University of Texas

Displaying 1-40 of 269 results

  • White Papers // Jan 2015

    KLOS: A High Performance Kernel-Less Operating System

    Operating systems provide services that are accessed by processes via mechanisms that involve a ring transition to transfer control to the kernel where the required function is performed. This has one significant drawback that every service call involves an overhead of a context switch where processor state is saved and...

    Provided By University of Texas

  • White Papers // Nov 2014

    Encoded Archival Description: Data Quality and Analysis

    In order to authenticate the meaning of collections and to preserve their evidentiary value, archivists create documents (finding aids) that describe the provenance and original order of the records. Metadata standards such as Encoded Archival Description (EAD) enable finding aids to be encoded, searched, and displayed online. However, recent research...

    Provided By University of Texas

  • White Papers // Jun 2013

    Graduates' Perception of Employment in SMEs and Large Enterprises

    This paper looks at non business (n = 66) and business graduates (n = 18) and compares their employment preference in Small and Medium sized Enterprises (SME) or Large Enterprises (LE). In pursuit, a questionnaire was developed measuring the perception of graduates as regards on the content of a job,...

    Provided By University of Texas

  • White Papers // Aug 2012

    Offloading in Heterogeneous Networks: Modeling, Analysis and Design Insights

    Pushing data traffic from cellular to Wi-Fi is an example of inter-Radio Access Technology (RAT) offloading. While this clearly alleviates congestion on the over-loaded cellular network, the ultimate potential of such offloading and its effect on overall system performance is not well understood. To address this, the authors develop a...

    Provided By University of Texas

  • White Papers // Jul 2012

    Frankenstein: Stitching Malware From Benign Binaries

    This paper proposes a new self-camouflaging malware propagation system, Frankenstein, that overcomes shortcomings in the current generation of metamorphic malware. Specifically, although mutants produced by current state-of-the-art metamorphic engines are diverse, they still contain many characteristic binary features that reliably distinguish them from benign software. Frankenstein forgoes the concept of...

    Provided By University of Texas

  • White Papers // Jun 2012

    New Proof Methods for Attribute-Based Encryption: Achieving Full Security Through Selective Techniques

    The authors develop a new methodology for utilizing the prior techniques to prove selective security for functional encryption systems as a direct ingredient in devising proofs of full security. This deepens the relationship between the selective and full security models and provides a path for transferring the best qualities of...

    Provided By University of Texas

  • White Papers // May 2012

    Dependency Path Patterns as the Foundation of Access Control in Provenance-Aware Systems

    A unique characteristics of provenance data is that it forms a Directed Acyclic Graph (DAG) in accordance with the underlying causality dependencies between entities (acting users, action processes and data objects) involved in transactions. Data provenance raises at least two distinct security-related issues. One is how to control access to...

    Provided By University of Texas

  • White Papers // May 2012

    Tag-Based Information Flow Analysis for Document Classification in Provenance

    A crucial aspect of certain applications such as the ones pertaining to Intelligence domain or Health-care, is to manage and protect sensitive information effectively and efficiently. In this paper, the authors propose a tagging mechanism to track the flow of sensitive or valuable information in a provenance graph and automate...

    Provided By University of Texas

  • White Papers // May 2012

    AnonymousCloud: A Data Ownership Privacy Provider Framework in Cloud Computing

    A means of reliably concealing ownership of cloud data without impeding computation over the data is presented and evaluated. This facilitates information privacy enforcement in cloud environments by withholding data ownership information from cloud nodes that compute using the data. As a result, nodes that have access to private data...

    Provided By University of Texas

  • White Papers // May 2012

    Dual Form Signatures: An Approach for Proving Security From Static Assumptions

    In this paper, the authors introduce the abstraction of Dual Form Signatures as a useful framework for proving security (existential unforgeability) from static assumptions for schemes with special structure that are used as a basis of other cryptographic protocols and applications. They describe the power of this framework by proving...

    Provided By University of Texas

  • White Papers // May 2012

    Hatman: Intra-Cloud Trust Management for Hadoop

    Data and computation integrity and security are major concerns for users of cloud computing facilities. Many production-level clouds optimistically assume that all cloud nodes are equally trustworthy when dispatching jobs; jobs are dispatched based on node load, not reputation. This increases their vulnerability to attack, since compromising even one node...

    Provided By University of Texas

  • White Papers // Apr 2012

    An Empirical Study of Supplementary Bug Fixes

    A recent study finds that errors of omission are harder for programmers to detect than errors of commission. While several change recommendation systems already exist to prevent or reduce omission errors during software development, there have been very few studies on why errors of omission occur in practice and how...

    Provided By University of Texas

  • White Papers // Apr 2012

    Towards Understanding the Fundamentals of Mobility in Cellular Networks

    Despite the central role of mobility in wireless networks, there are surprisingly few fundamental results on its properties. This paper aims to address this gap by proposing a new Random Way-Point (RWP) mobility model defined on the entire plane and applying it to analyze two key cellular network parameters: handover...

    Provided By University of Texas

  • White Papers // Apr 2012

    Vdiff: A Program Differencing Algorithm for Verilog Hardware Description Language

    During code review tasks, comparing two versions of a hardware design description using existing program differencing tools such as diff is inherently limited because these tools implicitly assume sequential execution semantics, while hardware description languages are designed to model concurrent computation. The authors designed a position-independent differencing algorithm to robustly...

    Provided By University of Texas

  • White Papers // Apr 2012

    BRACE: An Assertion Framework for Debugging Cyber-Physical Systems

    Developing Cyber-Physical Systems (CPS) is challenging because correctness depends on both logical and physical states, which are collectively difficult to observe. The developer often need to repeatedly rerun the system while observing its behavior and tweak the hardware and software until it meets minimum requirements. This process is tedious, error-prone,...

    Provided By University of Texas

  • White Papers // Apr 2012

    Extending Java for Android Programming

    Android is one of the most popular platforms for developing mobile applications. However, its framework relies on programming conventions and styles to implement framework-specific concepts like activities and intents, causing problems such as reliability, readability, understandability, and maintainability. The authors propose to extend Java to support Android framework concepts explicitly...

    Provided By University of Texas

  • White Papers // Feb 2012

    A-Serv: A Novel Architecture Providing Scalable Quality of Service

    QoS architectures define how routers process packets to ensure QoS service guarantees enforced. Existing QoS architectures such as Integrated Services (IntServ), Differentiated Services (DiffServ), and Dynamic Packet State (DPS) share one common property that the packet structure and the function of the routers are closely connected. Packets of one data...

    Provided By University of Texas

  • White Papers // Feb 2012

    Security Analysis and Enhancement for Prefix-Preserving Encryption Schemes

    Prefix-Preserving Encryption (PPE) is an important type of encryption scheme, having a wide range of applications, such as IP addresses anonymization, prefix-matching search, and rang search. There are two issues in PPE schemes, security proof and single key requirement. Existing security proofs for PPE only reduce the security of a...

    Provided By University of Texas

  • White Papers // Feb 2012

    Decoupled Dynamic Cache Segmentation

    The Least Recently Used (LRU) replacement policy performs poorly in the Last-Level Cache (LLC) because temporal locality of memory accesses is filtered by first and second level caches. The authors propose a cache segmentation technique that dynamically adapts to cache access patterns by predicting the best number of not-yet-referenced and...

    Provided By University of Texas

  • White Papers // Jan 2012

    Identifying Failure-Inducing Combinations in a Combinatorial Test Set

    A t-way combinatorial test set is designed to detect failures that are triggered by combinations involving no more than t parameters. Assume that the authors have executed a t-way test set and some tests have failed. A natural question to ask is: what combinations have caused these failures? Identifying such...

    Provided By University of Texas

  • White Papers // Jan 2012

    Optimal Surface Deployment Problem in Wireless Sensor Networks

    Sensor deployment is a fundamental issue in a wireless sensor network, which often dictates the overall network performance. Previous studies on sensor deployment mainly focused on sensor networks on 2D plane or in 3D volume. In this paper, the authors tackle the problem of optimal sensor deployment on 3 surfaces,...

    Provided By University of Texas

  • White Papers // Jan 2012

    Detecting Dangerous Queries: A New Approach for Chosen Ciphertext Security

    The authors present a new approach for creating chosen ciphertext secure encryption. The focal point of their work is a new abstraction that they call Detectable Chosen Ciphertext Security (DCCA). Intuitively, this notion is meant to capture systems that are not necessarily Chosen Ciphertext Attack (CCA) secure, but where they...

    Provided By University of Texas

  • White Papers // Jan 2012

    XML Query Routing in Structured P2P Systems

    This paper addresses the problem of data placement, indexing, and querying large XML data repositories distributed over an existing P2P service infrastructure. The authors' architecture scales gracefully to the network and data sizes, is fully distributed, fault tolerant and self-organizing, and handles complex queries efficiently, even those queries that use...

    Provided By University of Texas

  • White Papers // Jan 2012

    A Lightweight Algorithm for Causal Message Ordering in Mobile Computing Systems

    Causally ordered message delivery is a required property for several distributed applications particularly those that involve human interactions (such as teleconferencing and collaborative work). In this paper, the authors present an efficient protocol for causal ordering in mobile computing systems. This protocol requires minimal resources on mobile hosts and wireless...

    Provided By University of Texas

  • White Papers // Dec 2011

    Making Argument Systems for Outsourced Computation Practical (Sometimes)

    This paper describes the design, implementation, and evaluation of a system for performing verifiable outsourced computation. It has long been known that this problem can be solved in theory using Probabilistically Checkable Proofs (PCPs) coupled with modern cryptographic tools, and these solutions have wholly impractical performance, according to the conventional...

    Provided By University of Texas

  • White Papers // Nov 2011

    Heterogeneous Cellular Networks: From Theory to Practice

    The proliferation of internet-connected mobile devices will continue to drive growth in data traffic in an exponential fashion, forcing network operators to dramatically increase the capacity of their networks. To do this cost-effectively, a paradigm shift in cellular network infrastructure deployment is occurring away from traditional (expensive) high-power tower-mounted base...

    Provided By University of Texas

  • White Papers // Nov 2011

    Efficient Similarity Search Over Encrypted Data

    In recent years, due to the appealing features of cloud computing, large amount of data have been stored in the cloud. Although cloud based services offer many advantages, privacy and security of the sensitive data is a big concern. To mitigate the concerns, it is desirable to outsource sensitive data...

    Provided By University of Texas

  • White Papers // Nov 2011

    Leakage - Delay Tradeoff in Wide-Bit Nanoscale CMOS Adders

    The scaling of nanometer technology has had a major impact on the power dissipation of CMOS circuits. As transistor size decreases it has become apparent that leakage power is becoming a dominant fighting force against future technology. In this paper, the importance of static power consumption on the design of...

    Provided By University of Texas

  • White Papers // Nov 2011

    Insider Threat Detection Using Stream Mining and Graph Mining

    Evidence of malicious insider activity is often buried within large data streams, such as system logs accumulated over months or years. Ensemble-based stream mining leverages multiple classification models to achieve highly accurate anomaly detection in such streams even when the stream is unbounded, evolving, and unlabeled. This makes the approach...

    Provided By University of Texas

  • White Papers // Nov 2011

    Functional Verification of Class Invariants in CleanJava

    In Cleanroom-style functional program verification, a program is viewed as a mathematical function from one program state to another, and the program is verified by comparing two functions, the implemented and the expected behaviors of a program. The technique requires a minimal mathematical background and supports forward reasoning, but it...

    Provided By University of Texas

  • White Papers // Nov 2011

    Program Interferometry

    Modern microprocessors have many micro-architectural features. Quantifying the performance impact of one feature such as dynamic branch prediction can be difficult. On one hand, a timing simulator can predict the difference in performance given two different implementations of the technique, but simulators can be quite inaccurate. On the other hand,...

    Provided By University of Texas

  • White Papers // Oct 2011

    An Optimized Scaled Neural Branch Predictor

    Conditional branch prediction remains one of the most important enabling technologies for high-performance microprocessors. A small improvement in accuracy can result in a large improvement in performance as well as a significant reduction in energy wasted on wrong-path instructions. Neural-based branch predictors have been among the most accurate in the...

    Provided By University of Texas

  • White Papers // Sep 2011

    Transmission Capacity of Ad-Hoc Networks With Multiple Antennas Using Transmit Stream Adaptation and Interference Cancelation

    The transmission capacity of an ad-hoc network is the maximum density of active transmitters per unit area, given an outage constraint at each receiver for a fixed rate of transmission. Assuming that the transmitter locations are distributed as a Poisson point process, this paper derives upper and lower bounds on...

    Provided By University of Texas

  • White Papers // Sep 2011

    Supervised Learning for Insider Threat Detection Using Stream Mining

    Insider threat detection requires the identification of rare anomalies in contexts where evolving behaviors tend to mask such anomalies. This paper proposes and tests an ensemble-based stream mining algorithm based on supervised learning that addresses this challenge by maintaining an evolving collection of multiple models to classify dynamic data streams...

    Provided By University of Texas

  • White Papers // Sep 2011

    Toward the Verification of a Simple Hypervisor

    Virtualization promises significant benefits in security, efficiency, dependability, and cost. Achieving these benefits depends upon the reliability of the underlying virtual machine monitors (hypervisors). This paper describes an ongoing project to develop and verify MinVisor, a simple but functional Type-I x86 hypervisor, proving protection properties at the assembly level using...

    Provided By University of Texas

  • White Papers // Sep 2011

    AOVis: A Model-Driven Multiple-Graph Approach to Program Fact Extraction for AspectJ/Java Source Code

    AspectJ reverse engineering and visualization remains a challenge at the architectural and design levels, with fewer tools available for reverse engineers compared to other languages such as Java. Prior work on AspectJ modeling focused on forward engineering or detailed-design reverse engineering, or required special instrumentation to identify cross-cutting relationships. Effective...

    Provided By University of Texas

  • White Papers // Sep 2011

    Building Malware Infection Trees

    "Dynamic analysis of malware is an ever evolving and challenging task. A Malware infection Tree (MiT) can assist in analysis by identifying processes and files related to a specific malware sample. In this paper, the authors propose an abstract approach to building a comprehensive MiT based on rules describing execution...

    Provided By University of Texas

  • White Papers // Aug 2011

    Remote Batch Invocation for SQL Databases

    Batch services are a new approach to distributed computation in which clients send batches of operations for execution on a server and receive hierarchical results sets in response. In this paper, the authors show how batch services provide a simple and powerful interface to relational databases, with support for arbitrary...

    Provided By University of Texas

  • White Papers // Aug 2011

    The CleanJava Language for Functional Program Verification

    Unlike Hoare-style program verification, functional program verification supports forward reasoning by viewing a program as a mathematical function from one program state to another and proving its correctness by essentially comparing two mathematical functions, the function computed by the program and its specification. Since it requires a minimal mathematical background...

    Provided By University of Texas

  • White Papers // Aug 2011

    A Tutorial on Functional Program Verification

    This paper gives a quick tutorial introduction to functional program verification. In functional program verification, a program is viewed as a mathematical function from one program state to another, and proving its correctness is essentially comparing two mathematical functions, the function computed by the program and the specification of the...

    Provided By University of Texas

  • White Papers // Nov 2014

    Encoded Archival Description: Data Quality and Analysis

    In order to authenticate the meaning of collections and to preserve their evidentiary value, archivists create documents (finding aids) that describe the provenance and original order of the records. Metadata standards such as Encoded Archival Description (EAD) enable finding aids to be encoded, searched, and displayed online. However, recent research...

    Provided By University of Texas

  • White Papers // Nov 2008

    WebOS: Operating System Services for Wide Area Applications

    In this paper, the authors demonstrate the power of providing a common set of operating system services to wide-area applications, including mechanisms for naming, persistent storage, remote process execution, resource management, authentication, and security. On a single machine, application developers can rely on the local operating system to provide these...

    Provided By University of Texas

  • White Papers // Jan 2015

    KLOS: A High Performance Kernel-Less Operating System

    Operating systems provide services that are accessed by processes via mechanisms that involve a ring transition to transfer control to the kernel where the required function is performed. This has one significant drawback that every service call involves an overhead of a context switch where processor state is saved and...

    Provided By University of Texas

  • White Papers // May 2011

    Architecture and Abstractions for Environment and Traffic Aware System-Level Coordination of Wireless Networks

    This paper presents a system level approach to interference management in an infrastructure based wireless network with full frequency reuse. The key idea is to use loose base station coordination that is tailored to the spatial load distribution and the propagation environment to exploit the diversity in a user population's...

    Provided By University of Texas

  • White Papers // May 2011

    Practical Adaptive User Association Policies for Wireless Systems With Dynamic Interference

    The authors study the impact of user association policies on flow-level performance in interference-limited wireless networks. Most research in this area has used static interference models (neighboring base stations are always active) and resorted to intuitive objectives such as load balancing. In this paper, they show that this can be...

    Provided By University of Texas

  • White Papers // Nov 2009

    Opportunistic Routing for Interactive Traffic in Wireless Networks

    To take advantage of the broadcast nature of wireless communication, a number of opportunistic routing techniques have recently been proposed. In order to manage the extra signaling overhead associated with operation of the opportunistic routing, these schemes work in terms of 'Batches' consisting of multiple packets. While these opportunistic techniques...

    Provided By University of Texas

  • White Papers // May 2010

    Query Processing in Connectivity-Challenged Environments

    This paper presents a discussion of issues that need to be addressed for processing relational queries in distributed environments where the connectivity is unstable and is changing continuously. Query processing over data across nodes that are collecting information is an example of such an environment. Traditional distributed query processing techniques...

    Provided By University of Texas

  • White Papers // Mar 2011

    Fuzzy Optimization for Mobile Ad Hoc Networks: A Bottom-up Cross-Layer Approach

    In this paper, the authors introduce a new method for cross-layer design in mobile ad hoc networks. They use Fuzzy Logic System (FLS) to coordinate physical layer, data-link layer and application layer for cross-layer design. Ground speed, average delay and packets successful transmission ratio are selected as antecedents for the...

    Provided By University of Texas

  • White Papers // Mar 2010

    Lightweight Checkpoint Mechanism and Modeling in GPGPU Environment

    While High Performance Computing (HPC) systems continue to scale in volume of computing elements and overall computing powers, the performance/cost benefit of these systems is subject to their abilities to provide high reliability, availability, and transparency in utilizing the underlying computing resources. This is evidenced by a recent announcement from...

    Provided By University of Texas

  • White Papers // Jun 2011

    Fundamentals of Inter-Cell Overhead Signaling in Heterogeneous Cellular Networks

    Heterogeneous base stations (e.g. picocells, microcells, femtocells and distributed antennas) will become increasingly essential for cellular network capacity and coverage. Up until now, little basic research has been done on the fundamentals of managing so many infrastructures - much of it unplanned - together with the carefully planned macrocellular network....

    Provided By University of Texas

  • White Papers // Jul 2011

    Heterogeneous Cellular Networks With Flexible Cell Association: A Comprehensive Downlink SINR Analysis

    In this paper, the authors develop a tractable framework for SINR analysis in downlink Heterogeneous Cellular Networks (HCNs) with flexible cell association policies. The HCN is modeled as a multi-tier cellular network where each tier's Base Stations (BSs) are randomly located and have a particular transmit power, path loss exponent,...

    Provided By University of Texas

  • White Papers // Jul 2011

    Distributed SIR-Aware Scheduling in Large-Scale Wireless Networks

    Opportunistic scheduling and routing can in principle greatly increase the throughput of decentralized wireless networks, but to be practical such algorithms must do so with small amounts of timely side information. In this paper, the authors propose three related techniques for low-overhead Distributed Opportunistic Scheduling (DOS) and precisely determine their...

    Provided By University of Texas

  • White Papers // May 2011

    Broadcast Channels With Delayed Finite-Rate Feedback: Predict or Observe?

    Most multiuser pre-coding techniques require accurate Transmitter Channel State Information (CSIT) to maintain orthogonality between the users. Such techniques have proven quite fragile in time-varying channels because the CSIT is inherently imperfect due to estimation and feedback delay, as well quantization noise. An alternative approach recently proposed by Maddah-Ali and...

    Provided By University of Texas

  • White Papers // May 2011

    Characterizing Decentralized Wireless Networks With Temporal Correlation in the Low Outage Regime

    Communication in decentralized wireless networks is limited by interference. Because transmissions typically last for more than a single contention time slot, interference often exhibits strong statistical dependence over time that results in temporally correlated communication performance. The temporal dependence in interference increases as user mobility decreases and/or the total transmission...

    Provided By University of Texas

  • White Papers // Mar 2010

    An Overview of the Transmission Capacity of Wireless Networks

    This paper surveys and unifies a number of recent contributions that have collectively developed a metric for decentralized wireless network analysis known as transmission capacity. Although it is notoriously difficult to derive general end-to-end capacity results for multi-terminal or ad hoc networks, the Transmission Capacity (TC) framework allows for quantification...

    Provided By University of Texas

  • White Papers // Mar 2010

    Multi-Mode Transmission for the MIMO Broadcast Channel With Imperfect Channel State Information

    This paper proposes an adaptive multi-mode transmission strategy to improve the spectral efficiency achieved in the Multiple-Input Multiple-Output (MIMO) broadcast channel with delayed and quantized channel state information. The adaptive strategy adjusts the number of active users, denoted as the transmission mode, to balance transmit array gain, spatial division multiplexing...

    Provided By University of Texas

  • White Papers // Mar 2011

    Ergodic Transmission Capacity of Wireless Ad Hoc Networks With Interference Management

    Most work on wireless network throughput ignores the temporal correlation inherent to wireless channels because it degrades tractability. To better model and quantify the temporal variations of wireless network throughput, this paper introduces a metric termed Ergodic Transmission Capacity (ETC), which includes spatial and temporal ergodicity. All transmitters in the...

    Provided By University of Texas

  • White Papers // Nov 2010

    Cooperative Spectral Covariance Sensing Under Correlated Shadowing

    This paper investigates the theoretical limits of white space sensing in a Cognitive Radio (CR) network limited by channel correlation. In a log-normal shadowing channel, the received signal power is correlated based on the distance between the sensors and this makes sensing the presence of a signal difficult, even with...

    Provided By University of Texas

  • White Papers // Apr 2010

    An Upper Bound on Multi-Hop Transmission Capacity With Dynamic Multipath Routing

    This paper develops upper bounds on the end-to-end transmission capacity of multi-hop wireless networks. Potential source-destination paths are dynamically selected from a pool of randomly located relays, from which a closed-form lower bound on the outage probability is derived in terms of the expected number of potential paths. This is...

    Provided By University of Texas

  • White Papers // Jul 2011

    Capacity Bounds on Multiuser MIMO Transmission in Random Wireless Networks

    The authors consider a large wireless ad hoc network in which each multi-antenna transmitting node sends multiple independent streams to different receivers in a Poisson field of interferers. They provide exact expressions and simplified approximations on the outage probability, contention density, and transmission capacity for dirty paper coding with perfect...

    Provided By University of Texas

  • White Papers // Mar 2011

    Outage Probability for Heterogeneous Cellular Networks With Biased Cell Association

    In this paper, the authors develop a tractable framework for SINR analysis in downlink Heterogeneous Cellular Networks (HCNs) with flexible cell association policies. The HCN is modeled as a multi-tier cellular network where each tier's BSs are randomly located and have a unique transmit power, path loss exponent, spatial density,...

    Provided By University of Texas

  • White Papers // Jun 2011

    Coverage in Two-Tier Cellular Networks With Fractional Frequency Reuse

    Fractional Frequency Reuse (FFR) is an interference management technique well-suited to OFDMA-based cellular networks wherein the cells are partitioned into spatial regions with different frequency reuse factors. These techniques are of further relevance when considered in the context of heterogeneous networks whose performance is often limited by intercell and inter-tier...

    Provided By University of Texas

  • White Papers // Feb 2011

    A New Model for Coverage With Fractional Frequency Reuse in OFDMA Cellular Networks

    Fractional Frequency Reuse (FFR) is an interference management technique well-suited to OFDMA-based cellular networks wherein the cells are partitioned into spatial regions with different frequency reuse factors. To date, FFR techniques have been typically been evaluated through system-level simulations using a hexagonal grid for the base station locations. This paper...

    Provided By University of Texas

  • White Papers // Jul 2011

    Multiuser Zero-Forcing Beamforming With Limited Feedback in Wireless Ad Hoc Networks

    The effect of limited feedback on point-to-multipoint communication is investigated in multi-antennas wireless ad hoc networks. The authors consider zero-forcing beamforming with quantized channel direction information and derive new closed-form expressions for the outage probability, throughput, transmission capacity, and average user rate. Expressions for the performance degradation due to finite...

    Provided By University of Texas

  • White Papers // Jul 2011

    Downlink Femtocell Networks: Open or Closed?

    A fundamental choice in femtocell deployments is the set of users which are allowed to access each femtocell. Closed access restricts the set to specifically registered users, while open access allows any mobile subscriber to use any femtocell. The main results of the paper are lemmas which provide expressions for...

    Provided By University of Texas

  • White Papers // Mar 2011

    A New Way of Computing Rate in Cellular Networks

    It is common practice to model the Base Station (BS) locations in a cellular system by a grid, such as a hexagonal or square lattice. This model is usually analytically intractable as well as quite idealized. Therefore, system designers resort to complex simulations to evaluate network performance. In this paper,...

    Provided By University of Texas

  • White Papers // Sep 2010

    On the Accuracy of the Wyner Model in Downlink Cellular Networks

    Compared to real cellular systems where users are spatially distributed and interference levels vary by several orders of magnitude over a cell, in the Wyner model user locations are fixed and the interference intensity is characterized by a single fixed parameter. Although it is a fairly extreme simplification, the Wyner...

    Provided By University of Texas

  • White Papers // Sep 2010

    The Effect of Interference Cancellation on Spectrum-Sharing Transmission Capacity

    The efficiency of spectrum sharing can be improved by interference suppression and/or cancellation. This paper analyzes the performance of spectrum sharing networks with Interference Cancellation (IC) based on the Spectrum-sharing Transmission Capacity (S-TC), defined as the number of successful transmissions per unit area while guaranteeing all target outage probabilities of...

    Provided By University of Texas

  • White Papers // Feb 2011

    Ergodic Spatial Throughput of Wireless Ad Hoc Networks With Markovian Fading Channels

    Most work on wireless network throughput ignores the temporal correlation inherent to wireless channels, due to trouble with tractability. In order to better capture the temporal variations of wireless network throughput, this paper introduces the metric of Ergodic Spatial Throughput (EST), which includes spatial and temporal ergodicity. All transmitters in...

    Provided By University of Texas

  • White Papers // Jun 2011

    A Tractable Framework for Coverage and Outage in Heterogeneous Cellular Networks

    The authors develop a tractable, flexible, and accurate model for downlink heterogeneous cellular networks. It consists of K tiers of randomly-located Base Stations (BSs), where each tier may differ in terms of the average transmit power, the supported data rate and the BS density. This allows elements spanning traditional, micro,...

    Provided By University of Texas

  • White Papers // Mar 2010

    A Graphical Model Approach to Downlink Cooperative MIMO Systems

    The authors propose a new method for computing transmit beamforming vectors for downlink multi-cell Multiple-Input Multiple-Output (MIMO) networks. The key novelty of the work is the application of graphical model theory to the intercell interference problem. An index restriction beamforming strategy is adopted to mitigate intercell interference, and is implemented...

    Provided By University of Texas

  • White Papers // Jul 2010

    Femtocell Access Control in the TDMA/OFDMA Uplink

    This paper investigates open vs. closed access in the uplink of femtocell networks, for the particular case of orthogonal multiple access protocols like TDMA or OFDMA. Open access reduces near-far interference and provides an inexpensive way to expand the capacity of the operator's network. Additionally, with a cap on the...

    Provided By University of Texas

  • White Papers // Aug 2010

    CDMA Uplink Capacity in Both Open and Closed Access Two-Tier Femtocell Networks

    Femtocells are assuming an increasingly important role in cellular coverage. Femtocells can be configured to be either open access or closed access. Seemingly, the network operator would prefer an open access deployment since this provides an inexpensive way to expand their network capabilities, whereas the femtocell owner would prefer closed...

    Provided By University of Texas

  • White Papers // Sep 2010

    Comparison of Fractional Frequency Reuse Approaches in the OFDMA Cellular Downlink

    Fractional Frequency Reuse (FFR) is an interference coordination technique well-suited to OFDMA based wireless networks wherein cells are partitioned into spatial regions with different frequency reuse factors. This paper focuses on evaluating the two main types of FFR deployments: strict FFR and Soft Frequency Reuse (SFR). Relevant metrics are discussed,...

    Provided By University of Texas

  • White Papers // Mar 2010

    Analog Equalization for Low Power 60 GHz Receivers in Realistic Multipath Channels

    Multi-gigabit per second wireless network devices are emerging for Personal Area Networks (PAN) in the 60 GHz band. Such devices are typically power hungry, largely due to the requisite high speed Analog to Digital Converters (ADCs) that can consume hundreds of milliwatts of power. This paper studies the use of...

    Provided By University of Texas

  • White Papers // Jan 2011

    Correlation of Link Outages in Low-Mobility Spatial Wireless Networks

    In this paper, the authors consider a network where the nodes' locations are modeled by a realization of a Poisson point process and remain fixed or change very slowly over time. Most of the literature focuses on the spatial average of the link outage probabilities. But each link in the...

    Provided By University of Texas

  • White Papers // Jan 2010

    A Simple SINR Characterization for Linear Interference Alignment Over Uncertain MIMO Channels

    This paper provides a simple closed-form SINR expression for interference alignment over MIMO channels with channel uncertainty. Assuming linear processing (specifically, zero-forcing) at the transmitters and receivers and a complex Gaussian interference channel, the authors show that random matrix theory can be successfully applied to find the SINR distribution of...

    Provided By University of Texas

  • White Papers // Sep 2010

    A New Tractable Model for Cellular Coverage

    Cellular networks are usually modeled by placing the base stations according to a regular geometry such as a grid, with the mobile users scattered around the network either as a Poisson point process (i.e. uniform distribution) or deterministically. These models have been used extensively for cellular design and analysis but...

    Provided By University of Texas

  • White Papers // Jun 2011

    Average Rate Achievable in K-Tier Downlink Heterogeneous Cellular Networks

    Cellular networks are becoming increasingly heterogeneous due to the co-deployment of many disparate infrastructure elements, including micro, pico and femtocells, and distributed antennas. This introduces new challenges in the modeling, analysis, and design of these networks. While grid-based models have been quite popular in modeling classical macrocell networks, they are...

    Provided By University of Texas

  • White Papers // Mar 2011

    Cooperative Spectral Covariance Sensing: Properties and Analysis

    This paper investigates the theoretical limits of white space sensing in a Cognitive Radio (CR) network limited by channel correlation. In a log-normal shadowing channel, the received signal power is correlated based on the distance among the sensors and this makes sensing the presence of a signal difficult, even with...

    Provided By University of Texas