共查询到20条相似文献,搜索用时 15 毫秒
1.
Min-Ho Shin Joon-Sung Kim Hong-Yeop Song 《Communications Letters, IEEE》2005,9(3):240-242
Tanner derived minimum distance bounds of regular codes in terms of the eigenvalues of the adjacency matrix by using some graphical analysis on the associated graph of the code. In this letter, we generalize Tanner's results by deriving a bit-oriented bound and a parity-oriented bound on the minimum distances of both regular and block-wise irregular LDPC codes. 相似文献
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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
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On the minimum distance of cyclic codes 总被引:3,自引:0,他引:3
《IEEE transactions on information theory / Professional Technical Group on Information Theory》1986,32(1):23-40
The main result is a new lower bound for the minimum distance of cyclic codes that includes earlier bounds (i.e., BCH bound, HT bound, Roos bound). This bound is related to a second method for bounding the minimum distance of a cyclic code, which we call shifting. This method can be even stronger than the first one. For all binary cyclic codes of length< 63 (with two exceptions), we show that our methods yield the true minimum distance. The two exceptions at the end of our list are a code and its even-weight subcode. We treat several examples of cyclic codes of lengthgeq 63 . 相似文献
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Johannes Pittermann Michael Lentmaier Kamil Sh. Zigangirov 《AEUE-International Journal of Electronics and Communications》2005,59(4):254-257
A new construction combining LDPC convolutional codes and multilevel coding/modulation is suggested and analyzed. In the case of QPSK, we demonstrate that it has a better performance than an LDPC convolutional code combined with conventional Gray mapping. 相似文献
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Ben-Haim Y. Litsyn S. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2006,52(5):2092-2100
New upper bounds on the rate of low-density parity-check (LDPC) codes as a function of the minimum distance of the code are derived. The bounds apply to regular LDPC codes, and sometimes also to right-regular LDPC codes. Their derivation is based on combinatorial arguments and linear programming. The new bounds improve upon the previous bounds due to Burshtein et al. It is proved that at least for high rates, regular LDPC codes with full-rank parity-check matrices have worse relative minimum distance than the one guaranteed by the Gilbert-Varshamov bound. 相似文献
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Shu-Tao Xia Fang-Wei Fu 《Communications Letters, IEEE》2006,10(5):381-383
In this letter, the stopping sets and stopping distance of finite geometry LDPC (FG-LDPC) codes are studied. It is known that FG-LDPC codes are majority-logic decodable and a lower bound on the minimum distance can be thus obtained. It is shown in this letter that this lower bound on the minimum distance of FG-LDPC codes is also a lower bound on the stopping distance of FG-LDPC codes, which implies that FG-LDPC codes have considerably large stopping distance. This may explain in one respect why some FG-LDPC codes perform well with iterative decoding in spite of having many cycles of length 4 in their Tanner graphs. 相似文献
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V. V. Zyablov K. A. Kondrashov O. D. Skopintsev 《Journal of Communications Technology and Electronics》2013,58(6):636-647
Partial unit memory (PUM) convolutional codes constructed from block codes make it possible to obtain convolutional codes with high correcting properties. An ensemble of binary PUM convolutional codes based on low-density parity-check block codes is introduced. This ensemble is specified by semi-infinite parity-check matrices with partial unit memory. The asymptotic bounds on a free distance and active row distances are derived for codes of the specified ensemble. It is proved that the ensemble codes have the positive slope of active row distances. 相似文献
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Minimum redundancy coding (also known as Huffman coding) is one of the enduring techniques of data compression. Many efforts have been made to improve the efficiency of minimum redundancy coding, the majority based on the use of improved representations for explicit Huffman trees. In this paper, we examine how minimum redundancy coding can be implemented efficiently by divorcing coding from a code tree, with emphasis on the situation when n is large, perhaps on the order of 10 6. We review techniques for devising minimum redundancy codes, and consider in detail how encoding and decoding should be accomplished. In particular, we describe a modified decoding method that allows improved decoding speed, requiring just a few machine operations per output symbol (rather than for each decoded bit), and uses just a few hundred bytes of memory above and beyond the space required to store an enumeration of the source alphabet 相似文献
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Khayrallah A.S. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1995,41(5):1457-1466
We investigate the bit-error rate (BER) of linear block codes. The BER is a function of the encoder realization of the code. We express the BER in terms of the weight profiles of the subspaces of the code. We also discuss the relation between the Hadamard transform and the BER 相似文献
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van Eupen M. van Lint J.H. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1993,39(2):409-422
There are many ways to find lower bounds for the minimum distance of a cyclic code, based on investigation of the defining set. Some new theorems are derived. These and earlier techniques are applied to find lower bounds for the minimum distance of ternary cyclic codes. Furthermore, the exact minimum distance of ternary cyclic codes of length less than 40 is computed numerically. A table is given containing all ternary cyclic codes of length less than 40 and having a minimum distance exceeding the BCH bound. It seems that almost all lower bounds are equal to the minimum distance. Especially shifting, which is also done by computer, seems to be very powerful. For length 40⩽n ⩽50, only lower bounds are computed. In many cases (derived theoretically), however, these lower bounds are equal to the minimum distance 相似文献
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Dianwu Yue Hongbo Zhu 《Communications Letters, IEEE》1999,3(9):269-271
In this letter, we derive a theorem which generalizes Theorem 3 in Chapter 9 of the book “The Theory of Error-Correcting Codes” by F.J. MacWilliams and N.J.A. Sloane (North-Holland, 1977). By this theorem, we are able to give several classes of BCH codes of composite length whose minimum distance does not exceed the BCH bound. Moreover, we show that this theorem can also be used to determine the true minimum distance of some other cyclic codes with composite-length 相似文献
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Bennatan A. Burshtein D. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2004,50(3):417-438
We discuss three structures of modified low-density parity-check (LDPC) code ensembles designed for transmission over arbitrary discrete memoryless channels. The first structure is based on the well-known binary LDPC codes following constructions proposed by Gallager and McEliece, the second is based on LDPC codes of arbitrary (q-ary) alphabets employing modulo-q addition, as presented by Gallager, and the third is based on LDPC codes defined over the field GF(q). All structures are obtained by applying a quantization mapping on a coset LDPC ensemble. We present tools for the analysis of nonbinary codes and show that all configurations, under maximum-likelihood (ML) decoding, are capable of reliable communication at rates arbitrarily close to the capacity of any discrete memoryless channel. We discuss practical iterative decoding of our structures and present simulation results for the additive white Gaussian noise (AWGN) channel confirming the effectiveness of the codes. 相似文献
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Jing Li Narayanan K.R. Kurtas E. Georghiades C.N. 《Communications, IEEE Transactions on》2002,50(5):723-734
This paper evaluates two-dimensional turbo product codes based on single-parity check codes (TPC/SPC) and low-density parity check (LDPC) codes for use in digital magnetic recording systems. It is first shown that the combination of a TPC/SPC code and a precoded partial response (PR) channel results in a good distance spectrum due to the interleaving gain. Then, density evolution is used to compute the thresholds for TPC/SPC codes and LDPC codes over PR channels. Analysis shows that TPC/SPC codes have a performance close to that of LDPC codes for large codeword lengths. Simulation results for practical block lengths show that TPC/SPC codes perform as well as LDPC codes in terms of bit error rate, but possess better burst error statistics which is important in the presence of an outer Reed-Solomon code. Further, the encoding complexity of TPC/SPC codes is only linear in the codeword length and the generator matrix does not have to be stored explicitly. Based on. the results in the paper and these advantages, TPC/SPC codes seem like a viable alternative to LDPC codes 相似文献
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A class of Quasi-Systematic Block-Circulant Low-Density Parity-Check (QSBC-LDPC) codes is proposed. Block-circulant LDPC codes have been studied a lot recently, because the simple structures of their parity-check matrices are very helpful to reduce the implementation complexities. QSBC-LDPC codes are special block-circulant LDPC codes with quasi-systematic parity-check matrices. The memories for encoders of QSBC-LDPC codes are limited, and the encoding process can be carried out in a simple recursive way with low complexities. Researches show that the QSBC-LDPC codes can provide remarkable performances with low encoding complexities. 相似文献
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The offset BP-based algorithm is a reduced-complexity derivative of the belief-propagation algorithm for decoding of low-density parity- check codes. It uses a constant offset term to simplify decoding, but at the cost of performance. A method to obtain a 'variable' offset parameter is presented here, to improve the performance of the algorithm. 相似文献
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The notion of low-density parity-check (LDPC) codes over mixed alphabets is introduced. It is shown that these codes can provide good performance/complexity trade-offs compared to their single-alphabet counterparts 相似文献