共查询到20条相似文献,搜索用时 125 毫秒
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本文研究了Goppa码、BCH码的广义Hamming重量,给出了Goppa码的广义Hamming重量的一个下界以及求该下界的一个算法;对于本原、狭义BCH码,给出了后面一些广义Hamming重量的确切值。 相似文献
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上 线性码c的汉明重量谱为序列 ,其中,dr是c的r维子码的最小支撑重量。第VI类5维q元线性码的汉明重量谱,按照新的必要条件可以分成6个子类。运用有限射影几何方法研究VI-2类的5维q元线性码的汉明重量谱,确定VI-2类5维q元线性码的几乎所有汉明重量谱。 相似文献
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设计高质量的核酸分子集合能有效提高DNA计算的可靠性、有效性和可求解问题的规模。DNA分子需要满足热力学约束、相似度约束、GC含量约束等多个相互冲突的目标函数,是典型的多目标优化问题。该文提出一种多目标进化策略(MOES)算法求解DNA分子序列设计问题,算法设计了随机碱基变异算子实现高效的局部搜索和全局搜索。改进的评价函数综合考虑了候选解的支配关系和冲突目标的平衡程度,选取符合DNA编码约束的核酸序列。实验结果证明,该文提出的算法具有高效的搜索效率和快速收敛能力,可以产生高质量的DNA序列集合,优于其他对比算法产生的DNA分子序列集合。 相似文献
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New construction of multiwavelength optical orthogonal codes 总被引:1,自引:0,他引:1
Ssang-Soo Lee Seung-Woo Seo 《Communications, IEEE Transactions on》2002,50(12):2003-2008
We investigate multiwavelength optical orthogonal codes (MWOOCs) for optical code-division multiple access. Particularly, we present a new construction method for (mn,/spl lambda/+2,/spl lambda/) MWOOCs with the number of available wavelengths m, codeword length n, and constant Hamming weight /spl lambda/+2 that have autocorrelation and cross-correlation values not exceeding /spl lambda/. In the proposed scheme, there is no constraint on the relationship between the number of available wavelengths and the codeword length, and it is also possible to use an arbitrary /spl lambda/. We show that the constructed code is optimal, especially for /spl lambda/=1. Finally, we analyze the bit error rate of the new code and compare it with that of other optical codes. 相似文献
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Optical orthogonal codes with large crosscorrelation and their performance bound for asynchronous optical CDMA systems 总被引:2,自引:0,他引:2
Chi-Shun Weng Jingshown Wu 《Lightwave Technology, Journal of》2003,21(3):735-742
Optical orthogonal codes (OOCs) are commonly used as signature codes for optical code-division multiple-access (OCDMA) communication systems. Many OOCs have been proposed and investigated. Asynchronous OCDMA systems using conventional OOCs have a very limited number of subscribers and few simultaneous users. Recently, we reported a new code family with large code size by relaxing the crosscorrelation constraint to 2. In this paper, by further loosening the crosscorrelation constraint, we adopt the random greedy algorithm to construct a code family which has larger code size and more simultaneous users. We also derive an upper bound of the number of simultaneous users for a given code length, code weight, and bit error rate. The study shows that it is possible to have codes approaching this bound. 相似文献
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Joint spatial-frequency blind multiuser detection based on LCCMA 总被引:1,自引:0,他引:1
ZHAO Fa-yong FENG Guang-zeng Department of Communication Information Engineering Nanjing University of Posts Telecommunications Nanjing China 《中国邮电高校学报(英文版)》2007,14(2):19-22
Multicarrier code division multiple access (MC-CDMA) has the ability to combat with frequency selective fading and antenna array can enhance the performance of system. The paper proposes a novel joint spatial-frequency blind multiuser detection for antenna array MC-CDMA based on linear constraint constant modulation algorithm (LCCMA), which has robust performance and can ensue the weight vectors to converge to that of the desired user. Simulation indicates the proposed algorithm has better bit error ratio (BER) performance than that of the traditional beamforming-based two-step algorithm. 相似文献
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极大等重等距码结构的再分析 总被引:2,自引:0,他引:2
本文根据文[1]提出的极大等重等距码的概念,利用等重等距码窗口矩阵设计原理,对(n,4,m)极大等重等距码结构重新进行了分析.讨论了码重基本情形,对称情形与非对称情形等几类特殊结构类型,并组合了各种不同结构的极大等重等距码,其结果比较完整地解决了(n,4,m)极大等重等距码的结构等价类问题. 相似文献
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Xin-Mei Wang Yi-Xian Yang 《Communications, IEEE Transactions on》1994,42(7):2390-2394
The undetected error probability (UEP) of binary (n, 2δ, m) nonlinear constant weight codes over the binary symmetric channel (BSC) is investigated, where n is the blocklength, m is the weight of codeword and 2δ is the minimum distance of the codes. The distance distribution of the (n, 2, m) nonlinear constant weight codes is evaluated. It is proven in this paper that the (5, 2, 2) code, (5, 2, 3) code, (6, 2, 3) code, (7, 2, 4) code, (7, 2, 3) code and (8, 2, 4) code are the only proper error-detecting codes in the (n, 2, m) nonlinear constant weight codes for n⩾5, in the sense that their UEP is increased monotonically with the channel error rate p, of course all these proper codes are m-out-of-n codes. Furthermore, it is conjectured that except for the cases of n⩽4δ, there are no proper error-detecting binary (n, 2δ, m) nonlinear constant weight codes, for n>8 and δ⩾1 相似文献
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Optical orthogonal codes with nonideal cross correlation 总被引:1,自引:0,他引:1
Chi-Shun Weng Jingshown Wu 《Lightwave Technology, Journal of》2001,19(12):1856-1863
For optical code division multiple access (OCDMA) networks, many optical orthogonal codes (OOCs) with ideal auto- and cross-correlation properties had been studied widely. In this paper, we relax the cross-correlation constraint slightly and propose a new code family based on perfect difference codes. Given the same code weight and code length, the size of new codes may increase 10 times more than that of ideal OOCs. Although the maximum cross correlation of new codes is larger than one, the cross correlation is less than or equal to one, for the most part. Consequently, the performance of new codes approaches that of ideal OOCs. Numerical results show that the performance of proposed codes was almost the same as that of conventional OOCs under the same code length and code weight 相似文献
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Chung-Li Wang Fossorier M.P.C. 《Selected Areas in Communications, IEEE Journal on》2009,27(6):899-907
For LDPC-like codes such as LDPC, GLDPC, and DGLDPC codes, it is well known that the error floor can be caused by the codewords of small weights or stopping sets of small sizes. In this paper, we investigate the computation of asymptotic weight enumerators such that it becomes a convenient tool to determine a good distribution of code ensembles. In addition, by analyzing the first order approximation, we derive a condition to obtain a negative asymptotic growth rate of the codewords of small linear-sized weights, which is an important constraint for distribution optimization. Also the weight enumerators of turbo and repeat-accumulate codes are investigated. Furthermore, we extend our results to nonbinary DGLDPC codes. Generalization to N-layer and convolutional code based LDPC-like codes are also developed. 相似文献