1,720,969 research outputs found
Game-Theoretic Resource Pricing and Provisioning Strategies in Cloud Systems
Get PDFWe consider several Software as a Service (SaaS) providers that offer services using the Cloud resources provided by an Infrastructure as a Service (IaaS) provider which adopts a pay-per-use scheme similar to the Amazon EC2 service, comprising flat, on demand, and spot virtual machine instances. For this scenario, we study the virtual machine provisioning and spot pricing strategies.We consider a two-stage provisioning scheme. In the first stage, the SaaS providers determine the optimal number of required flat and on demand instances. Then, in the second stage, the IaaS provider sells its unused capacity as spot instances for which the SaaS providers compete by submitting a bid. We study two different IaaS provider pricing strategies: the first assumes the IaaS provider sets a unique price; in the second, instead, the IaaS provider can set different prices for different customers. We model the resulting problem as a Stackelberg game. For each pricing scheme, we show the existence of the game equilibrium and provide the solution algorithms. Through numerical evaluation we compare the provisioning and spot price under the two different pricing strategies as function of the system parameters
Wake-up radio-based data forwarding for green wireless networks
Get PDFThis paper presents G-WHARP, for Green Wake-up and HARvesting-based energy-Predictive forwarding, a wake-up radio-based forwarding strategy for wireless networks equipped with energy harvesting capabilities (green wireless networks). Following a learning-based approach, G-WHARP blends energy harvesting and wake-up radio technology to maximize energy efficiency and obtain superior network performance. Nodes autonomously decide on their forwarding availability based on a Markov Decision Process (MDP) that takes into account a variety of energy-related aspects, including the currently available energy and that harvestable in the foreseeable future. Solution of the MDP is provided by a computationally light heuristic based on a simple threshold policy, thus obtaining further computational energy savings. The performance of G-WHARP is evaluated via GreenCastalia simulations, where we accurately model wake-up radios, harvestable energy, and the computational power needed to solve the MDP. Key network and system parameters are varied, including the source of harvestable energy, the network density, wake-up radio data rate and data traffic. We also compare the performance of G-WHARP to that of two state-of-the-art data forwarding strategies, namely GreenRoutes and CTP-WUR. Results show that G-WHARP limits energy expenditures while achieving low end-to-end latency and high packet delivery ratio. Particularly, it consumes up to 34% and 59% less energy than CTP-WUR and GreenRoutes, respectively
The METASAT Model-Based Engineering Workflow and Digital Twin Concept
No full textConsidering the complexity in the design of future satellites and the need for compliance with ECSS standards, the METASAT project proposes a novel design methodology based on model-based engineering and supported by open architecture hardware. The initiative highlights the potential of software vir-tualisation layers, like hypervisors, to meet standards compliance on high-performance computing platforms. Our focus is on the development of a toolchain tailored for these advanced hard-ware/software layers. In our view, without such innovation, the satellite industry may face high and unsustainable development costs and timelines, which could affect its competitiveness and reliability. This paper provides an overview of the model-based engineering toolchain, the workflow, and the digital twin concept proposed for the METASAT project. We present the purpose of each component and how they work together in the broader METASAT vision, with the objective of showing how this approach can make the development process more efficient and enhance dependability in the sector.The research presented throughout this paper has received funding from the European Commission’s Horizon Europe programme under the METASATproject (grant agreement 101082622).Peer Reviewed"Article signat per 11 autors/es: Calderón, Alejandro J. and Yarza, Irune and Sinisi, Stefano and Lazzara, Lorenzo and Di Valerio, Valerio and Stazi, Giulia and Kosmidis, Leonidas and Trompouki, Matina M. and Ulisse, Alessandro and Amonarriz, Aitor and Onaindia, Peio
A game-theoretic approach to computation offloading in mobile cloud computing
Get PDFWe consider a three-tier architecture for mobile and pervasive computing
scenarios, consisting of a local tier ofmobile nodes, a middle tier (cloudlets) of nearby
computing nodes, typically located at the mobile nodes access points but characterized by a limited amount of resources, and a remote tier of distant cloud servers, which have
practically infinite resources. This architecture has been proposed to get the benefits of
computation offloading from mobile nodes to external servers while limiting the use
of distant servers whose higher latency could negatively impact the user experience.
For this architecture, we consider a usage scenario where no central authority exists
and multiple non-cooperative mobile users share the limited computing resources of
a close-by cloudlet and can selfishly decide to send their computations to any of the
three tiers. We define a model to capture the users interaction and to investigate the
effects of computation offloading on the users’ perceived performance. We formulate
the problem as a generalized Nash equilibrium problem and show existence of an
equilibrium.We present a distributed algorithm for the computation of an equilibrium
which is tailored to the problem structure and is based on an in-depth analysis of
the underlying equilibrium problem. Through numerical examples, we illustrate its
behavior and the characteristics of the achieved equilibria
Optimal pricing and service provisioning strategies in cloud systems: a Stackelberg game approach
Get PDFCloud computing is a recent advancement where service providers offer hardware infrastructures, platforms, and software applications as services to users on the basis of a usage-based pricing model. As Cloud-based systems have been increasing in size and complexity and operate in a continuously and unpredictably changing environment, it has become increasingly more important and challenging to develop effective provisioning and pricing schemes. In this paper we consider several Software as a Service (SaaS) providers, that offer a set of Web services using the Cloud facilities provided by an Infrastructure as a Service (IaaS) provider.
We assume that the IaaS provider offers a pay only what you use scheme similar to the Amazon EC2 service, comprising flat, on demand, and spot virtual machine instances. We propose a two stage provisioning scheme. In the first stage, the SaaS providers determine the number of required flat and on demand instances by means of standard optimization techniques. In the second stage the SaaS providers compete, by bidding for the spot instances which are instantiated using the unused IaaS capacity. We assume that the SaaS providers want to maximize a suitable utility function which accounts for both the QoS delivered to their users and the associated cost. The IaaS provider, on the other hand, wants to maximize his revenue by determining the spot prices given the SaaS bids. We model the second stage as a Stackelberg game, and we compute its equilibrium price and allocation strategy by solving a Mathematical Program with Equilibrium Constraints (MPEC) problem. Through numerical evaluation we study the equilibrium solutions as function of the system parameters
A Reinforcement learning-based data-link protocol for underwater acoustic communications
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
- …
