Shuffled LDPC decoding

A method of iteratively decoding an LDPC code on a Galois Field where the code is represented by a predetermined M×N parity check matrix H comprising a plurality of sub-matrices where each sub-matrix is either a zero-matrix or a matrix with a same number of non-zero elements in each row and column;

• the LDPC decoding method being based on a Log-Likelihood Ratio Belief-Propagation algorithm, hereinafter referred to a LLR-BP algorithm, representing passing symbol messages λnm from a respective symbol-node n (0<=n<N) to a connected check-node m (0<=m<M) and passing check node messages Λmn from a respective check-node m to a connected symbol-node n;
• connections between symbol nodes and check nodes being defined by the parity check matrix H;
• the LDPC decoding method comprising:
• storing, for each symbol node, a representation of a respective symbol value of a corresponding symbol of the LDPC code in a first memory;
• storing a representation of the respective check node messages Λmn in a second memory;
• performing a first computation including computing, for a next iteration, symbol messages λnm from the representation of a corresponding symbol value stored in the first memory and check node messages from a previous iteration;
• performing a shuffling operation by receiving symbol messages produced by the first computation arranged in a first sequence and supplying the symbol message in a different sequence in dependence on a position of the non-zero elements in a corresponding sub-matrix;
• performing a second computation including computing, in accordance with the LLR-BP algorithm, check node messages and storing a representation of the computed check node messages in the second memory;
• the computation being in dependence on symbol messages received from the shuffler by the respective check node;
• and
• updating the representation of the symbol values in the first memory in dependence on output of the first and second computation.