62639812
Traffic grooming in WDM/SONET BLSR rings with multiple line speeds
WDM/SONET provides a natural migration path to support traffic growth. In WDM/SONET, each wavelength is a separate SONET ring and each ring can be set to one of several line speeds. The line speed should be high if there is enough traffic to realize the economy of scale, otherwise, it should be low to reduce the cost. Despite of the advantages, there are no general tools and methodologies available to help network designers enjoy the benefits of multiple line speeds. For the first time, we propose a comprehensive approach to solve the traffic grooming problem, which includes both novel, complete ILP formulations that can be used to solve small size problems exactly and an efficient heuristic algorithm that can be used to solve large problems quickly. Using the tools we developed, we study the trade-offs of shortest path routing, study the cost benefits of traffic switching, compare UPSR and BLSR, and show that multiple line speeds can significantly reduce cost
17590289
Power-Law Tradeoffs Between Optical and Electronic Switching
Designing a transport network requires finding the most cost-effective combination of electronic and optical switching to support the given demands. This task is not trivial because the solution space is so large. Furthermore, there are many interacting design variables. In electronic switching, the cost is a function of the number of packets that are switched in the routers, which directly corresponds to the average hop count (H̄). The dominant cost of optical switching is a function of the total number of wavelengths used in the network (S) or the maximum number of wavelengths used on any fiber (W ) and the number of transceivers (L) used. In this paper, we show that there is a power-law relationship between each pair of these variables, and we quantify the power-law exponent for many different types of topologies. Our results allow a network designer to choose not only the most cost-effective combination of electronic and optical switching, but also the best fiber topology to achieve the minimal total cost.
16781216
Fast hierarchical clustering and its validation
Clustering is the task of grouping similar objects into clusters. A prominent and useful class of algorithm is hierarchical agglomerative clustering (HAC) which iteratively agglomerates the closest pair until all data points belong to one cluster. It outputs a dendrogram showing all N levels of agglomerations where N is the number of objects in the dataset. However, HAC methods have several drawbacks: (1) high time and memory complexities for clustering, and (2) inefficient and inaccurate cluster validation. In this paper we show that these drawbacks can be alleviated by closely studying the dendrogram. Empirical study shows that most HAC algorithms follow a trend where, except for a number of top levels of the dendrogram, all lower levels agglomerate clusters which are very small in size and close in proximity to other clusters. Methods are proposed that exploit this characteristic to reduce the time and memory complexities significantly and to make validation very efficient and accurate. Analyses and experiments show the effectiveness of the proposed method.
17605363
Handling concept drifts in incremental learning with support vector machines
With the increase in the size of real-world databases, there is an ever-increasing need to scale up inductive learning algorithms. Incremental learning techniques are one possible solution to the scalability problem. In this paper, we propose three ctiteria to evaluate the robustness and reliability of incremental learning methods, and use them to study the robustness of an incremental training method for Support Vector Machines. We provide empirical results using benchmark machine learning datasets to show that support vectors form a svccdnct and suficient set for block-by-block incremental learning.
2465876
Two sufficient conditions for dominating cycles
A cycle C of a graph G is dominating if each component of GnC is edgeless. In the paper, we will give two sufficient conditions for each longest cycle of a 3-connected graph to be a dominating cycle. 2005 Wiley Periodicals, Inc. J Graph Theory 49: 135–150, 2005
14550653
QoS Topology Control with Minimal Total Energy Cost in Ad Hoc Wireless Networks
This paper discusses the energy efficient QoS topology control problem in ad hoc wireless networks. Given a set of nodes in a plane, end-to-end traffic demands and delay bounds between node pairs, the problem is to find a network topology that can meet the QoS requirements and the total transmission power of nodes is minimized. We consider two cases of the problem: 1) the traffic demands are not splittable, and 2) the traffic demands are splittable. The first case is formulated as an integer linear programming problem. The latter case is formulated as a mixed integer linear programming problem. A greedy algorithm and an approximation algorithm with ratio n are proposed to solve the problem, where n is the number of nodes. Extensive simulations are conducted to evaluate the performance of proposed algorithms.
14433108
Using amino acid patterns to accurately predict translation initiation sites
The translation initiation site (TIS) prediction problem is about how to correctly identify TIS in mRNA, cDNA, or other types of genomic sequences. High prediction accuracy can be helpful in a better understanding of protein coding from nucleotide sequences. This is an important step in genomic analysis to determine protein coding from nucleotide sequences. In this paper, we present an in silico method to predict translation initiation sites in vertebrate cDNA or mRNA sequences. This method consists of three sequential steps as follows. In the first step, candidate features are generated using k-gram amino acid patterns. In the second step, a small number of top-ranked features are selected by an entropy-based algorithm. In the third step, a classification model is built to recognize true TISs by applying support vector machines or ensembles of decision trees to the selected features. We have tested our method on several independent data sets, including two public ones and our own extracted sequences. The experimental results achieved are better than those reported previously using the same data sets. Our high accuracy not only demonstrates the feasibility of our method, but also indicates that there might be "amino acid" patterns around TIS in cDNA and mRNA sequences.