grouping the check nodes into at least one group, the check nodes of each group being connected by variable nodes called internal variable nodes, b) performing for each group (GRj) the following sub-steps b1) and b2): b1) jointly updating (71) all the check nodes of said group by using an algorithm of the Maximum-A-Posteriori (MAP) type on a two-state trellis, b2) updating (72, 73) all the first variable nodes and all the second variable nodes (PNi-1,i; PNi,i+1) connected to said group except said at least one internal second variable node, c) iteratively repeating step b). When using a plurality of groups, a corresponding plurality of trellis windows are LogMAP decoded without training period since connecting parity nodes are updated according to the sum-product algorithm.