共查询到20条相似文献,搜索用时 31 毫秒
1.
Fossorier M.P.C. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2004,50(8):1788-1793
In this correspondence, the construction of low-density parity-check (LDPC) codes from circulant permutation matrices is investigated. It is shown that such codes cannot have a Tanner graph representation with girth larger than 12, and a relatively mild necessary and sufficient condition for the code to have a girth of 6, 8,10, or 12 is derived. These results suggest that families of LDPC codes with such girth values are relatively easy to obtain and, consequently, additional parameters such as the minimum distance or the number of redundant check sums should be considered. To this end, a necessary condition for the codes investigated to reach their maximum possible minimum Hamming distance is proposed. 相似文献
2.
Gao J. Rudolph L.D. Hartmann C.R.P. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1988,34(3):480-485
The authors propose a class of spherical codes which can be easily decoded by an efficient iterative maximum likelihood decoding algorithm. A necessary and sufficient condition for a spherical code to be iteratively maximum likelihood decodable is formulated. A systematic construction method for such codes based on shrinking of Voronoi corners is analyzed. The base code used for construction is the binary maximal length sequence code. The second-level construction is described. Computer simulation results for selected codes constructed by the proposed method are given 相似文献
3.
In this letter, we use the well-known Walsh-Hadamard codes to construct larger sets of linearly dependent codes such that their matrix of correlations is band-diagonal. Optimal detection for systems employing these spreading codes can be efficiently accomplished by a trellis decoder. Analysis and simulation show that with a processing gain of N, up to 2N users can be accommodated without much performance degradation. This proposed approach is quite general and larger code set can be constructed analogously. 相似文献
4.
This letter presents an algebraic method for constructing regular low-density parity-check (LDPC) codes based on Reed-Solomon codes with two information symbols. The construction method results in a class of LDPC codes in Gallager's original form. Codes in this class are free of cycles of length 4 in their Tanner graphs and have good minimum distances. They perform well with iterative decoding. 相似文献
5.
本文刻画了双完备认证码的结构,给出了r阶完备认证码的定义,并给出判定r阶完备认证码的一个充要条件,由组合设计构造了r阶完备认证码。 相似文献
6.
Huang Zhonghu Shen Lianfeng 《电子科学学刊(英文版)》2006,23(1):124-127
This letter gives a random construction for Low Density Parity Check (LDPC) codes, which uses an iterative algorithm to avoid short cycles in the Tanner graph. The construction method has great flexible choice in LDPC code's parameters including codelength, code rate, the least girth of the graph, the weight of column and row in the parity check matrix. The method can be applied to the irregular LDPC codes and strict regular LDPC codes. Systemic codes have many applications in digital communication, so this letter proposes a construction of the generator matrix of systemic LDPC codes from the parity check matrix. Simulations show that the method performs well with iterative decoding. 相似文献
7.
In this letter, the construction of irregular LDPC codes obtained by concatenating regular ones is considered. These codes are analyzed for the binary symmetric channel (BSC). It is shown via proper distribution evolution that such concatenated codes have in general a threshold value weaker (but not necessarily much different) than their unconstrained counterparts for the BSC. On the other hand, they can offer advantages in term of convergence and error performance for lengths of practical interest and long enough to validate the degree distribution selection. 相似文献
8.
Huang Zhonghu Shen Lianfeng 《电子科学学刊(英文版)》2006,23(1)
This letter gives a random construction for Low Density Parity Check (LDPC) codes, which uses an iterative algorithm to avoid short cycles in the Tanner graph. The construction method has great flexible choice in LDPC code's parameters including codelength, code rate, the least girth of the graph, the weight of column and row in the parity check matrix. The method can be applied to the irregular LDPC codes and strict regular LDPC codes. Systemic codes have many applications in digital communication, so this letter proposes a construction of the generator matrix of systemic LDPC codes from the parity check matrix. Simulations show that the method performs well with iterative decoding. 相似文献
9.
This letter presents a systematic and recursive method to construct good low-density parity-check (LDPC) codes, especially those with high rate. The proposed method uses a parity check matrix of a quasi-cyclic LDPC code with given row and column weights as a core upon which the larger code is recursively constructed with extensive use of pseudorandom permutation matrices. This construction preserves the minimum distance and girth properties of the core matrix and can generate either regular, or irregular LDPC codes. The method provides a unique representation of the code in compact notation. 相似文献
10.
11.
《IEEE transactions on information theory / Professional Technical Group on Information Theory》1979,25(2):246-250
Several theorems are presented which characterize Goppa codes having the property of becoming cyclic when an overall parity cheek is added. If such a Goppa code has location setL = GF (q^{m}) and a Goppa polynomialg(z) that is irreducible overGF(q^{m}) , theng(z) must be a quadratic. Goppa codes defined by(z- beta)^{a} and location setL with cardinalityn such thatn+l|q^{m}-1 are considered along with their subcodes. A sufficient condition onL is derived for the extended codes to become cyclic. This condition is also necessary whena = 1. The construction ofL for differentn satisfying the stated condition is investigated in some detail. Some irreversible Goppa codes have been shown to become cyclic when extended by an overall parity check. 相似文献
12.
Cheng L.M. Cheng L.L. Wei Sun 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2003,49(1):258-261
Based on the construction of linear codes proposed by Niederriter and Xing (see Applicable Algebra in Engineering, Communication and Computing, vol.10, p.425-32, 2000), a corresponding generator matrix is derived. The duality operator and the propagation operator of these extended linear codes are studied. A sufficient and necessary condition under which these two operators are commutative is obtained. This commutative property is found useful for constructing the corresponding parity-check matrix and, thus, the error detection/recovery codes. 相似文献
13.
In this letter, we propose and compare some design criteria for the search of good rate-compatible systematic turbo codes (RCPTC) families. The considerations presented by Benedetto et al. to find "best" component encoders for turbo-code construction are extended to find good rate-compatible puncturing patterns leading to codes with promising performances. 相似文献
14.
This letter investigates the so-called product lattice (PL) construction. A PL is obtained from two low-dimensional lattices by means of the Kronecker product. Fundamental properties, mainly those determining the performance of a lattice as an error-correcting scheme over a bandwidth-limited channel, are derived for PLs. Due to their special structure and properties, PLs can provide an attractive family of lattice codes of good performance/complexity tradeoffs 相似文献
15.
Chi-Fu Hong Guu-Chang Yang 《Communications Letters, IEEE》1999,3(9):260-262
This letter presents a new construction of frequency-hopping (FH) patterns, here designated as concatenated prime codes, for a multilevel frequency-shift-keying/frequency-hopping code-division multiple-access (MFSK/FH-CDMA) system. The concatenated prime codes are constructed by modifying prime codes and they possess ideal autocorrelation and nearly ideal cross-correlation properties. Furthermore, these concatenated prime codes can be partitioned into P+1 groups, of which the maximum cross-correlation between any two FH patterns in the same group is at most one 相似文献
16.
Mao-Ching Chiu 《Communications, IEEE Transactions on》2001,49(4):609-619
A new construction of direct current (DC)-free error-correcting codes based on convolutional codes is proposed. The new code is constructed by selecting a proper subcode from a convolutional code composed of two different component codes. The encoder employs a Viterbi algorithm as the codeword selector so that the selected code sequences satisfy the DC constraint. A lower bound on the free distance of such codes is proposed, and a procedure for obtaining this bound is presented. A sufficient condition for these codes to have a bounded running digital sum (RDS) is proposed. Under the assumption of a simplified codeword selection algorithm, we present an upper bound on the maximum absolute value of the RDS and derive the sum variance for a given code. A new construction of standard DC-free codes, i.e., DC-free codes without error-correcting capability, is also proposed. These codes have the property that the decoder can be implemented by simple symbol-by-symbol hard decisions. Finally, under the new construction, we propose several codes that are suitable for the systems that require small sum variance and good error-correction capability 相似文献
17.
In this letter, we present a framework for constructing rate-compatible low-density parity-check (LDPC) codes. The codes are linear-time encodable and are constructed from a mother code using puncturing and extending. Application of the proposed construction to a type-II hybrid automatic repeat request (ARQ) scheme with information block length k=1024 and code rates 8/19 to 8/10, using an optimized irregular mother code of rate 8/13, results in a throughput which is only about 0.7 dB away from Shannon limit. This outperforms existing similar schemes based on turbo codes and LDPC codes by up to 0.5 dB. 相似文献
18.
Ahlswede R. Ning Cai 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2004,50(6):1208-1219
After K. Bostro/spl uml/m and T. Felbinger observed that lossless quantum data compression does not exist unless decoders know the lengths of codewords, they introduced a classical noiseless channel to inform the decoder of a quantum source about the lengths of codewords. In this paper we analyze their codes and present: 1) a sufficient and necessary condition for the existence of such codes for given lists of lengths of codes; 2) a characterization of the optimal compression rate for their codes. However our main contribution is a more efficient way to use the classical channel. We propose a more general coding scheme. It turned out that the optimal compression can always be achieved by a code obtained by this scheme. A von Neumann entropy lower bound to rates of our codes and a necessary and sufficient condition to achieve the bound are obtained. The gap between this lower bound and the compression rates is also well analyzed. For a special family of quantum sources we provide a sharper lower bound in terms of Shannon entropy. Finally, we propose some problems for further research. 相似文献
19.
He Shanbao Zhao Chunming Shi Zhihua 《电子科学学刊(英文版)》2005,22(5):520-523
This letter proposes a novel and simple construction of regular Low-Density Parity-Check (LDPC) codes using sparse binary sequences. It utilizes the cyclic cross correlation function of sparse sequences to generate codes with girth 8. The new codes perform well using the sumproduct decoding. Low encoding complexity can also be achieved due to the inherent quasi-cyclic structure of the codes. 相似文献
20.
Perfect binary codes: constructions, properties, and enumeration 总被引:3,自引:0,他引:3
Etzion T. Vardy A. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1994,40(3):754-763
Properties of nonlinear perfect binary codes are investigated and several new constructions of perfect codes are derived from these properties. An upper bound on the cardinality of the intersection of two perfect codes of length n is presented, and perfect codes whose intersection attains the upper bound are constructed for all n. As an immediate consequence of the proof of the upper bound the authors obtain a simple closed-form expression for the weight distribution of a perfect code. Furthermore, they prove that the characters of a perfect code satisfy certain constraints, and provide a sufficient condition for a binary code to be perfect. The latter result is employed to derive a generalization of the construction of Phelps (1983), which is shown to give rise to some perfect codes that are nonequivalent to the perfect codes obtained from the known constructions. Moreover, for any m⩾4 the authors construct full-rank perfect binary codes of length 2m -1. These codes are obviously nonequivalent to any of the previously known perfect codes. Furthermore the latter construction exhibits the existence of full-rank perfect tilings. Finally, they construct a set of 2(2cn) nonequivalent perfect codes of length n, for sufficiently large n and a constant c=0.5-ϵ. Precise enumeration of the number of codes in this set provides a slight improvement over the results reported by Phelps 相似文献