Northwestern University

Displaying 1-40 of 149 results

  • White Papers // Aug 2013

    Scheduled Voltage Scaling for Increasing Lifetime in the Presence of NBTI

    Negative Bias Temperature Instability (NBTI) is a leading reliability concern for Integrated Circuits (ICs). It gradually increases the threshold voltages of PMOS transistors, thereby increasing delay. The authors propose scheduled voltage scaling, a technique that gradually increases the operating voltage of the IC to compensate for NBTI-related performance degradation. Scheduled...

    Provided By Northwestern University

  • White Papers // Apr 2013

    Guarded Execution of Privileged Code in the Guest

    Allowing a guest to have direct, privileged access to hardware can enhance its performance and functionality. Privileged access to hardware and the VMM also enables and improves the performance of virtualization services by allowing portions of their implementations to be hoisted into the guest, even uncooperatively. However, granting such privilege...

    Provided By Northwestern University

  • White Papers // Apr 2013

    VMM-based Emulation of Intel Hardware Transactional Memory

    The authors describe the design, implementation, and evaluation of emulated hardware transactional memory, specifically the Intel Haswell Restricted Transactional Memory (RTM) architectural extensions for x86/64, within a virtual machine monitor (VMM). Their system allows users to investigate RTM on hardware that does not provide it, debug their RTM-based transactional software,...

    Provided By Northwestern University

  • White Papers // Apr 2013

    Making JavaScript Better By Making It Even Slower

    On mobile devices, such as Smartphones and tablets, client-side JavaScript is a significant contributor to power consumption, and thus battery lifetime. The authors claim that this is partially due to JavaScript interpretation running faster than is necessary to maintain a satisfactory user experience, and they propose that JavaScript implementations include...

    Provided By Northwestern University

  • White Papers // Mar 2013

    The Public Safety Broadband Network: A Novel Architecture with Mobile Base Stations

    A nationwide interoperable public safety broadband network is being planned by the United States government. The network will be based on Long Term Evolution (LTE) standards and use recently designated spectrum in the 700 MHz band. The public safety network has different objectives and traffic patterns than commercial wireless networks....

    Provided By Northwestern University

  • White Papers // Jan 2013

    AppsPlayground: Automatic Security Analysis of Smartphone Applications

    Today's smartphone application markets host an ever increasing number of applications. The sheer number of applications makes their review a daunting task. The authors propose AppsPlayground, a framework for automatically driving smartphone applications using their user interface characteristics, supporting complex user interactions, including the ability to create and supply login...

    Provided By Northwestern University

  • White Papers // Jan 2013

    Trying Broadband Characterization at Home

    In recent years the quantity and diversity of Internet-enabled consumer devices in the home have increased significantly. These trends complicate device usability and home resource management and have implications for crowdsourced approaches to broadband characterization. The UPnP protocol has emerged as an open standard for device and service discovery to...

    Provided By Northwestern University

  • White Papers // Jan 2013

    Spectrum Markets with Interference Complementarities

    Extensive spectrum markets have the potential to enable more efficient use of this limited resource. Such markets must account for particular properties of the underlying wireless medium. In this paper the authors focus on one such aspect: the role of interference created among different agents who may purchase the right...

    Provided By Northwestern University

  • White Papers // Nov 2012

    Multi-Cell Distributed Interference Cancellation for Co-Operative Pico-Cell Clusters

    Alternative wireless topologies, e.g., an underlay network of Pico-cells, are increasingly seen as being necessary to enhance capacity and coverage in next generation wireless systems. Such networks of closely-spaced base-sites have to contend with high interference issues, wherein interference mitigation via power control or interference co-ordination may not be sufficient....

    Provided By Northwestern University

  • White Papers // Oct 2012

    Enhancing Parallelism of Pairwise Statistical Significance Estimation for Local Sequence Alignment

    Pairwise Statistical Significance (PSS) has been found to be able to accurately identify related sequences (homology detection), which is a fundamental step in numerous applications relating to sequence analysis. Although more accurate than database statistical significance, it is both computationally intensive and data intensive to construct the empirical score distribution...

    Provided By Northwestern University

  • White Papers // Sep 2012

    Complexity of Allocation Problems in Spectrum Markets with Interference Complementarities

    Markets are often viewed as a key ingredient in facilitating more efficient dynamic spectrum access. In this paper the authors consider how such spectrum markets are influenced by a key property of the wireless medium: interference. Interference can result in "Complementarities" among the "Spectrum goods" being traded, which complicates the...

    Provided By Northwestern University

  • White Papers // Aug 2012

    Selective Behavior in Online Social Networks

    According to the classical communication theories, known as Gatekeeping and Selective Exposure, individuals tend to have selective behavior when they disseminate and receive information based on their psychological preferences. Selective behavior related to these two theories have been broadly studied separately. While, thanks to the advent of Online Social Networks...

    Provided By Northwestern University

  • White Papers // Jul 2012

    Dynamic Directories: A Mechanism for Reducing On-Chip Interconnect Power in Multicores

    On-chip interconnection networks consume a significant fraction of the chip's power, and the rapidly increasing core counts in future technologies is going to further aggravate their impact on the chip's overall power consumption. A large fraction of the traffic originates not from data messages exchanged between sharing cores, but from...

    Provided By Northwestern University

  • White Papers // Jun 2012

    HAPPE: Human and Application Driven Frequency Scaling for Processor Power Efficiency

    Conventional dynamic voltage and frequency scaling techniques use high CPU utilization as a predictor for user dissatisfaction, to which they react by increasing CPU frequency. In this paper, the authors demonstrate that for many interactive applications, perceived performance is highly-dependent upon the particular user and application, and is not linearly...

    Provided By Northwestern University

  • White Papers // May 2012

    Security of Electrostatic Field Persistent Routing: Attacks and Defense Mechanisms

    Electrostatic Field-based Routing (EFR) is a form of geographical multi-path routing where packets are routed along a collection of electrostatic field lines, defined by electrostatic charges associated with source and sink nodes. EFR provides an efficient and scalable solution to the workload balancing problem. However, it assumes that nodes behave...

    Provided By Northwestern University

  • White Papers // May 2012

    On the Path to Sustainable, Scalable, and Energy-efficient Data Analytics: Challenges, Promises, and Future Directions

    As scientific data is reaching exascale, scalable and energy efficient data analytics is quickly becoming a top notch priority. Yet, a sustainable solution to this problem is hampered by a number of technical challenges that get exacerbated with the emerging hardware and software technology trends. In this paper, the authors...

    Provided By Northwestern University

  • White Papers // Apr 2012

    Wireless MIMO Switching With MMSE Relaying

    A wireless relay which forms a one-to-one mapping from the inputs (uplinks) to the outputs (downlinks) is called a Multiple-Input-Multiple-Output (MIMO) switch. The MIMO switch carries out pre-code-and-forward, where all users send their signals in the uplink and then the MIMO switch pre-codes the received vector signal for broadcasting in...

    Provided By Northwestern University

  • White Papers // Apr 2012

    A Sparse Octree Gravitational N-Body Code That Runs Entirely on the GPU Processor

    The authors present the implementation and performance of a new gravitational N- body tree-code that is specifically designed for the Graphics Processing Unit (GPU). All parts of the tree-code algorithm are executed on the GPU. They present algorithms for parallel construction and traversing of sparse oc-trees. These algorithms are implemented...

    Provided By Northwestern University

  • White Papers // Mar 2012

    Virtual-Machine-Based Emulation of Future Generation High-Performance Computing Systems

    In this paper, the authors describe the design of a system to enable research, development, and testing of new software stacks and hardware features for future high-end computing systems. Motivating uses include both small-scale research and development on simulated individual nodes of proposed high-performance computing systems, and large scaling studies...

    Provided By Northwestern University

  • White Papers // Mar 2012

    Uplink Distributed Power and Receiver Optimization Across Multiple Cells

    Interference mitigation approaches in the presence of multiple receive antennas in the uplink of a multi-cell wireless communications system are studied in this paper. A formulation based on interference pricing is proposed, where it is shown that a single price per base-station can be computed and exchanged, in order to...

    Provided By Northwestern University

  • White Papers // Mar 2012

    Characterization of Vision-Aided Indoor Localization and Landmark Routing

    GPS is the premier method of localization and way-finding in outdoor environments. Indoor environments prevent GPS from functioning properly or at all. RF-based solutions have been proposed using varieties of radio triangulation and spectral fingerprinting. Such technically attractive methods have not seen widespread adoption in places where the demand is...

    Provided By Northwestern University

  • White Papers // Mar 2012

    VirtualKnotter: Online Virtual Machine Shuffling for Congestion Resolving in Virtualized Datacenter

    The authors measurements on production datacenter traffic together with recently-reported results suggest that datacenter networks suffer from long-lived congestion caused by core network oversubscription and unbalanced workload placement. In contrast to traditional traffic engineering approaches that optimize flow routing, in this paper, they explore the opportunity to address the continuous...

    Provided By Northwestern University

  • White Papers // Jan 2012

    Supporting Computational Data Model Representation with High-Performance I/O in Parallel NetCDF

    Parallel computational scientific applications have been described by their computation and communication patterns. From a storage and I/O perspective, these applications can also be grouped into separate data models based on the way data is organized and accessed during simulation, analysis, and visualization. Parallel netCDF is a popular library used...

    Provided By Northwestern University

  • White Papers // Jan 2012

    Improving the Average Response Time in Collective I/O

    In collective I/O, MPI processes exchange requests so that the rearranged requests can result in the shortest file system access time. Scheduling the exchange sequence determines the response time of participating processes. Existing implementations that simply follow the increasing order of file offsets do not necessary produce the best performance....

    Provided By Northwestern University

  • White Papers // Jan 2012

    Reliability Constrained Packet-Sizing for Linear Multi-Hop Wireless Networks

    The authors consider optimizing the packet-sizes and the reuse factor to minimize the delay required to send a message between two nodes in a linear multi-hop wireless network subject to a reliability constraint. Initially, assuming no re-use, they give a bound on the required delay. Next, in an infinite system...

    Provided By Northwestern University

  • White Papers // Sep 2011

    Sum-Capacity of a Class of K-user Gaussian Interference Channels within O(K) Bits

    Though the capacity of the 2-user Gaussian interference channel has long eluded information theorists, recent progress has been made by focusing on approximations with provable bounds. However, extensions to a general K-user network has proven to be non-obvious, in particular due to the role of interference alignment in these cases....

    Provided By Northwestern University

  • White Papers // Sep 2011

    Wireless MIMO Switching With Zero-Forcing Relaying

    A wireless relay with multiple antennas is called a Multiple-Input-Multiple-Output (MIMO) switch if it forms a one-to-one mapping from the inputs (uplinks) to the outputs (downlinks). This paper studies the case with N source stations and N destination stations (which may be the same set), so that the mapping is...

    Provided By Northwestern University

  • White Papers // Aug 2011

    Achieving Target MTTF by Duplicating Reliability-Critical Components in High Performance Computing Systems

    Mean Time To failure, MTTF, is a commonly accepted metric for reliability. In this paper, the authors present a novel approach to achieve the desired MTTF with minimum redundancy. They analyze the failure behavior of large scale systems using failure logs collected by Los Alamos National Laboratory. They analyze the...

    Provided By Northwestern University

  • White Papers // Jul 2011

    An Efficient FPGA Implementation of Principle Component Analysis Based Network Intrusion Detection System

    Modern Network Intrsuion Detection Systems (NIDSs) use anomaly detection to capture malicious attacks. Since such connections are described by large set of dimensions, processing these huge amounts of network data becomes extremely slow. To solve this time-efficiency problem, statistical methods like Principal Component Analysis (PCA) can be used to reduce...

    Provided By Northwestern University

  • White Papers // Jul 2011

    Evaluating Voltage Islands in CMPs under Process Variations

    Parameter variations are a major factor causing power-performance asymmetry in chip multiprocessors. In this paper, the authors analyze the effects of With-In-Die (WID) process variations on chip multicore processors and then apply a variable voltage island scheme to minimize power dissipation. Their idea is based on the observation that due...

    Provided By Northwestern University

  • White Papers // Jul 2011

    Exploring I/O Strategies for Parallel Sequence-Search Tools with S3aSim

    Parallel sequence-search tools are rising in popularity among computational biologists. With the rapid growth of sequence databases, database segmentation is the trend of the future for such search tools. While I/O currently is not a significant bottleneck for parallel sequence-search tools, future technologies including faster processors, customized computational hardware such...

    Provided By Northwestern University

  • White Papers // Jul 2011

    Challenges for Parallel I/O in Grid Computing

    With virtually limitless resources, GRID computing has the potential to solve large-scale scientific problems that eclipse even applications that run on the largest computing clusters today. The architecture of a computing GRID simply consists of a heterogeneous network infrastructure connecting heterogeneous machines presumed to be larger than most clusters of...

    Provided By Northwestern University

  • White Papers // Jul 2011

    VNET/P: Bridging the Cloud and High Performance Computing Through Fast Overlay Networking

    Overlay networking with a layer 2 abstraction provides a powerful model for virtualized wide-area distributed computing resources, including for High Performance Computing (HPC) on collections of Virtual Machines (VMs). With the emergence of cloud computing, it is now possible to allow VMs hosting tightly-coupled HPC applications to seamlessly migrate between...

    Provided By Northwestern University

  • White Papers // Jul 2011

    Medium Access Control for Wireless Networks With Peer-to-Peer State Exchange

    Distributed Medium Access Control (MAC) protocols are proposed for wireless networks assuming that one-hop peers can periodically exchange a small amount of state information. Each station maintains a state and makes state transitions and transmission decisions based on its state and recent state information collected from its one-hop peers. A...

    Provided By Northwestern University

  • White Papers // Jul 2011

    Delay Performance of CSMA in Networks With Bounded Degree Conflict Graphs

    The authors analyze packet delay in CSMA-based random access schemes in networks under the protocol interference model. Using a stochastic coupling argument they identify a subset of the throughput-region where queue lengths can be bounded uniformly for all network sizes. This conclusion provides a throughput-region of interest for delay sensitive...

    Provided By Northwestern University

  • White Papers // Jun 2011

    High Performance Data Mining Using R on Heterogeneous Platforms

    The exponential increase in the generation and collection of data has led users in a new era of data analysis and information extraction. Conventional systems based on general-purpose processors are unable to keep pace with the heavy computational requirements of data mining techniques. High performance coprocessors like GPUs and FPGAs...

    Provided By Northwestern University

  • White Papers // Jun 2011

    Learning and Leveraging the Relationship Between Architecture-Level Measurements and Individual User Satisfaction

    The ultimate goal of computer design is to satisfy the end-user. In particular computing domains, such as interactive applications, there exists a variation in user expectations and user satisfaction relative to the performance of existing computer systems. In this paper, the authors leverage this variation to develop more efficient architectures...

    Provided By Northwestern University

  • White Papers // Jun 2011

    Understanding Crowds' Migration on the Web

    Consider a network where nodes are websites and the weight of a link that connects two nodes corresponds to the average number of users that visits both of the two websites over longer timescales. Such user-driven Web network is not only invaluable for understanding how crowds' interests collectively spread on...

    Provided By Northwestern University

  • White Papers // May 2011

    Exploiting Peer-to-Peer State Exchange for Distributed Medium Access Control

    Distributed Medium Access Control (MAC) protocols are proposed for wireless networks assuming that one-hop peers can exchange a small amount of state information periodically. Each station maintains a state and makes state transitions and transmission decisions based on its state and recent state information collected from its one-hop peers. A...

    Provided By Northwestern University

  • White Papers // May 2011

    Fusion of Live Audio Recordings for Blind Noise Reduction

    The prevalence of digital cameras and video-capable mobile phones enables the common practice of audiences capturing recordings of live music performances. It is now increasingly common to find some of these personal recordings online, uploaded to popular video hosting websites. Recognizing the desire of music fans to obtain a recording...

    Provided By Northwestern University

  • White Papers // Mar 2012

    Uplink Distributed Power and Receiver Optimization Across Multiple Cells

    Interference mitigation approaches in the presence of multiple receive antennas in the uplink of a multi-cell wireless communications system are studied in this paper. A formulation based on interference pricing is proposed, where it is shown that a single price per base-station can be computed and exchanged, in order to...

    Provided By Northwestern University

  • White Papers // Jan 2013

    Trying Broadband Characterization at Home

    In recent years the quantity and diversity of Internet-enabled consumer devices in the home have increased significantly. These trends complicate device usability and home resource management and have implications for crowdsourced approaches to broadband characterization. The UPnP protocol has emerged as an open standard for device and service discovery to...

    Provided By Northwestern University

  • White Papers // Aug 2012

    Selective Behavior in Online Social Networks

    According to the classical communication theories, known as Gatekeeping and Selective Exposure, individuals tend to have selective behavior when they disseminate and receive information based on their psychological preferences. Selective behavior related to these two theories have been broadly studied separately. While, thanks to the advent of Online Social Networks...

    Provided By Northwestern University

  • White Papers // Feb 2011

    Towards Street-Level Client-Independent IP Geolocation

    A highly accurate client-independent geolocation service stands to be an important goal for the Internet. Despite an extensive research effort and significant advances in this area, this goal has not yet been met. Motivated by the fact that the best results to date are achieved by utilizing additional 'Hints' beyond...

    Provided By Northwestern University

  • White Papers // Aug 2009

    Googling the Internet: Profiling Internet Endpoints via the World Wide Web

    Understanding Internet access trends at a global scale, i.e., how people use the Internet, is a challenging problem that is typically addressed by analyzing network traces. However, obtaining such traces presents its own set of challenges owing to either privacy concerns or to other operational difficulties. The key hypothesis of...

    Provided By Northwestern University

  • White Papers // Mar 2010

    Strange Bedfellows: Community Identification in BitTorrent

    While P2P systems benefit from large numbers of interconnected nodes, each of these connections provides an opportunity for eavesdropping. Using only the connection patterns gathered from 10,000 BitTorrent (BT) users during a one-month period, the authors determine whether randomized connection patterns give rise to communities of users. Even though connections...

    Provided By Northwestern University

  • White Papers // Apr 2010

    Network Positioning From the Edge: An Empirical Study of the Effectiveness of Network Positioning in P2P Systems

    Network positioning systems provide an important service to large-scale P2P systems, potentially enabling clients to achieve higher performance, reduce cross-ISP traffic and improve the robustness of the system to failures. Because traces representative of this environment are generally unavailable, and there is no platform suited for experimentation at the appropriate...

    Provided By Northwestern University

  • White Papers // May 2009

    Distributed or Centralized Traffic Advisory Systems-The Application's Take

    The authors consider the problem of data dissemination in vehicular networks. Their main goal is to compare the application-level performance of fully distributed and centralized data dissemination approaches in the context of traffic advisory systems. Vehicular networks are emerging as a new distributed system environment with myriad promising applications. Wirelessly-connected,...

    Provided By Northwestern University

  • White Papers // Mar 2009

    Down the Block and Around the Corner - The Impact of Radio Propagation on Inter-Vehicle Wireless Communication

    Vehicular networks are emerging as a new distributed system environment with myriad possible applications. Most studies on vehicular networks are carried out via simulation, given the logistical and economical problems with large-scale deployments. This paper investigates the impact of realistic radio propagation settings on the evaluation of VANET-based systems. Using...

    Provided By Northwestern University

  • White Papers // Apr 2009

    On the Effectiveness of Measurement Reuse for Performance-Based Detouring

    For both technological and economic reasons, the default path between two end systems in the wide-area Internet can be suboptimal. This observation has motivated a number of systems that attempt to improve reliability and performance by routing over one or more hops in an overlay. Most of the proposed solutions,...

    Provided By Northwestern University

  • White Papers // Jan 2013

    AppsPlayground: Automatic Security Analysis of Smartphone Applications

    Today's smartphone application markets host an ever increasing number of applications. The sheer number of applications makes their review a daunting task. The authors propose AppsPlayground, a framework for automatically driving smartphone applications using their user interface characteristics, supporting complex user interactions, including the ability to create and supply login...

    Provided By Northwestern University

  • White Papers // Mar 2012

    VirtualKnotter: Online Virtual Machine Shuffling for Congestion Resolving in Virtualized Datacenter

    The authors measurements on production datacenter traffic together with recently-reported results suggest that datacenter networks suffer from long-lived congestion caused by core network oversubscription and unbalanced workload placement. In contrast to traditional traffic engineering approaches that optimize flow routing, in this paper, they explore the opportunity to address the continuous...

    Provided By Northwestern University

  • White Papers // Jul 2012

    Dynamic Directories: A Mechanism for Reducing On-Chip Interconnect Power in Multicores

    On-chip interconnection networks consume a significant fraction of the chip's power, and the rapidly increasing core counts in future technologies is going to further aggravate their impact on the chip's overall power consumption. A large fraction of the traffic originates not from data messages exchanged between sharing cores, but from...

    Provided By Northwestern University

  • White Papers // Jan 2012

    Supporting Computational Data Model Representation with High-Performance I/O in Parallel NetCDF

    Parallel computational scientific applications have been described by their computation and communication patterns. From a storage and I/O perspective, these applications can also be grouped into separate data models based on the way data is organized and accessed during simulation, analysis, and visualization. Parallel netCDF is a popular library used...

    Provided By Northwestern University

  • White Papers // Apr 2009

    Implicit User Re-Authentication for Mobile Devices

    Portable computers are used to store and access sensitive information. They are frequently used in insecure locations with little or no physical protection, and are therefore susceptible to theft and unauthorized access. The paper proposes an implicit user re-authentication system for portable computers that requires no application changes or hardware...

    Provided By Northwestern University

  • White Papers // Jan 2009

    Exception Triggered DoS Attacks on Wireless Networks

    Security protocols are not as secure as one assumed. This paper identified a practical way to launch DoS attacks on security protocols by triggering exceptions. Through experiments, the author shows that even the latest strongly authenticated protocols such as PEAP, EAP-TLS and EAP-TTLS are vulnerable to these attacks. Real attacks...

    Provided By Northwestern University

  • White Papers // Mar 2009

    High-Density Optical Data Storage Enabled by the Photonic Nanojet From a Dielectric Microsphere

    This paper discusses the usage of the photonic nanojet to detect deeply subwavelength pits in a metal substrate for the purpose of high-density optical data storage. Three-dimensional Finite-Difference Time-Domain (FDTD) computational solutions of Maxwell's equations are used to analyze and design the system. The paper finds that nanojet-illuminated pits having...

    Provided By Northwestern University

  • White Papers // Jul 2010

    Complementarities in Spectrum Markets

    It is widely recognized that current policies for allocating wireless spectrum have led to inefficiencies and underutilization. One proposed solution to this is to enable "Spectrum markets", which allow for entities to sell and/or lease spectrum dynamically over time. In this paper, the authors consider the design of such a...

    Provided By Northwestern University

  • White Papers // Aug 2009

    Local Interference Pricing for Distributed Beamforming in MIMO Networks

    The authors study a distributed algorithm for adjusting beamforming vectors in a peer-to-peer wireless network with Multiple-Input Multiple-Output (MIMO) channels. Each transmitter precoding matrix has rank one, and a linear Minimum Mean Squared Error (MMSE) filter is applied at each receiver. Their objective is to maximize the total utility summed...

    Provided By Northwestern University

  • White Papers // Oct 2009

    On Proportional Power Sharing Mechanisms for Secondary Spectrum Markets

    The authors consider a proportional sharing mechanism for allocating spectrum to secondary users. Each user bids for a portion of the received power at a measurement point and receives a share that is proportional to its bid while paying a charge equal to the bid. The users then transmit over...

    Provided By Northwestern University

  • White Papers // Nov 2009

    On Information Theoretic Interference Games with More Than Two Users

    The authors consider a model for information theoretic games on interference channels introduced in previous work. The players in these games are the users, who autonomously select their encoding and decoding strategy with the objective of maximizing their own rate. In previous paper, a Nash equilibrium region for this game...

    Provided By Northwestern University

  • White Papers // Aug 2010

    The Maximum Stable Broadcast Throughput for Wireless Line Networks with Network Coding and Topology Control

    The authors consider broadcasting from a single source to multiple destinations in a linear wireless erasure network with feedback. The problem is to find the maximum stable throughput under different transmission policies with opportunistic network coding and forwarding. Given stochastically varying traffic, they assume that network coding decisions are based...

    Provided By Northwestern University

  • White Papers // Mar 2010

    Adaptive Beamforming in Interference Networks via Bi-Directional Training

    The authors study distributed algorithms for adjusting beam-forming vectors and receiver filters in Multiple-Input Multiple-Output (MIMO) interference networks, with the assumption that each user uses a single beam and a linear filter at the receiver. In such a setting there have been several distributed algorithms studied for maximizing the sum-rate...

    Provided By Northwestern University

  • White Papers // Aug 2010

    Medium Access Control via Nearest-Neighbor Interactions for Regular Wireless Networks

    This paper studies Medium Access Control (MAC) protocols for regular wireless networks, where only nearest-neighbor interactions are involved. Each station chooses a state in the current time slot, which determines whether it transmits or not, based on its own state and the states of all its nearest neighbors in the...

    Provided By Northwestern University

  • White Papers // Aug 2010

    Minimum Delay Packet-sizing for Linear Multi-hop Networks with Cooperative Transmissions

    The authors consider optimizing packet sizes and the reuse factor to minimize the delay required to send a message between two nodes in a linear multi-hop wireless networks subject to a reliability constraint. In earlier work, this problem was considered for a network in which each node only decoded the...

    Provided By Northwestern University

  • White Papers // Nov 2010

    On Information Theoretic Games for Interference Networks

    The Nash equilibrium region for a 2-user game was defined and characterized first for a linear deterministic channel and then for a Gaussian channel. Challenges in extending this understanding to some special K-user cases have also been explored. In this paper, the authors study two indices which compare the performance...

    Provided By Northwestern University

  • White Papers // Nov 2010

    The Impact of Additional Unlicensed Spectrum on Wireless Services Competition

    The FCC in the U.S. has recently increased the amount of spectrum available for wireless broadband data services by permitting unlicensed access to television whitespaces. While this additional unlicensed spectrum allows for market expansion, it also influences competition among providers and can increase congestion (interference) among consumers of wireless services....

    Provided By Northwestern University

  • White Papers // May 2011

    Exploiting Peer-to-Peer State Exchange for Distributed Medium Access Control

    Distributed Medium Access Control (MAC) protocols are proposed for wireless networks assuming that one-hop peers can exchange a small amount of state information periodically. Each station maintains a state and makes state transitions and transmission decisions based on its state and recent state information collected from its one-hop peers. A...

    Provided By Northwestern University

  • White Papers // Sep 2011

    Sum-Capacity of a Class of K-user Gaussian Interference Channels within O(K) Bits

    Though the capacity of the 2-user Gaussian interference channel has long eluded information theorists, recent progress has been made by focusing on approximations with provable bounds. However, extensions to a general K-user network has proven to be non-obvious, in particular due to the role of interference alignment in these cases....

    Provided By Northwestern University

  • White Papers // Nov 2012

    Multi-Cell Distributed Interference Cancellation for Co-Operative Pico-Cell Clusters

    Alternative wireless topologies, e.g., an underlay network of Pico-cells, are increasingly seen as being necessary to enhance capacity and coverage in next generation wireless systems. Such networks of closely-spaced base-sites have to contend with high interference issues, wherein interference mitigation via power control or interference co-ordination may not be sufficient....

    Provided By Northwestern University

  • White Papers // Mar 2013

    The Public Safety Broadband Network: A Novel Architecture with Mobile Base Stations

    A nationwide interoperable public safety broadband network is being planned by the United States government. The network will be based on Long Term Evolution (LTE) standards and use recently designated spectrum in the 700 MHz band. The public safety network has different objectives and traffic patterns than commercial wireless networks....

    Provided By Northwestern University

  • White Papers // Oct 2012

    Enhancing Parallelism of Pairwise Statistical Significance Estimation for Local Sequence Alignment

    Pairwise Statistical Significance (PSS) has been found to be able to accurately identify related sequences (homology detection), which is a fundamental step in numerous applications relating to sequence analysis. Although more accurate than database statistical significance, it is both computationally intensive and data intensive to construct the empirical score distribution...

    Provided By Northwestern University

  • White Papers // Aug 2011

    Achieving Target MTTF by Duplicating Reliability-Critical Components in High Performance Computing Systems

    Mean Time To failure, MTTF, is a commonly accepted metric for reliability. In this paper, the authors present a novel approach to achieve the desired MTTF with minimum redundancy. They analyze the failure behavior of large scale systems using failure logs collected by Los Alamos National Laboratory. They analyze the...

    Provided By Northwestern University

  • White Papers // Sep 2012

    Complexity of Allocation Problems in Spectrum Markets with Interference Complementarities

    Markets are often viewed as a key ingredient in facilitating more efficient dynamic spectrum access. In this paper the authors consider how such spectrum markets are influenced by a key property of the wireless medium: interference. Interference can result in "Complementarities" among the "Spectrum goods" being traded, which complicates the...

    Provided By Northwestern University

  • White Papers // May 2011

    A Potential Function View of Information Theoretic Interference Games

    Recently, Berry-Tse introduced a model for information theoretic games on interference channels, which combines game theory and information theory to analyze the interaction of selfish users. The fundamental quantity in such games is the Nash equilibrium region which has been characterized in several specific interference channels. This paper uses the...

    Provided By Northwestern University

  • White Papers // Jan 2013

    Spectrum Markets with Interference Complementarities

    Extensive spectrum markets have the potential to enable more efficient use of this limited resource. Such markets must account for particular properties of the underlying wireless medium. In this paper the authors focus on one such aspect: the role of interference created among different agents who may purchase the right...

    Provided By Northwestern University

  • White Papers // Apr 2013

    Guarded Execution of Privileged Code in the Guest

    Allowing a guest to have direct, privileged access to hardware can enhance its performance and functionality. Privileged access to hardware and the VMM also enables and improves the performance of virtualization services by allowing portions of their implementations to be hoisted into the guest, even uncooperatively. However, granting such privilege...

    Provided By Northwestern University

  • White Papers // Apr 2013

    VMM-based Emulation of Intel Hardware Transactional Memory

    The authors describe the design, implementation, and evaluation of emulated hardware transactional memory, specifically the Intel Haswell Restricted Transactional Memory (RTM) architectural extensions for x86/64, within a virtual machine monitor (VMM). Their system allows users to investigate RTM on hardware that does not provide it, debug their RTM-based transactional software,...

    Provided By Northwestern University

  • White Papers // Mar 2012

    Virtual-Machine-Based Emulation of Future Generation High-Performance Computing Systems

    In this paper, the authors describe the design of a system to enable research, development, and testing of new software stacks and hardware features for future high-end computing systems. Motivating uses include both small-scale research and development on simulated individual nodes of proposed high-performance computing systems, and large scaling studies...

    Provided By Northwestern University

  • White Papers // Jun 2012

    HAPPE: Human and Application Driven Frequency Scaling for Processor Power Efficiency

    Conventional dynamic voltage and frequency scaling techniques use high CPU utilization as a predictor for user dissatisfaction, to which they react by increasing CPU frequency. In this paper, the authors demonstrate that for many interactive applications, perceived performance is highly-dependent upon the particular user and application, and is not linearly...

    Provided By Northwestern University