Jacobs University Bremen

Displaying 1-28 of 28 results

  • White Papers // May 2012

    A General Framework for Optimizing AF Based Multi-Relay OFDM Systems

    In this paper, the authors study the joint resource allocation problem in multi-carrier multi-relay aided dual hop single-user communication. They adopt Orthogonal Frequency Division Multiplexing (OFDM) as the transmission modulation and consider Amplify-and-Forward (AF) relaying scheme. The optimization is performed over power allocation at source node, beamforming at relay nodes...

    Provided By Jacobs University Bremen

  • White Papers // May 2012

    Improved Error Localization in DSL Systems Based on the Common Mode

    The authors propose a scheme to improve system performance in Discrete MultiTone systems, which combines the joint differential and common mode processing at the receiver side with erasure marking. This is achieved by using the strong correlation between differential and common mode in the case of a few strong interferers...

    Provided By Jacobs University Bremen

  • White Papers // Mar 2012

    A Comparative Analysis of Array Models for Databases

    While the database collection types set, list, and record have received in-depth attention, the fourth type, array, is still far from being integrated into database modeling. Due to this lack of attention there is only insufficient array support by today's database technology. This is surprising given that large, multi-dimensional arrays...

    Provided By Jacobs University Bremen

  • White Papers // May 2011

    A Joint Resource Allocation Scheme for Multiuser Two-Way Relay Networks

    In this paper, the authors study the problem of resource allocation in Amplify-and-Forward (AF) based multiuser two-way relay network that is operated under Orthogonal Frequency Division Multiple Access (OFDMA) modulation. They formulate an end-to-end throughput maximization problem subject to limited power constraint at individual user and relay. The optimization targets...

    Provided By Jacobs University Bremen

  • White Papers // May 2011

    The Timing Of Repeated And Unrepeated Monopoly Investment Under Wear And Tear And Demand

    In an intertemporal model, the authors analyze the timing of irreversible and lumpy monopoly investment under certainty. There are two reasons for investing, i.e. wear and tear leading to replacement investment and demand growth leading to expansion investment. Both in a single investment setting and in a repeated investment setting,...

    Provided By Jacobs University Bremen

  • White Papers // May 2011

    The Effect Of Monopoly Regulation On The Timing Of Investment

    This paper contributes a theoretical analysis of the effects of different types of regulation on the timing of monopoly investment in a setting with lumpy investment outlays. Concentrating on the case where investment increases the regulatory asset base, the authors distinguish between price-based regulation and cost-based regulation. Under cost-based regulation,...

    Provided By Jacobs University Bremen

  • White Papers // Feb 2011

    Regulation And Regulatory Risk In The Face Of Large Transmission Investment

    Most transmission systems in Europe are currently in need of large network expansions, in particular to cope with increasing shares of load remote renewable energy sources. Given that the scope for further cost reductions is largely exhausted, the authors observe a paradigm shift into the direction of implementing more cost-pass-through...

    Provided By Jacobs University Bremen

  • White Papers // Aug 2010

    Vertical Unbundling, The Coordination Of Investment, And Network Pricing

    This paper provides a formal analysis on the investment coordination problem in a vertically separated electricity supply industry, although the analysis may apply also to other network industries. In an electricity system, the investment decisions of network and power plants need to be coordinated. In unbundled markets, firm-internal coordination no...

    Provided By Jacobs University Bremen

  • White Papers // Apr 2010

    Dimensions of Formality: A Case Study for MKM in Software Engineering

    The authors study the formalization of a collection of documents created for a Software Engineering project from an MKM perspective. They analyze how document and collection markup formats can cope with an open-ended, multi-dimensional space of primary and secondary classifications and relationships. They show that RDF a-based extensions of MKM...

    Provided By Jacobs University Bremen

  • White Papers // Apr 2010

    Green's Function Models and Measurements for Body Area Network (BAN) Channels

    In wireless Body Area Networks (BANs), communicating nodes are present near, directly on, or inside the body. Designing high-performance BAN systems is challenging due to competing goals of high capacity, minimal interference, robustness, and low power consumption. Since the body forms an integral part of the communications channel and near-field...

    Provided By Jacobs University Bremen

  • White Papers // Feb 2010

    Experimental Investigation of MIMO Reciprocal Channel Key Generation

    There is growing interest in physical-layer key generation schemes that provide very strong or even perfect security in wireless communication systems. One such scheme is reciprocal channel key generation, where two nodes quantize reciprocal channel state information to generate keys. Although the use of Multiple-Input Multiple-Output (MIMO) techniques is interesting...

    Provided By Jacobs University Bremen

  • White Papers // Feb 2010

    Exploring Beamforming Performance Versus Complexity in Reconfigurable Aperture Antennas

    REConfigurable APerture (RECAP) antennas consist of a regular array of reconfigurable elements confined to an aperture, representing a generalization of the reconfigurable antenna concept. RECAPs have the potential of supporting operations like beamforming, null steering, interference suppression, adaptive matching, and frequency and bandwidth agility in a single aperture. Although very...

    Provided By Jacobs University Bremen

  • White Papers // Feb 2010

    Improved Autocorrelation-Based Sensing Using Correlation Distribution Information

    Accurate and efficient spectrum sensing is a critical component of cognitive radio, which is a technology poised to improve dynamic resource management in future wireless networks. Autocorrelation exploitation has been shown to provide improvements in sensing performance over simple methods like energy detection. A new upper bound on the performance...

    Provided By Jacobs University Bremen

  • White Papers // Jan 2010

    Investigation of Complexity-Constrained Peformance of Planar REConfigurable APerture Antennas (RECAPs)

    A REConfigurable APerture (RECAP) antenna is a regular array of reconfigurable elements whose state can be changed dynamically. RECAPs have shown the potential to support many antenna operations (beamsteering, interference suppression, frequency agility, matching etc.) in a single aperture, but the level to which increasing complexity helps in achieving peak...

    Provided By Jacobs University Bremen

  • White Papers // Jan 2010

    Measured Statistics of Reciprocal Channel Key Generation of Indoor MIMO Channels

    There is growing interest in physical-layer security methods that exploit the random nature of the physical propagation channel to strengthen existing crypto-systems. In Reciprocal Channel Key Generation (RCKG), legitimate nodes (Alice and Bob) observe a common fluctuating channel to generate keys that are safe from the Eavesdropper (Eve). Previous work...

    Provided By Jacobs University Bremen

  • White Papers // Sep 2009

    Ascending-Bid Auction for Unequal-Erasure-Protected Network Coding

    According to the authors' previous paper, Global Encoding Kernels (GEKs) describing linear network codes have different levels of built-in Unequal-Erasure-Protecting (UEP) capability. This creates conflicts among sink nodes in a multicast session since a particular assignment of GEKs favors one sink node over another. This paper proposes a resolution to...

    Provided By Jacobs University Bremen

  • White Papers // Jun 2009

    Power Control and Interference Awareness Using Busy Bursts

    This paper presents the integration of power control and the Busy Burst (BB) technique for a TDD OFDMA (Time Division Duplex Orthogonal Frequency Division Multiple Access) system in an urban Manhattan grid type of environment. The objective is to combine power control with the BB protocol to develop a power...

    Provided By Jacobs University Bremen

  • White Papers // May 2009

    Spreadsheet Interaction With Frames: Exploring a Mathematical Practice

    Since Mathematics really is about what mathematicians do, this paper will look at the mathematical practice of framing, in which an object of interest is viewed in terms of well-understood mathematical structures. The new perspective not only allows to deepen the understanding of a resp. object, it also facilitates new...

    Provided By Jacobs University Bremen

  • White Papers // May 2009

    Design of Learning Based MIMO Cognitive Radio Systems

    This paper addresses the design issues of the multi-antenna-based Cognitive Radio (CR) system that is able to operate concurrently with the licensed Primary Radio (PR) system. The authors propose a practical CR transmission strategy consisting of three major stages: environment learning, channel training, and data transmission. In the environment learning...

    Provided By Jacobs University Bremen

  • White Papers // Feb 2009

    Local Information Busy Burst Thresholding

    This paper presents a novel approach for setting the thresholds for Busy Burst (BB) enabled interference avoidance in TDD (Time Division Duplex) systems. One of the key issues in the BB concept is the appropriate choice of the threshold, which determines whether a user is allowed to transmit on a...

    Provided By Jacobs University Bremen

  • White Papers // Feb 2009

    Analysis of Fusion and Combining for wireless Source Detection

    In wireless detection scenarios such as sensor networks or cognitive radio, "Hidden nodes" can occur due to channel fading, which can be overcome by collaborative sensing. This paper considers the performance of collaboration with combining and fusion methods for both static and fading environments, where each node employs energy detection...

    Provided By Jacobs University Bremen

  • White Papers // Jan 2009

    Indoor Shadowing Correlation Measurements for Cognitive Radio Studies

    Cognitive radio is a potential technology for increasing spectral efficiency in wireless communications systems, where in a hypothetical future overlay policy, secondary cognitive radios temporarily use spectrum that is not utilized, as long as negligible impact is caused to primary licensed users. Dependable spectrum sensing is needed to overcome the...

    Provided By Jacobs University Bremen

  • White Papers // Jan 2009

    Ultra-Wideband Sensing of Speech Production

    Ultra-WideBand (UWB) technology has been identified as an attractive solution for certain biomedical sensing applications due to its safety, no requirement of physical contact, real-time capability, and low cost. This paper considers UWB sensing of human speech production, potentially allowing significant improvements in synthetic speech production, speech pathology, and speech...

    Provided By Jacobs University Bremen

  • White Papers // Jan 2009

    Improved Spectrum Sensing by Utilizing Signal Autocorrelation

    A method that exploits the autocorrelation of transmission signals for primary user detection in cognitive radio is proposed. A closed-form analysis of the method is presented and compared with Monte Carlo simulations. Analytical and simulation results indicate that the method provides significant improvement in the probability of detection for moderate...

    Provided By Jacobs University Bremen

  • White Papers // Jan 2009

    Experimental Characterization of Indoor Multiuser Shadowing for Collaborative Cognitive Radio

    Cross-correlation of multiuser shadowing in an indoor environment at 2.55 GHz is presented, indicating that shadowing is mostly uncorrelated after 2-4 m in the indoor environment. Similar shadowing correlation was obtained for autocorrelation measurements, moving primary (versus moving secondary's), as well as near and far primary measurements. Cognitive radio is...

    Provided By Jacobs University Bremen

  • White Papers // Jan 2009

    Key Generation Exploiting MIMO Channel Evolution: Algorithms and Theoretical Limits

    An emerging area of research in wireless communications is the generation of secret encryption keys based on the shared (or common) randomness of the wireless channel between two legitimate nodes in a communication network. However, to date, little work has appeared on methods to use the increased randomness available when...

    Provided By Jacobs University Bremen

  • White Papers // Oct 2008

    Secure Physical Layer Key Generation Schemes: Performance and Information Theoretic Limits

    There is growing interest in wireless security methods that provide strong or even perfect secrecy by taking advantage of features of the physical propagation channel. In advantage-based methods, high channel quality in an average or opportunistic sense is exploited between two legitimate nodes, such that non-zero secrecy capacity can be...

    Provided By Jacobs University Bremen

  • White Papers // Aug 2008

    UEP Network Coding for Scalable Data

    It is proven by Ahlswede et al. that, the maximum data flow from the source to each destination in a multicast session can only be guaranteed if network coding is applied. Later, Li et al. proved that a simple class of network coding, called linear network coding, suffices to achieve...

    Provided By Jacobs University Bremen

  • White Papers // May 2012

    A General Framework for Optimizing AF Based Multi-Relay OFDM Systems

    In this paper, the authors study the joint resource allocation problem in multi-carrier multi-relay aided dual hop single-user communication. They adopt Orthogonal Frequency Division Multiplexing (OFDM) as the transmission modulation and consider Amplify-and-Forward (AF) relaying scheme. The optimization is performed over power allocation at source node, beamforming at relay nodes...

    Provided By Jacobs University Bremen

  • White Papers // May 2012

    Improved Error Localization in DSL Systems Based on the Common Mode

    The authors propose a scheme to improve system performance in Discrete MultiTone systems, which combines the joint differential and common mode processing at the receiver side with erasure marking. This is achieved by using the strong correlation between differential and common mode in the case of a few strong interferers...

    Provided By Jacobs University Bremen

  • White Papers // Aug 2008

    UEP Network Coding for Scalable Data

    It is proven by Ahlswede et al. that, the maximum data flow from the source to each destination in a multicast session can only be guaranteed if network coding is applied. Later, Li et al. proved that a simple class of network coding, called linear network coding, suffices to achieve...

    Provided By Jacobs University Bremen

  • White Papers // Sep 2009

    Ascending-Bid Auction for Unequal-Erasure-Protected Network Coding

    According to the authors' previous paper, Global Encoding Kernels (GEKs) describing linear network codes have different levels of built-in Unequal-Erasure-Protecting (UEP) capability. This creates conflicts among sink nodes in a multicast session since a particular assignment of GEKs favors one sink node over another. This paper proposes a resolution to...

    Provided By Jacobs University Bremen

  • White Papers // May 2009

    Spreadsheet Interaction With Frames: Exploring a Mathematical Practice

    Since Mathematics really is about what mathematicians do, this paper will look at the mathematical practice of framing, in which an object of interest is viewed in terms of well-understood mathematical structures. The new perspective not only allows to deepen the understanding of a resp. object, it also facilitates new...

    Provided By Jacobs University Bremen

  • White Papers // May 2009

    Design of Learning Based MIMO Cognitive Radio Systems

    This paper addresses the design issues of the multi-antenna-based Cognitive Radio (CR) system that is able to operate concurrently with the licensed Primary Radio (PR) system. The authors propose a practical CR transmission strategy consisting of three major stages: environment learning, channel training, and data transmission. In the environment learning...

    Provided By Jacobs University Bremen

  • White Papers // May 2011

    The Timing Of Repeated And Unrepeated Monopoly Investment Under Wear And Tear And Demand

    In an intertemporal model, the authors analyze the timing of irreversible and lumpy monopoly investment under certainty. There are two reasons for investing, i.e. wear and tear leading to replacement investment and demand growth leading to expansion investment. Both in a single investment setting and in a repeated investment setting,...

    Provided By Jacobs University Bremen

  • White Papers // May 2011

    The Effect Of Monopoly Regulation On The Timing Of Investment

    This paper contributes a theoretical analysis of the effects of different types of regulation on the timing of monopoly investment in a setting with lumpy investment outlays. Concentrating on the case where investment increases the regulatory asset base, the authors distinguish between price-based regulation and cost-based regulation. Under cost-based regulation,...

    Provided By Jacobs University Bremen

  • White Papers // Feb 2011

    Regulation And Regulatory Risk In The Face Of Large Transmission Investment

    Most transmission systems in Europe are currently in need of large network expansions, in particular to cope with increasing shares of load remote renewable energy sources. Given that the scope for further cost reductions is largely exhausted, the authors observe a paradigm shift into the direction of implementing more cost-pass-through...

    Provided By Jacobs University Bremen

  • White Papers // Aug 2010

    Vertical Unbundling, The Coordination Of Investment, And Network Pricing

    This paper provides a formal analysis on the investment coordination problem in a vertically separated electricity supply industry, although the analysis may apply also to other network industries. In an electricity system, the investment decisions of network and power plants need to be coordinated. In unbundled markets, firm-internal coordination no...

    Provided By Jacobs University Bremen

  • White Papers // Jun 2009

    Power Control and Interference Awareness Using Busy Bursts

    This paper presents the integration of power control and the Busy Burst (BB) technique for a TDD OFDMA (Time Division Duplex Orthogonal Frequency Division Multiple Access) system in an urban Manhattan grid type of environment. The objective is to combine power control with the BB protocol to develop a power...

    Provided By Jacobs University Bremen

  • White Papers // Feb 2009

    Local Information Busy Burst Thresholding

    This paper presents a novel approach for setting the thresholds for Busy Burst (BB) enabled interference avoidance in TDD (Time Division Duplex) systems. One of the key issues in the BB concept is the appropriate choice of the threshold, which determines whether a user is allowed to transmit on a...

    Provided By Jacobs University Bremen

  • White Papers // Feb 2009

    Analysis of Fusion and Combining for wireless Source Detection

    In wireless detection scenarios such as sensor networks or cognitive radio, "Hidden nodes" can occur due to channel fading, which can be overcome by collaborative sensing. This paper considers the performance of collaboration with combining and fusion methods for both static and fading environments, where each node employs energy detection...

    Provided By Jacobs University Bremen

  • White Papers // Apr 2010

    Green's Function Models and Measurements for Body Area Network (BAN) Channels

    In wireless Body Area Networks (BANs), communicating nodes are present near, directly on, or inside the body. Designing high-performance BAN systems is challenging due to competing goals of high capacity, minimal interference, robustness, and low power consumption. Since the body forms an integral part of the communications channel and near-field...

    Provided By Jacobs University Bremen

  • White Papers // Jan 2010

    Measured Statistics of Reciprocal Channel Key Generation of Indoor MIMO Channels

    There is growing interest in physical-layer security methods that exploit the random nature of the physical propagation channel to strengthen existing crypto-systems. In Reciprocal Channel Key Generation (RCKG), legitimate nodes (Alice and Bob) observe a common fluctuating channel to generate keys that are safe from the Eavesdropper (Eve). Previous work...

    Provided By Jacobs University Bremen

  • White Papers // Jan 2010

    Investigation of Complexity-Constrained Peformance of Planar REConfigurable APerture Antennas (RECAPs)

    A REConfigurable APerture (RECAP) antenna is a regular array of reconfigurable elements whose state can be changed dynamically. RECAPs have shown the potential to support many antenna operations (beamsteering, interference suppression, frequency agility, matching etc.) in a single aperture, but the level to which increasing complexity helps in achieving peak...

    Provided By Jacobs University Bremen

  • White Papers // Feb 2010

    Experimental Investigation of MIMO Reciprocal Channel Key Generation

    There is growing interest in physical-layer key generation schemes that provide very strong or even perfect security in wireless communication systems. One such scheme is reciprocal channel key generation, where two nodes quantize reciprocal channel state information to generate keys. Although the use of Multiple-Input Multiple-Output (MIMO) techniques is interesting...

    Provided By Jacobs University Bremen

  • White Papers // Feb 2010

    Exploring Beamforming Performance Versus Complexity in Reconfigurable Aperture Antennas

    REConfigurable APerture (RECAP) antennas consist of a regular array of reconfigurable elements confined to an aperture, representing a generalization of the reconfigurable antenna concept. RECAPs have the potential of supporting operations like beamforming, null steering, interference suppression, adaptive matching, and frequency and bandwidth agility in a single aperture. Although very...

    Provided By Jacobs University Bremen

  • White Papers // Feb 2010

    Improved Autocorrelation-Based Sensing Using Correlation Distribution Information

    Accurate and efficient spectrum sensing is a critical component of cognitive radio, which is a technology poised to improve dynamic resource management in future wireless networks. Autocorrelation exploitation has been shown to provide improvements in sensing performance over simple methods like energy detection. A new upper bound on the performance...

    Provided By Jacobs University Bremen

  • White Papers // Oct 2008

    Secure Physical Layer Key Generation Schemes: Performance and Information Theoretic Limits

    There is growing interest in wireless security methods that provide strong or even perfect secrecy by taking advantage of features of the physical propagation channel. In advantage-based methods, high channel quality in an average or opportunistic sense is exploited between two legitimate nodes, such that non-zero secrecy capacity can be...

    Provided By Jacobs University Bremen

  • White Papers // Jan 2009

    Indoor Shadowing Correlation Measurements for Cognitive Radio Studies

    Cognitive radio is a potential technology for increasing spectral efficiency in wireless communications systems, where in a hypothetical future overlay policy, secondary cognitive radios temporarily use spectrum that is not utilized, as long as negligible impact is caused to primary licensed users. Dependable spectrum sensing is needed to overcome the...

    Provided By Jacobs University Bremen

  • White Papers // Jan 2009

    Ultra-Wideband Sensing of Speech Production

    Ultra-WideBand (UWB) technology has been identified as an attractive solution for certain biomedical sensing applications due to its safety, no requirement of physical contact, real-time capability, and low cost. This paper considers UWB sensing of human speech production, potentially allowing significant improvements in synthetic speech production, speech pathology, and speech...

    Provided By Jacobs University Bremen

  • White Papers // Jan 2009

    Improved Spectrum Sensing by Utilizing Signal Autocorrelation

    A method that exploits the autocorrelation of transmission signals for primary user detection in cognitive radio is proposed. A closed-form analysis of the method is presented and compared with Monte Carlo simulations. Analytical and simulation results indicate that the method provides significant improvement in the probability of detection for moderate...

    Provided By Jacobs University Bremen

  • White Papers // Jan 2009

    Key Generation Exploiting MIMO Channel Evolution: Algorithms and Theoretical Limits

    An emerging area of research in wireless communications is the generation of secret encryption keys based on the shared (or common) randomness of the wireless channel between two legitimate nodes in a communication network. However, to date, little work has appeared on methods to use the increased randomness available when...

    Provided By Jacobs University Bremen

  • White Papers // Jan 2009

    Experimental Characterization of Indoor Multiuser Shadowing for Collaborative Cognitive Radio

    Cross-correlation of multiuser shadowing in an indoor environment at 2.55 GHz is presented, indicating that shadowing is mostly uncorrelated after 2-4 m in the indoor environment. Similar shadowing correlation was obtained for autocorrelation measurements, moving primary (versus moving secondary's), as well as near and far primary measurements. Cognitive radio is...

    Provided By Jacobs University Bremen

  • White Papers // May 2011

    A Joint Resource Allocation Scheme for Multiuser Two-Way Relay Networks

    In this paper, the authors study the problem of resource allocation in Amplify-and-Forward (AF) based multiuser two-way relay network that is operated under Orthogonal Frequency Division Multiple Access (OFDMA) modulation. They formulate an end-to-end throughput maximization problem subject to limited power constraint at individual user and relay. The optimization targets...

    Provided By Jacobs University Bremen

  • White Papers // Apr 2010

    Dimensions of Formality: A Case Study for MKM in Software Engineering

    The authors study the formalization of a collection of documents created for a Software Engineering project from an MKM perspective. They analyze how document and collection markup formats can cope with an open-ended, multi-dimensional space of primary and secondary classifications and relationships. They show that RDF a-based extensions of MKM...

    Provided By Jacobs University Bremen

  • White Papers // Mar 2012

    A Comparative Analysis of Array Models for Databases

    While the database collection types set, list, and record have received in-depth attention, the fourth type, array, is still far from being integrated into database modeling. Due to this lack of attention there is only insufficient array support by today's database technology. This is surprising given that large, multi-dimensional arrays...

    Provided By Jacobs University Bremen