IMDEA Networks Institute Digital Repository
Not a member yet
1915 research outputs found
Sort by
Design, Implementation and Evaluation of SPOCs at the Universidad Carlos III de Madrid
Get PDFThe Universidad Carlos III de Madrid has been offering several face-to-face remedial courses for new students to review or learn concepts and practical skills that they should know before starting their degree program. During 2012 and 2013, our University adopted MOOC-like technologies to support some of these courses so that a blended learning methodology could be applied in a particular educational context, i.e. by using SPOCs (Small Private Online Courses). This paper gathers a list of issues, challenges and solutions when implementing these SPOCs. Based on these challenges and issues, a design process is proposed for the implementation of SPOCs. In addition, an evaluation is presented of the different use of the offered courses based on indicators such as the number of videos accessed, number of exercises accessed, number of videos completed, number of exercises correctly solved or time spent on the platform.pu
Panel: Innovation through Joint Industry-Academic Partnerships
No full textPanelists:
1. Dr. Nada Golmie, Chief, Wireless Division, National Institute of Standards and Technology (NIST), USA
2. Dr. Haris Gačanin, Department Head, Indoor Networking Systems, Nokia Bell Labs, Belgium
3. Dr. Jeff Foerster, Principal Engineer at Intel, USA
4. Dr. Arturo Azcorra, Director, IMDEA Networks Institute, Spain
5. Mr. Paul Challoner, Vice President Network Product Solutions, Ericsson USAIndustry and academia are the two major pillars that drive innovation and research, and historically, significant cross-pollination of ideas and expertise occurs between them. The goal of this panel is to discuss shared experiences, identify time-tested and new strategies, as well as role responsibilities in situations when industry and academia work together towards driving ambitious, open-ended research. The panel includes representatives from major research laboratories associated with the leading networking companies, startups, as well as industry consortiums for large wireless platform development projects committed to working with academic partners.FALSEpu
Recharging Vehicle Distance Minimization in Wireless Sensor Networks
Get PDFWireless sensor networks suffer from increased energy consumption close to the sink node, known as the energy
hole problem. Various policies for recharging battery exhausted nodes have been proposed using special recharging vehicles. The focus in this paper is on a simple recharging policy that permits a recharging vehicle, stationed at the sink node, to move around and replenish any node’s exhausted battery when a certain recharging threshold is violated. The minimization of the recharging distance covered by the recharging vehicle is shown to be a facility location problem, and particularly a 1-median one. Simulation results investigate various aspects of the recharging policy related to the recharging threshold and the level of the energy left in the network nodes’ batteries. In addition, it is shown that when the sink’s positioning is set to the solution
of the particular facility location problem, then the recharging distance is minimized irrespectively of the recharging threshold.TRUEpu
Relay Selection for mmWave Communications
Get PDFDue to high propagation loss and directivity, mmWave links are very susceptible to obstacles blocking the direct line-of-sight path for communication. In this case, indirect communication via a relay may help to circumvent the blockage. In this paper, we propose a two-hop relay selection algorithm for mmWave communications. For the relay selection, we analyze the probability that an indirect path is available given that the direct path is blocked trough geometric analysis. We then choose the most promising node among neighbors as relay. The analysis shows that the probability of an indirect path is a function of the obstacle density as well as the location of relay nodes. When the density is low, the correlation between the direct path and an indirect path is dominant, i.e., the angle between the direct path and the path to relay should be large, whereas the blockage probability of an indirect path becomes more dominant as the density increases, i.e., relay links should not be too long. The probability analysis also allows to decide an initial antenna angle for beam training in mobile mmWave environments. Through numerical studies, we verify our analytical results.TRUEpu
DORE: An Experimental Framework to Enable Outband D2D Relay in Cellular Networks
No full textDevice-to-Device (D2D) communications represent a paradigm shift in cellular networks. In particular, analytical results on D2D performance for offloading and relay are very promising, but no experimental evidence validates these results to date. This paper is the first to provide an experimental analysis of outband D2D relay schemes. Moreover, we design D2D opportunistic relay with QoS enforcement (DORE), a complete framework for handling channel opportunities offered by outband D2D relay nodes. DORE consists of resource allocation optimization tools and protocols suitable to integrate QoS-aware opportunistic D2D communications within the architecture of 3GPP Proximity-based Services. We implement DORE using an SDR framework to profile cellular network dynamics in the presence of opportunistic outband D2D communication schemes. Our experiments reveal that outband D2D communications are
suitable for relaying in a large variety of delay-sensitive cellular applications, and that DORE enables notable gains even with a few active D2D relay nodes.pu
Dissecting DNS Stakeholders in Mobile Networks
Get PDFWhen using mobile apps, users ignite a complex set of network operations. Among all protocols and elements behind the scenes, Domain Name System (DNS) is an almost omnipresent component. Despite being one of the oldest Internet system, DNS still operates with semi-obscure interactions among its stakeholders, i.e., domain owners, network operators, and apps/operating system (OS) developers. The goal of this work is to understand the dynamics of DNS in mobile traffic, and quantify the role of each of its stakeholders. To do so, we use two different but complementary anonymized datasets: traffic logs provided by an European mobile operator with about 19M customers, and a second one containing traffic logs from 5,000 Lumen users, an Android traffic monitoring app. Our analysis show that 10k domains (out of 198M) are responsible for 87% of total network flows. We complement our traffic analysis with active measurements which reveal that i) TTL values for such domains are mostly short (< 1 min) despite IPs mapping changes occurring at a lower pace, and ii) DNS lookup time cost, about 10% of page load time (PLT), can potentially be reduced with optimisations, but those are rarely used in the wild.TRUEpu
5G Crosshaul Architecture Implementation
No full textOther invited speakers: Dr. Ali Sadri (Senior Director, Intel), Pearse O’donohue (Area Director of Future Networks, DG Connect, European Commission), Luis Jorge Romero (Director General, ETSI)FALSEpu
A Cost-Effective Distributed Framework for Data Collection in Cloud-based Mobile Crowd Sensing Architectures
Get PDFMobile crowd sensing received significant attention in the recent years and has become a popular paradigm for sensing. It operates relying on the rich set of built-in sensors equipped in mobile devices, such as smartphones, tablets and wearable devices. To be effective, mobile crowd sensing systems require a large number of users to contribute data. While several studies focus on developing efficient incentive mechanisms to foster user participation, data collection policies still require investigation. In this paper, we propose a novel distributed and sustainable framework for gathering information in cloud-based mobile crowd sensing systems with opportunistic reporting. The proposed framework minimizes cost of both sensing and reporting, while maximizing the utility of data collection and, as a result, the quality of contributed information. Analytical and simulation results provide performance evaluation for the proposed framework by providing a fine-grained analysis on the energy consumed. The simulations, performed in a real urban environment and with a large number of participants, aim at verifying the performance and scalability of the proposed approach on a large scale under different user arrival patterns.TRUEpu
Scaling to Massiveness With ANALYSE: A Learning Analytics Tool for Open edX
Get PDFThe emergence of massive open online courses (MOOCs) has caused a major impact on online education. However, learning analytics support for MOOCs still needs to improve to fulfill requirements of instructors and students. In addition, MOOCs pose challenges for learning analytics tools due to the number of learners, such as scalability in terms of computing time and visualizations. In this work, we present different visualizations of our “Add-on of the learNing AnaLYtics Support for open Edx” (ANALYSE), which is a learning analytics tool that we have designed and implemented for Open edX, based on MOOC features, teacher feedback, and pedagogical foundations. In addition, we provide a technical solution that addresses scalability at two levels: first, in terms of performance scalability, where we propose an architecture for handling massive amounts of data within educational settings; and, second, regarding the representation of visualizations under massiveness conditions, as well as advice on color usage and plot types. Finally, we provide some examples on how to use these visualizations to evaluate student performance and detect problems in resources.pu
Algorithms for Sensor Systems - 12th International Symposium on Algorithms and Experiments for Wireless Sensor Networks, ALGOSENSORS 2016, Aarhus, Denmark, August 25-26, 2016, Revised Selected Papers
No full textDOI: 10.1007/978-3-319-53058-1
Series Title: Computer Communication Networks and TelecommunicationsThis book constitutes revised selected papers from the 12th International Symposium on Algorithms and Experiments for Wireless Sensor Networks, ALGOSENSORS 2016, held in Aarhus, Denmark, in August 2016.
The 9 full papers presented in this volume were carefully reviewed and selected from 19 submissions. This year papers were solicited into three tracks: Distributed and Mobile, Experiments and Applications, and Wireless and Geometry.TRUEpu