Mesodiakaki A.,Polytechnic University of Catalonia |
Adelantado F.,Open University of Catalonia |
Alonso L.,Polytechnic University of Catalonia
IEEE Communications Magazine | Year: 2014
Due to the ever increasing data traffic demands, which are directly connected to increased energy consumption, it becomes challenging for operators to achieve capacity enhancement while limiting their electric bill. To that end, exploiting the context awareness of future cognitive networks is expected to play a key role. Next generation cellular networks are about to include a plethora of small cells, with users being able to communicate via multiple bands. Given that small cells are expected to be eventually as close as 50 m apart, not all of them will have a direct connection to the core network; thus, multihop communication through neighboring small cells may be required. In such architectures, the user association problem becomes challenging, with backhaul energy consumption being a definitive parameter. Thus, in this article, we study the user association problem in cognitive heterogeneous networks. We evaluate the existing approaches in terms of energy efficiency and show the potential of exploiting the available context-aware information (i.e., users' measurements and requirements, knowledge of the network architecture, and the available spectrum resources of each base station) to associate the users in an energyefficient way, while maintaining high spectrum efficiency. Our study considers both the access network and backhaul energy consumption, while the performance of the association algorithms is evaluated under two different case study scenarios. © 2014 IEEE.
Tseliou G.,Open University of Catalonia |
Adelantado F.,Open University of Catalonia
IEEE Transactions on Vehicular Technology | Year: 2016
Cellular communications are evolving to facilitate the current and expected increasing needs of quality of service, high data rates, and diversity of offered services. Toward this direction, radio access network (RAN) virtualization aims at providing solutions of mapping virtual network elements onto radio resources of the existing physical network. This paper proposes the Resources nEgotiation for NEtwork Virtualization (RENEV) algorithm, which is suitable for application in heterogeneous networks in Long-Term Evolution Advanced (LTE-A) environments, consisting of a macro evolved Node B overlaid with small cells (SCs). By exploiting radio resource management principles, RENEV achieves slicing and on-demand delivery of resources. Leveraging the multitenancy approach, radio resources are transferred in terms of physical radio resource blocks among multiple heterogeneous base stations, which are interconnected via the X2 interface. The main target is to deal with traffic variations in geographical dimension. All signaling design considerations under the current Third-Generation Partnership Project LTE-A architecture are also investigated. Analytical studies and simulation experiments are conducted to evaluate RENEV in terms of the network's throughput and additional signaling overhead. Moreover, we show that RENEV can be applied independently on top of already proposed schemes for RAN virtualization to improve their performance. The results indicate that significant advantages are achieved both from the network's and users' perspective and that it is a scalable solution for different numbers of SCs. © 2015 IEEE.
Martinez-Lopez F.J.,University of Granada |
Martinez-Lopez F.J.,The Open Group |
Pla-Garcia C.,Open University of Catalonia |
Gazquez-Abad J.C.,University of Almeria |
Rodriguez-Ardura I.,Applied Technology Internet
Electronic Commerce Research and Applications | Year: 2014
To date, the utilitarian benefits of online consumption have only been partially investigated. This study undertakes an exhaustive approach to fully delimit the dimensional structure related to the utilitarian motivations for online consumption. First, an in-depth literature review is carried out, in order to allow the proposal of an aprioristic base structure of eleven categories of utilitarian motivations. Next, qualitative analyses (focus groups and personal interviews) are applied to assess and eventually refine the structure of utilitarian motivations proposed after the literature review, their labels and respective measurement scales. Finally, this qualitative phase concludes with ten motivational categories and 46 items. Then, quantitative analyses (exploratory and detailed confirmatory factor analyses) are applied, based on a questionnaire administered to a sample of 667 Internet users, to keep refining and to eventually validate both the dimensional structure of motivations and the related measurement scales. Finally, a structure of 9 utilitarian motivations (and corresponding set of 36 items) is established, with the following labels: assortment, economy, convenience, availability of information, adaptability/customization, desire for control, payment services, anonymity, and absence of social interaction. The nomological validity of this structure is satisfactorily tested using a second-order factor model. The article finishes by discussing some implications for practitioners. © 2014 Elsevier B.V. All rights reserved.
Pascual V.S.,Open University of Catalonia |
Xhafa F.,Polytechnic University of Catalonia
Mathematical and Computer Modelling | Year: 2013
Synchronization protocols have been widely investigated in distributed systems aiming to achieve real-time and scalable properties. With the fast development of large-scale distributed systems, and due to their heterogenous nature involving wired, wireless, and mobile nodes, synchronization has again come into play. In this work, we have studied contact synchronization and handling, which is an important feature in corporate environments. Indeed, it has become very important to support collaboration of teams of mobile users by enabling anytime and anywhere access to shared contact data. We characterize the problem as a distributed systems problem, identify its desirable properties, and outline its main characteristics. A simple algorithm is proposed as an efficient solution to contact synchronization when some nodes of the system are assumed to be mobile phones under the Android operating system. The features required at both ends of the distributed system are explained in order to guarantee the correctness of the algorithm. We also analyze the implementation of the algorithm coupling the Android platform and the SugarCRM server, and provide an experimental evaluation of the performance of the proposed approach. © 2011 Elsevier Ltd.
News Article | November 30, 2015
« TMFB researchers investigate engine performance of two possible future tailor-made biofuels | Main | 11 states assessing fees on EV owners in lieu of traditional fuel taxes » SEAT has developed the Parkfinder app, which indicates where there is available street parking thanks to data gathered via Barcelona's iCity platform. Drivers simply enter where they are headed, or once at their location, ask the app where there is available parking. As any other iCity Project App, it can be used in every European Country as long as it has opened its Information System to the iCity Project. iCity Project started in January 2012 when the cities of Barcelona, Genoa and Bologna started working together with other partners of the project: Abertis, CISCO, Fraunhofer Institute, Citilab and the Open University of Catalonia Foundation (UOC) and the Institute for Advanced Architecture of Catalonia (IAAC). The project, which has been supported by the European Commission, is now in its concluding phase. Most people spend an average of 20 minutes finding street parking in Europe’s main cities, said Jordi Caus, who is responsible for New Projects on Alternative Mobility at SEAT. At any given time, 30% on average of Europeans driving in cities are looking for a place to park. This challenge will be even greater in the future, as a UN report points to 66% of the world population living in urban areas by 2050, which will result in “more vehicles on city roads, more traffic congestion and ultimately, more parking problems”, says Jordi Ortuño, Barcelona Council Smart Cities project coordinator. The app is in pilot testing in the Les Corts neighborhood after an agreement was struck with the Barcelona Council, but the more ambitious goal is for this app to perform many other functions. New technologies will not focus solely on solving parking problems—there are many other challenges in urban mobility. One of these is to prevent traffic congestion, “by getting cars to spread out on several city streets before any arteries get clogged”, says Jordi Caus. “In the near future we should be able to achieve much more efficient urban mobility. That’s what we’re working on—getting driving to be much more relaxed, safer and more economical as well”, he concludes.
News Article | November 2, 2016
Researchers from North Carolina State University and the Open University of Catalonia have developed a technique for creating complex predictive tools that can be used to make effective decisions about word-of-mouth marketing for online products and services. "We were initially approached by an online game provider that used a 'freemium' model -- players could play for free, but could receive upgrades by paying a fee to become premium users," says William Rand, an assistant professor of business management at NC State and co-author of a paper on the work. "The company wanted to know what incentives would be most likely to convince players to become premium users. That was the impetus for the work, but what we found is actually relevant for any company or developer interested in incentivizing user investment in apps or online services." A preliminary assessment indicated that access to new content was not the primary driver in convincing players to pay a user fee. Instead, player investment seemed to be connected to a player's social networks. To learn more, the researchers evaluated three months' worth of data on 1.4 million users of the online game, including when each player began playing the game; each player's in-game connections with other players; and whether a player became a premium user. Using that data, the researchers created a computer model using agent-based modeling, a method that creates a computational agent to represent a single user or group of users. The computer model allowed them to assess the role that social connections may have played in getting players to pay user fees. They found that two different behavioral models worked very well, but in different ways. "We found that the best model for accurately predicting the overall rate of players becoming premium users was the so-called 'Bass model,' which holds that the larger the fraction of direct connections you have who use a product, the more likely you are to use the product," Rand says. However, the researchers found that the best model for predicting the behavior of any specific individual was the complex contagion model. "The Bass model looks at the fraction of your direct connections who adopt a product, whereas the complex contagion model simply looks at the overall number of your direct connections who adopt," Rand says. Both techniques have utility for businesses. For example, being able to predict how many players would become premium users could help a company make sustainable business decisions; whereas being able to predict the behavior of an individual player may help a company target players who are near the threshold of becoming premium users. "By merging these two modeling approaches, we created a tool that would allow a company to predict how many additional premium users it would gain, depending on various degrees of investment in marketing to individual players who are the threshold of becoming premium users," Rand says. "This could be used to make informed decisions about how much to invest in 'seeded,' or targeted, marketing in order to capitalize on word-of-mouth marketing. "The bottom line here is that the approach we took to developing this tool could be used to develop a custom tool for any company that's marketing an online product or service via word of mouth," Rand says. The paper, "Building Agent-Based Decision Support Systems for Word-Of-Mouth Programs. A Freemium Application," is published online in the Journal of Marketing Research.
Fernandez-Ardevol M.,Open University of Catalonia |
Ivan L.,National School of Political Studies and Public Administration
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2015
We analyze the influence of age on mobile computer anxiety in a sample of 158 individuals 55+ by means of path analysis modeling. Taking as the endogenous variable a mobile computer anxiety scale (MCAS, Wang 2007), models include demographic and socioeconomic variables and a computer experience scale – based on the familiarity and frequency of use of different information and communication technologies. Results confirm a positive influence of age on mobile computer anxiety which is mediated by both socio-economic variables and computer experience. The influence of age on mobile computer anxiety is comparatively low. Age is not the relevant dimension to explain computer anxiety, as socio-economic background and computer experience have higher explanatory capacity. This result may explain the inconsistent results regarding the direct relationship between age and computer anxiety available in the literature. © Springer International Publishing Switzerland 2015
Domingo M.G.,Open University of Catalonia |
Gargante A.B.,Open University of Catalonia
Computers in Human Behavior | Year: 2016
Mobile technology has become popular worldwide with a broad range of users, including students from all levels of education. Although the impact of mobile technology in classrooms has been extensively studied, less is known about teachers' perceptions of how mobile technology impacts in learning and its relation to Applications (Apps) use in the classroom. This state of affairs is problematic since we know that teachers' perceptions have a great influence on their teaching practices. This study used survey data gathered from 102 teachers of 12 different primary schools in Spain. The questionnaire collected data about teachers' individual information, teachers' perceptions on the impact of mobile technology in learning, and use of a set of selected Apps in the classroom. Findings suggest that facilitating access to information and increasing engagement to learning are the two main impacts of mobile technology in the classroom. Findings also show that the choice of Apps is related to the teachers' perception of how mobile technology impacts in learning. Findings could help teachers to take advantage of the combination of affordances of mobile technology and Apps that actually improve some aspects of learning practice. © 2015 Elsevier Ltd.
Izard O.M.,Open University of Catalonia
Proceedings of the IADIS International Conference Web Based Communities and Social Media 2013, Proceedings of the IADIS International Conference Collaborative Technologies 2013 | Year: 2013
This research proposes a model to test the influence of special factors that have been found as critical for the acceptance and use of social networking sites for knowledge exchange adjusting it to different technology adoption theories. The key factors of the model are based on the perception of users of their autonomy, the openness of the sites, the diversity of the members of the networks and the interactivity. We have tested the model with case study of virtual communities of professionals and we used the SEM (Structural Equation Modeling) analysis. The results certify the validity of the model affording a better understanding on the relations between the different factors and how they influence the user's behavior of the social networking sites. © 2013 IADIS.
Espasa A.,Open University of Catalonia |
Guasch T.,Open University of Catalonia |
Alvarez I.M.,Open University of Catalonia
Digital Education Review | Year: 2013
The aim of this article is to present a methodological model to analyze students' group interaction to improve their essays in online learning environments, based on asynchronous and written communication. In these environments teacher and student scaffolds for discussion are essential to promote interaction. One of these scaffolds can be the feedback. Research on feedback processes has predominantly focused on feedback design rather than on how students utilize feedback to improve learning. This methodological model fills this gap contributing to analyse the implementation of the feedback processes while students discuss collaboratively in a specific case of writing assignments. A review of different methodological models was carried out to define a framework adjusted to the analysis of the relationship of written and asynchronous group interaction, and students' activity and changes incorporated into the final text. The model proposed includes the following dimensions: 1) student participation 2) nature of student learning and 3) quality of student learning. The main contribution of this article is to present the methodological model and also to ascertain the model's operativity regarding how students incorporate such feedback into their essays.