IMDEA Networks Institute Digital Repository
Not a member yet
1915 research outputs found
Sort by
Panel: Crosshaul (Xhaul) – The fusion of Fronthaul and Backhaul in 5G!
No full textModerator:
Alan Carlton, Vice-President International Labs (InterDigital, UK)
Panelists:
Diego Lopez
Senior Technology Expert (Telefonica, Spain)
Theodore Sizer
Head of Mobile Radio Research (Nokia Bell Labs, USA)
Li Fung Chang
Chief Architect (5G Office, Taiwan)
Arturo Azcorra
Vice-President 5TONIC (Spain)
Project Coordinator of 5G-PPP 5G-CrosshaulLooking at various research and standardization forums leading the development of 5G, such as 5G-PPP, NGMN, 3GPP, IEEE, ITU, IETF, ETSI, etc., all seem to align on the vision that the fronthaul and backhaul will converge or fuse in 5G into what is now popularly referred to as Crosshaul or Xhaul. So what requirements are driving such a fusion in 5G? Which enabling technologies could make it happen? Where are the remaining gaps and what is the industry doing to make it happen? And when are we going to see it? Featuring leading experts in the industry, this panel aims at discussing the Crosshaul (Xhaul) topic from the various angles of requirements, architecture, enabling technologies, standardization, and market deployment.FALSEpu
Detecting and Clustering Students by their Gamification Behavior with Badges: A Case Study in Engineering Education
Get PDFSpecial Issue: Engineering Behind Technology-Based Educational InnovationsEngineering degrees are often regarded as complex and one usual issue is that students struggle and feel discouraged during the learning process. Gamification is starting to play an important role in education with the objective of providing engagement and improving the motivation of students. One specific example is the use of badges. The analysis of users' interactions and behaviors with the badge system can be used to improve the learning process, e.g., by adapting the learning materials and giving game-based activities to students depending on their interest toward badges. In this work, we propose some metrics that provide information regarding the behavior of students with badges, including if they are intentionally earning them, the concentration for achieving them and their time efficiency. We validate these metrics by providing an extensive analysis of 291 different students interacting with a local instance of Khan Academy within our courses for freshmen at Universidad Carlos III de Madrid. This analysis includes relationship mining between badge indicators and others related to the learning process, the analysis of specific archetypal profiles of students that represent a broader population and also by clustering students by their badge indicators with the objective of customizing learning experiences. We finalize by discussing the implications of the results for engineering education, providing guidelines into how instructors can take advantage of the findings of the research and how researchers can replicate experiments similar to this one in other general contexts.pu
Copying@Scale: Using Harvesting Accounts for Collecting Correct Answers in a MOOC
Get PDFThis paper presents a detailed study of a form of academic dishonesty that involves the use of multiple accounts for harvesting solutions in a Massive Open Online Course (MOOC). It is termed CAMEO – Copying Answers using Multiple Existence Online. A person using CAMEO sets up one or more harvesting accounts for collecting correct answers; these are then submitted in the user's master account for credit.
The study has three main goals: Determining the prevalence of CAMEO, studying its detailed characteristics, and inferring the motivation(s) for using it. For the physics course that we studied, about 10% of the certificate earners used this method to obtain more than 1% of their correct answers, and more than 3% of the certificate earners used it to obtain the majority (>50%) of their correct answers. We discuss two of the likely consequences of CAMEO: jeopardizing the value of MOOC certificates as academic credentials, and generating misleading conclusions in educational research. Based on our study, we suggest methods for reducing CAMEO. Although this study was conducted on a MOOC, CAMEO can be used in any learning environment that enables students to have multiple accounts.pu
Energy-optimal collaborative file distribution in wired networks
Get PDFThe impact of the ICT sector in worldwide power consumption is an increasing concern, motivating the research community to devote an important effort to define novel energy efficient networking solutions. Despite file distribution is responsible for a major portion of the current Internet traffic, little effort has been dedicated to address the issue of its energy efficiency so far. Most of the previous literature focuses on optimizing the download time of file distribution schemes (e.g. centralized server-based or distributed peer-to-peer solutions) while it is yet unclear how to optimize file distribution schemes from the point of view of energy consumed. In this paper, we present a general modelling framework to analyze the energy consumption of file distribution systems. First, we show that the general problem of minimizing energy consumption in file distribution is NP-hard. Then, for restricted versions of the problem, we establish theoretical bounds to minimal energy consumption. Furthermore, we define a set of optimal algorithms for a variety of system settings, which exploit the service capabilities of hosts in a P2P fashion. We show that our schemes are capable of reducing at least 50 % of the energy consumed by traditional (yet largely used) centralized distribution schemes even when considering effects such as network congestion and heterogeneous access speed across nodes.pu
60 GHz Range Boost: Exploiting Frequency Selectivity in Millimeter-Wave Networks
Get PDFThe directional nature of communication in millimeter-wave bands suggests that the frequency selectivity of the channel may be limited due to the absence of reflected paths. However, our measurement studies show that reflections often cause significant frequency selectivity in practical scenarios, which we can exploit to increase the otherwise limited range of 60 GHz networks. Specifically, we measure real-world indoor 60 GHz channels with a bandwidth of 2 GHz, and study their behavior with respect to techniques such as bitloading, subcarrier switch-off, and waterfilling. To this end, we consider Orthogonal Frequency-Division Multiplexing (OFDM) as defined in the IEEE 802.11ad standard and show that in contrast to common belief, these techniques are highly beneficial in millimeter-wave networks. We analyze this in practice for both horn antennas as well as an electronically-steerable phased antenna array. Most importantly, our practical results demonstrate that for the specific case of the 60 GHz band, this selectivity allows for a range extension of up to 50\%. Hence, our approach enables us to alleviate one of the main limitations of millimeter-wave networks.TRUEpu
The Importance of Worker Reputation Information in Microtask-Based Crowd Work Systems
Get PDFThis paper presents the first systematic investigation of the potential performance gains for crowd work systems, deriving from available information at the requester about individual worker reputation. In particular, we first formalize the optimal task assignment problem when workers' reputation estimates are available, as the maximization of a monotone (submodular) function subject to Matroid constraints. Then, being the optimal problem NP-hard, we propose a simple but efficient greedy heuristic task allocation algorithm. We also propose a simple “maximum a-posteriori” decision rule and a decision algorithm based on message passing. Finally, we test and compare different solutions, showing that system performance can greatly benefit from information about workers' reputation. Our main findings are that: i) even largely inaccurate estimates of workers' reputation can be effectively exploited in the task assignment to greatly improve system performance; ii) the performance of the maximum a-posteriori decision rule quickly degrades as worker reputation estimates become inaccurate; iii) when workers' reputation estimates are significantly inaccurate, the best performance can be obtained by combining our proposed task assignment algorithm with the message-passing decision algorithm.pu
Position: Health Effects in LED-based Communication Systems and Possible Mitigations
Get PDFWith the invention of Blue LEDs (awarded with the Nobel Prize), white LEDs are now pervasively present in the market, and Visible Light Communication Systems (VLCS) are the result of intensive scientific investigations in the last years. In this work, we review the health effects of LED technology studied in vision science, implications of using VLC with LEDs, and new VLCS design considerations.TRUEpu
Accessing Resources in (city-wide) Networked Environments: Issues and alternatives
No full textAccess to a common (communication) resource has been one of the fundamental problems in the various networking technologies that have emerged over the last half a century. Among those, the problem of accessing a common resource by distributed, non-communicating users (i.e., through an uncoordinated approach) has been a central one and has received wide attention since the appearance of the ALOHA approach. The lack of coordination brings some advantages or keeps complexity low, but it also incurs some cost in terms of resource capacity waste and reduced throughput. Recent advances in Information and Communication Technologies (ICT) have enabled the generation and dissemination of vast amounts of information that enhance awareness about the environment and its resources. While such resource awareness brings benefits, it also intensifies competition and results in potentially significant congestion penalties for the distributed users attempting to access such resources in uncoordinated fashion.
After a brief review of the classical problem of accessing a common channel by distributed non-communicating users, the problem of accessing city-wide, distributed resources by non-communicating users will be presented through the case of the search for a (public) parking spot. The role of some informationthat can be available to the competing users will be discussed and optimal or “stable” solutions to this competition will be presented. In the sequel it will be discussed how ICT technologies can provide for some coordination in accessing such resources and also discuss significant side issues that emerge. Finally, a distributed, resource auctioning approach will be briefly presented as a means of bringing some coordination in the resource accessing problem and shifting the competition to the price arena.FALSEpu
Toward the network of the future: From enabling technologies to 5G concepts
Get PDFThere is a wide consensus by the research community and the industry that it will not be possible to satisfy future mobile traffic demand and application requirements by simply evolving the current fourth-generation architecture. Instead, there is a need for a considerable revision of the mobile network system: such an effort is commonly referred to as the future fifth-generation (5G) architecture, and large-scale initiatives all around the globe have been launched worldwide to address this challenge. While these initiatives have not yet defined the future 5G architecture, the research community has already invested a very substantial effort on the definition of new individual technologies. The fact that all new proposals are tagged as 5G has created a lot of confusion on what 5G really is. The aim of this article is to shed some light on the current status of the 5G architecture definition and the trends on the required technologies. Our key contributions are the following: (1) we review the requirements for 5G identified by the different worldwide initiatives, highlighting similarities and differences; (2) we discuss current trends in technologies, showing that there is a wide consensus on the key enablers for 5G; and (3) we make an effort to understand the new concepts that need to be devised, building on the enablers, to satisfy the desired requirements.pu
Energy Efficient Data Collection in Opportunistic Mobile Crowdsensing Architectures for Smart Cities
Get PDFSmart cities employ latest information and communication
technologies to enhance services for citizens. Sensing
is essential to monitor current status of infrastructures
and the environment. In Mobile Crowdsensing (MCS), citizens
participate in the sensing process contributing data with their mobile devices such as smartphones, tablets and wearables. To be effective, MCS 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 energy-efficient framework for data collection in opportunistic MCS architectures. Opportunistic sensing systems require minimal intervention from the user side as sensing decisions are application- or device-driven. The
proposed framework minimizes the cost of both sensing and
reporting, while maximizing the utility of data collection and, as a result, the quality of contributed information. We evaluate performance of the framework with simulations, performed in a real urban environment and with a large number of participants. The simulation results verify cost-effectiveness of the framework and assess efficiency of the data generation process.TRUEpu