University of Vienna

Displaying 1-40 of 46 results

  • White Papers // Aug 2012

    Overlay Spectrum Reuse in a Broadcast Network: Covering the Whole Grayscale of Spaces

    In this paper, the authors address the problem of allowing secondary access to the spectrum assigned to a broadcast operator. They assume that the secondary transmitter knows of the primary message but is not able to apply interference cancellation techniques due to the lack of channel state information. Thus, interference...

    Provided By University of Vienna

  • White Papers // Feb 2013

    A Cognitive Mobile BTS Solution with Software-Defined Radioelectric Sensing

    Private communications inside large vehicles such as ships may be effectively provided using standard cellular systems. In this paper, the authors propose a new solution based on software-defined radio with electromagnetic sensing support. Software-defined radio allows low-cost developments and, potentially, added-value services not available in commercial cellular networks. The platform...

    Provided By University of Vienna

  • White Papers // Jan 2013

    Least Squares Disclosure Attacks: User Profiling for Mix-Based Anonymous Communication Systems

    Mixes, relaying routers that hide the relation between incoming and outgoing messages, are the main building block of high-latency anonymous communication systems. A number of so-called Disclosure Attacks have been proposed that effectively de-anonymize traffic sent through these systems. Yet, the dependence of their success on the system parameters is...

    Provided By University of Vienna

  • White Papers // Jan 2013

    A Novel Heuristic Approach for Distance- and Connectivity-Based Multihop Node Localization in Wireless Sensor Networks

    In this paper, the authors focus on anchor-based networks where the position of some few nodes are assumed to be fixed and known a priori, whereas the location of all other nodes is to be estimated based on noisy pair-wise distance measurements. This localization task embodies a non-convex optimization problem...

    Provided By University of Vienna

  • White Papers // Feb 2012

    An Adaptive Feedback Canceller for Full-Duplex Relays Based on Spectrum Shaping

    Although full-duplex relaying schemes are appealing in order to improve spectral efficiency, simultaneous reception and transmission in the same frequency results in self-interference, distorting the retransmitted signal and making the relay prone to oscillation. Current feedback cancellation techniques by means of adaptive filters are hampered by the fact that the...

    Provided By University of Vienna

  • White Papers // Feb 2012

    Adaptive Self-Interference Suppression for Full-Duplex Relays with Multiple Receive Antennas

    In full-duplex relays, simultaneous reception and transmission in the same frequency results in self-interference which distorts the retransmitted signal and makes the relay prone to oscillation. The authors present an adaptive feedback canceller for Multiple-Input Single-Output (MISO) relays, efficiently combining spatial and temporal processing. The receive array is adaptively steered...

    Provided By University of Vienna

  • White Papers // Jul 2012

    Adaptive Transmission Techniques for Mobile Satellite Links

    Adapting the transmission rate in an LMS channel is a challenging task because of the relatively fast time variations, of the long delays involved, and of the difficulty in mapping the parameters of a time-varying channel into communication performance. In this paper, the authors propose two strategies for dealing with...

    Provided By University of Vienna

  • White Papers // Feb 2012

    Detection of Gaussian Signals in Unknown Time-Varying Channels

    The detection of signals in noisy channels is an important problem arising in a wide variety of applications such as sonar, radar or spectrum sensing for Cognitive Radio. Although most existing detection rules assume that the channel is time-invariant, such assumption may be unrealistic in many scenarios. For example, in...

    Provided By University of Vienna

  • White Papers // Jan 2012

    Detection of Unknown Constant Magnitude Signals in Time-Varying Channels

    Spectrum sensing constitutes a key ingredient in many cognitive radio paradigms in order to detect and protect primary transmissions. Most sensing schemes in the literature assume a time-invariant channel. However, when operating in low Signal-to-Noise Ratio (SNR) conditions, observation times are necessarily long and may become larger than the coherence...

    Provided By University of Vienna

  • White Papers // Jul 2012

    On the Effect of Echoes in Hybrid Terrestrial-Satellite Single Frequency Networks: Analysis and Countermeasures

    Hybrid terrestrial-satellite Single Frequency Networks (SFN) achieve large spectral efficiencies due to a higher frequency reuse, which is attained by transmitting the same waveform in the same frequency band from satellite and terrestrial transmitters. However, the presence of multiple transmitters propitiates the existence of the so-called SFN echoes, which can...

    Provided By University of Vienna

  • White Papers // Apr 2011

    Using Event Logs to Derive Role Engineering Artifacts

    Process-aware information systems are used to execute business processes to reach the operational goals of an organization. In this context, access control policies are defined to govern the choice in behavior of such systems. In a role engineering process these access control policies can be defined and customized. This paper...

    Provided By University of Vienna

  • White Papers // Sep 2011

    Responsibility-Driven Design and Development of Process-Aware Security Policies

    Process-Aware Information Systems (PAIS) enable the automated support of business processes that are executed by a combination of human actors and systems. As processes typically require access to sensitive data, security policies are of high importance. Typically security policies in PAIS range from access rules and authorization constraints to context...

    Provided By University of Vienna

  • White Papers // Apr 2011

    Consistency Checks for Duties in Extended UML2 Activity Models

    Process-aware information systems sup-port the execution of business processes. In this con-text, organizations require the precise specification of security policies that govern the behavior of subjects in the systems. Obligation policies specify duties to be fulfilled by certain subjects. In organizational contexts, duties are often associated with a certain task...

    Provided By University of Vienna

  • White Papers // Sep 2011

    AW-RBAC: Access Control in Adaptive Workflow Systems

    Flexibility is one of the key challenges for work-flow systems nowadays. Typically, a work-flow covers the following four aspects which might all be subject to change: control flow, data flow, organizational structures, and application components (services). Existing work in research and practice shows that changes must be applied in a...

    Provided By University of Vienna

  • White Papers // Feb 2012

    SPRINT- Responsibilities: Design and Development of Security Policies in Process-Aware Information Systemsy

    Process-Aware Information Systems (PAIS) enable the definition, execution, and management of business processes. Typically, processes are specified by control flow, data flow, and users or services, authorized to execute process tasks. During process execution, it is often necessary to access sensitive data such as patient or customer information. To secure...

    Provided By University of Vienna

  • White Papers // Apr 2010

    Exploiting Diverse Observation Perspectives to Get Insights on the Malware Landscape

    The authors are witnessing an increasing complexity in the malware analysis scenario. The usage of polymorphic techniques generates a new challenge: it is often difficult to discern the instance of a known polymorphic malware from that of a newly encountered malware family, and to evaluate the impact of patching and...

    Provided By University of Vienna

  • White Papers // Jan 2010

    Data Management in an International Data Grid Project

    This paper reports on preliminary work and architectural design carried out in the "Data Management" work package in the International Data Grid project. The aim within a time scale of three years is to provide Grid middleware services supporting the I/O- intensive world-wide distributed next generation experiments in High-Energy Physics,...

    Provided By University of Vienna

  • White Papers // Jan 2010

    High-Level Composition of QoS-Aware Grid Workflows: An Approach That Considers Location Affinity

    At a high level of abstraction Grid applications are commonly specified based on the workflow paradigm. This paper considers that for the wide acceptance of Grid technology it is relevant that the user has the possibility to express requirements on Quality of Service (QoS) at workflow specification time. However, most...

    Provided By University of Vienna

  • White Papers // Jul 2010

    Towards Negotiable SLA-Based QoS Support for Biomedical Data Services

    Researchers in data intensive domains, like the Virtual Physiological Human Initiative (VPH-I), are commonly overwhelmed with the vast and increasing amount of information available. Advanced studies in biomedicine and other domains often require a considerable amount of effort to achieve data access to a critical mass of relevant data to...

    Provided By University of Vienna

  • White Papers // Jun 2009

    Research Productivity In Business Economics: A Second Reply

    The allegation that CRM monopolizes information is simply not true. The CRM ranking is a joint venture of Verein fur Sozialpolitik and Handelsblatt and is partially funded by the latter. Therefore, CRM's data are not otherwise directly available for commercial purposes. Thus, a respective request by Albers was turned down...

    Provided By University of Vienna

  • White Papers // Jul 2010

    Import Competition And Domestic Response: New Evidence From Mexico

    How does import competition affect the innovative activity of firms? Employing a new data set of Mexican manufacturers from 1998 and 2004, the authors exploit the emergence of China on the world markets as an exogenous competition shock. Innovation is captured through the introduction of quality control systems such as...

    Provided By University of Vienna

  • White Papers // Oct 2009

    New Panel Tests To Assess Inflation Persistence

    In this paper the authors propose new panel tests to detect changes in persistence. The test statistics are used to test the null hypothesis of stationarity against the alternative of a change in persistence from I(0) to I(1), from I(1) to I(0), and in an unknown direction. The limiting distributions...

    Provided By University of Vienna

  • White Papers // Aug 2008

    Supply-Side Triggers For Inflation In Austria

    The supply-side analysis of sectors that have determined price developments in Austria since fall 2007 strongly suggests a lack of competition in the following industries in the medium term: processing and wholesaling of dairy products, pasta production, electricity and gas supply, cement production, and pharmaceutical retailing. Signs of weak competition...

    Provided By University of Vienna

  • White Papers // Apr 2010

    Dynamic Investment Strategies With Demand-Side And Cost-Side Risks

    Investments in cost reductions are critical for the long run success of companies that operate in dynamic and stochastic market environments. This paper studies optimal investment in cost reductions as a real option under the assumption that a single firm faces two different sources of risk, stochastic demand and input...

    Provided By University of Vienna

  • White Papers // Apr 2011

    Towards A Role For Regional Banks - Comment On "The Economics Of Regional Demarcation In Banking"

    In its attempts to open up European markets and thus to foster competition, improve consumer welfare, and perhaps also increase growth potentials, the regional demarcation of banking markets has finally come under serious scrutiny by the European Commission (2007). As Raab and Welzel (2011) demonstrate from a purely industrial economics...

    Provided By University of Vienna

  • White Papers // Jan 2012

    Enterprise 2.0 Integrated Communication and Collaboration Platform

    The intensification of collaborative networking in the enterprises, wide adoption of mobile applications and other progressive IT technologies by businesses, influence enterprise development. Thus, the authors focus in this paper onto the evaluating the role and place of communication&collaborative platforms in new generation of enterprise management paradigm dependent onto the...

    Provided By University of Vienna

  • White Papers // Oct 2012

    Multimedia Operator Chain Topology and Ordering Estimation Based on Detection and Information Theoretic Tools

    The extensive use of multimedia editing tools suitable for non-skilled users has significantly reduced the trust on audiovisual contents. Simultaneously, a new branch of multimedia security, named multimedia forensics, has been developed to cope with this problem. Nevertheless, most of the schemes proposed so far are heuristic and ad-hoc solutions...

    Provided By University of Vienna

  • White Papers // Jan 2013

    Multiuser Detection Performance in Multibeam Satellite Links Under Imperfect CSI

    In multibeam satellite systems, there is a growing need for signal processing techniques able to mitigate the interference among beams, since they could enable a much more aggressive spectrum reuse. In this paper, the authors investigate the effect of the absence of perfect Channel State Information (CSI) at the receiver...

    Provided By University of Vienna

  • White Papers // Nov 2012

    Optimum Training for CSI Acquisition in Cognitive Radio Channels

    One of the main issues in the Overlay Cognitive Radio Paradigm (a framework where the secondary transmitter partially cooperates with the primary user) is the acquisition of channel state information at the secondary transmitter. In a simple interaction framework that could allow the estimation of the channel values at the...

    Provided By University of Vienna

  • White Papers // Mar 2012

    Overlay Cognitive Transmission in OFDM Point to Point Systems Exploiting Primary Feedback

    A secondary user that tries to reuse the spectrum allocated to a primary user can exploit the knowledge of the primary message to perform this task. In particular, the overlay cognitive radio paradigm postulates the use of a fraction of the available power at the secondary transmitter to convey the...

    Provided By University of Vienna

  • White Papers // Apr 2012

    Overlay Spectrum Reuse in a Multicarrier Broadcast Network: Coverage Analysis

    A secondary cognitive user overlaying its message in a broadcast multicarrier network is studied. The secondary user exploits the primary message knowledge to convey its own information while preserving the primary user coverage area, determined by a bound on the BER, and taking into account the degradation due to the...

    Provided By University of Vienna

  • White Papers // Apr 2012

    Overlay Spectrum Reuse in a Multicarrier Broadcast Network: Single Receiver Analysis

    The overlay cognitive radio paradigm presents a framework where a secondary user exploits the knowledge of the primary user's message to improve spectrum utilization. A multicarrier broadcast network is one of the scenarios where this knowledge is possible: the secondary user could join a single frequency network and, therefore, gain...

    Provided By University of Vienna

  • White Papers // Jul 2012

    Performance Analysis of Multiuser Detection for Multibeam Satellites Under Rain Fading

    Multibeam satellite systems are nowadays widely employed, and their use is expected to grow in the next decades. This has raised the interest for signal processing techniques able to mitigate the interference among beams, since they could enable a much more aggressive spectrum reuse. In this paper, the authors investigate...

    Provided By University of Vienna

  • White Papers // Sep 2011

    On the Application of a Hybrid Harmony Search Algorithm to Node Localization in Anchor-Based Wireless Sensor Networks

    In many applications based on Wireless Sensor Networks (WSNs) with static sensor nodes, the availability of accurate location information of the network nodes may become essential. The node localization problem is to estimate all the unknown node positions, based on noisy pairwise distance measurements of nodes within range of each...

    Provided By University of Vienna

  • White Papers // Jul 2011

    Bandlimited or Constant Envelope - Exploiting Waveform Properties in Wireless Microphone Detection

    The detection of BandLimited (BL) Constant Magnitude (CM) signals in white noise of unknown power is analyzed. This is relevant in the context of Dynamic Spectrum Access since Wireless Microphones (WM) typically use analog FM modulation when transmitting in the TV bands and their bandwidth is much smaller than that...

    Provided By University of Vienna

  • White Papers // Feb 2011

    Distributed Spectrum Sensing with Multiantenna Sensors Under Calibration Errors

    Spectrum sensing design for Cognitive Radio systems is challenged by the nature of the wireless medium, which makes the detection requirements difficult to achieve by standalone sensors. To combat shadowing and fading, distributed strategies are usually proposed. However, most distributed approaches are based on the energy detector, which is not...

    Provided By University of Vienna

  • White Papers // Nov 2012

    An Effective Metaheuristic Approach to Node Localization in Wireless Sensor Networks

    In this paper, the authors propose to solve the localization problem by using a two - objective evolutionary algorithm which takes concurrently into account during the evolutionary process both the localization accuracy and certain topological constraints induced by the network connectivity. The proposed method is tested with different network configurations...

    Provided By University of Vienna

  • White Papers // Aug 2011

    Multiantenna Detection of Constant-Envelope Signals in Noise of Unknown Variance

    Detection of unknown signals with Constant Modulus (CM) using multiple antennas in additive white Gaussian noise of unknown variance is considered. The channels from the source to each antenna are assumed frequency-flat and unknown. This problem is of interest for spectrum sensing in cognitive radio systems in which primary signals...

    Provided By University of Vienna

  • White Papers // Nov 2012

    Solving the Node Localization Problem in WSNs by a Two-Objective Evolutionary Algorithm and Local Descent

    Given a small percentage of nodes whose actual positions are known, the problem of estimating the locations of the remaining nodes of a wireless sensor network has attracted a large interest in the last years. The localization task is based on the noisy estimates of the distances between pairs of...

    Provided By University of Vienna

  • White Papers // Sep 2011

    A Study on the Application of Different Two-Objective Evolutionary Algorithms to the Node Localization Problem in Wireless Sensor Networks

    A number of applications of wireless sensor networks required to know the location of the sensor nodes. Typically, however, mainly due to costs and limited capacity of the batteries powering the sensor nodes, only a few nodes of the network, denoted anchor nodes in the literature, are endowed with their...

    Provided By University of Vienna