Tadashi Wadayama

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A novel class of bit-flipping (BF) algorithms for decoding low-density parity-check (LDPC) codes is presented. The proposed algorithms, which are called gradient descent bit flipping (GDBF) algorithms, can be regarded as simplified gradient descent algorithms. Based on gradient descent formulation, the proposed algorithms are naturally derived from a simple(More)
A set of linearly constrained permutation matrices are proposed for constructing a class of permutation codes. The main feature of this class of permutation codes, called linear programming (LP)-decodable permutation codes, is this LP decodability. It is demonstrated that the LP decoding performance of the proposed class of permutation codes is(More)
In this paper, an idea of the cutting plane method is employed to improve the fractional distance of a given binary parity check matrix. The fractional distance is the minimum weight (with respect to `1-distance) of vertices of the fundamental polytope. The cutting polytope is defined based on redundant rows of the parity check matrix and it plays a key(More)
An information theoretical analysis of nonadaptive group testing schemes based on <italic>sparse pooling graphs</italic> is presented. A pooling graph is a bipartite graph for which the adjacency matrix is a pooling matrix. The binary status of the objects to be tested are modeled by independent identically distributed. Bernoulli random variables with(More)
Linear codes for a coding problem of correlated sources are considered. It is proved that we can construct codes by using low-density parity-check (LDPC) matrices with maximum-likelihood (or typical set) decoding. As applications of the above coding problem, a construction of codes is presented for multiple-access channel with correlated additive noises and(More)
In this correspondence, the average coset weight distributions of Gallager's low-density parity-check (LDPC) code ensemble are investigated. Gallager's LDPC code ensemble consists of regular mtimesn-LDPC matrices with column weight j and row weight k. The average coset weight distribution can be derived by enumerating the number of parity-check matrices in(More)
In this paper, the minimum span of stopping sets of regular LDPC codes are defined and analyzed. The minimum span of an LDPC code is closely related to immunity to burst erasures when an LDPC code is decoded with belief propagation (BP) for erasure channels. The minimum span of stopping sets is the smallest span of a non-empty stopping set. If a single(More)
In the present paper, a novel decoding algorithm for low-density parity-check (LDPC) codes based on convex optimization is presented. The decoding algorithm, which is referred to hereinafter as interior point decoding, is designed for linear vector channels. The linear vector channels include several practically important channels, such as inter-symbol(More)
In this paper, a modified Index-Less Indexed Flash Codes (ILIFC) for flash memory storage system is presented. Although, the ILIFC proposed by Mahdavifar et al. has excellent worst case performance, the ILIFC can be further improved in terms of average case performance. The proposed scheme, called layered-ILIFC, is based on the original ILIFC but our main(More)