Browsing by Author "Chang, Chi-Yuan"

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New Group Shuffled BP Decoding Algorithms for LDPC Codes
(2009)
Chang, Chi-Yuan
;
Chen, Yu-Liang
;
Lee, Chang-Ming
;
Su, Yu T.
;
電信工程研究所
Implementing a belief propagation (BP) based LDPC decoder requires high degrees of parallelism using many component soft-in soft-output (SISO) decoding units to perform message passing from variable nodes to check nodes or vice versa. An obvious complexity-reduction solution is to serialize the decoding process, i.e., dividing a decoding iteration into several serial sub-iterations in which a sub-iteration performs only part of the complete parallel message-passing operation. The group horizontal shuffled BP (GHSBP) and vertical shuffled BP (GVSBP) algorithms respectively partition the check and variable nodes of the code graph into groups to perform group-by-group message-passing decoding. This paper proposes new techniques to improve three key elements of a GHSBP decoding algorithm, namely, the grouping method, the decoding schedule and the log-likelihood updating formulae. The (check nodes) grouping method and decoding schedule optimize certain design criterion. The new normalized min-sum updating formula with a self-adjustable correction (scaling) factor offers better nonlinear approximation. Numerical performance of new GHSBP algorithms that include part or all three new techniques indicate that the combination of the proposed grouping and decoding schedule yields a faster convergence rate and our modified min-sum algorithm gives performance superior to that of the conventional min-sum and normalized min-sum algorithm and is very close to that of the sum-product algorithm.
Product codes and parallel concatenated product codes
(2007)
Huang, Tina D. -H.
;
Chang, Chi-Yuan
;
Zheng, Yan-Xiu
;
Su, Yu T.
;
電信工程研究所
We study the decoding of product codes and a class of parallel concatenated product codes (PCP/). PCPC improves the minimum distance while retaining the merit of low decoding complexity of turbo product codes (TPC). We prove that using the Fibonacci interleaver does help increasing the minimum distance. The regularity of the interleaver also reduces the implementation complexity and makes parallel interleaving feasible. We show that Pyndiah's algorithm for decoding product codes produce an annealing effect similar to that of the so-called annealed belief propagation (ABP) algorithms which adjusts the "temperature" of an augmented cost surface. Decoding methods based on modified Pyndiah and annealed BCJR algorithms for both PC and PCPC are proposed and their performance is compared.