University of Bristol

Displaying 1-40 of 98 results

  • White Papers // Apr 2014

    Evaluating the Error Resilience of Parallel Programs

    As a consequence of increasing hardware fault rates, HPC systems face significant challenges in terms of reliability. Evaluating the error resilience of HPC applications is an essential step for building efficient fault-tolerant mechanisms for these applications. In this paper, the authors propose a methodology to characterize the resilience of OpenMP...

    Provided By University of Bristol

  • White Papers // Jan 2014

    A Scalable Multi-Path Microarchitecture for Efficient GPU Control Flow

    Graphics Processing Units (GPUs) are increasingly used for non-graphics computing. However, applications with divergent control flow incur performance degradation on current GPUs. These GPUs implement the SIMT execution model by serializing the execution of different control flow paths encountered by a warp. This serialization can mask thread level parallelism among...

    Provided By University of Bristol

  • White Papers // Jan 2014

    GPU-Qin: A Methodology for Evaluating the Error Resilience of GPGPU Applications

    While Graphics Processing Units (GPUs) have gained wide adoption as accelerators for General-Purpose applications (GPGPU), the end-to-end reliability implications of their use have not been quantified. Fault injection is a widely used method for evaluating the reliability of applications. However, building a fault injector for GPGPU applications is challenging due...

    Provided By University of Bristol

  • White Papers // Dec 2013

    Efficient Large-Scale Graph Processing on Hybrid CPU and GPU Systems

    The increasing scale and wealth of inter-connected data, such as those accrued by social network applications, demand the design of new techniques and platforms to efficiently derive actionable knowledge from large-scale graphs. However, large real-world graphs are famously difficult to process efficiently. Not only they have a large memory footprint,...

    Provided By University of Bristol

  • White Papers // Jul 2013

    Evaporating Firewalls

    In this paper, the authors begin by reviewing an argument (independent from 1304.6483) suggesting that large AdS black holes dual to typical high-energy pure states of a single holographic CFT must have some structure at the horizon (i.e. a fuzzball/firewall). By weakly coupling the CFT to an auxiliary system, such...

    Provided By University of Bristol

  • White Papers // Jun 2013

    Predicting Intermediate Storage Performance for Workflow Applications

    System provisioning, resource allocation, and system configuration decisions for work flow I/O-intensive applications are complex even for expert users. One factor making the problem space more complex is that users face decisions at multiple levels: allocating resources to individual sub-systems (e.g., the application layer, the storage layer) and configuring each...

    Provided By University of Bristol

  • White Papers // Jun 2013

    Cross-Tier Application & Data Partitioning of Web Applications for Hybrid Cloud Deployment

    Hybrid cloud deployment offers flexibility in trade-o s between the cost-savings/scalability of the public cloud and control over data resources provided at a private premise. However, this flexibility comes at the expense of complexity in distributing a system over these two locations. For multi-tier web applications, this challenge manifests itself...

    Provided By University of Bristol

  • White Papers // Apr 2013

    Safe Overclocking of Tightly Coupled CGRAs and Processor Arrays Using Razor

    Overclocking a CPU is a common practice among home-built PC enthusiasts where the CPU is operated at a higher frequency than its speed rating. This practice is unsafe because timing errors cannot be detected by modern CPUs and they can be practically undetectable by the end user. Using a timing...

    Provided By University of Bristol

  • White Papers // Mar 2013

    Relay Selection for Simultaneous Information Transmission and Wireless Energy Transfer: A Tradeoff Perspective

    In certain applications, relay terminals can be employed to simultaneously deliver information and energy to a designated receiver and a Radio Frequency (RF) energy harvester, respectively. In such scenarios, the relay that is preferable for information transmission does not necessarily coincide with the relay with the strongest channel to the...

    Provided By University of Bristol

  • White Papers // Jan 2013

    On Graphs, GPUs, and Blind Dating a Workload to Processor Matchmaking Quest

    Graph processing has gained renewed attention. The increasing large scale and wealth of connected data, such as those accrued by social network applications, demand the design of new techniques and platforms to efficiently derive actionable information from large scale graphs. Hybrid systems that host processing units optimized for both fast...

    Provided By University of Bristol

  • White Papers // Jan 2013

    Cache Coherence for GPU Architectures

    While scalable coherence has been extensively studied in the context of general purpose Chip Multi-Processors (CMPs), GPU architectures present a new set of challenges. Introducing conventional directory protocols adds unnecessary coherence traffic overhead to existing GPU applications. Moreover, these protocols increase the verification complexity of the GPU memory system. Recent...

    Provided By University of Bristol

  • White Papers // Dec 2012

    Password Authenticated Cluster-Based Group-Key Agreement for Smart Grid Communication

    Several multi-party systems supporting group- and cloud-based applications have been proposed in the context of Smart Grid. An important requirement of these systems is that the devices/parties need to communicate with each other as members of a group. In this paper, the authors present an efficient Group-Key (GK) management scheme...

    Provided By University of Bristol

  • White Papers // Dec 2012

    On Extracting Unit Tests From Interactive Programming Sessions

    Software engineering methodologies propose that developers should capture their efforts in ensuring that programs run correctly in repeatable and automated artifacts, such as unit tests. However, when looking at developer activities on a spectrum from exploratory testing to scripted testing the authors find that many engineering activities include bursts of...

    Provided By University of Bristol

  • White Papers // Nov 2012

    Towards Building Error Resilient GPGPU Applications

    GPUs (Graphics Processing Units) have gained wide adoption as accelerators for general purpose computing. They are widely used in error-sensitive applications, i.e. General Purpose GPU (GPGPU) applications However, the reliability implications of using GPUs are unclear. This paper presents a fault injection study to investigate the end-to-end reliability characteristics of...

    Provided By University of Bristol

  • White Papers // Nov 2012

    Full-Duplex Transmissions in Fiber-Connected Distributed Relay Antenna Systems

    Distributed Antenna Systems (DAS) have been studied extensively to improve spectral efficiency and extend coverage. Different from the previous studies that focused mostly on the enhancement of downlink or uplink performance through cooperation of distributed antennas, this paper proposes and investigates a novel communication configuration in which a fiber-connected DAS...

    Provided By University of Bristol

  • White Papers // Nov 2012

    Privacy Preserving Web Query Log Publishing: A Survey on Anonymization Techniques

    Web search queries are generally stored by search engines for the purpose of improving result ranking, query refinement, user modeling, language-based applications, and sharing data for academic research or commercial needs. Releasing Web query logs which contain valuable information for research or marketing, can breach the privacy of search engine...

    Provided By University of Bristol

  • White Papers // Nov 2012

    Cache-Conscious Wavefront Scheduling

    In this paper, the authors study the effects of hardware thread scheduling on cache management in GPUs. They propose Cache-Conscious Wave-front Scheduling (CCWS), an adaptive hardware mechanism that makes use of a novel intra-wavefront locality detector to capture locality that is lost by other schedulers due to excessive contention for...

    Provided By University of Bristol

  • White Papers // Oct 2012

    On Graphs, GPUs, and Blind Dating: A Workload to Processor Matchmaking Quest

    Graph processing has gained renewed attention. The increasing large scale and wealth of connected data, such as those accrued by social network applications, demand the design of new techniques and platforms to efficiently derive actionable information from large scale graphs. Hybrid systems that host processing units optimized for both fast...

    Provided By University of Bristol

  • White Papers // Sep 2012

    MANTICORE: a Framework for Partitioning Software Services for Hybrid Cloud

    Hybrid cloud deployment can be an attractive option for companies wanting to deploy software services on scalable public clouds, while still assuming local control over sensitive data resources. A hybrid deployment, despite providing better control, is difficult to design since code must be partitioned and distributed efficiently between public and...

    Provided By University of Bristol

  • White Papers // Sep 2012

    Boosting FMAX of Processor Pipelines Using Intentional Memory Clock Skew

    FPGAs are increasingly being used to implement many new applications, including pipelined processor designs. Designers often employ memories to communicate and pass data between these pipeline stages. However, one-cycle communication between sender and receiver is often required. To implement this read-immediately-after-write functionality, bypass registers are needed by most FPGA memory...

    Provided By University of Bristol

  • White Papers // Jul 2012

    Transmit Antenna Selection for Security Enhancement in MIMO Wiretap Channels

    Information security has become a pivotal concern in wireless communications, due to the fact that the broadcast nature of the wireless medium allows eavesdroppers to intercept transmissions in the network. Traditionally, cryptographic protocols have been designed and implemented to provide security in the upper layers (e.g., the network layer), based...

    Provided By University of Bristol

  • White Papers // May 2012

    Avoiding the Disk Bottleneck in Deduplicated VM Transfer

    Data de-duplication is a commonly adopted optimization in the cloud infrastructure for optimizing the storage and the transfer of Virtual Machines (VM). Data de-duplication efficiently identifies and eliminates similarity across VM image files leading to a reduction in the amount of data that needs to be stored and/or transferred. This...

    Provided By University of Bristol

  • White Papers // May 2012

    An Optimal Energy Allocation Algorithm for Energy Harvesting Wireless Sensor Networks

    With the use of energy harvesting technologies, the lifetime of a Wireless Sensor Network (WSN) can be prolonged significantly. Unlike a traditional WSN powered by non-rechargeable batteries, the energy management policy of an energy harvesting WSN needs to take into account the energy replenishment process. In this paper, the authors...

    Provided By University of Bristol

  • White Papers // May 2012

    Dual-hop Amplify-and-Forward Transmission With Imperfect Channel Estimates at the Relay

    With reference to the typical three-node Amplify-and-Forward (AF) relaying setup, where a single relay assists the communication between a source terminal and a destination terminal, the authors investigate the effect of outdated Channel State Information (CSI) at the relay on the overall performance. In particular, they consider CSI-assisted (i.e., variable-gain)...

    Provided By University of Bristol

  • White Papers // May 2012

    Optimal Power Allocation in a Multi-Hop Decode-and-Forward Communication System

    This paper analyzes optimal power allocation schemes for a multi-hop decode-and-forward relay system in a Rayleigh fading environment at high signal-to-noise ratio. Analysis is done for two kinds of modulation schemes: M-ary phase-shift keying with coherent detection and orthogonal ??'?-ary frequency-shift keying with non-coherent detection. An optimal power allocation scheme...

    Provided By University of Bristol

  • White Papers // May 2012

    Efficient Authentication and Key Management for the Home Area Network

    Due to the extensive use of wireless technologies, security is one of the most important and challenging issues in smart grid networks. To secure data communications, strong authentication and key management mechanisms are needed. In this paper, the authors propose a mutual authentication scheme and key management protocol tailored for...

    Provided By University of Bristol

  • White Papers // May 2012

    Robust Power Allocation Designs for Cognitive Radio Networks With Cooperative Relays

    In this paper, the authors develop robust power allocation schemes for Cognitive Radio Networks (CRNs) that can operate in multiple bands with cooperative relays considering uncertainty among the channels of Secondary User (SU) network and among the channels of SU transmitters to Primary User (PU) receivers. Their objective is to...

    Provided By University of Bristol

  • White Papers // May 2012

    Power Line Network Topology Inference Using Frequency Domain Reflectometry

    Frequency Domain Reflectometry (FDR) is a technique that was proposed for fault detection in Digital Subscriber Line (DSL) cables. In this paper, the authors describe how FDR can be used to determine the topology of power line networks. To this end, they first infer distance information from the multiple signal...

    Provided By University of Bristol

  • White Papers // May 2012

    GPUs as Storage System Accelerators

    Massively multicore processors, such as Graphics Processing Units (GPUs), provide, at a comparable price, a one order of magnitude higher peak performance than traditional CPUs. This drop in the cost of computation, as any order-of-magnitude drop in the cost per unit of performance for a class of system components, triggers...

    Provided By University of Bristol

  • White Papers // May 2012

    LOS and NLOS Classification for Underwater Acoustic Localization

    The low sound speed in water makes Propagation Delay (PD) based range estimation attractive for UnderWater Acoustic Localization (UWAL). However, due to the long channel impulse response and the existence of reflecting objects, PD-based UWAL suffers from significant degradation when PD measurements of Non-Line-Of-Sight (NLOS) communication links are falsely identified...

    Provided By University of Bristol

  • White Papers // Apr 2012

    Model-Based Intrusion Detection for Home Area Networks in Smart Grids

    In this paper, the authors present a model-based Intrusion Detection System (IDS) for Home Area Networks (HANs) within the smart grid. Considering that ZigBee is the dominant technology in future HAN, the proposed IDS is designed to target ZigBee standard. Their focus is on the physical and Medium Access Control...

    Provided By University of Bristol

  • White Papers // Mar 2012

    Key Challenges in Defending Against Malicious Socialbots

    The ease with which the authors adopt online personas and relationships has created a soft spot that cyber criminals are willing to exploit. Advances in artificial intelligence make it feasible to design bots that sense, think and act cooperatively in social settings just like human beings. In the wrong hands,...

    Provided By University of Bristol

  • White Papers // Mar 2012

    Distance Based Heuristic for Power and Rate Allocation of Video Sensor Networks

    Video Sensor Networks (VSNs) offer an alternative to several existing surveillance technologies. However, unlike in conventional sensor network, video processing and transmission requires large amount of resources both in signal processing, i.e., encoding, and transmission of the encoded data. For such networks, an optimal encoding power and rate allocation method...

    Provided By University of Bristol

  • White Papers // Mar 2012

    Distributed Dynamic Scheduling for Body Area Networks

    Body Area Networks (BANs), targeting everywhere anytime health monitoring, operate in license-exempt frequency bands. They require a cross layer design that jointly considers the requirements of access delay to the medium and Packet Delivery Ratio (PDR). In this paper, the authors experimentally evaluate the PDR of a BAN under static...

    Provided By University of Bristol

  • White Papers // Mar 2012

    A Workflow-Aware Storage System: An Opportunity Study

    This paper evaluates the potential gains a workflow-aware storage system can bring. Two observations make one to believe such storage system is crucial to efficiently support workflow-based applications: First, workflows generate irregular and application-dependent data access patterns. These patterns render existing storage systems unable to harness all optimization opportunities as...

    Provided By University of Bristol

  • White Papers // Feb 2012

    Characterizing and Evaluating a Key-Value Store Application on Heterogeneous CPU-GPU Systems

    With the introduction of programmable functional units, Graphics Processing Units (GPUs) have expanded to general-purpose, High-Performance Computing (HPC) applications. These types of applications are known to efficiently utilize the underlying GPU hardware to maximize performance. The recent use of Graphics Processing Units (GPUs) in several top supercomputers demonstrates their ability...

    Provided By University of Bristol

  • White Papers // Jan 2012

    Combinatorial Channel Signature Modulation for Wireless Ad-Hoc Networks

    In this paper, the authors introduce a novel modulation and multiplexing method which facilitates highly efficient and simultaneous communication between multiple terminals in wireless ad-hoc networks. They term this method Combinatorial Channel Signature Modulation (CCSM). The CCSM method is particularly efficient in situations where communicating nodes operate in highly time...

    Provided By University of Bristol

  • White Papers // Nov 2011

    Progressive-BackSpace: Efficient Predecessor Computation for Post-Silicon Debug

    As microprocessors become more complex, finding errors in their design becomes more difficult. Most design errors are caught before the chip is fabricated; however, some make it into the fabricated design. One challenge in determining what is wrong with a new design after fabrication is the lack of observability into...

    Provided By University of Bristol

  • White Papers // Jun 2011

    SPECI-2 an Open-Source Framework for Predictive Simulation of Cloud-Scale Data-Centres

    The authors introduce Version 2 of SPECI (Simulation Program for Elastic Computing Infrastructure), a system for predictive simulation modelling of ultra-largescale Data-Centers (DCs), i.e. warehouse-sized facilities containing hundreds of thousands of servers, as used to provide cloud computing services. The move toward cloud computing is driving the construction of ever...

    Provided By University of Bristol

  • White Papers // Jun 2011

    Modelling Resilience in Cloud-Scale Data Centres

    The trend for cloud computing has initiated a race towards Data Centers (DC) of an ever-increasing size. The largest DCs now contain many hundreds of thousands of Virtual Machine (VM) services. Given the finite lifespan of hardware, such large DCs are subject to frequent hardware failure events that can lead...

    Provided By University of Bristol

  • White Papers // Nov 2012

    Full-Duplex Transmissions in Fiber-Connected Distributed Relay Antenna Systems

    Distributed Antenna Systems (DAS) have been studied extensively to improve spectral efficiency and extend coverage. Different from the previous studies that focused mostly on the enhancement of downlink or uplink performance through cooperation of distributed antennas, this paper proposes and investigates a novel communication configuration in which a fiber-connected DAS...

    Provided By University of Bristol

  • White Papers // Mar 2009

    Multiple - Symbol Differential Decision Fusion for Mobile Wireless Sensor Networks

    The authors consider the problem of decision fusion in mobile wireless sensor networks where the channels between the sensors and the fusion center are time - variant. They assume that the sensors make independent local decisions on the M hypotheses under test and report these decisions to the fusion center...

    Provided By University of Bristol

  • White Papers // Mar 2013

    Relay Selection for Simultaneous Information Transmission and Wireless Energy Transfer: A Tradeoff Perspective

    In certain applications, relay terminals can be employed to simultaneously deliver information and energy to a designated receiver and a Radio Frequency (RF) energy harvester, respectively. In such scenarios, the relay that is preferable for information transmission does not necessarily coincide with the relay with the strongest channel to the...

    Provided By University of Bristol

  • White Papers // Oct 2009

    Multiple-Symbol Differential Decision Fusion for Mobile Wireless Sensor Networks

    The authors consider the problem of decision fusion in mobile Wireless Sensor Networks where the channels between the sensors and the fusion center are time - variant. They assume that the sensors make independent local decisions on the M hypotheses under test and report these decisions to the fusion center...

    Provided By University of Bristol

  • White Papers // Jan 2010

    A Tutorial on Stochastic Approximation Algorithms for Training Restricted Boltzmann Machines and Deep Belief Nets

    In this paper, the authors provide a direct comparison of the Stochastic Maximum Likelihood algorithm and Contrastive Divergence for training Restricted Boltzmann Machines using the MNIST data set. They demonstrate that Stochastic Maximum Likelihood is superior when using the Restricted Boltzmann Machine as a classifier, and that the algorithm can...

    Provided By University of Bristol

  • White Papers // Nov 2012

    Towards Building Error Resilient GPGPU Applications

    GPUs (Graphics Processing Units) have gained wide adoption as accelerators for general purpose computing. They are widely used in error-sensitive applications, i.e. General Purpose GPU (GPGPU) applications However, the reliability implications of using GPUs are unclear. This paper presents a fault injection study to investigate the end-to-end reliability characteristics of...

    Provided By University of Bristol

  • White Papers // Jan 2013

    On Graphs, GPUs, and Blind Dating a Workload to Processor Matchmaking Quest

    Graph processing has gained renewed attention. The increasing large scale and wealth of connected data, such as those accrued by social network applications, demand the design of new techniques and platforms to efficiently derive actionable information from large scale graphs. Hybrid systems that host processing units optimized for both fast...

    Provided By University of Bristol

  • White Papers // May 2012

    Avoiding the Disk Bottleneck in Deduplicated VM Transfer

    Data de-duplication is a commonly adopted optimization in the cloud infrastructure for optimizing the storage and the transfer of Virtual Machines (VM). Data de-duplication efficiently identifies and eliminates similarity across VM image files leading to a reduction in the amount of data that needs to be stored and/or transferred. This...

    Provided By University of Bristol

  • White Papers // Mar 2012

    Key Challenges in Defending Against Malicious Socialbots

    The ease with which the authors adopt online personas and relationships has created a soft spot that cyber criminals are willing to exploit. Advances in artificial intelligence make it feasible to design bots that sense, think and act cooperatively in social settings just like human beings. In the wrong hands,...

    Provided By University of Bristol

  • White Papers // May 2012

    GPUs as Storage System Accelerators

    Massively multicore processors, such as Graphics Processing Units (GPUs), provide, at a comparable price, a one order of magnitude higher peak performance than traditional CPUs. This drop in the cost of computation, as any order-of-magnitude drop in the cost per unit of performance for a class of system components, triggers...

    Provided By University of Bristol

  • White Papers // May 2012

    LOS and NLOS Classification for Underwater Acoustic Localization

    The low sound speed in water makes Propagation Delay (PD) based range estimation attractive for UnderWater Acoustic Localization (UWAL). However, due to the long channel impulse response and the existence of reflecting objects, PD-based UWAL suffers from significant degradation when PD measurements of Non-Line-Of-Sight (NLOS) communication links are falsely identified...

    Provided By University of Bristol

  • White Papers // Jul 2010

    NLOS Identification Using a Hybrid ToA-Signal Strength Algorithm for Underwater Acoustic Localization

    The existence of obstacles in harbors or near shore environments leads to Non-Line-Of-Sight (NLOS) links between two UnderWater Acoustic Communication (UWAC) nodes. That is, only echoes of the transmitted signal arrive at the receiving node. Mistaking the first (strong) echo as a Line-Of-sight (LOS) measurement and using it for ranging...

    Provided By University of Bristol

  • White Papers // Jul 2012

    Transmit Antenna Selection for Security Enhancement in MIMO Wiretap Channels

    Information security has become a pivotal concern in wireless communications, due to the fact that the broadcast nature of the wireless medium allows eavesdroppers to intercept transmissions in the network. Traditionally, cryptographic protocols have been designed and implemented to provide security in the upper layers (e.g., the network layer), based...

    Provided By University of Bristol

  • White Papers // May 2012

    An Optimal Energy Allocation Algorithm for Energy Harvesting Wireless Sensor Networks

    With the use of energy harvesting technologies, the lifetime of a Wireless Sensor Network (WSN) can be prolonged significantly. Unlike a traditional WSN powered by non-rechargeable batteries, the energy management policy of an energy harvesting WSN needs to take into account the energy replenishment process. In this paper, the authors...

    Provided By University of Bristol

  • White Papers // May 2012

    Dual-hop Amplify-and-Forward Transmission With Imperfect Channel Estimates at the Relay

    With reference to the typical three-node Amplify-and-Forward (AF) relaying setup, where a single relay assists the communication between a source terminal and a destination terminal, the authors investigate the effect of outdated Channel State Information (CSI) at the relay on the overall performance. In particular, they consider CSI-assisted (i.e., variable-gain)...

    Provided By University of Bristol

  • White Papers // May 2012

    Optimal Power Allocation in a Multi-Hop Decode-and-Forward Communication System

    This paper analyzes optimal power allocation schemes for a multi-hop decode-and-forward relay system in a Rayleigh fading environment at high signal-to-noise ratio. Analysis is done for two kinds of modulation schemes: M-ary phase-shift keying with coherent detection and orthogonal ??'?-ary frequency-shift keying with non-coherent detection. An optimal power allocation scheme...

    Provided By University of Bristol

  • White Papers // May 2012

    Efficient Authentication and Key Management for the Home Area Network

    Due to the extensive use of wireless technologies, security is one of the most important and challenging issues in smart grid networks. To secure data communications, strong authentication and key management mechanisms are needed. In this paper, the authors propose a mutual authentication scheme and key management protocol tailored for...

    Provided By University of Bristol

  • White Papers // May 2012

    Robust Power Allocation Designs for Cognitive Radio Networks With Cooperative Relays

    In this paper, the authors develop robust power allocation schemes for Cognitive Radio Networks (CRNs) that can operate in multiple bands with cooperative relays considering uncertainty among the channels of Secondary User (SU) network and among the channels of SU transmitters to Primary User (PU) receivers. Their objective is to...

    Provided By University of Bristol

  • White Papers // May 2012

    Power Line Network Topology Inference Using Frequency Domain Reflectometry

    Frequency Domain Reflectometry (FDR) is a technique that was proposed for fault detection in Digital Subscriber Line (DSL) cables. In this paper, the authors describe how FDR can be used to determine the topology of power line networks. To this end, they first infer distance information from the multiple signal...

    Provided By University of Bristol

  • White Papers // Mar 2012

    Distance Based Heuristic for Power and Rate Allocation of Video Sensor Networks

    Video Sensor Networks (VSNs) offer an alternative to several existing surveillance technologies. However, unlike in conventional sensor network, video processing and transmission requires large amount of resources both in signal processing, i.e., encoding, and transmission of the encoded data. For such networks, an optimal encoding power and rate allocation method...

    Provided By University of Bristol

  • White Papers // Mar 2012

    Distributed Dynamic Scheduling for Body Area Networks

    Body Area Networks (BANs), targeting everywhere anytime health monitoring, operate in license-exempt frequency bands. They require a cross layer design that jointly considers the requirements of access delay to the medium and Packet Delivery Ratio (PDR). In this paper, the authors experimentally evaluate the PDR of a BAN under static...

    Provided By University of Bristol

  • White Papers // Dec 2009

    Subcarrier and Power Adaptation for Multiuser OFDMA-Based Cognitive Radio Systems

    This paper investigates the subcarrier and power allocation problem for an OFDM-based multiuser Cognitive Radio (CR) system. For CR systems it is important to keep the interference introduced to the Primary User (PU) band within a tolerable range. Since the joint subcarrier and power allocation problem is a non-convex integer...

    Provided By University of Bristol

  • White Papers // Dec 2012

    On Extracting Unit Tests From Interactive Programming Sessions

    Software engineering methodologies propose that developers should capture their efforts in ensuring that programs run correctly in repeatable and automated artifacts, such as unit tests. However, when looking at developer activities on a spectrum from exploratory testing to scripted testing the authors find that many engineering activities include bursts of...

    Provided By University of Bristol

  • White Papers // Nov 2008

    GA-Based Optimization of Sigma-Delta Modulators for Wireless Transceivers

    Over-sampling sigma-delta Analog-to-Digital Converters (ADCs) are one of the key building blocks of state of the art wireless transceivers. In sigma-delta modulator design, the scaling coefficients determine the peak signal-to-noise ratio. Therefore, selecting the optimum value of the coefficient is very important. To this end, this paper addresses the design...

    Provided By University of Bristol

  • White Papers // Jan 2010

    Improving Accuracy and Cost of Two-Class and Multi-Class Probabilistic Classifiers Using ROC Curves

    The probability estimates of a naive Bayes classifier are inaccurate if some of its underlying independence assumptions are violated. The decision criterion for using these estimates for classification therefore has to be learned from the data. This paper proposes the use of ROC curves for this purpose. For two classes,...

    Provided By University of Bristol

  • White Papers // Jun 2009

    Using Excel to Individualise Basic Mathematics Assignments

    This paper sets out a method for creating and marking individualised mathematics assessments for students based on their ID numbers. It therefore provides a means for setting assessed coursework questions that give students the incentive to put in the practice needed to master mathematical techniques without the risk of collusion...

    Provided By University of Bristol

  • White Papers // Jan 2009

    Mobile WiMAX: Multi-Cell Network Evaluation and Capacity Optimization

    The performance of a mobile WiMAX system is highly dependent on the application environment. Local clutter has a significant impact on the path loss exponent and the observed multipath statistics. The spectral efficiency of a WiMAX network can be enhanced if channel quality information is included as part of the...

    Provided By University of Bristol

  • White Papers // Sep 2008

    Financial Structure And Corporate Growth: Evidence From Italian Panel Data

    The authors study the relationships between firm financial structure and growth for a large sample of Italian firms (1998-2003). They expand upon existing analyses testing whether liquidity constraints affect firm performance by considering among growth determinants also firm debt structure. Panel regression analyses show that more liquid firms tend to...

    Provided By University of Bristol

  • White Papers // Dec 2010

    An Evaluation of Hash Functions on a Power Analysis Resistant Processor Architecture

    Cryptographic hash functions are omnipresent components in security-critical software and devices; they support, for example, digital signature and data authenticity schemes, mechanisms for key derivation, pseudo-random number generation and so on. A criteria for candidate hash functions in the SHA-3 contest is resistance against side-channel analysis which is a major...

    Provided By University of Bristol

  • White Papers // Jan 2010

    Research Challenges for Enterprise Cloud Computing

    Cloud computing represents a shift away from computing as a product that is purchased, to computing as a service that is delivered to consumers over the internet from large-scale data centers - or 'Clouds'. This paper discusses some of the research challenges for cloud computing from an enterprise or organizational...

    Provided By University of Bristol

  • White Papers // Jan 2010

    Research Agenda in Cloud Technologies

    Cloud computing is the latest effort in delivering computing resources as a service. It represents a shift away from computing as a product that is purchased, to computing as a service that is delivered to consumers over the internet from large-scale data centres - or "Clouds". Whilst cloud computing is...

    Provided By University of Bristol

  • White Papers // Mar 2011

    Fully Homomorphic SIMD Operations

    At PKC 2010 Smart and Vercauteren presented a variant of Gentry's fully homomorphic public key encryption scheme and mentioned that the scheme could support SIMD style operations. The slow key generation process of the Smart - Vercauteren system was then addressed in a paper by Gentry and Halevi, but their...

    Provided By University of Bristol

  • White Papers // Jan 2011

    Adaptive Pseudo-Free Groups and Applications

    A computational group is pseudo-free if an adversary cannot find solutions in this group for equations that are not trivially solvable in the free group. This notion was put forth by Rivest as a unifying abstraction of multiple group-related hardness assumptions commonly used in cryptography. Rivest's conjecture that the RSA...

    Provided By University of Bristol

  • White Papers // Dec 2010

    Differential Fault Analysis of AES Using a Single Multiple-Byte Fault

    In this paper the authors present an improved fault attack on the Advanced Encryption Standard (AES). This paper presents an improvement on a recently published differential fault analysis of AES that requires one fault to recover the secret key being used. This attack requires that one byte entering into the...

    Provided By University of Bristol

  • White Papers // Jan 2011

    Efficient Two-Move Blind Signatures in the Common Reference String Model

    Blind signatures provide a mechanism for achieving privacy and anonymity whereby a user gets the signer to sign a message of his choice without the signer learning the content of the message, nor linking message/signature request pairs when he sees the final signature. In this paper, the authors construct a...

    Provided By University of Bristol

  • White Papers // Mar 2011

    On CCA-Secure Fully Homomorphic Encryption

    It is well known that any encryption scheme which supports any form of homomorphic operation cannot be secure against adaptive chosen ciphertext attacks. The question then arises as to what is the most stringent security definition which is achievable by homomorphic encryption schemes. Prior work has shown that various schemes...

    Provided By University of Bristol

  • White Papers // Sep 2010

    Side-Channel Attacks on the McEliece and Niederreiter Public-Key Cryptosystems

    Research within "Post-quantum" cryptography has focused on development of schemes that resist quantum cryptanalysis. However, if such schemes are to be deployed, practical questions of efficiency and physical security should also be addressed; this is particularly important for embedded systems. To this end, the authors investigate issues relating to side-channel...

    Provided By University of Bristol

  • White Papers // Aug 2010

    Constructing Certificateless Encryption and ID-Based Encryption From ID-Based Key Agreement

    The authors discuss the relationship between ID-based key agreement protocols, certificateless encryption and ID-based key encapsulation mechanisms. In particular they show how in some sense ID-based key agreement is a primitive from which all others can be derived. In doing so they focus on distinctions between what they term pure...

    Provided By University of Bristol

  • White Papers // Dec 2009

    Fully Homomorphic Encryption With Relatively Small Key and Ciphertext Sizes

    The authors present a fully homomorphic encryption scheme which has both relatively small key and ciphertext size. The construction follows that of Gentry by producing a fully homomorphic scheme from a "Somewhat" homomorphic scheme. For the somewhat homomorphic scheme the public and private keys consist of two large integers (one...

    Provided By University of Bristol

  • White Papers // Feb 2011

    Differential Fault Analysis of the Advanced Encryption Standard Using a Single Fault

    In this paper the authors present a differential fault attack that can be applied to the AES using a single fault. They demonstrate that when a single random byte fault is induced at the input of the eighth round, the AES key can be deduced using a two stage algorithm....

    Provided By University of Bristol