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Articles 301 - 330 of 683
Full-Text Articles in Computer Engineering
Scheduling Algorithms For Cioq Switches, Prashanth Pappu, Jonathan S. Turner
Scheduling Algorithms For Cioq Switches, Prashanth Pappu, Jonathan S. Turner
All Computer Science and Engineering Research
Most scalable switches are required to buffer packets at both their inputs and outputs to overcome the slow memory speeds of packet queues. This thesis deals with the design of scheduling algorithms for such Combined Input and Output Queued (CIOQ) switches. For crossbar based CIOQ switches, we demonstrate the underperformance of commercially used scheduling algorithms under overload traffic conditions using targeted stress tests and present ideas to develop robust, stress resistant versions of these algorithms that are still simple enough to be implemented in high speed switches. To regulate the flow of traffic in buffered, multi-stage switches, we introduce a …
Discovering Transcriptional Regulatory Rules From Gene Expression And Tf-Dna Binding Data By Decision Tree Learning, Jianhua Ruan, Weixiong Zhang
Discovering Transcriptional Regulatory Rules From Gene Expression And Tf-Dna Binding Data By Decision Tree Learning, Jianhua Ruan, Weixiong Zhang
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Background: One of the most promising but challenging task in the post-genomic era is to reconstruct the transcriptional regulatory networks. The goal is to reveal, for each gene that responds to a certain biological event, which transcription factors affect its transcription, and how several transcription factors coordinate to accomplish specific regulations. Results: Here we propose a supervised machine learning approach to address these questions. We build decision trees to associate the expression level of a gene with the transcription factor binding data of its promoter. From the decision trees, we extract regulatory rules that specify how the binding of a …
A Spatiotemporal Query Service For Mobile Users In Sensor Networks, Chenyang Lu, Guoliang Xing, Octav Chipara, Chien-Liang Fok, Sangeeta Bhattacharya
A Spatiotemporal Query Service For Mobile Users In Sensor Networks, Chenyang Lu, Guoliang Xing, Octav Chipara, Chien-Liang Fok, Sangeeta Bhattacharya
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This paper presents MobiQuery, a spatiotemporal query service that allows mobile users to periodically gather information from their surrounding areas through a wireless sensor network. A key advantage of MobiQuery lies in its capability to meet stringent spatiotemporal performance constraints crucial to many applications. These constraints include query latency, data freshness and fidelity, and changing query areas due to user mobility. A novel just-in-time prefetching algorithm enables MobiQuery to main-tain robust spatiotemporal guarantees even when nodes op-erate under extremely low duty cycles. Furthermore, it sig-nificantly reduces the storage cost and network contention caused by continuous queries from mobile users. We …
Composing Systemic Aspects Into Component-Oriented Doc Middleware, Nanbor Wang
Composing Systemic Aspects Into Component-Oriented Doc Middleware, Nanbor Wang
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The advent and maturation of component-based middleware frameworks have sim-plified the development of large-scale distributed applications by separating system devel-opment and configuration concerns into different aspects that can be specified and com-posed at various stages of the application development lifecycle. Conventional component middleware technologies, such as J2EE [73] and .NET [34], were designed to meet the quality of service (QoS) requirements of enterprise applications, which focus largely on scalability and reliability. Therefore, conventional component middleware specifications and implementations are not well suited for distributed real-time and embedded (DRE) ap-plications with more stringent QoS requirements, such as low latency/jitter, timeliness, and …
Fusion And Perspective Correction Of Multiple Networked Video Sensors, Christopher E. Neely, John W. Lookwood
Fusion And Perspective Correction Of Multiple Networked Video Sensors, Christopher E. Neely, John W. Lookwood
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A network of adaptive processing elements has been developed that transforms and fuses video captured from multiple sensors. Unlike systems that rely on end-systems to process data, this system distributes the computation throughout the network in order to reduce overall network bandwidth. The network architecture is scalable because it uses a hierarchy of processing engines to perform signal processing. Nodes within the network can be dynamically reprogrammed in order to compose video from multiple sources, digitally transform camera perspectives, and adapt the video format to meet the needs of specific applications. A prototype has been developed using reconfigurable hardware that …
Run-Time Modification Of The Class Hierachy In A Live Java Development Environment, Joel R. Brandt
Run-Time Modification Of The Class Hierachy In A Live Java Development Environment, Joel R. Brandt
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Class hierarchy design is central to object-oriented software development. How-ever, it is sometimes difficult for developers to anticipate all the implications of a design until implementation is underway. To support experimentation with different designs, we extend prior work on live development environments to allow run-time modification of the class hierarchy. The result is a more fluid object-oriented development process, in which immediate feedback from the executing program can be used to guide hierarchy design. This thesis presents a framework and developer support for run-time modification of class inheritance relations in JPie, a live visual programming environment for Java. Most notably, …
Automatic Determination Of Factors For Real-Time Garbage Collection, Tobias Mann, Ron K. Cytron
Automatic Determination Of Factors For Real-Time Garbage Collection, Tobias Mann, Ron K. Cytron
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Several approaches to hard, real-time garbage collection have been recently proposed. All of these approaches require knowing certain statistical properties about a program's execution, such as the maximum extent of live storage, the rate of storage allocation, and the number of non-null object references. While these new approaches offer the possibility of guaranteed, reasonably bounded behavior for garbage collection, the determination of the required information may not be straight forward for the application programmer. In this paper we present evidence suggesting that the necessary factors can vary widely over the program's execution, indicating that an automatic, phased approach may be …
Static Analysis Of Memory-Accessing Gestures In Java, Christopher R. Hill
Static Analysis Of Memory-Accessing Gestures In Java, Christopher R. Hill
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We propose the notion of Java-program gestures that are composed of a series of memory-accessing instructions. By finding patterns in gestures whose execution can be atomic, we can load them in an intelligent memory controller. This process can improve performance of the Java Virtual Machine, decrease code footprint, and reduce power consumption in hardware. In this thesis we formally define a language of gestures and introduce a method of detecting them statically at compile-time. We introduce a simple heuristic for reducing the number of gestures that must be loaded into the memory controller and show that finding the minimum number …
Design And Implementation Of A String Matching System For Network Intrusion Detection Using Fpga-Based Bloom Filters, Sarang Dharmapurikar, Michael Attig, John Lockwood
Design And Implementation Of A String Matching System For Network Intrusion Detection Using Fpga-Based Bloom Filters, Sarang Dharmapurikar, Michael Attig, John Lockwood
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Modern Network Intrusion Detection Systems (NIDS) inspect the network packet payload to check if it conforms to the security policies of the given network. This process, of-ten referred to as deep packet inspection, involves detection of predefined signature strings or keywords starting at an arbitrary location in the payload. String matching is a computationally intensive task and can become a potential bottleneck without high-speed processing. Since the conventional software-implemented string matching algorithms have not kept pace with the increasing network speeds, special purpose hardware solutions have been introduced. In this paper we show how Bloom filters can be used effectively …
Service Oriented Computing Imperatives In Ad Hoc Wireless Settings, Rohan Sen, Radu Handorean, Gruia-Catalin Roman, Christopher Gill
Service Oriented Computing Imperatives In Ad Hoc Wireless Settings, Rohan Sen, Radu Handorean, Gruia-Catalin Roman, Christopher Gill
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Service oriented computing is a new paradigm that is gaining popularity in dis-tributed computing environments due to its emphasis on highly specialized, modular and platform-agnostic code facilitating interoperability of systems. It borrows concepts from more mature paradigms such as object-oriented and component computing. This results in a progression from object-oriented computing to component computing and finally to service oriented computing, a new paradigm for designing and delivering software. Just as an object encapsulates state and behavior at a fine level of granularity, a service offers similar encapsulation at a larger scale. This evolution raises the level of abstraction at which …
Camrit: Control-Based Adaptive Middleware For Real-Time Image Transmission, Xiaorui Wang, Huang-Ming Huang, Venkita Subramonian, Chenyang Lu, Christopher Gill
Camrit: Control-Based Adaptive Middleware For Real-Time Image Transmission, Xiaorui Wang, Huang-Ming Huang, Venkita Subramonian, Chenyang Lu, Christopher Gill
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Real-time image transmission is crucial to an emerging class of distributed embedded systems operating in open network environments. Examples include avionics mission re-planning over Link-16, security systems based on wireless camera networks, and online collaboration using camera phones. Meeting image transmission deadlines is a key chal-lenge in such systems due to unpredictable network condi-tions. In this paper, we present the design, modeling, and analysis of CAMRIT, a Control-based Adaptive Middleware framework for Real-time Image Transmission in distributed real-time embedded systems. CAMRIT features a distributed feedback control loop that meets image transmission dead-lines by dynamically adjusting the quality of image tiles. …
An Iterative Beam Search Algorithm For Degenerate Primer Selection, Richard Souvenir
An Iterative Beam Search Algorithm For Degenerate Primer Selection, Richard Souvenir
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Single Nucleotide Polymorphism (SNP) Genotyping is an important molecular genetics process in the early stages of producing results that will be useful in the medical field. Due to inherent complexities in DNA manipulation and analysis, many different methods have been proposed for a standard assay. One of the proposed techniques for performing SNP Genotyping requires amplifying regions of DNA surrounding a large number of SNP loci. In order to automate a portion of this particular method, it is necessary to select a set of primers for the experiment. Selecting these primers can be formulated as the Multiple Degenerate Primer Design …
Resource Configuration And Network Design In Extensible Networks, Sumi Y. Choi
Resource Configuration And Network Design In Extensible Networks, Sumi Y. Choi
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The goal of packet-switched networks has conventionally been delivering data to users. This concept is changing rapidly as current technologies make it possible to build network processing engines that apply intermediary services to data traffic. This trend introduces an extensive range of ways to develop and operate applications by allowing processing services customized for applications' needs at intermediate network users, as it can relieve individuals from the need to acquire, install, and maintain software in end systems to perform required functions. As such network services become more widely used, it will become increasingly important for service providers to have effective …
Efficient Customizable Middleware, Ravi Pratap Maddimsetty
Efficient Customizable Middleware, Ravi Pratap Maddimsetty
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The rather large feature set of current Distributed Object Computing (DOC) middleware can be a liability for certain applications which have a need for only a certain subset of these features but have to suffer performance degradation and code bloat due to all the present features. To address this concern, a unique approach to building fully customizable middleware was undertaken in FACET, a CORBA event channel written using AspectJ. FACET consists of a small, essential core that represents the basic structure and functionality of an event channel into which additional features are woven using aspects so that the resulting event …
Hardware-Based Dynamic Storage Management For High-Performance And Real-Time Systems, Victor H. Lai
Hardware-Based Dynamic Storage Management For High-Performance And Real-Time Systems, Victor H. Lai
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Most modern application programs depend on dynamic storage management to handle allocation and deallocation of memory. Unfortunately conventional software-based storage managers are relatively low performance due to the latency associated with accessing DRAM memory. Consequently, developers of programs with very specialized memory requirements, such a real-time systems, often choose to manage memory manually at the application-code level. This practice can greatly increase performance but it can also significantly complicate the development process. In this thesis we present the design, VHDL implementation and performance evaluation of hardware-based storage manager called the Optimized Hardware Estranged Buddy System (OHEBS). The OHEBS implements four …
Storage Coalescing, Delvin C. Defoe
Storage Coalescing, Delvin C. Defoe
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Typically, when a program executes, it creates objects dynamically and requests storage for its objects from the underlying storage allocator. The patterns of such requests can potentially lead to internal fragmentation as well as external fragmentation. Internal fragmentation occurs when the storage allocator allocates a contiguous block of storage to a program, but the program uses only a fraction of that block to satisfy a request. The unused portion of that block is wasted since the allocator cannot use it to satisfy a subsequent allocation request. External fragmentation, on the other hand, concerns chunks of memory that reside between allocated …
Secure Remote Control And Configuration Of Fpx Platform In Gigabit Ethernet Environment, Haoyu Song
Secure Remote Control And Configuration Of Fpx Platform In Gigabit Ethernet Environment, Haoyu Song
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Because of its flexibility and high performance, reconfigurable logic functions implemented on the Field-programmable Port Extender (FPX ) are well suited for implementing network processing such as packet classification, filtering and intrusion detection functions. This project focuses on two key aspects of the FPX system. One is providing a Gigabit Ethernet interface by designing logic for a FPGA which is located on a line card. Address Resolution Protocol (ARP) packets are handled in hardware and Ethernet frames are processed and transformed into cells suitable for standard FPX application. The other effort is to provide a secure channel to enable remote …
A Generative Programming Framework For Adaptive Middleware, Venkita Subramonian, Christopher Gill
A Generative Programming Framework For Adaptive Middleware, Venkita Subramonian, Christopher Gill
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Historically, many distributed real-time and embedded (DRE) systems were developed manually from scratch, leading to stove-piped solutions that while correct in both functional and QoS properties were very expensive to develop and difficult to maintain and extend. First-generation middleware technologies such as CORBA 2.x [1], XML [2], and SOAP [3], served to shield application developers from low-level platform details, thus raising the level of abstraction at which distributed systems are developed and supporting reuse of infrastructure to amortize development costs over the lifetime of a system. However, interdependencies between services and object interfaces resulting from these programming models significantly limited …
Compressed Data Structures For Recursive Flow Classification, Edward W. Spitznagel
Compressed Data Structures For Recursive Flow Classification, Edward W. Spitznagel
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High-speed packet classification is crucial to the implementation of several advanced network services and protocols; many QoS implementations, active networking platforms, and security devices (such as firewalls and intrusion-detection systems) require it. But performing classification on multiple fields, at the speed of modern networks, is known to be a difficult problem. The Recursive Flow Classification (RFC) algorithm described by Gupta and McKeown performs classification very quickly, but can require excessive storage when using thousands of rules. This paper studies a compressed representation for the tables used in RFC, trading some memory accesses for space. The compression’s efficiency can be improved …
A Performance-Driven Framework For Customizing Csp Middleware Support, Guoliang Xing
A Performance-Driven Framework For Customizing Csp Middleware Support, Guoliang Xing
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A Distributed Constraint Satisfaction Problem (DCSP) aims to find consistent assignments of values to a set of variables distributed on multiple nodes. Despite its simple definition, DCSPs can model a broad variety of traditional artificial intelligence problems. Furthermore, many problems found in emerging sensor-actuator networks can be formalized to DCSPs. However, due to the platform limitations of networked embedded systems such as sensor-actuators networks, building real-world applications for solving DCSPs not only requires the improved DCSP algorithms but also novel system approaches. This thesis first develops a performance-driven middleware framework for solving DCSP problems. Then the prototype system built with …
Specialized Hardware Support For Dynamic Storage Allocation, Steven M. Donahue
Specialized Hardware Support For Dynamic Storage Allocation, Steven M. Donahue
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With the advent of operating systems and programming languages that can evaluate and guarantee real-time specifications, applications with real-time requirements can be authored in higher-level languages. For example, a version of Java suitable for real-time (RTSJ) has recently reached the status of a reference implementation, and it is likely that other implementations will follow. Analysis to show the feasibility of a given set of tasks must take into account their worst-case execution time, including any storage allocation or deallocation associated with those tasks. In this thesis, we present a hardware-based solution to the problem of storage allocation and (explicit) deallocation …
Using Contaminated Garbage Collection And Reference Counting Garbage Collection To Provide Automatic Storage Reclamation For Real-Time Systems, Matthew P. Hampton
Using Contaminated Garbage Collection And Reference Counting Garbage Collection To Provide Automatic Storage Reclamation For Real-Time Systems, Matthew P. Hampton
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Language support of dynamic storage management simplifies the application programming task immensely. As a result, dynamic storage allocation and garbage collection have become common in general purpose computing. Garbage collection research has led to the development of algorithms for locating program memory that is no longer in use and returning the unused memory to the run-time system for late use by the program. While many programming languages have adopted automatic memory reclamation features, this has not been the trend in Real-Time systems. Many garbage collection methods involve some form of marking the objects in memory. This marking requires time proportional …
Hashtables For Real-Time And Embedded Systems, Anand Krishnan
Hashtables For Real-Time And Embedded Systems, Anand Krishnan
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Real-time are beginning to appear in advanced, high-level programming languages such as Java. When complemented by a real-time operating system, the Real-Time Specification for Java (RTSJ) offers strong execution constraints for applications developed in Java. While the RTSJ make the basic services of Java such as storage and thread management ready for many real-time applications, the collection objects, and the rest of the application run-time library, cannot be used by RTSJ applications until their run-time properties are examined and modified as necessary to make them suitable for use by real-time applications. In this work, we examine the Hashtable collection facility …
Dynamic Assignment Of Scoped Memory Regions In The Translation Of Java To Real-Time Java, Morgan G. Deters
Dynamic Assignment Of Scoped Memory Regions In The Translation Of Java To Real-Time Java, Morgan G. Deters
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Advances in middleware, operating systems, and popular, general-purpose languages have brought the ideal of reasonably-bound execution time closer to developers who need such assurances for real-time and embedded systems applications. Extensions to the Java libraries and virtual machine have been proposed in a real-time Java standard, which provides for specification of release times, execution costs, and deadlines for a restricted class of threads. To use such features, the programmer is required to use unwieldy code constructs to create region-like areas of storage, associate them with execution scopes, and allocate objects from them. Further, the developer must ensure that they do …
Integrated Coverage And Connectivity Configuration In Wireless Sensor Networks, Xiaorui Wang, Guoliang Xing, Yuanfang Zhang, Chenyang Lu, Robert Pless, Christopher Gill
Integrated Coverage And Connectivity Configuration In Wireless Sensor Networks, Xiaorui Wang, Guoliang Xing, Yuanfang Zhang, Chenyang Lu, Robert Pless, Christopher Gill
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An effective approach for energy conservation in wireless sensor networks is scheduling sleep intervals for extraneous nodes, while the remaining nodes stay active to provide continuous service. For the sensor network to operate successfully, the active nodes must maintain both sensing coverage and network connectivity. Furthermore, the network must be able to configure itself to any feasible degrees of coverage and connectivity in order to support different applications and environments with diverse requirements. This paper presents the design and analysis of novel protocols that can dynamically configure a network to achieve guaranteed degrees of coverage and connectivity. This work differs …
Multiflow Tcp, Udp, Ip, And Atm Traffic Generation Module, Eliot I. Sinclair, John W. Lockwood
Multiflow Tcp, Udp, Ip, And Atm Traffic Generation Module, Eliot I. Sinclair, John W. Lockwood
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Networking devices must be capable of processing traffic flows from multiple sources. In order to verify that such devices operates properly, a network testbench can be used to inject traffic into the device. The specification of the traffic flows can be difficult. At the low level, there are header fields, data checksums, and packet length fields that all must be formatted correctly. Further, there can be multiple flows of traffic that will arrive simultaneously. It is desirable to specify traffic at a high level of abstraction. A software program can then be written to parse the specification and generate the …
System-On-Chip Packet Processor For An Experimental Network Services Platform, David Taylor, Alex Chandra, Yuhua Chen, Sarang Dharmapurikar, John Lockwood, Wenjing Tang, Jonathan Turner
System-On-Chip Packet Processor For An Experimental Network Services Platform, David Taylor, Alex Chandra, Yuhua Chen, Sarang Dharmapurikar, John Lockwood, Wenjing Tang, Jonathan Turner
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As the focus of networking research shifts from raw performance to the delivery of advanced network services, there is a growing need for open-platform systems for extensible networking research. The Applied Research Laboratory at Washington University in Saint Louis has developed a flexible Network Services Platform (NSP) to meet this need. The NSP provides an extensible platform for prototyping next-generation network services and applications. This paper describes the design of a system-on-chip Packet Processor for the NSP which performs all core packet processing functions including segmentation and reassembly, packet classification, route lookup, and queue management. Targeted to a commercial configurable …
A Thesis On A 3d Input Device For Sketching Characters, Mark A. Schroering
A Thesis On A 3d Input Device For Sketching Characters, Mark A. Schroering
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The goal of this project is to develop a 3D input device using a stiff piece of paper and a camera. The camera tracks the piece of paper in 3D space. The user orients the paper in 3D space and then draws on the paper using a pen-like device. The camera tracks the movement of the pen on the piece of paper. The location of the pen in 3D space can then be calculated from the orientation of the paper. A drawing application that uses this 3D input device was also developed. The application allows a user to make characters …
A Study In Java Bytecode Engineering With Pcesjava, Martin R. Linenweber
A Study In Java Bytecode Engineering With Pcesjava, Martin R. Linenweber
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This thesis reports on experience with PCESjava, a collection of tools which we have developed for the purpose of aiding programmers. Particular applications optimize and instrument JAVA bytecode programs. Using these tools, we have successfully identified impediments to real-time performance in a popular JAVA collections object. Our approach here is based on automatic instruction to obtain traces that show paths whose execution time is not reasonably bounded. We also report on the application of our tool to reduce program footprint in JAVA programs by rewriting the bytecodes to occupy less space. Our transformations also improves the running time of set …
An Iterative Loop Matching Approach To The Prediction Of Rna Secondary Structures With Pseudoknots, Jianhua Ruan, Weixiong Zhang
An Iterative Loop Matching Approach To The Prediction Of Rna Secondary Structures With Pseudoknots, Jianhua Ruan, Weixiong Zhang
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Motivation: Pseudoknots have generally been excluded from the prediction of RNA secondary structures due to the difficulty in modeling and complexity in computing. Although several dynamic programming algorithms exist for the prediction of pseudoknots using thermodynamic approaches, they are neither reliable nor efficient. On the other hand, comparative methods are more reliable, but are often done in an ad hoc manner and require expert intervention. Maximum weighted matching (Tabaska et. al, Bioinformatics, 14:691-9, 1998), an algorithm for pseudoknot prediction with comparative analysis, suffers from low prediction accuracy in many cases. Here we present an algorithm, iterative loop matching, for predict-ing …