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1.
LDPC码相关技术研究   总被引:6,自引:5,他引:1  
徐华 《微电子学与计算机》2005,22(3):178-180,184
文章首先简要介绍了LDPC码适于新一代移动通信应用的良好特性,接着阐述了码的结构和二分图分析方法,对LDPC码的几种基本编码技术进行了讨论,最后论述了LDPC码的MP译码算法基本思想,并对MP算法集合中的特例信度传播算法(BP)进行了评述.  相似文献   
2.
可重排无阻塞全混洗光网络光学实现方法   总被引:1,自引:0,他引:1  
杨俊波  苏显渝  徐平 《光电工程》2007,34(5):103-108
针对全混洗互连网络在光通信和光信息处理中的应用,提出一种利用二元光学方法制作的深浮雕微闪耀光栅列阵构建全混洗(Perfect Shuffle,PS)光互连网络的方法.该方法通过逆混洗(Inverse Perfect Shuffle,IPS)和左混洗(Left Perfect Shuffle,LPS)的串联,构成多级的可重排、无阻塞的Omega网络,采用二分图法(Bipartition Graph)依次确定各级节点开关的状态(直通或交叉),最后通过偏振分光棱镜(Polarizing Beam Splitter,PBS)、半波片(λ/2wave plate)和PS Plate的组合,得到可重排、无阻塞的Omega网络交换模块.理论分析和实验结果表明该模块可以实现N=8输入信号按任意序列输出,不会发生路径冲突.该方法实现的全光交换和排序具有自由空间交换、交换透明、串扰小、带宽高的特点,在光通信以及信号处理中具有一定的应用.  相似文献   
3.
This paper presents BSR-parallel algorithms for some problems in fundamental graph theory : transitive closure, connected components, spanning tree, bridges and articulation points of a graph and bipartite graph recognition. There already exist constant time algorithms to solve these problems on a mesh with reconfigurable bus system using O(N 4) processors. Here we show that these problems can be solved in constant time using only O(N 2) processors on the BSR model (N is the number of vertices of the graph G). Therefore, our algorithms are more work-efficient. These new results suggest that many other problems in graph theory can be solved in constant time using the BSR model.  相似文献   
4.
This paper discusses current techniques for proving lower bounds on the size of resolution proofs from sets of clauses expressing assertions about matchings in bipartite graphs (a class including the well-known pigeon-hole clauses). The techniques are illustrated by demonstrating an improved lower bound for some examples discussed by Kleine Büning. The final section discusses some problems where current techniques appear inadequate, and new ideas seem to be required.  相似文献   
5.
Let A and B be two sets of n objects in \reals d , and let Match be a (one-to-one) matching between A and B . Let min(Match ), max(Match ), and Σ(Match) denote the length of the shortest edge, the length of the longest edge, and the sum of the lengths of the edges of Match , respectively. Bottleneck matching— a matching that minimizes max(Match )— is suggested as a convenient way for measuring the resemblance between A and B . Several algorithms for computing, as well as approximating, this resemblance are proposed. The running time of all the algorithms involving planar objects is roughly O(n 1.5 ) . For instance, if the objects are points in the plane, the running time of the exact algorithm is O(n 1.5 log n ) . A semidynamic data structure for answering containment problems for a set of congruent disks in the plane is developed. This data structure may be of independent interest. Next, the problem of finding a translation of B that maximizes the resemblance to A under the bottleneck matching criterion is considered. When A and B are point-sets in the plane, an O(n 5 log n) -time algorithm for determining whether for some translated copy the resemblance gets below a given ρ is presented, thus improving the previous result of Alt, Mehlhorn, Wagener, and Welzl by a factor of almost n . This result is used to compute the smallest such ρ in time O(n 5 log 2 n ) , and an efficient approximation scheme for this problem is also given. The uniform matching problem (also called the balanced assignment problem, or the fair matching problem) is to find Match * U , a matching that minimizes max (Match)-min(Match) . A minimum deviation matching Match * D is a matching that minimizes (1/n)Σ(Match) - min(Match) . Algorithms for computing Match * U and Match * D in roughly O(n 10/3 ) time are presented. These algorithms are more efficient than the previous O(n 4 ) -time algorithms of Martello, Pulleyblank, Toth, and de Werra, and of Gupta and Punnen, who studied these problems for general bipartite graphs. Received October 21, 1997; revised July 16, 1998.  相似文献   
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A set of solutions for the equationsf(x)±f(y) =k is described, where fis a 2-quasiperiodic and strictly monotonous function in No. The results are applied for investigation of a diametrically-threshold function for graphs and of a maximal type of complete bipartite graph. Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 170–174, March–April, 2000  相似文献   
9.
构造接近香农极限的低密度校验码   总被引:3,自引:0,他引:3  
低密度校验(LDPC)码的性能优劣在很大程度上取决于该码的最小环长(Girth)和最小码距。本文采用几何构造方法构造最小环长为8的LDPC码,联合随机搜索算法改善其码重分布,所构造的LDPC码在码长为4k、编码效率为0.95时,距离香农极限仅1.1dB。  相似文献   
10.
Tornado codes have been used in the error control of data transmission in IP network. The efficiency of this erasure codes is critically affected by the short cycles in its bipartite graph. To remove this effect, two algorithms are introduced: (1) while generating the graph, the cycle eliminating algorithm is used to reduce the number of the short cycles in it; (2) in the decoding algorithm, cycles that are inevitably in the graph are used to remove decoding efficiency degradation. The simulation results show that they have a better performance than that of general tornado codes.  相似文献   
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