1,720,970 research outputs found
Utility-based Optimisation of Resource Allocation for Wireless Networks
No full textFrom providing only voice communications, wireless networks aim to provide a wide range of services in which soft real-time, high priority critical data, and best effort connections seamlessly integrate. Some of these applications and services have firm resource requirements in order to function properly (e.g. videoconferences), others are flexible enough to adapt to whatever is available (e.g. FTP). Providing differentiation and resource assurance is often referred to as providing quality of service (QoS). In this thesis we study how novel resource allocation algorithms can improve the offered QoS of dynamic, unpredictable, and resource constrained distributed systems, such as a wireless network, during periods of overload. We propose and evaluate several bandwidth allocation schemes in the context of cellular, hybrid and pure ad hoc networks. Acceptable quality levels for a connection are specified using resource-utility functions, and our allocation aims to maximise accumulated systemwide utility. To keep allocation optimal in this changing environment, we need to periodically reallocate resources. The novelty of our approach is that we have augmented the utility function model by identifying and classifying the way reallocations affect the utility of different application classes. We modify the initial utility functions at runtime, such that connections become comparable regardless of their flexibility to reallocations or age-related importance. Another contribution is a combined utility/price-based bandwidth allocation and routing scheme for ad hoc networks. First we cast the problem of utility maximisation in a linear programming form. Then we propose a novel distributed allocation algorithm, where every flow bids for resources on the end-to-end path depending on the resource ``shadow price'', and the flow's ``utility efficiency''. Our periodic (re)allocation algorithms represent an iterative process that both adapts to changes in the network, and recalculates and improves the estimation of resource shadow prices. Finally, problems connected to allocation optimisation, such as modelling non-critical resources as costs, or using feedback to adapt to uncertainties in resource usage and availability, are addressed
Adaptive QoS-aware resource allocation for wireless networks
No full textWireless communication networks are facing a paradigm shift. From providing only voice communication, new generations of wireless networks are designed to provide different types of multimedia communications together with different types of data services and aim to seamlessly integrate in the big Internet infrastructure. Some of these applications and services have strong resource requirements in order to function properly (e.g. videoconferences), others are flexible enough to adapt to whatever is available (e.g. FTP). Also, different services (or different users), might have different importance levels, and should be treated accordingly. Providing resource assurance and differentiation is often referred to as quality of service (QoS). Moreover, due to the constrained and fluctuating bandwidth of the wireless link, and user mobility, wireless networks represent a class of distributed systems with a higher degree of unpredictability and dynamic change as compared to their wireline counterparts.In this thesis we study how novel resource allocation algorithms can improve the behaviour (the offered QoS) of dynamic unpredictable distributed systems, such as a wireless network, during periods of overload. This work concerns both low level enforcement mechanisms and high-level policy dependent optimisation algorithms.First, we propose and evaluate adaptive admission control algorithms for controlling the load on a processor in a radio network controller. We use feedback mechanisms inspired by automatic control techniques to prevent CPU overload, and policy-dependent deterministic algorithms to provide service differentiation.Second, we propose and evaluate a QoS-aware bandwidth admission control and allocation algorithm for the radio link in a network cell. The acceptable quality levels for a connection are specified using bandwidth dependent utility functions, and our scheme aims to maximise system-wide utility. The novelty in our approach is that we take into account bandwidth reallocation, which arise as a consequence of the dynamic environment, and their effects on the accumulated utility of the different connections. </p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Price/Utility-based optimized resource allocation in wireless ad hoc networks
No full textThis paper proposes a scheme for bandwidth allocation in wireless ad hoc networks. The Quality of Service (QoS) levels for each end-to-end flow are expressed using resource-utility functions, and our algorithms aim to maximise the aggregated utility of the flows. The scheme differentiates between applications with flexible resource requirements and rigid (real-time) requirements. As an abstract notion of resource, we use maximal cliques of mutual interfering links. Using concave piece-wise linear utility functions we present a linear programming (LP) formulation of the problem that can serve as an optimal though unrealistic solution. Then we replace this centralised approach with a distributed low complexity solution. A key concept, borrowed from the dual of the optimal allocation problem, is the shadow price of a resource. The contributions of the paper are twofold: (1) a distributed algorithm that allocates the bandwidth based on bids that are calculated using the shadow price of the resources and the flows utility function, (2) a utility-aware on-demand shortest path routing algorithm in which the shadow prices are used a natural distance metric. We compare the performance of the distributed allocation scheme with the centralised, optimal linear programming solution. We also compare with a non-utility-based QoS allocation scheme, that uses hop-based shortest path routing followed by highest possible bandwidth accommodation of the flow.</p
Time-aware Utility-based QoS Optimisation
No full textThis paper presents a time-aware admission control and resource allocation scheme in the context of a future generation mobile network. The quality levels (and their respective utility) of the different connections are specified using discrete resource-utility (R-U) functions. The scheme uses these R-U functions for allocating and reallocating bandwidth to connections, aiming to maximise the accumulated utility of the system. However, different applications react differently to resource reallocations. Therefore at each allocation timepoint we take into account the following factors: the age of the connection, a drop (disconnection) penalty and the sensitiveness to reallocation frequency. Finally, we show the superior performance of our approach compared to a recent adaptive bandwidth allocation scheme.</p
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