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Doppler frequency estimation-based handover algorithm for long-term evolution networks

IET NETWORKS 2014年第2期3卷 88-96页

作者： Altrad, Omar Muhaidat, Sami Yoo, Paul D. Simon Fraser Univ Burnaby BC Canada Khalifa Univ Abu Dhabi U Arab Emirates Univ Surrey CCSR Guildford Surrey England

Mobile cellular radio systems have become complex multi-layered systems with a mixed architecture of macro and micro cells;therefore, a dynamic method of triggering the handover algorithm in such systems is invaluable and required. In this paper the authors develop a simple handover mechanism to adapt for a fast moving mobile station requesting a handover, in which the authors utilise a Doppler frequency estimation in the downlink for adjustment and apply it to a long-term evolution (LTE) network. This method is beneficial for high speed mobiles in macro and/or micro cells, in which for the latter the cell radius is small and needs a dynamic algorithm to respond in a timely manner. The main objective of this study is to investigate the performance of the proposed algorithm;hence, a system layout is specifically designed for this study. Other factors, such as interference, which may affect the performance of the suggested system are not addressed here. The main concern is to study and compare the proposed algorithm to the standard handover algorithm currently implemented in LTE. Simulations at the system level show a marked decrease in the average number of handovers requested.

关键词： Frequency estimation Microcells Local thermodynamic equilibrium macro commands algorithms system level Handover dynamic algorithms Doppler frequency Long Term Evolution

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NOVEL algorithms FOR SEARCHING CONFORMATIONAL SPACE

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JOURNAL OF COMPUTER-AIDED MOLECULAR DESIGN 1994年第1期8卷 67-82页

作者： BYRNE, D LI, J PLATT, E ROBSON, B WEINER, P PROTEUS MOLEC DESIGN LTD PROTEUS HOUSELYME GREEN BUSINESS PKMACCLESFIELD SK11 0JLCHESHIREENGLAND AMBER SYST INC SOMERVILLEMA 02143

The modelling of biological molecules by molecular dynamics is beset by a range of problems. The most important of these is the multiple-minima problem. The deep metastable minima can cause difficulties in proper equilibration of a molecular system and result in the simulated system being trapped in a long-lived metastable state. One way to overcome these problems is to re-engineer the ''Newtonian Rules' in order to more efficiently search conformational space. Re-engineering of the 'Newtonian Rules' implies a redesign of the physical laws arising from them. This is done in various ways by the RUSH, Hybrid Monte Carlo and PEACS algorithms. This paper explores applications of these algorithms, and compares them to a traditional molecular dynamics method.

关键词： MOLECULAR SIMULATION CONFORMATIONAL SEARCH dynamic algorithms

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Just-In-Time Constraint-Based Inference for Qualitative Spatial and Temporal Reasoning

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KUNSTLICHE INTELLIGENZ 2020年第2期34卷 259-270页

作者： Sioutis, Michael Univ Bamberg Fac Informat Syst & Appl Comp Sci Weberei 5 D-96047 Bamberg Germany

We discuss a research roadmap for going beyond the state of the art in qualitative spatial and temporal reasoning (QSTR). Simply put, QSTR is a major field of study in Artificial Intelligence that abstracts from numerical quantities of space and time by using qualitative descriptions instead (e.g., precedes, contains, is left of);thus, it provides a concise framework that allows for rather inexpensive reasoning about entities located in space or time. Applications of QSTR can be found in a plethora of areas and domains such as smart environments, intelligent vehicles, and unmanned aircraft systems. Our discussion involves researching novel local consistencies in the aforementioned discipline, defining dynamic algorithms pertaining to these consistencies that can allow for efficient reasoning over changing spatio-temporal information, and leveraging the structures of the locally consistent related problems with regard to novel decomposability and theoretical tractability properties. Ultimately, we argue for pushing the envelope in QSTR via defining tools for tackling dynamic variants of the fundamental reasoning problems in this discipline, i.e., problems stated in terms of changing input data. Indeed, time is a continuous flow and spatial objects can change (e.g., in shape, size, or structure) as time passes;therefore, it is pertinent to be able to efficiently reason about dynamic spatio-temporal data. Finally, these tools are to be integrated into the larger context of highly active areas such as neuro-symbolic learning and reasoning, planning, data mining, and robotic applications. Our final goal is to inspire further discussion in the community about constraint-based QSTR in general, and the possible lines of future research that we outline here in particular.

关键词： Qualitative constraints Spatio-temporal reasoning Just-in-time inference Local consistencies Singleton checks dynamic algorithms Decomposability Adaptivity Parallelization

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An O(n^2.75) Algorithm for Incremental Topological Ordering

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ACM TRANSACTIONS ON algorithms 2008年第4期4卷 1–14页

作者： Ajwani, Deepak Friedrich, Tobias Meyer, Ulrich Max Planck Inst Informat D-66123 Saarbrucken Germany Goethe Univ Frankfurt Inst Comp Sci D-60325 Frankfurt Germany

We present a simple algorithm which maintains the topological order of a directed acyclic graph (DAG) with n nodes, under an online edge insertion sequence, in O(n(2.75)) time, independent of the number m of edges inserted. For dense DAGs, this is an improvement over the previous best result of O(min{m(3/2) log n, m (3/2) + n(2) log n}) by Katriel and Bodlaender [2006]. We also provide an empirical comparison of our algorithm with other algorithms for incremental topological sorting.

关键词： dynamic algorithms graphs online algorithms topological order

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Big data algorithms beyond machine learning

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KUNSTLICHE INTELLIGENZ 2018年第1期32卷 9-17页

作者： Mnich, Matthias Maastricht Univ Dept Quantitat Econ POB 616 NL-6200 MD Maastricht Netherlands Univ Bonn Inst Informat Friedrich Ebert Allee 144 D-53113 Bonn Germany

The availability of big data sets in research, industry and society in general has opened up many possibilities of how to use this data. In many applications, however, it is not the data itself that is of interest but rather we want to answer some question about it. These answers may sometimes be phrased as solutions to an optimization problem. We survey some algorithmic methods that optimize over large-scale data sets, beyond the realm of machine learning.

关键词： Big data algorithms Large-scale optimization Kernelization dynamic algorithms

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Impact of condition number on total sum rate for NOMA systems

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ELECTRONICS LETTERS 2020年第20期56卷 1091-+页

作者： Vidal-Beltran, S. Lopez-Bonilla, J. L. Martinez-Pinon, F. Cuenca-Alvarez, R. Inst Politecn Nacl Escuela Super Ingn Mecan & Elect Zacatenco Mexico City DF Mexico Inst Politecn Nacl Ctr Invest & Innovac Tecnol Azcapotzalco Mexico City DF Mexico

In the fifth-generation mobile communications networks, several resource allocation techniques have been used, such as static allocation and dynamic algorithms (greedy or matching theory);this work proposes a new subcarrier allocation scheme based on the evaluation of the instantaneous behaviour of the wireless channel using the condition number of the channel matrix H. Simulation results reveal that the proposed scheme increases the total sum rate of the system, compared to their predecessors.

关键词： wireless channels resource allocation 5G mobile communication multi-access systems greedy algorithms matrix algebra NOMA systems fifth-generation mobile communications networks resource allocation techniques static allocation dynamic algorithms greedy theory matching theory subcarrier allocation scheme instantaneous behaviour wireless channel channel matrix condition number impact

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dynamically switching vertices in planar graphs

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ALGORITHMICA 2000年第1期28卷 76-103页

作者： Frigioni, D Italiano, GF Univ Roma La Sapienza Dipartimento Informat & Sistemist I-00198 Rome Italy Max Planck Inst Informat D-66123 Saarbrucken Germany Univ Aquila Dipartimento Ingn Elettr I-67040 Laquila Italy Univ Roma Tor Vergata Dipartimento Sistemi & Prod Rome Italy

We consider graphs whose vertices may be in one of two different states: either on or off. We wish to maintain dynamically such graphs under an intermixed sequence of updates and queries. An update may reverse the status of a vertex, by switching it either on or off, and may insert a new edge or delete an existing edge. A query tests whether any two given vertices are connected in the subgraph induced by the vertices that are on. We give efficient algorithms that maintain information about connectivity on planar graphs in O(log(3) n) amortized time per query, insert, delete, switch-on, and switch-off operation over sequences of at least Omega(n) operations, where n is the number of vertices of the graph.

关键词： planar graphs dynamic algorithms connectivity separators

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Two methods for the generation of chordal graphs

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ANNALS OF OPERATIONS RESEARCH 2008年第1期157卷 47-60页

作者： Markenzon, Lilian Vernet, Oswaldo Araujo, Luiz Henrique Univ Fed Rio de Janeiro Nucl Comp Elect Rio De Janeiro Brazil Inst Militar Engn Rio De Janeiro Brazil

In this paper two methods for automatic generation of connected chordal graphs are proposed: the first one is based on new results concerning the dynamic maintenance of chordality under edge insertions;the second is based on expansion/merging of maximal cliques. Theoretical and experimental results are presented. In both methods, chordality is preserved along the whole generation process.

关键词： chordal graphs dynamic algorithms clique-tree graph generation

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Ensemble-based methods for describing protein dynamics

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CURRENT OPINION IN PHARMACOLOGY 2010年第6期10卷 760-769页

作者： Jacobs, Donald J. Univ N Carolina Dept Phys & Opt Sci Charlotte NC 28223 USA

Molecular dynamics (MD) simulation is a natural approach for studying protein dynamics, and coupled with the ideas of multiscale modeling, MD proves to be the gold standard in computational biology to investigate mechanistic details related to protein function In principle if MD trajectories are long enough, the ensemble of protein conformations generated allows thermodynamic and kinetic properties to be predicted We know from experiments that proteins exhibit a high degree of fidelity in function and that empirical kinetic models are successful in describing kinetics suggesting that the ensemble of conformations cluster into well-defined thermodynamic states, which are frequently metastable The experimental evidence suggest that more efficient computational models that retain only essential properties of the protein can be constructed to faithfully reproduce the relatively few observed thermodynamic states, and perhaps describe transition states if the model is sufficiently detailed Indeed, there are many so-called ensemble-based methods that attempt to generate more complete ensembles than MD can provide by focusing on the most important driving forces through simplified representations of how elements within the protein interact Although coarse-graining is employed in MD and other approaches, such as in elastic network models, the key distinguishing factor of ensemble-based methods is that they are meant to efficiently generate a large ensemble of conformations without solving explicit equations of motion This review highlights three types of ensemble-based methods illustrated by COREX and the Wako-Saito-Munoz-Eaton (WSME) model the Framework Rigidity Optimized dynamic Algorithm (FRODA) and the distance constraint model (DCM)

关键词： Protein Conformation Computational Biology protein structure function Ensembles Thermodynamics Kinetics Equations of motion dynamic algorithms Protein DRIVING FORCE Bioinformatics

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MAINTAINING SHORTEST PATHS UNDER DELETIONS IN WEIGHTED DIRECTED GRAPHS

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SIAM JOURNAL ON COMPUTING 2016年第2期45卷 548-574页

作者： Bernstein, Aaron Columbia Univ Dept Comp Sci New York NY 10027 USA

We present an improved algorithm for maintaining all-pairs (1 + epsilon) approximate shortest paths under deletions and weight-increases. The previous state of the art for this problem is total update time (O) over tilde (n(2)root m/epsilon) over all updates for directed unweighted graphs [ S. Baswana, R. Hariharan, and S. Sen, J. algorithms, 62 (2007), pp. 74-92], and (O) over tilde (mn/epsilon) for undirected unweighted graphs [ L. Roditty and U. Zwick, in Proceedings of the 45th FOCS, Rome, Italy, 2004, pp. 499-508]. Both algorithms are randomized and have constant query time. Very recently, Henzinger, Krinninger, and Nanongkai presented a deterministic version of the latter algorithm [ M. Henzinger, S. Krinninger, and D. Nanongkai, in IEEE FOCS, 2013, pp. 538-547]. Note that (O) over tilde (mn) is a natural barrier because even with a (1 + epsilon) approximation, there is no o(mn) combinatorial algorithm for the static all-pairs shortest path problem. Our algorithm works on directed weighted graphs and has total (randomized) update time (O) over tilde (mn log R/epsilon) where R is the ratio of the largest edge weight to appear at any point in the update sequence to the smallest such weight. (As with previous algorithms, our query time is constant.) Technically, the running time is (O) over tilde (mn log R/epsilon) + O(Delta), where Delta is the total number of updates;the same O(Delta) term is also implicitly present in all other algorithms for the problem, since a constant time per update is clearly unavoidable. Note that log R = O(log(n)) as long as weights are polynomial in n;thus, we effectively expand the (O) over tilde (mn/epsilon) total update time bound from undirected unweighted graphs to directed graphs with polynomial weights. This is in fact the first nontrivial algorithm for decremental all-pairs shortest paths that works on weighted graphs (previous algorithms could only handle small integer weights). By a well-known reduction from decremental algo

关键词： graph algorithms dynamic algorithms approximation shortest paths

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