Northwestern University

Displaying 1-40 of 154 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 // Mar 2013

    Evaluating Android Anti-Malware Against Transformation Attacks

    Mobile malware threats (e.g., on Android) have recently become a real concern. In this paper, the authors evaluate the state-of-the-art commercial mobile anti-malware products for Android and test how resistant they are against various common obfuscation techniques (even with known malware). Such an evaluation is important for not only measuring...

    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 // 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 // Jan 2009

    Behavioral Interview Tips

    Behavioral interviewing is based on the premise that your past behavior predicts your future performance. Even if you do not have a lot of work experience, companies expect you to be able to relate any experience to the job for which you are interviewing. First, know that the basic rules...

    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 // Apr 2010

    Palacios and Kitten: New High Performance Operating Systems for Scalable Virtualized and Native Supercomputing

    Palacios is a new open-source VMM under development at Northwestern University and the University of New Mexico that enables applications executing in a virtualized environment to achieve scalable high performance on large machines. Palacios functions as a modularized extension to Kitten, a high performance operating system being developed at Sandia...

    Provided By Northwestern University

  • White Papers // Jan 2010

    Modeling and Taming Parallel TCP on the Wide Area Network

    Parallel TCP flows are broadly used in the high performance distributed computing community to enhance network throughput, particularly for large data transfers. Previous research has studied the mechanism by which parallel TCP improves aggregate throughput, but there doesn't exist any practical mechanism to predict its throughput. In this work, authors...

    Provided By Northwestern University

  • White Papers // Dec 2009

    EmNet: Satisfying the Individual User Through Empathic Home Networks

    The authors consider optimizing the control of the wide-area link of home routers based on the needs of individual users instead of assuming a canonical user. A careful user study clearly demonstrates that measured end-user satisfaction with a given set of home network conditions is highly variable - user perception...

    Provided By Northwestern University

  • White Papers // Apr 2010

    Evaluating the Impact of Data Center Network Architectures on Application Performance in Virtualized Environments

    In recent years, Data Center Network (DCN) architectures (e.g., DCell, FiConn, BCube, FatTree, and VL2) received a surge of interest from both the industry and academia. However, none of existing efforts provide an in-depth understanding of the impact of these architectures on application performance in practical multi-tier systems under realistic...

    Provided By Northwestern University

  • White Papers // May 2010

    SureCall: Towards Glitch-Free Real-Time Audio/Video Conferencing

    Global enterprises are increasingly adopting unified communication solutions over traditional telephone systems. Such solutions provide integrated audio/video conferencing and messaging services, and enable flexible working environments by allowing mobile and dispersed users to communicate and collaborate easily and efficiently. The ultimate goal of unified communications is to ensure a smooth...

    Provided By Northwestern University

  • White Papers // May 2009

    Supporting Application Network Flows With Multiple QoS Constraints

    There is a growing need to support real-time applications over the Internet. Real-time interactive applications often have multiple Quality-of-Service (QoS) requirements which are application specific. Provisioning QoS in the Internet through IP routing - Intserv or Diffserv - faces many technical challenges, and is also deterred by the huge deployment...

    Provided By Northwestern University

  • White Papers // Jun 2010

    How To Improve Your Google Ranking: Myths And Reality

    Search engines have greatly influenced the way people access information on the Internet as such engines provide the preferred entry point to billions of pages on the Web. Therefore, highly ranked web pages generally have higher visibility to people and pushing the ranking higher has become the top priority for...

    Provided By Northwestern University

  • White Papers // Oct 2008

    Investment In Next Generation Networks And Wholesale Telecommunications Regulation

    The rapidly-accumulating evidence from the international arena is that investment in Information and Communications Technology (ICT) is the principal driver of labor productivity growth and, therefore, overall economic growth in developed nations. A major component of ICT capital is the broadband infrastructure required to transmit information in the modern economy....

    Provided By Northwestern University

  • White Papers // Oct 2010

    Market-Based Loss Mitigation Practices For Troubled Mortgages Following The Financial Crisis

    The meltdown in residential real-estate prices that commenced in 2006 resulted in unprecedented mortgage delinquency rates. Until mid-2009, lenders and servicers pursued their own individual loss mitigation practices without being significantly influenced by government intervention. Using a unique dataset that precisely identifies loss mitigation actions, the authors study these methods...

    Provided By Northwestern University

  • White Papers // Apr 2010

    A Case for Alternative Nested Paging Models for Virtualized Systems

    Address translation often emerges as a critical performance bottleneck for virtualized systems and has recently been the impetus for hardware paging mechanisms. These mechanisms apply similar translation models for both guest and host address translations. The authors make an important observation that the model employed to translate from Guest Physical...

    Provided By Northwestern University

  • White Papers // Nov 2009

    Using the Crowd to Monitor the Cloud: Network Event Detection From Edge Systems

    The authors believe that the most effective way to detect service-level events is by monitoring the end systems where the services are used. This paper describes an implementation of this approach for BitTorrent called NEWS (Network Early Warning System), a system that provides real-time detection of network events impacting the...

    Provided By Northwestern University

  • White Papers // May 2009

    Investigating Virtual Passthrough I/O on Commodity Devices

    A commodity I/O device has no support for virtualization. A VMM can assign such a device to a single guest with direct, fast, but insecure access by the guest's native device driver. Alternatively, the VMM can build virtual devices on top of the physical device, allowing it to be multiplexed...

    Provided By Northwestern University

  • White Papers // Nov 2008

    Towards Virtual Passthrough I/O on Commodity Devices

    A commodity I/O device has no support for virtualization. A VMM can assign such a device to a single guest with direct, fast, but insecure access by the guest's native device driver. Alternatively, the VMM can build virtual devices on top of the physical device, allowing it to be multiplexed...

    Provided By Northwestern University

  • White Papers // Oct 2009

    A Single-Letter Characterization of Optimal Noisy Compressed Sensing

    Compressed sensing deals with the reconstruction of a high-dimensional signal from far fewer linear measurements, where the signal is known to admit a sparse representation in a certain linear space. The asymptotic scaling of the number of measurements needed for reconstruction as the dimension of the signal increases has been...

    Provided By Northwestern University

  • White Papers // Mar 2010

    Network Monitoring Is People: Understanding End-User Perception of Network Problems

    It is widely assumed that certain network characteristics cause end-user irritation with network performance. These assumptions then drive the selection of quality of service parameters or the goals of adaptive systems. The authors have developed a methodology and toolchain, SoylentLogger that employs user studies to empirically investigate such assumptions. SoylentLogger...

    Provided By Northwestern University

  • White Papers // Apr 2010

    Comparing Approaches to Virtualized Page Translation in Modern VMMs

    Virtual machine monitors for modern x86 processors can use a variety of approaches to virtualize address translation. These include the widely-used software approach of shadow paging, with and without caching or prefetching, as well as the widely used hardware approach of nested paging. The authors compare and analyze the measured...

    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 // Jan 2011

    Hardness of Approximation and Greedy Algorithms for the Adaptation Problem in Virtual Environments

    Over the past decade, wide-area distributed computing has emerged as a powerful computing paradigm. Virtual machines greatly simplify wide-area distributed computing by lowering the abstraction to benefit both resource users and providers. A virtual execution environment consisting of Virtual Machines (VMs) interconnected with virtual networks provides opportunities to dynamically optimize,...

    Provided By Northwestern University

  • White Papers // Mar 2011

    Simplified Programming of Faulty Sensor Networks Via Code Transformation and Run-Time Interval Computation

    Detecting and reacting to faults is an indispensable capability for many wireless sensor network applications. Unfortunately, implementing fault detection and error correction algorithms is challenging. Programming languages and fault tolerance mechanisms for sensor networks have historically been designed in isolation. This is the first work to combine them. The goal...

    Provided By Northwestern University

  • White Papers // Apr 2010

    Pitfalls for Testbed Evaluations of Internet Systems

    Today's open platforms for network measurement and distributed system research, which the authors collectively refer to as testbeds in this papeer, provide opportunities for controllable experimentation and evaluations of systems at the scale of hundreds or thousands of hosts. In this paper, the authors identify several issues with extending results...

    Provided By Northwestern University

  • White Papers // Oct 2008

    Removing Exponential Backoff From TCP

    The well-accepted wisdom is that TCP's exponential backoff mechanism, introduced by Jacobson 20 years ago, is essential for preserving the stability of the Internet. In this paper, the authors show that removing exponential backoff from TCP altogether can be done without inducing any stability side-effects. They introduce the implicit packet...

    Provided By Northwestern University

  • White Papers // Nov 2008

    Giving Credit To Credit - Finance And Banking

    In Afghanistan the wives of Pashtu herdsmen traditionally wear heavy silver bracelets to show off their beauty and to store the family's savings. Robbing a woman provokes clan revenge feared by thieves, so women are good protectors of wealth. In India poor people developed another way to store wealth -...

    Provided By Northwestern University

  • White Papers // Mar 2009

    Towards Running Parallel Programs on the Bare Metal Via Virtualization

    Decades of parallel computing practice have proven that highly parallel code runs efficiently only when it has uninterrupted access to the hardware. The authors report on a project whose goal is to support compiling Data Parallel Haskell code into bootable disk images. Their toolchain layers the Data Parallel Haskell runtime...

    Provided By Northwestern University

  • White Papers // Jan 2009

    Limited-Rate Channel State Feedback for Multicarrier Block Fading Channels

    The capacity of a fading channel can be substantially increased by feeding back channel state information from the receiver to the transmitter. With limited-rate feedback what state information to feed back and how to encode it are important open questions. This paper studies power loading in a multicarrier system using...

    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 // Nov 2010

    Caught in the Clouds: The Web 2.0, Cloud Computing, and Privacy?

    According to a recent study by The Nielsen Company, the average American Internet user spends over fifty-five hours per month online. However, despite the wide range of possibilities offered by the Internet, Americans spend about half of their online time on social networks, games, e-mail, and instant messaging. As consumers...

    Provided By Northwestern University

  • White Papers // Dec 2010

    Wireless Peer-to-Peer Mutual Broadcast Via Sparse Recovery

    Consider a problem frequently seen in wireless peer-to-peer networks: every node has messages to broadcast to its peers, namely, all nodes within one hop. Conventional schemes allow only one transmission to succeed at a time in a two-hop neighborhood, because simultaneous transmissions in the neighborhood collide, and affordable radio is...

    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 2010

    Shannon Meets Nash on the Interference Channel

    The interference channel is the simplest communication scenario where multiple autonomous users compete for shared resources. The authors combine game theory and information theory to define a notion of a Nash equilibrium region of the interference channel. The notion is game theoretic: it captures the selfish behavior of each user...

    Provided By Northwestern University

  • White Papers // Jan 2010

    Distributed Resource Allocation Schemes: Pricing Algorithms for Power Control and Beamformer Design in Interference Networks

    Achieving high spectral efficiencies in wireless networks requires the ability to mitigate and manage the associated interference. This becomes especially important in networks where many transmitters and receivers are randomly placed, so that in the absence of coordination a particular receiver is likely to encounter significant interference from a neighboring...

    Provided By Northwestern University

  • White Papers // Jan 2011

    Limited Feedback Schemes for Downlink OFDMA Based on Sub-Channel Groups

    In a downlink Orthogonal Frequency Division Multiple Access (OFDMA) system, optimally allocating sub-channels across mobile users can require excessive feedback of Channel State Information (CSI). The authors consider an OFDMA model in which the feedback overhead is explicitly taken into account, given a fixed feedback rate and finite coherence time....

    Provided By Northwestern University

  • White Papers // Oct 2009

    Exploiting Locality to Improve Circuit-Level Timing Speculation

    Circuit-level timing speculation has been proposed as a technique to reduce dependence on design margins, eliminating power and performance overheads. Recent work has proposed micro-architectural methods to dynamically detect and recover from timing errors in processor logic. This paper has not evaluated or exploited the disparity of error rates at...

    Provided By Northwestern University

  • White Papers // Dec 2008

    Modeling and Characterizing Power Variability in Multicore Architectures

    Parameter variation due to manufacturing error will be an unavoidable consequence of technology scaling in future generations. The impact of random variation in physical factors such as gate length and interconnect spacing will have a profound impact on not only performance of chips, but also their power behavior. While circuit-level...

    Provided By Northwestern University

  • White Papers // Dec 2010

    Hardware/Software Techniques for DRAM Thermal Management

    The performance of the main memory is an important factor on overall system performance. To improve DRAM performance, designers have been increasing chip densities and the number of memory modules. However, these approaches increase power consumption and operating temperatures: temperatures in existing DRAM modules can rise to over 95?C. Another...

    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