DIT - Artículos en Revistas Internacionales / International Journals

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Now showing 1 - 20 of 26
  • Publication
    Digital sources: a case study of the analysis of the Recovery of Historical Memory in Spain on the social network Twitter
    (CSIC, 2018-12-01) Congosto Martínez, María Luz
    The incorporation of digital sources from online social media into historical research brings great opportunities, although it is not without technological challenges. The huge amount of information that can be obtained from these platforms obliges us to resort to the use of quantitative methodologies in which algorithms have special relevance, especially regarding network analysis and data mining. The Recovery of Historical Memory in Spain on the social network Twitter will be analysed in this article. An open-code tool called T-Hoarder was used; it is based on objectivity, transparency and knowledge-sharing. It has been in use since 2012.
  • Publication
    Performance trade-offs of auto scaling schemes for NFV with reliability requirements
    (Elsevier, 2023-12-01) Perez-Valero, Jesus; García Reinoso, Jaime José; Banchs Roca, Albert; Serrano Yáñez-Mingot, Pablo; Ortin, Jorge; Costa-Pérez, Xavier; European Commission; Ministerio de Economía y Competitividad (España)
    A major concern for future mobile networks is to meet extremely stringent reliability requirements without incurring very high energy consumption. To this aim, we need auto-scaling techniques to switch on/off servers on demand, ensuring that they are active when required. One key challenge is to keep the right number of active servers while accounting for both the fallibility of servers and their non-zero boot up time: if this number is too small we risk service disruption, but if it is too large resources will be wasted. In this paper, we analyze this challenge by assessing the performance of different strategies to support an energy-efficient highly-reliable service, which range from deploying few blade (i.e., reliable) servers to deploying many nano (i.e., unreliable) servers. Our main take-away message is two-fold: (1) a server farm of nano servers can provide a more energy efficient operation than a farm of blade servers, but (2) it involves a very dynamic operation both in terms of task migrations and (de)activations, which challenges the endurance of the hardware.
  • Publication
    Noise sources, effects and countermeasures in narrowband power-line communications networks: a practical approach
    (MDPI, 2017-08) López López, Gregorio Ignacio; Moreno Novella, José Ignacio; Sanchez, Eutimio; Martínez, Cristina; Martin, Fernando; Ministerio de Economía y Competitividad (España)
    The integration of Distributed Generation, Electric Vehicles, and storage without compromising the quality of the power delivery requires the deployment of a communications overlay that allows monitoring and controlling low voltage networks in almost real time. Power Line Communications are gaining momentum for this purpose since they present a great trade-off between economic and technical features. However, the power lines also represent a harsh communications medium which presents different problems such as noise, which is indeed affected by Distributed Generation, Electric Vehicles, and storage. This paper provides a comprehensive overview of the types of noise that affects Narrowband Power Line Communications, including normative noises, noises coming from common electronic devices measured in actual operational power distribution networks, and noises coming from photovoltaic inverters and electric vehicle charging spots measured in a controlled environment. The paper also reviews several techniques to mitigate the effects of noise, paying special attention to passive filtering, as for being one of the most widely used solution to avoid this kind of problems in the field. In addition, the paper presents a set of tests carried out to evaluate the impact of some representative noises on Narrowband Power Line Communications network performance, as well as the effectiveness of different passive filter configurations to mitigate such an impact. In addition, the considered sources of noise can also bring value to further improve PLC communications in the new scenarios of the Smart Grid as an input to theoretical models or simulations.
  • Publication
    DQN-based intelligent controller for multiple edge domains
    (Elsevier, 2023-09-01) Llorens-Carrodeguas, Alejandro; Cervelló Pastor, Cristina; Valera Pintor, Francisco; European Commission; Agencia Estatal de Investigación (España)
    Advanced technologies like network function virtualization (NFV) and multi-access edge computing (MEC) have been used to build flexible, highly programmable, and autonomously manageable infrastructures close to the end-users, at the edge of the network. In this vein, the use of single-board computers (SBCs) in commodity clusters has gained attention to deploy virtual network functions (VNFs) due to their low cost, low energy consumption, and easy programmability. This paper deals with the problem of deploying VNFs in a multi-cluster system formed by this kind of node which is characterized by limited computational and battery capacities. Additionally, existing platforms to orchestrate and manage VNFs do not consider energy levels during their placement decisions, and therefore, they are not optimized for energy-constrained environments. In this regard, this study proposes an intelligent controller as a global allocation mechanism based on deep reinforcement learning (DRL), specifically on deep Q-network (DQN). The conceived mechanism optimizes energy consumption in SBCs by selecting the most suitable nodes across several clusters to deploy event requests in terms of nodes’ resources and events’ demands. A comparison with available allocation algorithms revealed that our solution required 28% fewer resource costs and reduced 35% the energy consumption in the clusters’ computing nodes while maintaining high levels of acceptance ratio.
  • Publication
    Evaluation of a Learning Analytics Application for Open edX Platform
    (ComSIS Consortium, 2017-01-01) Ruiperez Valiente, Jose Antonio; Muñoz Merino, Pedro José; Pijeira Diaz, Hector J; Santofimia Ruiz, Javier; Delgado Kloos, Carlos; Comunidad de Madrid; Ministerio de Economía y Competitividad (España)
    Massive open online courses (MOOCs) have recently emerged as a revolution in education. Due to the huge amount of users, it is difficult for teachers to provide personalized instruction. Learning analytics computer applications have emerged as a solution. At present, MOOC platforms provide low support for learning analytics visualizations, and a challenge is to provide useful and effective visualization applications about the learning process. At this paper we review the learning analytics functionality of Open edX and make an overview of our learning analytics application ANALYSE. We present a usability and effectiveness evaluation of ANALYSE tool with 40 students taking a Design of Telematics Applications course. The survey obtained very positive results in a system usability scale (SUS) questionnaire (78.44/100) in terms of the usefulness of visualizations (3.68/5) and the effectiveness ratio (92/100) of the actions required for the respondents. Therefore, we can conclude that the implemented learning analytics application is usable and effective.
  • Publication
    Cybersecurity Vulnerability Analysis of the PLC PRIME Standard
    (Hindawi Limited, 2017-07-05) Seijo Simo, Miguel; López López, Gregorio Ignacio; Moreno Novella, José Ignacio; Ministerio de Economía y Competitividad (España)
    Security in critical infrastructures such as the power grid is of vital importance. The Smart Grid puts power grid classical security approach on the ropes, since it introduces cyberphysical systems where devices, communications, and information systems must be protected. PoweRline Intelligent Metering Evolution (PRIME) is a Narrowband Power-Line Communications (NB-PLC) protocol widely used in the last mile of Advanced Metering Infrastructure (AMI) deployments, playing a key role in the Smart Grid. Therefore, this work aims to unveil the cybersecurity vulnerabilities present in PRIME standard, proposing solutions and validating and discussing the results obtained.
  • Publication
    Evaluating emotion visualizations using AffectVis, an affect-aware dashboard for students
    (Emerald Publishing Limited, 2017-07-01) Leony Arreaga, Derick Antonio; Sedrakyan, Gayane; Muñoz Merino, Pedro José; Delgado Kloos, Carlos; Verbert, Katrien; Comunidad de Madrid; Ministerio de Economía y Competitividad (España)
    Purpose: The purpose of this paper is to evaluate four visualizations that represent affective states of students. Design/methodology/approach: An empirical-experimental study approach was used to assess the usability of affective state visualizations in a learning context. The first study was conducted with students who had knowledge of visualization techniques (n=10). The insights from this pilot study were used to improve the interpretability and ease of use of the visualizations. The second study was conducted with the improved visualizations with students who had no or limited knowledge of visualization techniques (n=105). Findings: The results indicate that usability, measured by perceived usefulness and insight, is overall acceptable. However, the findings also suggest that interpretability of some visualizations, in terms of the capability to support emotional awareness, still needs to be improved. The level of students" awareness of their emotions during learning activities based on the visualization interpretation varied depending on previous knowledge of information visualization techniques. Awareness was found to be high for the most frequently experienced emotions and activities that were the most frustrating, but lower for more complex insights such as interpreting differences with peers. Furthermore, simpler visualizations resulted in better outcomes than more complex techniques. Originality/value: Detection of affective states of students and visualizations of these states in computer-based learning environments have been proposed to support student awareness and improve learning. However, the evaluation of visualizations of these affective states with students to support awareness in real life settings is an open issue.
  • Publication
    Serverless Vehicular Edge Computing for the Internet of Vehicles
    (IEEE, 2023-05-01) Alam, Faisal; Toosi, Adel N.; Cheema, Muhammad Aamir; Cicconetti, Claudio; Serrano Yáñez-Mingot, Pablo; Iosup, Alexandru; Tari, Zahir; Sarvi, Majid; Ministerio de Asuntos Económicos y Transformación Digital (España); European Commission
    Rapid growth in the popularity of smart vehicles and increasing demand for vehicle autonomy brings new opportunities for vehicular edge computing (VEC). VEC aims at offloading the time-sensitive computational load of connected vehicles to edge devices, e.g., roadside units. However, VEC offloading raises complex resource management challenges and, thus, remains largely inaccessible to automotive companies. Recently, serverless computing emerged as a convenient approach to the execution of functions without the hassle of infrastructure management. In this work, we propose the idea of serverless VEC as the execution paradigm for Internet of Vehicles applications. Further, we analyze its benefits and drawbacks as well as identify technology gaps. We also propose emulation as a design, evaluation, and experimentation methodology for serverless VEC solutions. Using our emulation toolkit, we validate the feasibility of serverless VEC for real-world traffic scenarios.
  • Publication
    A baseline roadmap for advanced wireless research beyond 5G
    (MPDI, 2020-02-19) Mourad, Alain; Yang, Rui; Lehne, Per Hjalmar; Oliva Delgado, Antonio de la; European Commission
    This paper presents a baseline roadmap for the evolution of 5G new radio over the next decade. Three timescales are considered, namely short-term (2022-ish), medium-term (2025-ish), and long-term (2030-ish). The evolution of the target key performance indicators (KPIs) is first analyzed by accounting for forecasts on the emerging use cases and their requirements, together with assumptions on the pace of technology advancements. The baseline roadmap is derived next by capturing the top-10 and next the top-5 technology trends envisioned to bring significant added value at each timescale. Being intrinsically predictive, our proposed baseline roadmap cannot assert with certainty the values of the target KPIs and the shortlisting of the technology trends. It is, however, aimed at driving discussions and collecting feedback from the wireless research community for future tuning and refinement as the 5G evolution journey progresses.
  • Publication
    Communication Manager for Hyper-Connected RPAS Environments
    (MDPI, 2023-02-01) Sánchez Agüero, Víctor; Valera Pintor, Francisco; Vidal Fernández, Iván; Nogales Dorado, Borja; European Commission; Agencia Estatal de Investigación (España)
    The revolution of Remotely Piloted Aircraft Systems (RPASs), both in the commercial and the research field, has accelerated the arrival of innovative and complex services to the civilian environment within non-segregated airspace. The extensive deployment of these services will still require solving relevant challenges in several topics, such as regulation, security, or diverse technical defiance. In particular, the services to be provided increasingly demand network resources and performance improvements. This scenario will be strongly exacerbated by the upcoming resources provided by the 5G/6G architectures, where Remotely Piloted Aircrafts (RPAs) will likely support multiple communication interfaces and will be able to establish multi-hop network connectivity with numerous devices leading to an unprecedented hyper-connected RPA environment. In addition, future RPASs will have to enhance the management of their connectivity capabilities to comply with the latest regulations, which demand an uninterrupted link for the Control and Non-Payload Communications (CNPC). This article presents a flexible Communication Infrastructure Manager (CIM) based on Software-Defined Networking (SDN) and virtualization technologies capable of handling the complexity inherent to this ecosystem and being adapted to different operation requirements to cope with all these communication challenges. Finally, the article shows several validation experiences to demonstrate the potential of the CIM versus the standard approach.
  • Publication
    Analytic Evaluation and Experimental Validation of a Network-Based IPv6 Distributed Mobility Management Solution
    (IEEE, 2014-11-01) Giust, Fabio; Bernardos Cano, Carlos Jesús; Oliva Delgado, Antonio de la; European Commission; Ministerio de Ciencia e Innovación (España)
    Mobile Internet traffic is growing steeply, mainly due to the deployment of new broadband wireless technologies and the ever increasing connectivity demand coming from new services being available to mobile users. Current mobile network architectures rely on centralized mobility protocols which intrinsically pose enormous burdens on the central anchors, both in terms of connectivity needs and user mobility management. In order to face these issues, a new paradigm, called Distributed Mobility Management, is being explored, based on flattening the network architecture by deploying multiple mobility anchors at the edge of the network. In this article we conduct an analytic and experimental evaluation of a network-based IP distributed mobility management solution that leverages Proxy Mobile IPv6 protocol operations. We develop an analytic model of the signaling and packet delivery costs, as well as the handover latency of both Proxy Mobile IPv6 and our distributed solution. We have also implemented a Linux-based prototype of our proposal, which has been used to experimentally assess the handover latency in a real IEEE 802.11 scenario. Finally, we use the results obtained from the analytic and experimental performance to evaluate the benefits that could be achieved by deploying a distributed mobility management solution.
  • Publication
    Bartolomeu: An SDN rebalancing system across multiple interdomain paths
    (Elsevier, 2020-03-14) Torres Jr, Pedro R; García Martínez, Alberto; Bagnulo Braun, Marcelo Gabriel; Parente Ribeiro, Eduardo; European Commission; Ministerio de Economía y Competitividad (España)
    Bartolomeu is a solution to enable stub networks to perform adaptive egress traffic load balancing across multiple interdomain routes by spreading the traffic across available paths according to a passive measurement of their performance. It defines a BGP-SDN architecture that increases the number of BGP routes that can be used by stub networks. Bartolomeu measures the available capacity of each path to any destination prefix, and allocates to each path a number of large flows that is proportional to its capacity. This strategy reduces the mean sojourn time, i.e., mean time to flow completion, compared to state-of-the-art traffic balancing techniques as ECMP. We develop a mathematical model to compute this time and compare with ECMP and single path (fast path) selection. An analysis of the traffic traces of two content providers was performed to ensure that our solution is deployable. An experiment with traffic exchange over the Internet is used to show that Bartolomeu can provide gains with real interfering traffic. A discrete-event simulator fed with the traces captured is used to asses Bartolomeu's gains with prefixes with different number of flows, and flows with different sizes and arrival time. We observe in this experiment that Bartolomeu can reduce the sojourn time, compared to ECMP, by half when path rates differ in a factor of 3, or to a sixth when path rates differ in a factor of 10. We compute the maximum number of per-flow entries and the maximum entry change request rate to show that the resources required fit in with the specifications of the current generation of SDN switches.
  • Publication
    An experimental evaluation of LEDBAT++
    (Elsevier, 2022-07-20) Bagnulo Braun, Marcelo Gabriel; García Martínez, Alberto; Comunidad de Madrid; European Commission
    LEDBAT++ is the evolution of LEDBAT, a congestion control algorithm originally designed to provide lessthan- best-effort transport on the Internet. LEDBAT++ aims to address a number of shortcomings present in LEDBAT, including late-comer advantage, latency drift, competition on equal grounds with best effort traffic in the presence of small buffers and difficulties experienced while measuring the variations on the delay. In this paper, we perform an experimental evaluation of LEDBAT++ using the Windows Server’s LEDBAT++ implementation. We find that while LEDBAT++ overcomes all the limitations identified in LEDBAT, the change introduced in LEDBAT++ to do so results in a performance penalty that prevents LEDBAT++ flows to seize all the available capacity when there is no competing traffic. We propose two simple modifications to the LEDBAT++ algorithm that would address the identified issues and reduce the penalty.
  • Publication
    Practicable route leak detection and protection with ASIRIA
    (Elsevier, 2022-07-05) Bagnulo Braun, Marcelo Gabriel; García Martínez, Alberto; Angieri, Stefano; Lutu, Andra Elena; Yang, Jinze; Comunidad de Madrid
    Route leak events have historically caused many wide-scale disruptions on the Internet. Leaks are particularly hard to detect because they most frequently involve routes with legitimate origin announced through legitimate paths that are propagated beyond their legitimate scope. In this paper we present ASIRIA, a mechanism for detecting and avoiding leaked routes and protecting against leakage events that uses AS relationship information inferred from the Internet Routing Registries. By relying on existing information, ASIRIA provides immediate benefits to early adopters. In particular, we consider the deployment of ASIRIA to detect leaks caused by over 300 ASes and we show that it can detect over 99% of the leakage events generated by a customer or a peer solely using currently available information in 90% of the cases.
  • Publication
    Validation of a diagnostic support system for diabetic retinopathy based on clinical parameters
    (Association for Research in Vision and Ophthalmology (ARVO), 2021-03) Romero-Aroca, Pedro; Verges-Pujol, Raquel; Santos-Blanco, Esther; Maarof, Najlaa; Valls, Aida; Mundet, Xavier; Baratas Moreno, Juan Antonio; Galindo Sanchez, Luis Angel; Baget-Bernaldiz, Marc
    Purpose: To validate a clinical decision support system (CDSS) that estimates risk of diabetic retinopathy (DR) and to personalize screening protocols in type 2 diabetes mellitus (T2DM) patients. Methods: We utilized a CDSS based on a fuzzy random forest, integrated by fuzzy decision trees with the following variables: current age, sex, arterial hypertension, diabetes duration and treatment, HbA1c, glomerular filtration rate, microalbuminuria, and body mass index. Validation was made using the electronic health records of a sample of 101,802 T2DM patients. Diagnosis was made by retinal photographs, according to EURODIAB guidelines and the International Diabetic Retinopathy Classification. Results: The prevalence of DR was 19,759 patients (19.98%). Results yielded 16,593 (16.31%) true positives, 72,617 (71.33%) true negatives, 3165 (3.1%) false positives, and 9427 (9.26%) false negatives, with an accuracy of 0.876 (95% confidence interval [CI], 0.858–0.886), sensitivity of 84% (95% CI, 83.46–84.49), specificity of 88.5% (95% CI, 88.29–88.72), positive predictive value of 63.8% (95% CI, 63.18–64.35), negative predictive value of 95.8% (95% CI, 95.68–95.96), positive likelihood ratio of 7.30, and negative likelihood ratio of 0.18. The type 1 error was 0.115, and the type 2 error was 0.16. Conclusions: We confirmed a good prediction rate for DR from a representative sample of T2DM in our population. Furthermore, the CDSS was able to offer an individualized screening protocol for each patient according to the calculated risk confidence value. Translational Relevance: Results from this study will help to establish a novel strategy for personalizing screening for DR according to patient risk factors.
  • Publication
    Analysis of mobility homophily in Stockholm based on social network data
    (Public Library of Science (PLOS), 2021-03-09) Heine, Cate; Márquez Colás, María Cristina; Santi, Paolo; Sundberg, Marcus; Nordfors, Miriam; Ratti, Carlo; European Commission
    We present a novel metric for measuring relative connection between parts of a city using geotagged Twitter data as a proxy for co-occurrence of city residents. We find that socioeconomic similarity is a significant predictor of this connectivity metric, which we call “linkage strength”: neighborhoods that are similar to one another in terms of residents’ median income, education level, and (to a lesser extent) immigration history are more strongly connected in terms of the of people who spend time there, indicating some level of homophily in the way that individuals choose to move throughout a city’s districts.
  • Publication
    GLOVE: towards privacy-preserving publishing of record-level-truthful mobile phone trajectories
    (ACM, 2021-08) Gramaglia, Marco; Fiore, Marco; Furno, Angelo; Stanica, Razvan; Comunidad de Madrid
    Datasets of mobile phone trajectories collected by network operators offer an unprecedented opportunity to discover new knowledge from the activity of large populations of millions. However, publishing such trajectories also raises significant privacy concerns, as they contain personal data in the form of individual movement patterns. Privacy risks induce network operators to enforce restrictive confidential agreements in the rare occasions when they grant access to collected trajectories, whereas a less involved circulation of these data would fuel research and enable reproducibility in many disciplines. In this work, we contribute a building block toward the design of privacy-preserving datasets of mobile phone trajectories that are truthful at the record level. We present GLOVE, an algorithm that implements k-anonymity, hence solving the crucial unicity problem that affects this type of data while ensuring that the anonymized trajectories correspond to real-life users. GLOVE builds on original insights about the root causes behind the undesirable unicity of mobile phone trajectories, and leverages generalization and suppression to remove them. Proof-of-concept validations with large-scale real-world datasets demonstrate that the approach adopted by GLOVE allows preserving a substantial level of accuracy in the data, higher than that granted by previous methodologies.
  • Publication
    Three-Tier Capacity and Traffic Allocation for Core, Edges, and Devices for Mobile Edge Computing
    (IEEE, 2018-07-03) Lin, Ying-Dar; Lai, Yuan-Cheng; Huang, Jian-Xun; Chien, Hsu-Tung; European Commission
    In order to satisfy the 5G requirements of ultra-low latency, mobile edge computing (MEC)-based architecture, composed of three-tier nodes, core, edges, and devices, is proposed. In MEC-based architecture, previous studies focused on the controlplane issue, i.e., how to allocate traffic to be processed at different nodes to meet this ultra-low latency requirement. Also important is how to allocate the capacity to different nodes in the management plane so as to establish a minimal-capacity network. The objectives of this paper is to solve two problems: 1) to allocate the capacity of all nodes in MEC-based architecture so as to provide a minimal-capacity network and 2) to allocate the traffic to satisfy the latency percentage constraint, i.e., at least a percentage of traffic satisfying the latency constraint. In order to achieve these objectives, a two-phase iterative optimization (TPIO) method is proposed to try to optimize capacity and traffic allocation in MEC-based architecture. TPIO iteratively uses two phases to adjust capacity and traffic allocation respectively because they are tightly coupled. In the first phase, using queuing theory calculates the optimal traffic allocation under fixed allocated capacity, while in the second phase, allocated capacity is further reduced under fixed traffic allocation to satisfy the latency percentage constraint. Simulation results show that MEC-based architecture can save about 20.7% of capacity of two-tier architecture. Further, an extra 12.2% capacity must be forfeited when the percentage of satisfying latency is 90%, compared to 50%.
  • Publication
    Potential Applicability of Distributed Ledger to Wireless Networking Technologies
    (IEEE, 2018-09-04) Kuo, Ping-Heng; Mourad, Alain; Ahn, Jaehyun; European Commission
    In recent years, the rise of cryptocurrency has received enormous attention around the world. Since a centralized entity (e.g., a bank) is no longer needed for transactions in this currency platform, its potential impact on the financial sector in the future has been examined closely. Apart from the transaction platform itself, the driving technology behind cryptocurrency, namely blockchain, has also kindled huge research interest across different disciplines.
  • Publication
    User-Centric Multi-RATs Coordination for 5G Heterogeneous Ultra-Dense Networks
    (IEEE, 2018-02-28) Kuo, Ping-Heng; Mourad, Alain; European Commission
    This column reviews the concept of user-centric access, which permits the network to tailor a “follow me” virtual cell for a user via multipoint coordination in a UDN environment. We further discuss the feasibility of extending such a virtual cell by considering tight integration of heterogeneous RATs exposed to the user, by taking the context information and instantaneous status of the user device into account. In particular, we conceive an edge/fog computing platform capable of acquiring and jointly processing information from multiple heterogeneous RATs and the users. Such a framework may have great potential to play key roles in 5G and beyond, in terms of realizing truly flexible radio access that can be customized for each individual user in the network.
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