Aristotle University of Thessaloniki

Displaying 1-40 of 64 results

  • White Papers // May 2014

    Cloud Elasticity Using Probabilistic Model Checking

    Cloud computing has become the leading paradigm for deploying large-scale infrastructures and running big data applications, due to its capacity of achieving economies of scale. In this paper, the authors focus on one of the most prominent advantages of cloud computing, namely the on-demand resource provisioning, this is commonly referred...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Mar 2014

    Design Space Exploration Tools for the ByoRISC Configurable Processor Family

    In this paper, the ByoRISC (\"Build your own RISC\") configurable Application-Specific Instruction-set Processor (ASIP) family is presented. ByoRISCs, as vendor-independent cores, provide extensive architectural parameters over a baseline processor, which can be customized by Application-Specific Hardware Extensions (ASHEs). Such extensions realize Multi-Input Multi-Output (MIMO) custom instructions with local state and...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jun 2013

    Declarative Expression and Optimization of Data-Intensive Flows

    Data-intensive analytic flows, such as populating a data-warehouse or analyzing a click stream at runtime, are very common in modern business intelligence scenarios. Current state-of-the-art data flow management techniques rely on the users to specify the flow structure without performing automated optimization of that structure. In this paper, the authors...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Feb 2013

    Extracting Components From Open Source the Component Adaptation Environment (COPE) Approach

    Open Source Software (OSS) represents an extremely valuable resource that is reused systematically almost in every software project. The reuse of OSS components however is restricted to ready-made components and developers who want to reuse code that exists in OSS projects but is not offered as a black-box component often...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Dec 2012

    Throughput and Delay Fairness Through an Agile Medium-Transparent MAC Protocol for 60GHz Fiber-Wireless LAN Networks

    The authors demonstrate a novel Medium-Transparent MAC (MT-MAC) protocol with enhanced end-user service delivery fairness properties for use in Gbps capable, 60 GHz Fiber-Wireless (FiWi) LAN networks. Their approach relies on incorporating a Client Weighted Algorithm (CWA) in the optical capacity allocation mechanism employed in the MT-MAC scheme, so as...

    Provided By Aristotle University of Thessaloniki

  • White Papers // May 2012

    XOR-Based Coding for the 3-User Broadcast Erasure Channel With Feedback

    The authors study the case of the three-user broadcast erasure channel, with multiple unicast traffic, where feedback from the users is fed back to the transmitter in the form of ACK/NACK messages. The capacity region of this system has been recently derived and two capacity achieving algorithms, employing intersession linear...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Mar 2012

    A Universal MIMO Approach for 3GPP Wireless Standards

    The authors propose a generalized framework for handling Multiple-Input Multiple-Output (MIMO) schemes defined within the context of the Third Generation Partnership Project (3GPP) physical layer specifications. A detailed review of all the multi-antenna transmission techniques adopted by the 3GPP so far is firstly presented, starting from the Global System for...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jan 2012

    Synthesis of Attack Actions Using Model Checking for the Verification of Security Protocols

    Model checking cryptographic protocols have evolved to a valuable method for discovering counter-intuitive security flaws, which make possible for a hostile agent to subvert the goals of the protocol. Published works and existing security analysis tools are usually based on general intruder models that embody at least some aspects of...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jan 2012

    Social Network Analysis and Its Applications in Wireless Sensor and Vehicular Networks

    Ever since the introduction of wireless sensor networks in the research and development agenda, the corresponding community has been eager to harness the endless possibilities that this new technology has to offer. These micro sensor nodes, whose capabilities have skyrocketed over the last couple of years, have allowed for a...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Dec 2011

    60GHz Radio-Over-Fiber Networks: Optical-Wireless Convergence Through Medium-Transparent MAC Protocols

    The authors present for the first time to their knowledge a saturation throughput performance analysis for a Medium-Transparent MAC protocol for 60GHz Radio-over-fiber network. The theoretically obtained results are found to be in good agreement with simulation-based evaluation outcomes, confirming that the proposed MAC can offer successful arbitration over both...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Dec 2011

    Lifting the Burden of History in Adaptive Ordering of Pipelined Stream Filters

    Ordering of commutative and correlated pipelined stream filters in a dynamic environment is a problem of high interest due to its application in data stream scenarios and its relevance to many query optimization problems. Current state-of-the-art adaptive techniques continuously reoptimize filter orderings utilizing statistics that are collected during the execution...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Dec 2011

    Online Load Balancing in Parallel Database Queries With Model Predictive Control

    In this paper the authors deal with a commonly encountered instantiation of the more generic problem of runtime load balancing. More specifically, they study load balancing in the context of query plans that include partitioned database operators running on remote nodes with time-varying connection speeds and loads. In such query...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Sep 2011

    Model Checking and Code Generation for Transaction Processing Software

    In modern transaction processing software, the ACID properties (Atomicity, Consistency, Isolation, Durability) are often relaxed, in order to ad-dress requirements that arise in computing environments of today. Typical examples are the long-running transactions in mobile computing, in service oriented architectures and B2B collaborative applications. These new transaction models are collectively...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jul 2011

    Optimal Tradeoff Between Energy Consumption and Response Time in Large-Scale MapReduce Clusters

    The increasing growth of the size of the digital databases has given rise to the need for the development of infrastructures, such as large scale data centers and computational clusters, which are capable of storing and processing very large volumes of data. To date, most clusters have been designed for...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jun 2011

    Performance and Cost Evaluation of Gang Scheduling in a Cloud Computing System with Job Migrations and Starvation Handling

    Cloud Computing is an emerging technology in the area of parallel and distributed computing. Clouds consist of a collection of virtualized resources, which include both computational and storage facilities that can be provisioned on demand, depending on the users' needs. Gang Scheduling is an efficient technique for scheduling parallel jobs,...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jun 2011

    Average Outage and Non-Outage Duration of Selective Decode-and-Forward Relaying

    In this paper, assuming transmission with fixed rate and fixed power, the authors derive the average duration of capacity outage and non-outage events of selective decode-and-forward relaying with repetition coding over slow Rayleigh fading channels. Furthermore, they develop high Signal-to-Noise Ratio (SNR) approximations for both durations which provide significant insight...

    Provided By Aristotle University of Thessaloniki

  • White Papers // May 2011

    A Novel HMM-Based Learning Framework for Improving Dynamic Wireless Push Systems Performance

    A new machine learning framework is introduced in this paper, based on Hidden Markov Model (HMM), designed to provide scheduling in dynamic wireless push systems. In realistic wireless systems, the clients' intentions change dynamically, hence a cognitive scheduling scheme is needed to estimate the desirability of the connected clients. The...

    Provided By Aristotle University of Thessaloniki

  • White Papers // May 2011

    Probability of Early Detection of Ultra-Wideband Positioning Sensor Networks

    Ultra-WideBand (UWB) sensor networks can be efficiently applied to collect data through sensors deployed for preserving environment and rescuing lives. The high-precision positioning capabilities of UWB technology, based on its operation of ultra-short data bearing pulses, can be a reliable solution for such applications. Most of the UWB positioning techniques...

    Provided By Aristotle University of Thessaloniki

  • White Papers // May 2011

    Test-Driving Static Analysis Tools in Search of C Code Vulnerabilities

    Recently, a number of tools for automated code scanning came in the limelight. Due to the significant costs associated with incorporating such a tool in the software life-cycle, it is important to know what defects are detected and how accurate and efficient the analysis is. The authors focus specifically on...

    Provided By Aristotle University of Thessaloniki

  • White Papers // May 2011

    Minimization of the Response Time in Parallel Database Queries: An Adaptive Cost-Aware MPC-Based Solution

    Load balancing in partitioned database queries is a significant issue in efficient data management of large datasets. When such queries are processed in a volatile and unpredictable setting, as is the typical case today, continuous workload re-assignments need to take place to ensure that the workload allocated to each participating...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Apr 2011

    Quantitative Model Checking of an RSA-Based Email Protocol on Mobile Devices

    The current proliferation of mobile devices has resulted in a large diversity of hardware specifications, each designed for different services and applications (e.g., cell phones, smart phones, PDAs). At the same time, e-mail message delivery has become a vital part of everyday communications. This paper provides a cost-aware study of...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Apr 2011

    Using Learning Automata for Adaptively Adjusting the Downlink-to-Uplink Ratio in IEEE 802.16e Wireless Networks

    IEEE 802.16e allows for flexibly defining the relation of the downlink and uplink sub-frames' width from 3:1 to 1:1, respectively. However, the determination of the most suitable ratio is left open to the network designers and the research community. Existing scheduling and mapping schemes are inflexibly designed. In this paper,...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Apr 2011

    A Survey on Radio-and-Fiber FiWi Network Architectures

    The ultimate goal of Fiber-Wireless (FiWi) networks is the convergence of various optical and wireless technologies under a single infrastructure in order to take advantage of their complementary features and therefore provide a network capable of supporting bandwidth-hungry emerging applications in a seamless way for both fixed and mobile clients....

    Provided By Aristotle University of Thessaloniki

  • White Papers // Mar 2011

    Continuous Monitoring of Distance-Based Outliers Over Data Streams

    Anomaly detection is considered an important data mining task, aiming at the discovery of elements (also known as outliers) that show significant diversion from the expected case. More specifically, given a set of objects the problem is to return the suspicious objects that deviate significantly from the typical behavior. As...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Mar 2011

    Biometrics Applications: Technology, Ethics, and Health Hazards

    Biometrics is the science and technology of measuring and analyzing biological data for authentication purposes. Among the features measured are DNA, face, fingerprints, eye retinas and irises, hand geometry, handwriting, veins, and voice. Biometrics has fast emerged as a promising technology for authentication and has already found a place in...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jan 2011

    Integrating Web 2.0 Data Into Linked Open Data Cloud Via Clustering

    In this paper, the authors claim that useful information mined from social tagging systems can be published and shared as Linked Data, in order to be further exploited. The proposed approach aims: to be applied on any social tagging platform, and utilize information that concerns the collective activity of users,...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jan 2011

    On the Service Differentiation Capabilities of EY-NPMA and 802.11 DCF

    Most existing WLAN access mechanisms cannot provide QoS assurances. Even those that are QoS aware can only provide relative service differentiation. Based on EY-NPMA, the HIPERLAN Medium Access Control algorithm, the authors propose a dynamic priority medium access scheme to provide time-bounded services. By approximating an ideal Earliest Deadline First...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Dec 2010

    Quantitative Analysis of a Certified E-mail Protocol in Mobile Environments: A Probabilistic Model Checking Approach

    Formal analysis techniques, such as probabilistic model checking, offer an effective mechanism for model-based performance and verification studies of communication systems' behavior that can be abstractly described by a set of rules i.e., a protocol. This paper presents an integrated approach for the quantitative analysis of the Certified E-mail Message...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Nov 2010

    Component Certification as a Prerequisite for Widespread OSS Reuse

    Open source software is the product of a community process that in a single project may employ different development techniques and volunteers with diverse skills, interests and hardware. Reuse of OSS software in systems that will have to guarantee certain product properties is still complicated. The main reason is the...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Oct 2010

    Multiuser Broadcast Erasure Channel With Feedback - Capacity and Algorithms

    Broadcast channels have been extensively studied by the information theory community since their introduction in. Although their capacity remains unknown in the general case, special cases have been solved, including the important category of "Degraded" channels. Another class of channels that has received significant attention is erasure channels, where either...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jun 2010

    A Semi-Automated Process for Open Source Code Reuse

    It is clear that Free Libre/Open Source Software (FLOSS) has been demonstrating increasing importance continually for some years now. As a result, millions of lines of code are becoming available online. In many cases, this code, is carefully designed, implemented, tested and therefore represents a very good option for reusability....

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jun 2010

    Relaying Utilization Metrics of Diamond Cooperative Diversity Systems

    The authors introduce relaying utilization statistical metrics to quantify the contribution of a relay node to the overall relaying process in cooperative diversity systems. Motivated by the second order statistics of the relay fading channel, the following metrics are defined: the average relaying selection rate, the average relaying utilization time,...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jun 2010

    Topology Control Algorithms for Wireless Sensor Networks: A Critical Survey

    In a densely deployed wireless sensor network, a single node has many neighboring nodes with which direct communication would be possible when using sufficiently large transmission power. This is, however, not beneficial; high transmission power requires lots of energy, many neighbors are a burden for a MAC protocol, and routing...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jun 2010

    Estimation of the Maximum Domination Value in Multi-Dimensional Data Sets

    The last years there is an increasing interest for query processing techniques that take into consideration the dominance relationship between objects to select the most promising ones, based on user preferences. Skyline and top-k dominating queries are examples of such techniques. A skyline query computes the objects that are not...

    Provided By Aristotle University of Thessaloniki

  • White Papers // May 2010

    A Virtual Reality Laboratory for Distance Education in Chemistry

    Simulations play a major role in education not only because they provide realistic models with which students can interact to acquire real world experiences, but also because they constitute safe environments in which students can repeat processes without any risk in order to perceive easier concepts and theories. Virtual reality...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Feb 2010

    A Comparative Study of Two Alternative Wildfire Models, With Applications to WSN Topology Control

    In this paper two wildfire modelling methods are compared in terms of performance, scaling up flexibility and speed of model execution. The InteSys model is based on Cellular Automata (CA). Simple rules are applied to each cell, interacting with neighbouring cells. The cell based structure reflects the object oriented nature...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Feb 2010

    Software Tools for Wildfire Monitoring

    Phenomena in ecosystems such as forest fires, oil spills, tornados, etc., are complex processes both in time and space. Understanding their dynamics in order to predict their future states is a challenging procedure involving the propagation of several events concerning, e.g., the transfer of energy or material. A common solution...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Feb 2010

    A New Approach to the Design of MAC Protocols for WDM-EPONs

    Medium Access Control (MAC) protocols for WDM Ethernet Passive Optical Networks (WDM-EPONs) suffer from low performance when the users' round trip times are different. In this paper a new MAC protocol for WDM-EPONs is introduced which overcomes the above limitation by filling the gaps in the scheduling program. Moreover, the...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jan 2010

    On Efficient UHF RFID Coverage Inside a Room

    This paper investigates the problem of improving the identification performance of a UHF RFID system inside a room. The authors assume static reader, passive tags and availability of commodity antennas. In sharp contrast to prior art that has focused on free space or simple two-ray model, a ray-tracing propagation model...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Dec 2009

    Performance Evaluation of LDPC Codes on PLC Channel Compared to Other Coding Schemes

    In this paper, the authors study how power line communications are affected by different coding techniques. They investigate the case of LDPC coding scheme and its application to the PLC channel. The modulation method applied is BPSK while the transmission technique used is OFDM. They study regular LDPC codes, which...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Apr 2009

    High Performance, Low Complexity Cooperative Caching for Wireless Sensor Networks

    During the last decade, Wireless Sensor Networks (WSNs) have emerged and matured at such point that currently support several applications like environment control, intelligent buildings, target tracking in battlefields, and many more. The vast majority of these applications require an optimization to the communication among the sensors so as to...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jan 2012

    Synthesis of Attack Actions Using Model Checking for the Verification of Security Protocols

    Model checking cryptographic protocols have evolved to a valuable method for discovering counter-intuitive security flaws, which make possible for a hostile agent to subvert the goals of the protocol. Published works and existing security analysis tools are usually based on general intruder models that embody at least some aspects of...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Mar 2011

    Continuous Monitoring of Distance-Based Outliers Over Data Streams

    Anomaly detection is considered an important data mining task, aiming at the discovery of elements (also known as outliers) that show significant diversion from the expected case. More specifically, given a set of objects the problem is to return the suspicious objects that deviate significantly from the typical behavior. As...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jun 2009

    Synthetic Metrics for Evaluating Runtime Quality of Software Architectures With Complex Tradeoffs

    Run-time quality of software, such as availability and throughput, depends on architectural factors and execution environment characteristics (e.g., CPU speed, network latency). Although the specific properties of the underlying execution environment are unknown at design time, the software architecture can be used to assess the inherent impact of the adopted...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Nov 2008

    A Probabilistic Attacker Model for Quantitative Verification of DoS Security Threats

    This paper introduces probabilistic model checking as a viable tool-assisted approach for systematically quantifying DoS security threats. The proposed analysis is based on a probabilistic attacker model implementing simultaneous N zombie participants, which subvert secure authentication features in communication protocols and electronic commerce systems. DoS threats are expressed as probabilistic...

    Provided By Aristotle University of Thessaloniki

  • White Papers // May 2011

    Test-Driving Static Analysis Tools in Search of C Code Vulnerabilities

    Recently, a number of tools for automated code scanning came in the limelight. Due to the significant costs associated with incorporating such a tool in the software life-cycle, it is important to know what defects are detected and how accurate and efficient the analysis is. The authors focus specifically on...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Sep 2011

    Model Checking and Code Generation for Transaction Processing Software

    In modern transaction processing software, the ACID properties (Atomicity, Consistency, Isolation, Durability) are often relaxed, in order to ad-dress requirements that arise in computing environments of today. Typical examples are the long-running transactions in mobile computing, in service oriented architectures and B2B collaborative applications. These new transaction models are collectively...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jun 2009

    Database Oriented Grid Middlewares

    Efficient management of massive data sets is a key aspect in typical grid and e-science applications. To this end, the benefits of employing database technologies in such applications has been identified since the early days of grid computing, which aims at enabling coordinated resource sharing, knowledge generation and problem solving...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Mar 2011

    Biometrics Applications: Technology, Ethics, and Health Hazards

    Biometrics is the science and technology of measuring and analyzing biological data for authentication purposes. Among the features measured are DNA, face, fingerprints, eye retinas and irises, hand geometry, handwriting, veins, and voice. Biometrics has fast emerged as a promising technology for authentication and has already found a place in...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Feb 2010

    A Comparative Study of Two Alternative Wildfire Models, With Applications to WSN Topology Control

    In this paper two wildfire modelling methods are compared in terms of performance, scaling up flexibility and speed of model execution. The InteSys model is based on Cellular Automata (CA). Simple rules are applied to each cell, interacting with neighbouring cells. The cell based structure reflects the object oriented nature...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Feb 2010

    Software Tools for Wildfire Monitoring

    Phenomena in ecosystems such as forest fires, oil spills, tornados, etc., are complex processes both in time and space. Understanding their dynamics in order to predict their future states is a challenging procedure involving the propagation of several events concerning, e.g., the transfer of energy or material. A common solution...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Oct 2009

    Quasi-Cyclic Low-Density Parity-Check (QC-LDPC) Codes for Deep Space and High Data Rate Applications

    In this paper, the authors investigate and compare the performance of a selected class of Low-Density Parity-Check (LDPC) codes, i.e., Quasi-Cyclic (QC) LDPC codes, against the currently used turbo codes for deep space and high data rate applications. This is useful in future updates of the channel code option used...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Dec 2009

    Performance Evaluation of LDPC Codes on PLC Channel Compared to Other Coding Schemes

    In this paper, the authors study how power line communications are affected by different coding techniques. They investigate the case of LDPC coding scheme and its application to the PLC channel. The modulation method applied is BPSK while the transmission technique used is OFDM. They study regular LDPC codes, which...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Nov 2010

    Component Certification as a Prerequisite for Widespread OSS Reuse

    Open source software is the product of a community process that in a single project may employ different development techniques and volunteers with diverse skills, interests and hardware. Reuse of OSS software in systems that will have to guarantee certain product properties is still complicated. The main reason is the...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Dec 2011

    60GHz Radio-Over-Fiber Networks: Optical-Wireless Convergence Through Medium-Transparent MAC Protocols

    The authors present for the first time to their knowledge a saturation throughput performance analysis for a Medium-Transparent MAC protocol for 60GHz Radio-over-fiber network. The theoretically obtained results are found to be in good agreement with simulation-based evaluation outcomes, confirming that the proposed MAC can offer successful arbitration over both...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Mar 2012

    A Universal MIMO Approach for 3GPP Wireless Standards

    The authors propose a generalized framework for handling Multiple-Input Multiple-Output (MIMO) schemes defined within the context of the Third Generation Partnership Project (3GPP) physical layer specifications. A detailed review of all the multi-antenna transmission techniques adopted by the 3GPP so far is firstly presented, starting from the Global System for...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Dec 2012

    Throughput and Delay Fairness Through an Agile Medium-Transparent MAC Protocol for 60GHz Fiber-Wireless LAN Networks

    The authors demonstrate a novel Medium-Transparent MAC (MT-MAC) protocol with enhanced end-user service delivery fairness properties for use in Gbps capable, 60 GHz Fiber-Wireless (FiWi) LAN networks. Their approach relies on incorporating a Client Weighted Algorithm (CWA) in the optical capacity allocation mechanism employed in the MT-MAC scheme, so as...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jun 2009

    Honoring SLAs on Cloud Computing Services: A Control Perspective

    This work contains a short survey of recent results in the literature with a view to opening up new research directions for the problem of honoring SLAs on cloud computing services. This is a new problem that has attracted significant interest recently, due to the urgent need for providers to...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Feb 2009

    Bandwidth Clustering for Reliable and Prioritized Network Routing using Split Agent-Based Method

    Recent researches have highlighted the importance of developing a network with distributed problem solving abilities thus enhancing reliability with equal share of network resources. While several centralized schemes have been proposed for efficient path marking and capacity reservation, the decentralized approach is one of the motivating reasons for employing adaptive...

    Provided By Aristotle University of Thessaloniki

  • White Papers // May 2010

    A Virtual Reality Laboratory for Distance Education in Chemistry

    Simulations play a major role in education not only because they provide realistic models with which students can interact to acquire real world experiences, but also because they constitute safe environments in which students can repeat processes without any risk in order to perceive easier concepts and theories. Virtual reality...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jun 2009

    Attacking an OT-Based Blind Signature Scheme

    In this paper, the authors describe an attack against one of the Oblivious-Transfer-based blind signatures scheme, proposed in. An attacker with a primitive capability of producing specific-range random numbers, while exhibiting a partial MITM behavior, is able to corrupt the communication between the protocol participants. The attack is quite efficient...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Aug 2009

    Level Crossing Rate and Average Fade Duration of the Multihop Rayleigh Fading Channel

    Multihop communications, a viable option for providing broader and more efficient coverage, can be categorized as either non-regenerative (Amplify-and-Forward, AF) or regenerative Decode-and-Forward, DF) depending on the relay functionality. In DF systems, each relay decodes its received signal and then re-transmits this decoded version. In AF systems, the relays just...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Aug 2009

    State Space Reduction With Message Inspection in Security Protocol Model Checking

    Model checking is a widespread automatic formal analysis that has been successful in discovering flaws in security protocols. However existing possibilities for state space explosion still hinder analyses of complex protocols and protocol configurations. Message Inspection, is a technique that delimits the branching of the state space due to the...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Apr 2011

    A Survey on Radio-and-Fiber FiWi Network Architectures

    The ultimate goal of Fiber-Wireless (FiWi) networks is the convergence of various optical and wireless technologies under a single infrastructure in order to take advantage of their complementary features and therefore provide a network capable of supporting bandwidth-hungry emerging applications in a seamless way for both fixed and mobile clients....

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jul 2009

    A Game Theoretical Approach to Clustering of Ad-Hoc and Sensor Networks

    Game theory has been used for decades in fields of science such as economics and biology, but recently it was used to model routing and packet forwarding in wireless ad-hoc and sensor networks. However, the clustering problem, related to self-organization of nodes into large groups, has not been studied under...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Oct 2009

    An Efficient Approximation to the Correlated Nakagami-m Sums and Its Application in Equal Gain Diversity Receivers

    There are several cases in wireless communications theory where the statistics of the sum of independent or correlated Nakagami-m Random Variables (RVs) is necessary to be known. However, a closed-form solution to the distribution of this sum does not exist when the number of constituent RVs exceeds two, even for...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Dec 2009

    Iterative Near Maximum-Likelihood Sequence Detection for MIMO Optical Wireless Systems

    A major performance-limiting factor in terrestrial Optical Wireless (OW) systems is turbulence-induced fading. Exploiting the additional degrees of freedom in the spatial dimension, multiple laser transmitters combined with multiple receive apertures provide an effective solution for fading mitigation. Although MIMO (Multiple-Input Multiple-Output) OW systems have been extensively studied in recent...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jun 2010

    Topology Control Algorithms for Wireless Sensor Networks: A Critical Survey

    In a densely deployed wireless sensor network, a single node has many neighboring nodes with which direct communication would be possible when using sufficiently large transmission power. This is, however, not beneficial; high transmission power requires lots of energy, many neighbors are a burden for a MAC protocol, and routing...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jun 2011

    Average Outage and Non-Outage Duration of Selective Decode-and-Forward Relaying

    In this paper, assuming transmission with fixed rate and fixed power, the authors derive the average duration of capacity outage and non-outage events of selective decode-and-forward relaying with repetition coding over slow Rayleigh fading channels. Furthermore, they develop high Signal-to-Noise Ratio (SNR) approximations for both durations which provide significant insight...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jun 2010

    Relaying Utilization Metrics of Diamond Cooperative Diversity Systems

    The authors introduce relaying utilization statistical metrics to quantify the contribution of a relay node to the overall relaying process in cooperative diversity systems. Motivated by the second order statistics of the relay fading channel, the following metrics are defined: the average relaying selection rate, the average relaying utilization time,...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jan 2010

    On Efficient UHF RFID Coverage Inside a Room

    This paper investigates the problem of improving the identification performance of a UHF RFID system inside a room. The authors assume static reader, passive tags and availability of commodity antennas. In sharp contrast to prior art that has focused on free space or simple two-ray model, a ray-tracing propagation model...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Apr 2011

    Using Learning Automata for Adaptively Adjusting the Downlink-to-Uplink Ratio in IEEE 802.16e Wireless Networks

    IEEE 802.16e allows for flexibly defining the relation of the downlink and uplink sub-frames' width from 3:1 to 1:1, respectively. However, the determination of the most suitable ratio is left open to the network designers and the research community. Existing scheduling and mapping schemes are inflexibly designed. In this paper,...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Feb 2010

    A New Approach to the Design of MAC Protocols for WDM-EPONs

    Medium Access Control (MAC) protocols for WDM Ethernet Passive Optical Networks (WDM-EPONs) suffer from low performance when the users' round trip times are different. In this paper a new MAC protocol for WDM-EPONs is introduced which overcomes the above limitation by filling the gaps in the scheduling program. Moreover, the...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Oct 2009

    Speeding Up the Adaption Process in Adaptive Wireless Push Systems by Applying Spline Interpolation Technique

    In wireless push systems, the server schedules the broadcasts of its information items aiming at satisfying the clients' preferences efficiently. Latest research efforts have proposed adaptive push systems, enhanced with a learning automaton, in which the server has the ability to update its estimated item demand probability vector. This vector...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jun 2009

    Techniques for Improved Scheduling in Optical Burst Switched Networks

    Optical Burst Switching (OBS) has emerged as a viable switching alternative in backbone optical networks since it can support high data rates with an intermediate granularity compared to wavelength routing and optical packet switching. At the edges of an OBS cloud, packets are assembled to form bursts which enter the...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Oct 2008

    A Prediction-Based Scheme for Wireless Push Systems, Using a Statistical Hidden Markov Model

    In this paper a Hidden Markov Model (HMM) is applied at the broadcast server in order to provide accurate decisions for a wireless push system environment with unknown client demands. Clients are organized into groups and may request a set of items. The server side sends an item per time...

    Provided By Aristotle University of Thessaloniki

  • White Papers // May 2011

    A Novel HMM-Based Learning Framework for Improving Dynamic Wireless Push Systems Performance

    A new machine learning framework is introduced in this paper, based on Hidden Markov Model (HMM), designed to provide scheduling in dynamic wireless push systems. In realistic wireless systems, the clients' intentions change dynamically, hence a cognitive scheduling scheme is needed to estimate the desirability of the connected clients. The...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Jan 2011

    On the Service Differentiation Capabilities of EY-NPMA and 802.11 DCF

    Most existing WLAN access mechanisms cannot provide QoS assurances. Even those that are QoS aware can only provide relative service differentiation. Based on EY-NPMA, the HIPERLAN Medium Access Control algorithm, the authors propose a dynamic priority medium access scheme to provide time-bounded services. By approximating an ideal Earliest Deadline First...

    Provided By Aristotle University of Thessaloniki

  • White Papers // Sep 2008

    Graphical Representation as a Factor of 3D Software User Satisfaction: A Metric Based Approach

    During the last few years, an increase in the development and research activity on 3D applications, mainly motivated by the rigorous growth of the game industry, is observed. This paper deals with assessing user satisfaction, i.e. a critical aspect of 3D software quality, by measuring technical characteristics of virtual worlds....

    Provided By Aristotle University of Thessaloniki

  • White Papers // May 2011

    Probability of Early Detection of Ultra-Wideband Positioning Sensor Networks

    Ultra-WideBand (UWB) sensor networks can be efficiently applied to collect data through sensors deployed for preserving environment and rescuing lives. The high-precision positioning capabilities of UWB technology, based on its operation of ultra-short data bearing pulses, can be a reliable solution for such applications. Most of the UWB positioning techniques...

    Provided By Aristotle University of Thessaloniki