Universitat Oberta de Catalunya

Displaying 1-40 of 83 results

  • White Papers // May 2014

    Neural Network-Based Autonomous Allocation of Resources in Virtual Networks

    Network virtualization has received attention as a way to allow for sharing of physical network resources. Sharing resources involves mapping of virtual nodes and links onto physical nodes and links respectively, and thereafter managing the allocated resources to ensure efficient resource utilization. In this paper, the authors apply artificial neural...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Feb 2014

    Prototyping Incentive-Based Resource Assignment for Clouds in Community Networks

    Wireless community networks are a successful example of a collective where communities operate ICT infrastructure and provide IP connectivity based on the principle of reciprocal resource sharing of network bandwidth. This sharing, however, has not extended to computing and storage resources, resulting in very few applications and services which are...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Jan 2014

    Synthesis of Asynchronous Hardware from Petri Nets

    As semiconductor technology strides towards billions of transistors on a single die, problems concerned with deep sub-micron process features and design productivity call for new approaches in the area of behavioral models. This paper focuses on some of recent developments and new opportunities for Petri nets in designing asynchronous circuits...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Oct 2013

    Supporting Cloud Deployment in the Guifi.net Community Network

    Community networking is an emerging model of a shared communication infrastructure in which communities of citizens build and own open networks. Community networks offer successfully IP-based networking to the user. Cloud computing infrastructures however, while common in today's Internet, hardy exist in community networks. The authors explain their approach to...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Sep 2013

    Clouds of Small Things: Provisioning Infrastructure-as-a-Service from within Community Networks

    Community networks offer a shared communication infrastructure where communities of citizens build and own open networks. While the IP connectivity of the networking devices is successfully achieved, the number of services and applications available from within the community network is typically small and the usage of the community network is...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Sep 2013

    Towards Incentive-Based Resource Assignment and Regulation in Clouds for Community Networks

    Community networks are built with o -the-shelf communication equipment aiming to satisfy a community's demand for Internet access and services. These networks are a real world example of a collective that shares ICT resources. But while these community networks successfully achieve the IP connectivity over the shared network infrastructure, the...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Jul 2013

    Power-Aware Multi-DataCenter Management Using Machine Learning

    The cloud relies upon multi-DataCenter (multi-DC) infrastructures distributed along the world, where people and enterprises pay for resources to offer their web-services to worldwide clients. Intelligent management is required to automate and manage these infrastructures, as the amount of resources and data to manage exceeds the capacities of human operators....

    Provided By Universitat Oberta de Catalunya

  • White Papers // Jul 2013

    An Efficient Closed Frequent Itemset Miner for the MOA Stream Mining System

    Computing frequent itemsets is a central data mining task, both in the static and the streaming scenarios. Important research effort has produced a substantial number of methods for the streaming case, and the problem is relatively well understood now. The authors noticed, however, that there are almost no public, easy-to-use...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Jun 2013

    Conformance Checking in the Large: Partitioning and Topology

    The torrents of event data generated by today's systems are an important enabler for process mining. However, at the same time, the size and variability of the resulting event logs are challenging for today's process mining techniques. This paper focuses on \"Conformance checking in the large\" and presents a novel...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Apr 2013

    Insuring Sensitive Processes through Process Mining

    Any system, company or complex task is composed by processes, i.e., sequences of actions performed in some established order. Some of these processes are considered sensitive for the role they play within the system, or for the sensitive data they manage. In such cases, the trust in these processes is...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Mar 2013

    Receiver-Driven Routing for Community Mesh Networks

    Community wireless mesh networks are decentralized and cooperative structures with participation rules that define their freedom, openness and neutrality. The operation of these networks requires routing algorithms that may impose additional unnecessary technical restrictions in the determination of routes that can restrict the freedom of community users. The authors propose...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Feb 2013

    Area and Laser Power Scalability Analysis in Photonic Networks-on-Chip

    In the last decade, the field of microprocessor architecture has seen the rise of multicore processors, which consist of the interconnection of a set of independent processing units or cores in the same chip. As the number of cores per multiprocessor increases, the bandwidth and energy requirements for their interconnection...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Feb 2013

    Integrating ETL Processes from Information Requirements

    Data Warehouse (DW) design is based on a set of requirements expressed as Service Level Agreements (SLAs) and Business Level Objects (BLOs). Populating a DW system from a set of information sources is realized with Extract-Transform-Load (ETL) processes based on SLAs and BLOs. The entire task is complex, time consuming,...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Jan 2013

    Mutual Information Maximization for a Wireless Energy Harvesting Node Considering the Circuitry Power Consumption

    An energy harvesting transmitter operating in a point-to-point link through a discrete time fading channel is considered in this paper. Assuming non-causal knowledge of the harvested energy and channel state, the resource allocation that maximizes the mutual information is investigated by considering both the radiated power and the circuitry power...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Nov 2012

    Graphene-Enabled Wireless Communication for Massive Multicore Architectures

    Current trends in microprocessor architecture design are leading towards a dramatic increase of core-level parallelization, wherein a given number of independent processors or cores are interconnected. Since the main bottleneck is foreseen to migrate from computation to communication, efficient and scalable means of inter-core communication are crucial for guaranteeing steady...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Nov 2012

    On the Measurement of Privacy as An Attacker's Estimation Error

    A wide variety of privacy metrics have been proposed in the literature to evaluate the level of protection offered by privacy enhancing-technologies. Most of these metrics are specific to concrete systems and adversarial models, and are difficult to generalize or translate to other contexts. Furthermore, a better understanding of the...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Nov 2012

    Improving Soft Frequency Reuse for Realistic OFDMA-Based Cellular Deployments

    Effective interference management is a technical challenge of utmost importance for emerging OFDMA-based technologies such as Long Term Evolution (LTE) and Worldwide Interoperability for Microwave Access (WiMAX). Static Intercell Interference Coordination techniques including Soft Frequency Reuse (SFR) have enjoyed acceptance among mobile operators as a solution to deal with this...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Sep 2012

    Ideal Hierarchical Secret Sharing Schemes

    Hierarchical secret sharing is among the most natural generalizations of threshold secret sharing, and it has attracted a lot of attention from the invention of secret sharing until nowadays. Several constructions of ideal hierarchical secret sharing schemes have been pro-posed, but it was not known what access structures admit such...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Sep 2012

    Scalable NoC Architectures: Efficient and Low Energy Consumption Chip Communication

    Energy has been the primary reason for shifting from traditional single-core processors to current multicore processors. Such multicore designs require an interconnection network to communicate cores among themselves and with memory. As the number of cores per chip increases, the energy consumption of these Network-on-Chip (NoC) has become comparable to...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Sep 2012

    Networking Challenges and Principles in Diffusion-Based Molecular Communication

    Nanotechnology has allowed building nanomachines capable of performing simple tasks, such as sensing, data storage or actuation. Nanonetworks, networks of nanomachines, will allow cooperation and information sharing among them, thereby greatly expanding the applications of nanotechnology in the biomedical, environmental and industrial fields. One of the most promising paradigms to...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Sep 2012

    Hierarchical Identity-Based (Lossy) Trapdoor Functions

    Lossy trapdoor functions, introduced by Peikert and Waters, have received a lot of attention in the last years, because of their wide range of applications in theoretical cryptography. The notion has been recently extended to the identity-based setting by Bellare et al. (Eurocrypt'12). The authors provide one more step in...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Jul 2012

    Alignment Based Precision Checking

    Most organizations have process models describing how cases need to be handled. In fact, legislation and standardization (cf. the Sarbanes-Oxley Act, the Basel II Accord, and the ISO 9000 family of standards) are forcing organizations to document their processes. These processes are often not enforced by information systems. However, torrents...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Jun 2012

    Improved Energy Detection Spectrum Sensing for Cognitive Radio

    Energy detection constitutes a preferred approach for spectrum sensing in cognitive radio due to its simplicity and applicability (it works irrespective of the signal format to be detected) as well as its low computational and implementation costs. The main drawback, however, is its well-known detection performance limitations. Various alternative detection...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Jun 2012

    Graphene-Enabled Hybrid Architectures for Multiprocessors: Bridging Nanophotonics and Nanoscale Wireless Communication

    Due to their out-standing performance (huge bandwidth and high signal quality), optical communications have become the standardized technologies suited for long reach and high bit-rate communication systems. Nevertheless, the traditional incompatibility of CMOS with the optical technology, and the difficulty for all-optical implementation of some key functions such as buffering...

    Provided By Universitat Oberta de Catalunya

  • White Papers // May 2012

    Vertical WLAN Handover Algorithm and Protocol to Improve the IPTV QoS of the End User

    The appearance of several IEEE 802.11 variants made possible the availability of many wireless local area network access options for end users in the same location. Network requirements for IPTV service become higher when the quality of the delivered video is higher. Moreover, in wireless networks the network performance is...

    Provided By Universitat Oberta de Catalunya

  • White Papers // May 2012

    Optimal Pilot Design and Power Control in Correlated MISO Links

    The authors study the maximization of an achievable ergodic rate expression of a Multiple-Input Single-Output (MISO) channel where both ends are cognizant of the same erroneous estimate of the current fading state, yet they have complete knowledge of channel statistics. A training procedure estimates each channel state by means of...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Mar 2012

    Intruder Tracking in WSNs Using Binary Detection Sensors and Mobile Sinks

    Powered by digital transmission advances in recent years, Wireless Sensor Networks (WSNs) are beginning to experience a boom in different areas. Of special interest are those applications offering real-time tracking and monitoring of objects in motion, both indoors and outdoors. A WSN can have a large number of nodes, each...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Feb 2012

    Hardware/Software Mechanisms for Protecting an IDS Against Algorithmic Complexity Attacks

    Intrusion Detection Systems (IDS) have emerged as one of the most promising ways to secure systems in the network. An IDS like the popular snort detects attacks on the network using a database of previous attacks. So in order to detect these attack strings in the packet, Snort uses the...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Feb 2012

    An Analytical Model for the LISP Cache Size

    Concerns regarding the scalability of the inter-domain routing have encouraged researchers to start elaborating a more robust Internet architecture. While consensus on the exact form of the solution is yet to be found, the need for a semantic decoupling of a node's location and identity is generally accepted as the...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Feb 2012

    Quorum Sensing-Enabled Amplification for Molecular Nanonetworks

    Nanotechnology is enabling the development of devices in a scale ranging from a few to hundreds of nanometers. The nanonetworks that result from interconnecting these devices greatly expand the possible applications, by increasing the complexity and range of operation of the system. Molecular communication is regarded as a promising way...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Feb 2012

    Exploiting Temporal Locality in Network Traffic Using Commodity Multi-Cores

    Network traffic has traditionally exhibited temporal locality in the header field of packets. Such locality is intuitive and is very well studied over the years. In this paper, the authors study temporal locality in the packet payload. Temporal locality can also be viewed as redundancy and they observe significant redundancy...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Jan 2012

    Energy-Efficient and Multifaceted Resource Management for Profit-Driven Virtualized Data Centers

    As long as virtualization has been introduced in data centers, it has been opening new chances for resource management. Nowadays, it is not just used as a tool for consolidating underused nodes and save power; it also allows new solutions to well-known challenges, such as heterogeneity management. Virtualization helps to...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Dec 2011

    Static Task Mapping for Tiled Chip Multiprocessors with Multiple Voltage Islands

    The complexity of large Chip Multi-Processors (CMP) makes design reuse a practical approach to reduce the manufacturing and de-sign cost of high-performance systems. This paper proposes techniques for static task mapping onto general-purpose CMPs with multiple pre-defined voltage islands for power management. The CMPs are assumed to contain different classes...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Dec 2011

    Optimal Resource Allocation in a Virtualized Software Aging Platform With Software Rejuvenation

    Now-a-days, virtualized platforms have become the most popular option to deploy complex enough services. The reason is that virtualization allows resource providers to increase resource utilization. Deployed services are expected to be always available, but these long-running services are especially sensitive to suffer from software aging phenomenon. This term refers...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Oct 2011

    On the Memory System Requirements of Future Scientific Applications: Four Case-Studies

    In this paper, the authors observe and characterize the memory behavior, and specifically memory footprint, memory bandwidth and cache effectiveness, of several well-known parallel scientific applications running on a large processor cluster. Based on the analysis of their instrumented execution, they project some performance requirements from future memory systems serving...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Aug 2011

    DiDi: Mitigating The Performance Impact of TLB Shootdowns Using A Shared TLB Directory

    Translation Lookaside Buffers (TLBs) are ubiquitously used in modern architectures to cache virtual-to-physical mappings and, as they are looked up on every memory access, are paramount to performance scalability. The emergence of Chip Multi-Processors (CMPs) with per-core TLBs has brought the problem of TLB coherence to front stage. TLBs are...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Jun 2011

    A Comparison of Cache Hierarchies for SMT Processors

    In the multithread and multicore era, pro-grams are forced to share part of the processor structures. On one hand, the state of the art in multi-threading describes how efficiently manage and distribute inner resources such as reorder buffer or issue windows. On the other hand, there is a substantial body...

    Provided By Universitat Oberta de Catalunya

  • White Papers // May 2011

    Discrete-Time Spectrum Occupancy Model Based on Markov Chain and Duty Cycle Models

    This paper presents an empirical time-dimension model of spectrum use in the context of dynamic spectrum access. Concretely, a discrete-time two-state Markov chain with novel duty cycle models is proposed as an adequate mean to accurately describe spectrum occupancy in the time domain. The validity and accuracy of the proposed...

    Provided By Universitat Oberta de Catalunya

  • White Papers // May 2011

    An Overview of Spectrum Occupancy Models for Cognitive Radio Networks

    The Dynamic Spectrum Access (DSA) paradigm based on the Cognitive Radio (CR) technology has emerged as a promising solution to conciliate the existing conflicts between spectrum demand growth and current spectrum underutilization without changes to the existing legacy wireless systems. The basic underlying idea of DSA/CR is to allow unlicensed...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Apr 2011

    NoSQL: The Death of the Star

    In the last years, the problems of using generic storage techniques for very specific applications has been detected and outlined. Thus, some alternatives to relational DBMSs (e.g. BigTable and C-store) are blooming. On the other hand, cloud computing is already a reality that helps to save money by eliminating the...

    Provided By Universitat Oberta de Catalunya

  • White Papers // May 2009

    Reliable Process for Security Policy Deployment

    The authors focus in this paper on the problem of configuring and managing network security devices, such as Firewalls, Virtual Private Network (VPN) tunnels, and Intrusion Detection Systems (IDSs). The proposal is the following. First, they formally specify the security requirements of a given system by using an expressive access...

    Provided By Universitat Oberta de Catalunya

  • White Papers // May 2009

    A Survey on Cross-Site Scripting Attacks

    Web applications are becoming truly pervasive in all kinds of business models and organizations. Today, most critical systems such as those related to health care, banking, or even emergency response, are relying on these applications. They must therefore include, in addition to the expected value offered to their users, reliable...

    Provided By Universitat Oberta de Catalunya

  • White Papers // May 2012

    Vertical WLAN Handover Algorithm and Protocol to Improve the IPTV QoS of the End User

    The appearance of several IEEE 802.11 variants made possible the availability of many wireless local area network access options for end users in the same location. Network requirements for IPTV service become higher when the quality of the delivered video is higher. Moreover, in wireless networks the network performance is...

    Provided By Universitat Oberta de Catalunya

  • White Papers // May 2012

    Optimal Pilot Design and Power Control in Correlated MISO Links

    The authors study the maximization of an achievable ergodic rate expression of a Multiple-Input Single-Output (MISO) channel where both ends are cognizant of the same erroneous estimate of the current fading state, yet they have complete knowledge of channel statistics. A training procedure estimates each channel state by means of...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Mar 2012

    Intruder Tracking in WSNs Using Binary Detection Sensors and Mobile Sinks

    Powered by digital transmission advances in recent years, Wireless Sensor Networks (WSNs) are beginning to experience a boom in different areas. Of special interest are those applications offering real-time tracking and monitoring of objects in motion, both indoors and outdoors. A WSN can have a large number of nodes, each...

    Provided By Universitat Oberta de Catalunya

  • White Papers // May 2011

    Discrete-Time Spectrum Occupancy Model Based on Markov Chain and Duty Cycle Models

    This paper presents an empirical time-dimension model of spectrum use in the context of dynamic spectrum access. Concretely, a discrete-time two-state Markov chain with novel duty cycle models is proposed as an adequate mean to accurately describe spectrum occupancy in the time domain. The validity and accuracy of the proposed...

    Provided By Universitat Oberta de Catalunya

  • White Papers // May 2011

    An Overview of Spectrum Occupancy Models for Cognitive Radio Networks

    The Dynamic Spectrum Access (DSA) paradigm based on the Cognitive Radio (CR) technology has emerged as a promising solution to conciliate the existing conflicts between spectrum demand growth and current spectrum underutilization without changes to the existing legacy wireless systems. The basic underlying idea of DSA/CR is to allow unlicensed...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Nov 2012

    Graphene-Enabled Wireless Communication for Massive Multicore Architectures

    Current trends in microprocessor architecture design are leading towards a dramatic increase of core-level parallelization, wherein a given number of independent processors or cores are interconnected. Since the main bottleneck is foreseen to migrate from computation to communication, efficient and scalable means of inter-core communication are crucial for guaranteeing steady...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Feb 2012

    An Analytical Model for the LISP Cache Size

    Concerns regarding the scalability of the inter-domain routing have encouraged researchers to start elaborating a more robust Internet architecture. While consensus on the exact form of the solution is yet to be found, the need for a semantic decoupling of a node's location and identity is generally accepted as the...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Sep 2012

    Networking Challenges and Principles in Diffusion-Based Molecular Communication

    Nanotechnology has allowed building nanomachines capable of performing simple tasks, such as sensing, data storage or actuation. Nanonetworks, networks of nanomachines, will allow cooperation and information sharing among them, thereby greatly expanding the applications of nanotechnology in the biomedical, environmental and industrial fields. One of the most promising paradigms to...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Mar 2010

    LISP-TREE: A DNS Hierarchy to Support the LISP Mapping System

    During the last years several operators have expressed concerns about the continued growth of the BGP routing tables in the default-free zone. Proposed solutions for this issue are centered around the idea of separating the network node's identifier from its topological location. Among the existing proposals, the Locator/ID Separation Protocol...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Feb 2012

    Quorum Sensing-Enabled Amplification for Molecular Nanonetworks

    Nanotechnology is enabling the development of devices in a scale ranging from a few to hundreds of nanometers. The nanonetworks that result from interconnecting these devices greatly expand the possible applications, by increasing the complexity and range of operation of the system. Molecular communication is regarded as a promising way...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Nov 2012

    Improving Soft Frequency Reuse for Realistic OFDMA-Based Cellular Deployments

    Effective interference management is a technical challenge of utmost importance for emerging OFDMA-based technologies such as Long Term Evolution (LTE) and Worldwide Interoperability for Microwave Access (WiMAX). Static Intercell Interference Coordination techniques including Soft Frequency Reuse (SFR) have enjoyed acceptance among mobile operators as a solution to deal with this...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Dec 2011

    Optimal Resource Allocation in a Virtualized Software Aging Platform With Software Rejuvenation

    Now-a-days, virtualized platforms have become the most popular option to deploy complex enough services. The reason is that virtualization allows resource providers to increase resource utilization. Deployed services are expected to be always available, but these long-running services are especially sensitive to suffer from software aging phenomenon. This term refers...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Jan 2013

    Mutual Information Maximization for a Wireless Energy Harvesting Node Considering the Circuitry Power Consumption

    An energy harvesting transmitter operating in a point-to-point link through a discrete time fading channel is considered in this paper. Assuming non-causal knowledge of the harvested energy and channel state, the resource allocation that maximizes the mutual information is investigated by considering both the radiated power and the circuitry power...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Sep 2012

    Hierarchical Identity-Based (Lossy) Trapdoor Functions

    Lossy trapdoor functions, introduced by Peikert and Waters, have received a lot of attention in the last years, because of their wide range of applications in theoretical cryptography. The notion has been recently extended to the identity-based setting by Bellare et al. (Eurocrypt'12). The authors provide one more step in...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Apr 2010

    Spectrum Occupancy in Realistic Scenarios and Duty Cycle Model for Cognitive Radio

    Most of the spectrum occupancy measurement campaigns performed to the date in the context of cognitive radio are based on measurements in outdoor high points such as building roofs, balconies and towers. Although these measurement scenarios enable a more accurate estimation of the primary transmitters' spectral activity, they may not...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Sep 2010

    Methodological Aspects of Spectrum Occupancy Evaluation in the Context of Cognitive Radio

    Cognitive radio has recently emerged as a promising solution to conciliate the existing conflicts between spectrum demand growth and spectrum under-utilisation. The basic underlying idea is to allow unlicensed users to access in an opportunistic and non-interfering manner some licensed bands temporarily unoccupied by the licensed users. Within the framework...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Jan 2011

    Towards a More Efficient Spectrum Usage: Spectrum Sensing and Cognitive Radio Techniques

    The traditional approach of dealing with spectrum management in wireless communications has been the definition of a licensed user granted with exclusive exploitation rights for a specific frequency. While interference is easily avoided, this approach is unlikely to achieve the objective to maximize the value of spectrum, and in fact...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Jun 2012

    Improved Energy Detection Spectrum Sensing for Cognitive Radio

    Energy detection constitutes a preferred approach for spectrum sensing in cognitive radio due to its simplicity and applicability (it works irrespective of the signal format to be detected) as well as its low computational and implementation costs. The main drawback, however, is its well-known detection performance limitations. Various alternative detection...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Jan 2010

    A Real-Time Testbed for Heterogeneous Wireless Networks

    Trends in wireless communications are evolving towards the integration of different radio access networks and technologies into heterogeneous infrastructures. This type of communication networks are facing the challenge of providing continuous and ubiquitous connectivity through different technologies while preserving the negotiated end-user Quality of Service (QoS) level during the entire...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Jan 2010

    The Real-Time AROMA Testbed for All-IP Heterogeneous Wireless Access Networks

    This paper describes the real-time testbed that has been developed in the framework of the European AROMA project. The objective of the AROMA project is to devise and assess a set of specific resource management strategies and algorithms for both the access and core network parts of an all-IP heterogeneous...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Jan 2010

    A Real-Time Platform for End-to-Edge QoS Evaluation in Heterogeneous Networks

    This paper describes a platform developed in the framework of the European AROMA project that allows emulating in real-time a complex heterogeneous wireless access network. The objective of the AROMA project is to devise and assess a set of specific resource management strategies and algorithms for both the access and...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Jan 2010

    Quality of Experience Evaluation Under QoS-Aware Mobility Mechanisms

    Next generation wireless networks will encompass a wide range of heterogeneous technologies in the radio access part. In such networks, the all-IP paradigm has been identified as a promising solution that will contribute benefits by providing IP-based transport through the radio and core network parts. However, this concept requires a...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Jan 2010

    Spectral Occupancy Measurements in Urban Areas and Their Applicability to the Blind Standard Recognition Sensor Concept

    Cognitive Radio (CR) has been paid much attention in both academic and industrial domains during the last years for its potential capability to solve to the so-called spectrum scar-city problem. The CR concept arose as a result of the current spectrum underutilization, which was demonstrated in a number of spectrum...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Feb 2010

    Performance of Spectrum Sensing for Cognitive Radio Based on Field Measurements of Various Radio Technologies

    Despite its practical performance limitations, energy detection has gained popularity during the last years as a spectrum sensing technique for dynamic spectrum access in cognitive radio networks. The main advantages of energy detection-based spectrum sensing are its simplicity, low computational and implementation costs as well as its ability to work...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Jan 2010

    Spectral Occupation Measurements and Blind Standard Recognition Sensor for Cognitive Radio Networks

    Cognitive radio has been claimed to be a hopeful solution to the existing conflicts between spectrum demand growth and spectrum underutilization. The basic underlying idea of cognitive radio is to allow unlicensed users to access in an opportunistic and non-interfering manner some licensed bands temporarily unoccupied by licensed users. The...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Jun 2010

    On the Spectrum Occupancy Perception of Cognitive Radio Terminals in Realistic Scenarios

    Cognitive radio terminals sense the spectrum to detect temporarily unoccupied spectrum gaps and transmit. The behavior of a network of cognitive radio terminals therefore depends on the spectrum occupancy perceived by each terminal at its local environment. In this context, this paper explores (via empirical measurements) the spectrum occupancy that...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Oct 2010

    Spatial Duty Cycle Model for Cognitive Radio

    Spectrum occupancy modeling in the context of Dynamic Spectrum Access/Cognitive Radio (DSA/CR) constitutes a rather unexplored research area that still requires much more effort. This paper addresses the problem of modeling spectrum occupancy in the spatial domain by proposing a novel theoretical approach that enables modeling the occupancy level perceived...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Nov 2010

    Joint Learning-Detection Framework: An Empirical Analysis

    Within a context of Cognitive Radio, the authors explore the possibility to detect the presence of users on a given band with no a priori knowledge on the environment. This paper ventures the analysis of a joint learning-detection framework where the detector improves its detecting abilities online relying on past...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Mar 2011

    A Radio Spectrum Measurement Platform for Spectrum Surveying in Cognitive Radio

    This paper presents a sophisticated radio spectrum measurement platform specifically envisaged and designed for spectrum occupancy surveys in the context of Dynamic Spectrum Access/Cognitive Radio (DSA/CR). The presented tool is a very flexible computer-controlled radio measurement system, which has successfully been used in extensive spectrum measurement campaigns and empirical studies...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Sep 2012

    Ideal Hierarchical Secret Sharing Schemes

    Hierarchical secret sharing is among the most natural generalizations of threshold secret sharing, and it has attracted a lot of attention from the invention of secret sharing until nowadays. Several constructions of ideal hierarchical secret sharing schemes have been pro-posed, but it was not known what access structures admit such...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Apr 2007

    Mining Frequent Closed Unordered Trees Through Natural Representations

    Many knowledge representation mechanisms consist of link-based structures; they may be studied formally by means of unordered trees. Here, the authors consider the case where labels on the nodes are nonexistent or unreliable, and propose data mining processes focusing on just the link structure. They propose a representation of ordered...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Mar 2007

    Mining Frequent Closed Rooted Trees

    Many knowledge representation mechanisms are based on tree-like structures, thus symbolizing the fact that certain pieces of information are related in one sense or another. There exists a well-studied process of closure-based data mining in the itemset framework: the authors consider the extension of this process into trees. They focus...

    Provided By Universitat Oberta de Catalunya

  • White Papers // May 2009

    Adaptive XML Tree Mining on Evolving Data Streams

    Tree classification and the frequent tree discovery task have been important tasks over the last decade. Now-a-days, they are becoming harder, as the size of the trees datasets is increasing and the authors cannot assume that data has been generated from a static distribution. They propose a new method to...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Jul 2013

    An Efficient Closed Frequent Itemset Miner for the MOA Stream Mining System

    Computing frequent itemsets is a central data mining task, both in the static and the streaming scenarios. Important research effort has produced a substantial number of methods for the streaming case, and the problem is relatively well understood now. The authors noticed, however, that there are almost no public, easy-to-use...

    Provided By Universitat Oberta de Catalunya

  • White Papers // May 2009

    Adaptive Parameter-free Learning from Evolving Data Streams

    Data streams pose several challenges on data mining algorithm design. Limited use of resources (time and memory) is one. The necessity of dealing with data whose nature or distribution changes over time is another fundamental one. Dealing with time-changing data requires in turn strategies for detecting and quantifying change, forgetting...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Jan 2007

    Learning from Time-Changing Data with Adaptive Windowing

    The authors present a new approach for dealing with distribution change and concept drift when learning from data sequences that may vary with time. They use sliding windows whose size, instead of being fixed a priori, is recomputed online according to the rate of change observed from the data in...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Feb 2006

    Data Mining to Support Tutoring in Virtual Learning Communities: Experiences and Challenges

    Computers and Internet are becoming widely used in educational contexts. Particularly, the wide availability of Learning Management Systems (LMS) allows to easily set up virtual communities providing channels and workspaces to facilitate communication and information sharing. Most of these systems are able to track student's interaction within the workspaces and...

    Provided By Universitat Oberta de Catalunya

  • White Papers // Jan 2014

    Synthesis of Asynchronous Hardware from Petri Nets

    As semiconductor technology strides towards billions of transistors on a single die, problems concerned with deep sub-micron process features and design productivity call for new approaches in the area of behavioral models. This paper focuses on some of recent developments and new opportunities for Petri nets in designing asynchronous circuits...

    Provided By Universitat Oberta de Catalunya