Analysis and Design of Binary Message-Passing Decoders

IEEE Transactions on Communications (Impact Factor: 1.99). 04/2010; 60(3). DOI: 10.1109/TCOMM.2011.122111.100212
Source: arXiv


Binary message-passing decoders for low-density parity-check (LDPC) codes are studied by using extrinsic information transfer (EXIT) charts. The channel delivers hard or soft decisions and the variable node decoder performs all computations in the L-value domain. A hard decision channel results in the well-know Gallager B algorithm, and increasing the output alphabet from hard decisions to two bits yields a gain of more than 1.0 dB in the required signal to noise ratio when using optimized codes. The code optimization requires adapting the mixing property of EXIT functions to the case of binary message-passing decoders. Finally, it is shown that errors on cycles consisting only of degree two and three variable nodes cannot be corrected and a necessary and sufficient condition for the existence of a cycle-free subgraph is derived. Comment: 8 pages, 6 figures, submitted to the IEEE Transactions on Communications

Download full-text


Available from: Troels Pedersen,
  • Conference Paper: Absorbing sets and cycles
    [Show abstract] [Hide abstract]
    ABSTRACT: Absorbing sets have been identified as structures in the graph of a low-density parity-check code that cause error floors - in particular in combination with binary message passing decoding algorithms. In this paper it is shown that absorbing sets involving only variable nodes up to degree 3 are equivalent to cycles and a sufficient and necessary condition on the degree distribution to avoid these absorbing sets is derived. The results are extended to irregular graphs and simulation results demonstrate the improvement in the error floor region.
    Turbo Codes and Iterative Information Processing (ISTC), 2012 7th International Symposium on; 01/2012
  • [Show abstract] [Hide abstract]
    ABSTRACT: Binary message-passing (BMP) decoders for root-low-density parity-check (LDPC) codes over block fading channels (BFC) are studied using density evolution (DE) and outage boundary analysis. A-priori channel estimation techniques suitable for root-LDPC code are proposed based on DE. The results show that BMP decoders can achieve full diversity performance if soft decisions from the channel are available.