University of Crete

Displaying 1-17 of 17 results

  • White Papers // Mar 2012

    NUMA Implications for Storage I/O Throughput in Modern Servers

    Current server architectures have started to move away from traditional memory buses that do not scale and towards point-to-point interconnects for communication among processors, memories, and I/O devices. As a result, memory modules are not equidistant from all cores leading to significant differences in memory access performance from different cores....

    Provided By University of Crete

  • White Papers // Aug 2011

    On Multi-Layer Game-Theoretical Modelling of Spectrum Markets and Cognitive Radio Networks

    This paper presents a powerful innovative multi-layer game theoretical modelling framework for the evolution of spectrum markets. It integrates models of the channel, client and network operator (provider) paradigms, wireless infrastructures, types of interaction, and price adaptation. This modelling framework incorporates an extensive set of parameters that allow the modelling...

    Provided By University of Crete

  • White Papers // Jul 2011

    Azor: Using Two-Level Block Selection to Improve SSD-Based I/O Caches

    Flash-based Solid State Drives (SSDs) exhibit potential for solving I/O bottlenecks by offering superior performance over hard disks for several workloads. In this paper, the authors design Azor, an SSD-based I/O cache that operates at the block-level and is transparent to existing applications, such as databases. Their design provides various...

    Provided By University of Crete

  • White Papers // Apr 2011

    A Novel Multi-Layer Framework for Modeling the Evolution of Spectrum Markets and Cognitive-Radio Devices

    This paper presents a novel multi-layer modeling framework for the evolution of spectrum markets of multiple spectrum/network operators that provide wireless access to users. It integrates models of the channel, mobility, user preference, network operators (providers), infrastructure deployment, user distribution, and price-adaptation mechanisms. Providers aim to maximize their own profit,...

    Provided By University of Crete

  • White Papers // Feb 2011

    Indoor Positioning in Wireless LANs Using Compressive Sensing Signal-Strength Fingerprints

    Accurate indoor localization is a significant task for many ubiquitous and pervasive computing applications, with numerous solutions based on IEEE802.11, Bluetooth, ultrasound and infrared technologies being proposed. The inherent sparsity present in the problem of location estimation motivates in a natural fashion the use of the recently introduced theory of...

    Provided By University of Crete

  • White Papers // Feb 2011

    A Game-Theoretical Modeling Framework for Spectrum Markets and Cognitive-Radio Devices

    This paper presents a novel game-theoretical framework to model the evolution of spectrum markets that consists of multiple spectrum/network operators that provide wireless access to users. It integrates models about the channel, mobility, user preference, network operators (providers), infrastructure deployment, user distribution, and price-adaptation mechanisms. Providers aim to maximize their...

    Provided By University of Crete

  • White Papers // Nov 2010

    A Novel Approach for Allocating Network and It Resources Offered by Different Service Providers

    The pace of innovation in computer and networking technology allows many new IT services to emerge rapidly and often benefit from new network services that support faster connectivity and better performance. Centralized resources that are used to provide services to customers are impractical in a dynamic service-based system owned by...

    Provided By University of Crete

  • White Papers // Oct 2010

    Empirical Evaluation of Signal-Strength Fingerprint Positioning in Wireless LANs

    This paper proposes a novel localization technique based on a multivariate Gaussian modeling of the signal strength measurements collected from several Access Points (APs) at different locations. It considers a discretized grid-like form of the environment and computes a signature at each cell of the grid. At run time the...

    Provided By University of Crete

  • White Papers // May 2010

    Momentum Or Contrarian Investment Strategies: Evidence From Dutch Institutional Investors

    This paper analyzes investment strategies of three types of institutional investors - pension funds, life insurers and non-life insurers - over the period 1999-2005. The authors use balance sheet and cash flow data, including purchases and sales of equity, fixed income and real estate. They trace asset reallocations back to...

    Provided By University of Crete

  • White Papers // Apr 2010

    A Comparative Analysis of the Perceived Quality of VoIP Under Various Wireless Network Conditions

    This paper performs a comparative analysis of the perceived quality of (unidirectional, non-interactive) VoIP calls under various wireless network conditions (e.g., handover, high traffic demand). It employs the PESQ tool, E-model and auditory tests to evaluate the impact of these network conditions on the perceived quality of VoIP calls. It...

    Provided By University of Crete

  • White Papers // Apr 2010

    Analyzing the Impact of Various Wireless Network Conditions on the Perceived Quality of VoIP

    This paper focuses on a comparative statistical analysis of the performance of VoIP calls under various situations, namely, during a handover and under different background traffic conditions at a wireless Access Point (AP). Using empirical-based measurements, it demonstrates that these network conditions exhibit distinct statistical behaviour, in terms of SNR,...

    Provided By University of Crete

  • White Papers // Feb 2010

    ZBD: Using Transparent Compression at the Block Level to Increase Storage Space Efficiency

    In this paper, the authors examine how transparent compression in the I/O path can improve space efficiency for online storage. They extend the block layer with the ability to compress and decompress data as they flow between the file-system and the disk. Achieving transparent compression requires extensive metadata management for...

    Provided By University of Crete

  • White Papers // Dec 2009

    FLASH: Fine-Grained Localization in Wireless Sensor Networks Using Acoustic Sound Transmissions and High Precision Clock Synchronization

    Sensor localization in wireless sensor networks is an important component of many applications. Previous work has demonstrated how localization can be achieved using various methods. In this paper, the authors focus on achieving fine-grained localization that does not require external infrastructure, specialized hardware support, or excessive sensor resources. They use...

    Provided By University of Crete

  • White Papers // Oct 2009

    Histograms and Wavelets on Probabilistic Data

    There is a growing realization that uncertain information is a first-class citizen in modern database management. As such, the authors need techniques to correctly and efficiently process uncertain data in database systems. In particular, data reduction techniques that can produce concise, accurate synopses of large probabilistic relations are crucial. Similar...

    Provided By University of Crete

  • White Papers // Jun 2009

    Object-Relational Database Representations for Text Indexing

    One of the distinctive features of Information Retrieval systems comparing to Database Management systems, is that they offer better compression for posting lists, resulting in better I/O performance and thus faster query evaluation. In this paper, the authors introduce database representations of the index that reduce the size (and thus...

    Provided By University of Crete

  • White Papers // Mar 2009

    Reducing Disk I/O Performance Sensitivity for Large Numbers of Sequential Streams

    Retrieving sequential rich media content from modern commodity disks is a challenging task. As disk capacity increases, there is a need to increase the number of streams that are allocated to each disk. However, when multiple streams are accessing a single disk, throughput is dramatically reduced because of disk head...

    Provided By University of Crete

  • White Papers // Jun 2008

    The -January Effect- Results In The Athens Stock Exchange (ASE)

    This paper examines the so-called 'January effect' in the Athens Stock Exchange (ASE) for the period January 1985 to December 2001. This period is considered as one of the most significant in the economic and financial history of the country. In contrast with other studies, significantly higher returns are documented...

    Provided By University of Crete

  • White Papers // Jun 2008

    The -January Effect- Results In The Athens Stock Exchange (ASE)

    This paper examines the so-called 'January effect' in the Athens Stock Exchange (ASE) for the period January 1985 to December 2001. This period is considered as one of the most significant in the economic and financial history of the country. In contrast with other studies, significantly higher returns are documented...

    Provided By University of Crete

  • White Papers // Jun 2009

    Object-Relational Database Representations for Text Indexing

    One of the distinctive features of Information Retrieval systems comparing to Database Management systems, is that they offer better compression for posting lists, resulting in better I/O performance and thus faster query evaluation. In this paper, the authors introduce database representations of the index that reduce the size (and thus...

    Provided By University of Crete

  • White Papers // Nov 2010

    A Novel Approach for Allocating Network and It Resources Offered by Different Service Providers

    The pace of innovation in computer and networking technology allows many new IT services to emerge rapidly and often benefit from new network services that support faster connectivity and better performance. Centralized resources that are used to provide services to customers are impractical in a dynamic service-based system owned by...

    Provided By University of Crete

  • White Papers // May 2010

    Momentum Or Contrarian Investment Strategies: Evidence From Dutch Institutional Investors

    This paper analyzes investment strategies of three types of institutional investors - pension funds, life insurers and non-life insurers - over the period 1999-2005. The authors use balance sheet and cash flow data, including purchases and sales of equity, fixed income and real estate. They trace asset reallocations back to...

    Provided By University of Crete

  • White Papers // Apr 2010

    A Comparative Analysis of the Perceived Quality of VoIP Under Various Wireless Network Conditions

    This paper performs a comparative analysis of the perceived quality of (unidirectional, non-interactive) VoIP calls under various wireless network conditions (e.g., handover, high traffic demand). It employs the PESQ tool, E-model and auditory tests to evaluate the impact of these network conditions on the perceived quality of VoIP calls. It...

    Provided By University of Crete

  • White Papers // Feb 2011

    A Game-Theoretical Modeling Framework for Spectrum Markets and Cognitive-Radio Devices

    This paper presents a novel game-theoretical framework to model the evolution of spectrum markets that consists of multiple spectrum/network operators that provide wireless access to users. It integrates models about the channel, mobility, user preference, network operators (providers), infrastructure deployment, user distribution, and price-adaptation mechanisms. Providers aim to maximize their...

    Provided By University of Crete

  • White Papers // Oct 2010

    Empirical Evaluation of Signal-Strength Fingerprint Positioning in Wireless LANs

    This paper proposes a novel localization technique based on a multivariate Gaussian modeling of the signal strength measurements collected from several Access Points (APs) at different locations. It considers a discretized grid-like form of the environment and computes a signature at each cell of the grid. At run time the...

    Provided By University of Crete

  • White Papers // Apr 2010

    Analyzing the Impact of Various Wireless Network Conditions on the Perceived Quality of VoIP

    This paper focuses on a comparative statistical analysis of the performance of VoIP calls under various situations, namely, during a handover and under different background traffic conditions at a wireless Access Point (AP). Using empirical-based measurements, it demonstrates that these network conditions exhibit distinct statistical behaviour, in terms of SNR,...

    Provided By University of Crete

  • White Papers // Apr 2011

    A Novel Multi-Layer Framework for Modeling the Evolution of Spectrum Markets and Cognitive-Radio Devices

    This paper presents a novel multi-layer modeling framework for the evolution of spectrum markets of multiple spectrum/network operators that provide wireless access to users. It integrates models of the channel, mobility, user preference, network operators (providers), infrastructure deployment, user distribution, and price-adaptation mechanisms. Providers aim to maximize their own profit,...

    Provided By University of Crete

  • White Papers // Oct 2009

    Histograms and Wavelets on Probabilistic Data

    There is a growing realization that uncertain information is a first-class citizen in modern database management. As such, the authors need techniques to correctly and efficiently process uncertain data in database systems. In particular, data reduction techniques that can produce concise, accurate synopses of large probabilistic relations are crucial. Similar...

    Provided By University of Crete

  • White Papers // Feb 2011

    Indoor Positioning in Wireless LANs Using Compressive Sensing Signal-Strength Fingerprints

    Accurate indoor localization is a significant task for many ubiquitous and pervasive computing applications, with numerous solutions based on IEEE802.11, Bluetooth, ultrasound and infrared technologies being proposed. The inherent sparsity present in the problem of location estimation motivates in a natural fashion the use of the recently introduced theory of...

    Provided By University of Crete

  • White Papers // Aug 2011

    On Multi-Layer Game-Theoretical Modelling of Spectrum Markets and Cognitive Radio Networks

    This paper presents a powerful innovative multi-layer game theoretical modelling framework for the evolution of spectrum markets. It integrates models of the channel, client and network operator (provider) paradigms, wireless infrastructures, types of interaction, and price adaptation. This modelling framework incorporates an extensive set of parameters that allow the modelling...

    Provided By University of Crete

  • White Papers // Jul 2011

    Azor: Using Two-Level Block Selection to Improve SSD-Based I/O Caches

    Flash-based Solid State Drives (SSDs) exhibit potential for solving I/O bottlenecks by offering superior performance over hard disks for several workloads. In this paper, the authors design Azor, an SSD-based I/O cache that operates at the block-level and is transparent to existing applications, such as databases. Their design provides various...

    Provided By University of Crete

  • White Papers // Dec 2009

    FLASH: Fine-Grained Localization in Wireless Sensor Networks Using Acoustic Sound Transmissions and High Precision Clock Synchronization

    Sensor localization in wireless sensor networks is an important component of many applications. Previous work has demonstrated how localization can be achieved using various methods. In this paper, the authors focus on achieving fine-grained localization that does not require external infrastructure, specialized hardware support, or excessive sensor resources. They use...

    Provided By University of Crete

  • White Papers // Mar 2012

    NUMA Implications for Storage I/O Throughput in Modern Servers

    Current server architectures have started to move away from traditional memory buses that do not scale and towards point-to-point interconnects for communication among processors, memories, and I/O devices. As a result, memory modules are not equidistant from all cores leading to significant differences in memory access performance from different cores....

    Provided By University of Crete

  • White Papers // Feb 2010

    ZBD: Using Transparent Compression at the Block Level to Increase Storage Space Efficiency

    In this paper, the authors examine how transparent compression in the I/O path can improve space efficiency for online storage. They extend the block layer with the ability to compress and decompress data as they flow between the file-system and the disk. Achieving transparent compression requires extensive metadata management for...

    Provided By University of Crete

  • White Papers // Mar 2009

    Reducing Disk I/O Performance Sensitivity for Large Numbers of Sequential Streams

    Retrieving sequential rich media content from modern commodity disks is a challenging task. As disk capacity increases, there is a need to increase the number of streams that are allocated to each disk. However, when multiple streams are accessing a single disk, throughput is dramatically reduced because of disk head...

    Provided By University of Crete