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31.
32.
时延约束的链路选择平衡优化组播路由算法 总被引:2,自引:0,他引:2
针对时延约束的最小代价组播树生成方法,提出一种快速有效的时延约束组播路由算法。该算法改进了KPP算法,设计了代价和时延动态优化的链路选择函数。在选择路径时,该算法综合考虑了时延和代价两个参数,保证了组播树的性能,降低了时间复杂度低。仿真结果表明,该算法能正确地构造出时延约束组播树,同时还具有较低的代价和计算复杂度。 相似文献
33.
基于遗传算法的时延受限多播路由研究 总被引:1,自引:0,他引:1
该文探讨了包交换计算机网络中,具有端到端时延限制的多播路由问题。提出了一种基于遗传算法的多播路由优化算法,利用该算法可以实现在给定网络和多播需求的情况下,寻找费用最小的多播路由树,使该树覆盖所有的多播目的节点,并使网络费用达到最小。 相似文献
34.
Warren D. Smith 《Algorithmica》1992,7(1):137-177
This paper has two purposes. The first is to present a new way to find a Steiner minimum tree (SMT) connectingN sites ind-space,d >- 2. We present (in Appendix 1) a computer code for this purpose. This is the only procedure known to the author for finding Steiner minimal trees ind-space ford > 2, and also the first one which fits naturally into the framework of backtracking and branch-and-bound. Finding SMTs of up toN = 12 general sites ind-space (for anyd) now appears feasible.We tabulate Steiner minimal trees for many point sets, including the vertices of most of the regular and Archimedeand-polytopes with <- 16 vertices. As a consequence of these tables, the Gilbert-Pollak conjecture is shown to be false in dimensions 3–9. (The conjecture remains open in other dimensions; it is probably false in all dimensionsd withd 3, but it is probably true whend = 2.)The second purpose is to present some new theoretical results regarding the asymptotic computational complexity of finding SMTs to precision .We show that in two-dimensions, Steiner minimum trees may be found exactly in exponential time O(C
N
) on a real RAM. (All previous provable time bounds were superexponential.) If the tree is only wanted to precision , then there is an (N/)O(N)-time algorithm, which is subexponential if 1/ grows only polynomially withN. Also, therectilinear Steiner minimal tree ofN points in the plane may be found inN
O(N) time.J. S. Provan devised an O(N
6/4)-time algorithm for finding the SMT of a convexN-point set in the plane. (Also the rectilinear SMT of such a set may be found in O(N
6) time.) One therefore suspects that this problem may be solved exactly in polynomial time. We show that this suspicion is in fact true—if a certain conjecture about the size of Steiner sensitivity diagrams is correct.All of these algorithms are for a real RAM model of computation allowing infinite precision arithmetic. They make no probabilistic or other assumptions about the input; the time bounds are valid in the worst case; and all our algorithms may be implemented with a polynomial amount of space. Only algorithms yielding theexact optimum SMT, or trees with lengths (1 + ) × optimum, where is arbitrarily small, are considered here. 相似文献
35.
36.
Relay sensor placement in wireless sensor networks 总被引:4,自引:0,他引:4
This paper addresses the following relay sensor placement problem: given the set of duty sensors in the plane and the upper
bound of the transmission range, compute the minimum number of relay sensors such that the induced topology by all sensors
is globally connected. This problem is motivated by practically considering the tradeoff among performance, lifetime, and
cost when designing sensor networks. In our study, this problem is modelled by a NP-hard network optimization problem named
Steiner Minimum Tree with Minimum number of Steiner Points and bounded edge length (SMT-MSP). In this paper, we propose two approximate algorithms, and conduct detailed performance analysis. The first algorithm has
a performance ratio of 3 and the second has a performance ratio of 2.5.
Xiuzhen Cheng is an Assistant Professor in the Department of Computer Science at the George Washington University. She received her MS
and PhD degrees in Computer Science from the University of Minnesota - Twin Cities in 2000 and 2002, respectively. Her current
research interests include Wireless and Mobile Computing, Sensor Networks, Wireless Security, Statistical Pattern Recognition,
Approximation Algorithm Design and Analysis, and Computational Medicine. She is an editor for the International Journal on
Ad Hoc and Ubiquitous Computing and the International Journal of Sensor Networks. Dr. Cheng is a member of IEEE and ACM. She
received the National Science Foundation CAREER Award in 2004.
Ding-Zhu Du received his M.S. degree in 1982 from Institute of Applied Mathematics, Chinese Academy of Sciences, and his Ph.D. degree
in 1985 from the University of California at Santa Barbara. He worked at Mathematical Sciences Research Institutea, Berkeley
in 1985-86, at MIT in 1986-87, and at Princeton University in 1990-91. He was an associate-professor/professor at Department
of Computer Science and Engineering, University of Minnesota in 1991-2005, a professor at City University of Hong Kong in
1998-1999, a research professor at Institute of Applied Mathematics, Chinese Academy of Sciences in 1987-2002, and a Program
Director at National Science Foundation of USA in 2002-2005. Currently, he is a professor at Department of Computer Science,
University of Texas at Dallas and the Dean of Science at Xi’an Jiaotong University. His research interests include design
and analysis of algorithms for combinatorial optimization problems in communication networks and bioinformatics. He has published
more than 140 journal papers and 10 written books. He is the editor-in-chief of Journal of Combinatorial Optimization and
book series on Network Theory and Applications. He is also in editorial boards of more than 15 journals.
Lusheng Wang received his PhD degree from McMaster University in 1995. He is an associate professor at City University of Hong Kong. His
research interests include networks, algorithms and Bioinformatics. He is a member of IEEE and IEEE Computer Society.
Baogang Xu received his PhD degree from Shandong University in 1997. He is a professor at Nanjing Normal University. His research interests
include graph theory and algorithms on graphs. 相似文献
37.
阈值后处理是针对TD-SCDMA系统中B Steiner信道估计器受加性噪声影响而提出的一种去噪方法,该方法误滤除信息径,保留噪声径.本文提出一种基于阈值处理的多用户信道估计方法,它基于某一下行用户会收到所有其它下行用户的训练序列这一特性,设定一个值,与各用户幅度加权值比较,去掉信噪比很小的用户对应的信道估计窗,将其余用户的信道估计窗进行平均,然后将平均后的结果再进行阈值后处理,抑制由噪声贡献的信道响应.仿真结果表明,提出的方法与直接进行阈值后处理法在同一误码率下,所需平均信噪比(SNR)降低1~4dB;在SNR低于5dB时,与复杂度高的加权合并法具有相同的误码率. 相似文献
38.
主网与配电网协调规划的评价指标和规划方法 总被引:1,自引:0,他引:1
城市110 kV变电站作为连接主网与配电网的纽带,其选址和供电范围的划分是主网与配电网协调(以下简称主配网协调)规划的关键.文中提出协调因子及主配网协调规划评价模型,强调以提高总体运行均衡性为目标的电网规划思想.首先对变电站的基本属性进行分析,提出由运行率和关联度构成的负重系数的概念;然后利用约束圆环协调规划范围,将负重系数作为权值,利用改进后的加权Steiner最小树理论优化变电站选址;进而确定变电站的容量及供电范围.实际算例表明,从主配网协调程度考虑,所提出方法的规划结果优于传统选址规划结果. 相似文献
39.
40.
最小生成树数据描述方法在刻画高维空间样本点分布时,将所有图形的边作为新增虚拟样本以提供同类样本分布描述,这种描述存在分支多覆盖模型复杂,且局部覆盖不够合理的问题。针对该问题,依据特征空间中同类样本分布的连续性规律,提出基于高维空间典型样本Steiner最小树覆盖模型的一类分类算法,该算法首先对目标类训练集进行样本修剪,去除冗余信息和噪声信息,选择最具代表性的样本作为训练集,然后对保留的典型样本构建Steiner最小树覆盖模型。算法分析和仿真实验结果表明,相比最小生成树数据描述,文中提出的方法能在较低覆盖模型复杂度的前提下更合理的描述目标类样本空间分布,构建更合理的覆盖模型,在分类正确率和适用样本规模上都表现出一定的优越性。 相似文献