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Modular System-Level Simulator Concept for OFDMA Systems

IEEE COMMUNICATIONS MAGAZINE 2009年第3期47卷 150-156页

作者： Fernekess, Andreas Klein, Anja Wegmann, Bernhard Dietrich, Karl Tech Univ Darmstadt Inst Telecommun Darmstadt Germany

Modeling and simulation is essential for performance evaluation of wireless systems and specific algorithms used, for instance, during resource allocation. For Current and future wireless systems, several properties have to be considered such as data traffic, frequency selective fading channels, and radio resource management. Throughout this article, a new system-level simulator concept is presented for packet switched systems using OFDMA, which is called snapshot-based SLS;and represents a compromise between state-of-the-art static and dynamic SLSs. The proposed methodology only considers short time intervals within the busy hour by their statistics so that RRM and data traffic can be considered, as in dynamic SLS, but with lower computational complexity. In this article a description is given of how the cellular setup and traffic generation are performed for the proposed snapshot concept. Furthermore, a new methodology is proposed for a quality measure of resource units that is applicable to future wireless systems using an interleaved subcarrier allocation. Exemplary simulation results show that the developed concept is able to evaluate the performance of OFDMA systems considering the impact of, for example, data traffic and resource allocation strategies.

关键词： ORTHOGONAL frequency division multiplexing WIRELESS communication systems computer algorithms computer networks DATA transmission systems RESOURCE allocation computer systems computer simulation TELECOMMUNICATION

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A fine-grained analysis of the support provided by UML class diagrams and ER diagrams during data model maintenance

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SOFTWARE AND SYSTEMS MODELING 2015年第1期14卷 287-306页

作者： Bavota, Gabriele Gravino, Carmine Oliveto, Rocco De Lucia, Andrea Tortora, Genoveffa Genero, Marcela Cruz-Lemus, Jose A. Univ Salerno I-84100 Salerno Italy Univ Molise Pesche Isernia Italy Univ Castilla La Mancha La Mancha Spain

This paper presents the results of an empirical study aiming at comparing the support provided by ER and UML class diagrams during maintenance of data models. We performed one controlled experiment and two replications that focused on comprehension activities (the first activity in the maintenance process) and another controlled experiment on modification activities related to the implementation of given change requests. The results achieved were analyzed at a fine-grained level aiming at comparing the support given by each single building block of the two notations. Such an analysis is used to identify weaknesses (i.e., building blocks not easy to comprehend) in a notation and/or can justify the need of preferring ER or UML for data modeling. The analysis revealed that the UML class diagrams generally provided a better support for both comprehension and modification activities performed on data models as compared to ER diagrams. Nevertheless, the former has some weaknesses related to three building blocks, i.e., multi-value attribute, composite attribute, and weak entity. These findings suggest that an extension of UML class diagrams should be considered to overcome these weaknesses and improve the support provided by UML class diagrams during maintenance of data models.

关键词： DATA modeling SOFTWARE engineering computer software computer simulation DATA analysis computer algorithms

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Competitive algorithms for the dynamic selection of component implementations

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IBM SYSTEMS JOURNAL 2003年第1期42卷 85-97页

作者： Yellin, DM IBM Corp Div Res Thomas J Watson Res Ctr Yorktown Hts NY 10598 USA

As component-based development matures, more and more applications are built by integrating multiple distributed components. We suggest providing components with multiple implementations, each optimized for a particular workload,and augmenting the component run-time environment with a mechanism for switching between implementations. This mechanism monitors the types of requests the component is receiving, and adaptively switches implementations for optimal application performance. Achieving this optimal performance depends on making good choices as to when and how to switch implementations, a problem, we refer to as the adaptive component problem. We first formalize the generic problem and then provide an algorithm, named Delta, for switching implementations in the special case when the component has exactly two implementations. We show that this algorithm is (3 + epsilon)-competitive with respect to the optimal algorithm, where epsilon is a small fraction. We establish a 3-competitve lower bound for the problem, which implies that Delta is close to optimal. We describe the application of these results to the distributed pub/sub problem, and the data structure selection problem.

关键词： computer algorithms AUTOMATIC programming (computer science)

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Spectral matching approaches in hyperspectral image processing

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INTERNATIONAL JOURNAL OF REMOTE SENSING 2014年第24期35卷 8217-8251页

作者： Shanmugam, S. SrinivasaPerumal, P. Anna Univ Dept Geol Madras 600025 Tamil Nadu India

Many spectral matching algorithms, ranging from the traditional clustering techniques to the recent automated matching models, have evolved. This paper provides a review and up-to-date information on the past and current role of the spectral matching approaches adopted in hyperspectral satellite image processing. The need for spectral matching has been deliberated and a list of spectral matching algorithms has been compared and described. A review of the conventional spectral angle measures and the advanced automated spectral matching tools indicates that, for better performance of target detection, there is a need for combining two or more spectral matching techniques. From the studies of several authors, it is inferred that continuous improvement in the matching techniques over the past few years is due to the need to handle and analyse hyperspectral image data for various applications. The need to develop a well-built and specialized spectral library to accommodate the resources from enormous spectral data is suggested. This may improve accuracy in mineral and soil mapping, vegetation species identification and health monitoring, and target detection. The future role of cloud computing in accessing globally distributed spectral libraries and performing spectral matching is highlighted. Rather than inferring that a particular matching algorithm is the best, this paper points out the requirements of an ideal algorithm. With increasing usage of hyperspectral data for resources mapping, the review presented in this paper will certainly benefit the large and emerging community of hyperspectral image users.

关键词： RESEARCH Image registration Soil mapping Plant species computer algorithms Remote-sensing images Hyperspectral imaging systems

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Least Trimmed Squares Approach to Lucas-Kanade Algorithm in Object Tracking Problems

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MATHEMATICAL PROBLEMS IN ENGINEERING 2013年第1期2013卷 1-6页

作者： Lin, Yih-Lon I Shou Univ Dept Informat Engn Kaohsiung 84001 Taiwan

The object tracking problem is an important research topic in computer vision. For real applications such as vehicle tracking and face tracking, there are many efficient and real-time algorithms. In this study, we will focus on the Lucas-Kanade (LK) algorithm for object tracking. Although this method is time consuming, it is effective in tracking accuracy and environment adaptation. In the standard LK method, the sum of squared errors is used as the cost function, while least trimmed squares is adopted as the cost function in this study. The resulting estimator is robust against outliers caused by noises and occlusions in the tracking process. Simulations are provided to show that the proposed algorithm outperforms the standard LK method in the sense that it is robust against the outliers in the object tracking problems.

关键词： LEAST squares computer algorithms OBJECT tracking (computer vision) computer vision APPLICATION software REAL-time computing

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All I really need to know about pair programming I learned in kindergarten

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COMMUNICATIONS OF THE ACM 2000年第5期43卷 108-114页

作者： Williams, LA Kessler, RR Univ Utah Dept Comp Sci Salt Lake City UT 84112 USA

The article highlights the success of pair programming based on a 'pair programming survey,' in context of Robert L. Fulgham's essay titled 'All I Really Need to Know I Learned in Kindergarten.' The article reports that when it comes to programming practices, studies show two heads are almost better than one. Pair programming is a practice in which two programmers work side-by-side at one computer, continuously collaborating on the same design, algorithm, code, or test. Anecdotal and initial statistical evidence indicates pair programming is highly beneficial, which is also attributed by Extreme programming. In the case of transition to pair programming from solitary programming, to avoid hesitation and to work successfully, some principles referred to are sharing of the work, sharing of key board typing and continuous analysis, avoiding negative thoughts, leaving ego etc. As a final thought, the article points out that making transition to pair programming involves breaking down some personal barriers. The success lies in hands of them in understanding the value of intercommunication skills, in confidently sharing the work and accepting the ownership of the partner's work. INSET: All I Really Need to Know I Learned in Kindergarten..

关键词： computer algorithms computer programmers computer software Intercommunication systems Electronic systems

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Substation planning method based on the weighted Voronoi diagram using an intelligent optimisation algorithm

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IET GENERATION TRANSMISSION & DISTRIBUTION 2014年第12期8卷 2173-2182页

作者： Lu, Zhiying Wang, Shiju Ge, Shaoyun Wang, Chengshan Tianjin Univ Minist Educ Key Lab Power Syst Simulat & Control Tianjin 300072 Peoples R China

Distribution network planning is a very complicated, non-linear, large scale multi-objective and multi-constraint combinatorial optimisation problem. The capacity, location and power supply range of the substation and the distribution network are optimised based on the load forecasting. In previous studies, this problem usually decomposes into two sub-problems, one is substation planning and the other is distribution network planning. The authors propose a method based on the self-adjustment weighted Voronoi diagram (WVD) using genetic algorithms and particle swarm optimisation for planning substations, which can optimise the location and power range of the substations when both the number and capacity of the substations are known. The weight is calculated according to the substation capacity and load distribution, and then the authors form the self-adjusted WVD whose weight can be adaptively adjusted. This method ensures the convergence of the algorithm and also makes the location and power supply range of the substations more reasonable. On this basis, the self-adjusted WVD based on the elitist selection genetic algorithm (ESGA-WVD) or the particle swarm optimisation algorithm (PSO-WVD) is achieved using the global search feature of the ESGA or the PSO. Numerical results show that ESGA-WVD and PSO-WVD are more reliable and reasonable than single ESGA, PSO or WVD;both in the determination of substation location and in the division of the substation power supply range. Compared with ESGA-WVD, PSO-WVD is better in terms of running time, convergence rate and investment costs.

关键词： ELECTRIC power distribution -- Planning ELECTRIC substations VORONOI polygons INTELLIGENT control systems computer algorithms

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Photorealistic volume scattering model in the bidirectional stochastic ray tracing problem

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PROGRAMMING AND computer SOFTWARE 2015年第5期41卷 295-301页

作者： Zhdanov, D. D. Garbul, A. A. Potemin, I. S. Voloboy, A. G. Galaktionov, V. A. Ershov, S. V. Sokolov, V. G. St Petersburg Natl Res Univ Informat Technol Mech St Petersburg 197101 Russia Russian Acad Sci Keldysh Inst Appl Math Moscow 125047 Russia Vavilov State Opt Inst St Petersburg 99053 Russia

This paper is devoted to the development of physically correct rendering model of scenes containing volume scattering objects. The solution of the rendering equation is based on the Monte-Carlo bidirectional ray tracing. Two efficient approaches to the solution of the rendering equation for different parameters of the volume scattering medium (typically, concentration of scattering particles) are developed. Examples illustrate how the proposed models can be used for photorealistic visualization of scenes containing volume scattering objects and for the simulation of illuminators based on the volume scattering effect. Possible limitations of the application field of the proposed models are considered.

关键词： RAY tracing algorithms computer algorithms SCATTERING (Mathematics) MONTE Carlo method MATHEMATICAL models RESEARCH

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Best Speed Fit EDF Scheduling for Performance Asymmetric Multiprocessors

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MATHEMATICAL PROBLEMS IN ENGINEERING 2017年第1期2017卷 1-7页

作者： Wu, Peng Ryu, Minsoo Hanyang Univ Dept Elect & Comp Engn Seoul South Korea Hanyang Univ Dept Comp Sci & Engn Seoul South Korea

In order to improve the performance of a real-time system, asymmetric multiprocessors have been proposed. The benefits of improved system performance and reduced power consumption from such architectures cannot be fully exploited unless suitable task scheduling and task allocation approaches are implemented at the operating system level. Unfortunately, most of the previous research on scheduling algorithms for performance asymmetricmultiprocessors is focused on task priority assignment. They simply assign the highest priority task to the fastest processor. In this paper, we propose BSF-EDF (best speed fit for earliest deadline first) for performance asymmetric multiprocessor scheduling. This approach chooses a suitable processor rather than the fastest one, when allocating tasks. With this proposed BSF-EDF scheduling, we also derive an effective schedulability test.

关键词： INFORMATION asymmetry MULTIPROCESSORS REAL-time computing ENERGY consumption computer scheduling computer algorithms

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Thresholds and optimal binary comparison search trees

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JOURNAL OF algorithms-COGNITION INFORMATICS AND LOGIC 2002年第2期44卷 338-358页

作者： Anderson, R Kannan, S Karloff, H Ladner, RE Univ Washington Dept Comp Sci & Engn Seattle WA 98195 USA Univ Penn AT&T Labs Res Philadelphia PA 19104 USA Univ Penn Dept CIS Philadelphia PA 19104 USA AT&T Labs Res Florham Pk NJ 07932 USA Georgia Inst Technol Coll Comp Atlanta GA 30332 USA

We present an O(n(4))-time algorithm for the following problem: Given a set of items with known access frequencies, find the optimal binary search tree under the realistic assumption that each comparison can only result in a two-way decision: either an equality comparison or a less-than comparisons. This improves the best known result of O(n(5)) time, which is based on split tree algorithms. Our algorithm relies on establishing thresholds on the frequency of an item that can occur as an equality comparison at the root of an optimal tree. (C) 2002 Elsevier Science (USA). All rights reserved.

关键词： computer algorithms TREE graphs DATABASE searching

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