Density Evolution for Deterministic Generalized Product Codes with Higher-Order Modulation

Generalized product codes (GPCs) are extensions of product codes (PCs) where coded bits are protected by two component codes but not necessarily arranged in a rectangular array. It has recently been shown that there exists a large class of deterministic GPCs (including, e.g., irregular PCs, half-product codes, staircase codes, and certain braided codes) for which the asymptotic performance under iterative bounded-distance decoding over the binary erasure channel (BEC) can be rigorously characterized in terms of a density evolution analysis. In this paper, the analysis is extended to the case where transmission takes place over parallel BECs with different erasure probabilities. We use this model to predict the code performance in a coded modulation setup with higher-order signal constellations. We also discuss the design of the bit mapper that determines the allocation of the coded bits to the modulation bits of the signal constellation.Comment: invited and accepted paper for the special session "Recent Advances in Coding for Higher Order Modulation" at the International Symposium on Turbo Codes & Iterative Information Processing, Brest, France, 201

Approaching Capacity at High-Rates with Iterative Hard-Decision Decoding

A variety of low-density parity-check (LDPC) ensembles have now been observed to approach capacity with message-passing decoding. However, all of them use soft (i.e., non-binary) messages and a posteriori probability (APP) decoding of their component codes. In this paper, we show that one can approach capacity at high rates using iterative hard-decision decoding (HDD) of generalized product codes. Specifically, a class of spatially-coupled GLDPC codes with BCH component codes is considered, and it is observed that, in the high-rate regime, they can approach capacity under the proposed iterative HDD. These codes can be seen as generalized product codes and are closely related to braided block codes. An iterative HDD algorithm is proposed that enables one to analyze the performance of these codes via density evolution (DE).Comment: 22 pages, this version accepted to the IEEE Transactions on Information Theor

Generalized product expansions for pair‐correlated wavefunctions

A correlated wavefunction in the form of a linear combination of generalized products is proposed for describing electron correlation in N‐electron systems. The generalized product configurations are group functional products describing the correlated behavior of a pair of electrons in an N‐2‐electron independent particle sea. The linear expansion includes terms for all possible pairs and thus includes correlation effects for every pair of electrons. The structure of the wavefunction is given, the matrix elements of the Hamiltonian are determined, and some of the variational equations determining the optimal total wavefunction are discussed. The relation between second‐order Nesbet‐Bethe‐Goldstone calculations and the pair at a time CI method of Sinanoğlu and the pair‐correlated wavefunction developed here is discussed, and a method is given for obtaining a complete generalized product wavefunction from these type independent pair approximations.<br/

Maps preserving peripheral spectrum of generalized products of operators

Let $\mathcal{A}_1$ and $\mathcal{A}_2$ be standard operator algebras on complex Banach spaces $X_1$ and $X_2$, respectively. For $k\geq2$, let $(i_1,...,i_m)$ be a sequence with terms chosen from $\{1,\ldots,k\}$, and assume that at least one of the terms in $(i_1,\ldots,i_m)$ appears exactly once. Define the generalized product $T_1* T_2*\cdots* T_k=T_{i_1}T_{i_2}\cdots T_{i_m}$ on elements in $\mathcal{A}_i$. Let $\Phi:\mathcal{A}_1\rightarrow\mathcal{A}_2$ be a map with the range containing all operators of rank at most two. We show that $\Phi$ satisfies that $\sigma_\pi(\Phi(A_1)*\cdots*\Phi(A_k))=\sigma_\pi(A_1*\cdots* A_k)$ for all $A_1,\ldots, A_k$, where $\sigma_\pi(A)$ stands for the peripheral spectrum of $A$, if and only if $\Phi$ is an isomorphism or an anti-isomorphism multiplied by an $m$th root of unity, and the latter case occurs only if the generalized product is quasi-semi Jordan. If $X_1=H$ and $X_2=K$ are complex Hilbert spaces, we characterize also maps preserving the peripheral spectrum of the skew generalized products, and prove that such maps are of the form $A\mapsto cUAU^*$ or $A\mapsto cUA^tU^*$, where $U\in\mathcal{B}(H,K)$ is a unitary operator, $c\in\{1,-1\}$.Comment: 17 page

Generalized product of fuzzy subgroups and t-level subgroups

Ray (Fuzzy Sets and Systems 105(1999)181-183) studied some results of the product of two fuzzy subsets and fuzzy subgroups. In this paper, Ray\u27s results will be generalized. Furthermore, we define a t-level subset and t-level subgroups, and then we study some of their properties