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Computer Engineering Commons

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1996

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Articles 31 - 60 of 67

Full-Text Articles in Computer Engineering

Mobile Unity: Reasoning And Specification In Mobile Computing, Gruia-Catalin Roman, Peter J. Mccann Jan 1996

Mobile Unity: Reasoning And Specification In Mobile Computing, Gruia-Catalin Roman, Peter J. Mccann

All Computer Science and Engineering Research

Mobile computing represents a major point of departure from the traditional distributed computing paradigm. The potentially very large number of independent computing units, a decoupled computing style, frequent disconnections, continuous position changes, and the location-dependent nature of the behavior and communication patterns present designers with unprecedented challenges in the areas of modularity and dependability. So far, the literature on mobile computing is dominated by concerns having to do with the development of protocols and services. This paper complements this perspective by considering the nature of the underlying formal models that will enable us to specify and reason about such computations ...


Reconsidering Fragmentation And Reassembly, Girish P. Chandranmenon, George Varghese Jan 1996

Reconsidering Fragmentation And Reassembly, Girish P. Chandranmenon, George Varghese

All Computer Science and Engineering Research

We reconsider several issues related to fragmentation and reassembly in IP. We first reconsider reassembly. We describe a simple expected case optimization that improves reassembly performance to 38 instructions per fragment if the fragments arrive in FIFO order (the same assumption made in header prediction) which has been implemented in the NetBSD kernel. Next, we introduce the new idea of Graceful Intermediate Reassembly (GIR), which is a generalization of the existing IP mechanisms of destination and hop-by-hop reassembly. In GIR, we coalesce the fragments at an intermediate router in order to use the largest sized packets on its outgoing interface ...


Leap Forward Virtual Clock: An O(Loglogn) Fair Queuing Scheme With Guaranteed Delays And Throughput Fairness, Subhash Suri, George Varghese, Girish P. Chandranmenon Jan 1996

Leap Forward Virtual Clock: An O(Loglogn) Fair Queuing Scheme With Guaranteed Delays And Throughput Fairness, Subhash Suri, George Varghese, Girish P. Chandranmenon

All Computer Science and Engineering Research

We describe an efficient fair queuing scheme, Leap Forward Virtual Clock, that provides end-to-end delay bounds almost identical to that of PGPS fair queuing, along with throughput fairness. Our scheme can be implemented with a worst-case time O(loglogN) per packet guaranteed delay and throughput fairness. As its name suggests, our scheme is based on Zhang's virtual clock. While the original virtual clock scheme does not achieve throughput fairness, we can modify it with a simple leap forward mechanism that keeps the server clock from lagging too far behind the packet tags. We prove that our scheme guarantees a ...


Efficient User Space Protocol Implementations With Qos Guarantees Using Real-Time Upcalls, R. Gopalakrishnan, Guru M. Parulkar Jan 1996

Efficient User Space Protocol Implementations With Qos Guarantees Using Real-Time Upcalls, R. Gopalakrishnan, Guru M. Parulkar

All Computer Science and Engineering Research

Real-time upcalls (RTUs) are an operating systems mechanism to provide quality-of-service (QoS) guarantees to network applications, and to efficiently implement protocols in user space with (QoS) guarantees. Traditionally, threads (and real-time extensions to threads) have been used to structure concurrent activities in user space protocol implementations. However, preemptive scheduling required for real-time threads leads to excessive context switching, and introduces the need for expensive concurrency control mechanisms such as locking. The RTU mechanism exploits the iterative nature of protocol processing to eliminate the need for locking, and reduce asynchronous preemption, while ensuring real-time operation. In addition to efficiency, eliminating the ...


The Apic Approach To High Performance Network Interface Design: Protected Dma And Other Techniques, Zubin D. Dittia, Guru M. Parulkar, Jerome R. Cox Jr. Jan 1996

The Apic Approach To High Performance Network Interface Design: Protected Dma And Other Techniques, Zubin D. Dittia, Guru M. Parulkar, Jerome R. Cox Jr.

All Computer Science and Engineering Research

We are building a very high performance 1.2 Gb/s ATM network interface chip called the APIC (ATM Port Interconnect Controller). In addition to borrowing userful ideas from a number of research and commercial prototypes, the APIC design embraces several innovative features, and integrates all of these pieces into a coherent whole. This paper describes some of the novel ideas that have been incorporated in the APIC design with a view to improving the bandwidth and latency seen by end-applications. Among the techniques described, Protected DMA and Protected I/O were designed to allow applications to queue data for ...


On The Performance Of Early Packet Discard, Maurizio Casoni, Jonathan S. Turner Jan 1996

On The Performance Of Early Packet Discard, Maurizio Casoni, Jonathan S. Turner

All Computer Science and Engineering Research

In a previous paper [3], one of the authors, gave a worst-case analysis for the Early Packet Discard (EPD) technique for maintaining packet integrity during overload in ATM switches. This analysis showed that to ensure 100% goodput during overload under worst-case conditions, requires a buffer with enough storage for one maximum length packet from every active virtual circuit. This paper refines that analysis, using assumptions that are closer to what we expect to see in practice and examines how EPD performs when the buffer is not large enough to achieve 100% goodput. We show that 100% goodput can be achieved ...


Supporting Dis Applications Using Atm Multipoint Connection Caching, Anshul Kantawala, Guru Parulkar, John Dehart, Ted Marz Jan 1996

Supporting Dis Applications Using Atm Multipoint Connection Caching, Anshul Kantawala, Guru Parulkar, John Dehart, Ted Marz

All Computer Science and Engineering Research

This report describes an ATM Multipoint Connection Caching strategy (AMCC) to control the explosive growth of traffic within the network and at an endpoint in a large Distributed Interactive Simulation (DIS) application such as a battlefield simulation. For very large DIS applications with 100,000 entities, the current method of broadcasting information among entities will no longer be feasible due to computational and network bandwidth limitations. Our scheme divides the simulation space into grids and each grid square or a set of grid squares forms a multicast group. Entities join the groups within their perception range and thus, they receive ...


Optimal Solution Of Off-Line And On-Line Generalized Caching, Saied Hosseini-Khayat, Jerome R. Cox Jan 1996

Optimal Solution Of Off-Line And On-Line Generalized Caching, Saied Hosseini-Khayat, Jerome R. Cox

All Computer Science and Engineering Research

Network traffic can be reduced significantly if caching is utilized effectively. As an effort in this direction we study the replacement problem that arises in caching of multimedia objects. The size of objects and the cost of cache misses are assumed non-uniform. The non-uniformity of size is inherent in multimedia objects, and the non-uniformity of cost is due to the non-uniformity of size and the fact that the objects are scattered throughout the network. Although a special case of this problem, i.e. the case of uniform size and cost, has been extensively studied, the general case needs a great ...


Continuous Compilation For Software Development And Mobile Computing, Michael P. Plezbert Jan 1996

Continuous Compilation For Software Development And Mobile Computing, Michael P. Plezbert

All Computer Science and Engineering Research

Software developers typically must choose between interpreted and compiled environments for their programming activities. However, the current trends toward mobile computing and platform independence suggest moving to a new continuous compilation paradigm that integrates the advantages of each environment. Movement in this direction can already be seen in the development of Sun Microsystems' Java environment. The resulting continuous compiler operates not as a prelude to, but rather in tandem with, program execution. In this thesis we present the results of experiments that compare the performance of the continuous compilation model with a more traditional model and show that a performance ...


Negotiation As A Resource Allocation Process, Fernando Tohme Jan 1996

Negotiation As A Resource Allocation Process, Fernando Tohme

All Computer Science and Engineering Research

The main economic-theoretic approcahes to the problem of resource allocation make little if any reference to negotiation processes. These processes are fundamentally linguistic, based on the exchange of messages among agents. Communication being so fundamental in the characterization of negotiation processes, the analysis of negotiation must emphasize on the structure of the language in which the negotiations take place. Computer science and particularly Artificial Intelligence have provided interesting insights about that linguistic structure. In the first part of this work we present a brief survey of the literature on resource allocation processes in which communication among agents plays a relevant ...


New Results On Generalized Caching, Saied Hosseini-Khayat Jan 1996

New Results On Generalized Caching, Saied Hosseini-Khayat

All Computer Science and Engineering Research

We report a number of new results in generalized caching. This problem arises in modern computer networks in which data objects of various sizes are transmitted frequently. First it is shown that its optimal solution is NP-complete. Then we explore two methods of obtaining nearly optimal answers based on the dynamic programming algorithm that we provided in [5]. These methods enable a trade-off between optimality and speed. It is also shown that LFD (the longest forward distance algorithm which is the optimal policy in the classical case), is no longer optimal but is competitive. We also prove that LRU remains ...


An Algorithm For Message Delivery To Mobile Units, Amy L. Murphy, Gruia-Catalin Roman, George Varghese Jan 1996

An Algorithm For Message Delivery To Mobile Units, Amy L. Murphy, Gruia-Catalin Roman, George Varghese

All Computer Science and Engineering Research

With recent advances in wireless communication and the ubiquity of laptops, mobile computing has become an important research area. An essential problem in mobile computing is the delivery of a message from a source to either a single mobile node, unicast, or to a group of mobile nodes, multicast. Standard solutions used in Mobile IP and cellular phones for the unicast problem rely on tracking the mobile unit. Tracking solutions scale badly when mobile nodes move frequently, and do not generalize well to multicast delivery. Our paper proposes a new message delivery algorithm for micromobility based on a modification of ...


Building Distributed Applications With Design Patterns, Gruia-Catalin Roman, James C. Hu Jan 1996

Building Distributed Applications With Design Patterns, Gruia-Catalin Roman, James C. Hu

All Computer Science and Engineering Research

Design patterns are a topic of great current interest within the object-oriented programming community. The motivation is both economical and intellectual. On one hand, there is the hope of establishing a common culture and language that fosters communicatino and growth in the software engineering field. While a community dominated by empiricism is seeking to achieve higher levels of formality by capturing its experiences in the form of catalogs of design patterns, another community, deeply rooted in formal thinking, is seeking to make its mark on the every day workings of the software engineering process. Distributed algorithms and the heuristics used ...


Alchourron's Defeasible Conditionals And Defeasible Reasoning, Fernando Tohme, Ronald P. Loui Jan 1996

Alchourron's Defeasible Conditionals And Defeasible Reasoning, Fernando Tohme, Ronald P. Loui

All Computer Science and Engineering Research

No abstract provided.


An Optimistic Concurrency Control Mechanism Based On Clock Synchronization, Myoung Jin Park Jan 1996

An Optimistic Concurrency Control Mechanism Based On Clock Synchronization, Myoung Jin Park

Theses Digitization Project

No abstract provided.


A Usability Study Of End-User Construction Of Direct Manipulation User Interfaces, T Paul Mccartney Jan 1996

A Usability Study Of End-User Construction Of Direct Manipulation User Interfaces, T Paul Mccartney

All Computer Science and Engineering Research

This paper describes an empirical study of end-users that tested the usability of The Programmers' Playground graphical environment. The Programmers' Playground is a software library and run-time system for constructing distributed multimedia applications. Playground's graphical environment enables end-users to create direct manipulation graphical user interfaces (GUIs) and to dynamically configure communication among distributed application components. In this study, 28 end-users with no prior experience in distributed computing or user interface construction were timed and evaluated on several tasks using our graphical environment. Tasks included the use of direct and indirect constraint relationships, visual configuration of distributed applications, and graphical ...


Distributed Stream Filtering For Database Applications, William M. Shapiro, Kenneth J. Goldman Jan 1996

Distributed Stream Filtering For Database Applications, William M. Shapiro, Kenneth J. Goldman

All Computer Science and Engineering Research

Distributed stream filtering is a mechanism for implementing a new class of real-time applications with distributed processing requirements. These applications require scalable architectures to support the efficient processing and multiplexing of large volumes of continuously generated data. This paper provides an overview of a stream-oriented model for database query processing and presents a supporting implementation. To facilitate distributed stream filtering, we introduce several new query processing operations, including pipelined filtering that efficiently joins and eliminates duplicates from database streams and a new join method, the progressive join, that joins streams of tuples. Finally, recognizing that the stream-oriented model results in ...


Simulation Of Asynchronous Instruction Pipelines, Chia-Hsing Chien, Mark A. Franklin Jan 1996

Simulation Of Asynchronous Instruction Pipelines, Chia-Hsing Chien, Mark A. Franklin

All Computer Science and Engineering Research

This paper presents the ARAS simulator with which asynchronous instruction pipelines can be modelled, simulated and displayed. ARAS allows one to construct instruction pipelines by preparing various configuration files. Using these files and a number of benchmark programs, performance of the instruction pipelines can be obtained. The performance of asynchronous instruction pipelines can also be compared to synchronous case. Thus, one can decide the optimal design for instruction pipelines in asynchornous or synchronous cases and explore the deisng space of asynchronous instruction pipeline architectures.


Designing Minimum Cost Nonblocking Communication Networks, J. Andrew Fingerhut, Subhash Suri, Jonathan S. Turner Jan 1996

Designing Minimum Cost Nonblocking Communication Networks, J. Andrew Fingerhut, Subhash Suri, Jonathan S. Turner

All Computer Science and Engineering Research

This paper addresses the problem of topological design of ATM (and similar) communication networks. We formulate the problem from a worst-case point of view, seeking network desings that, subject to specified traffic constraints, are nonblocking for point-to-point and multicast virtual circuits. Within this model we give various conditions under which star networks are optimal or near-optimal. These conditions are approximately satisfied in many common situations making the results of practical significance. An important consequence of these results is that, where they apply, there is no added cost for nonblocking multicast communication, relative to networks that are nonblocking for point-to-point traffic ...


Mobile Unity Coordination Constructs Applied To Packet Forwarding For Mobile Hosts, Peter J. Mccann, Gruia-Catalin Roman Jan 1996

Mobile Unity Coordination Constructs Applied To Packet Forwarding For Mobile Hosts, Peter J. Mccann, Gruia-Catalin Roman

All Computer Science and Engineering Research

With recent advances in wireless communication technology, mobile computing is an increasingly important area of research. A mobile system is one where independently executing components may migrate through some space during the course of the computation, and where the pattern of connectivity among the components changes as they move in and out of proximity. Mobile UNITY is a language and logic for specifying and reasoning about mobile systems, the components of which must operate in a highly decoupled way. In this paper it is argued that Mobile UNITY contributes to the modular development of system specifications because of the declarative ...


Extending Atm Networks For Efficient Reliable Multicast, Jonathan S. Turner Jan 1996

Extending Atm Networks For Efficient Reliable Multicast, Jonathan S. Turner

All Computer Science and Engineering Research

One of the important features of ATM networks is their ability to support multicast communications. This facilitates the efficient distribution of multimedia information streams (such as audio and video) to large groups of receivers (potentially millions). Because ATM networks do not provide reliable delivery mechanisms, it is up to end systems to provide end-to-end reliability where it is needed. While this is straightforward for point-to-point virtual circuits, it is more difficult for one-to many and many-to-mamy virtual circuits. In this report, we propose some minimal extensions to the hardware of ATM switches that enables end systems to implement reliable multicast ...


A Pilot Study Of Speech And Pen User Interface For Graphical Editing, Karl E. Schmidt Jan 1996

A Pilot Study Of Speech And Pen User Interface For Graphical Editing, Karl E. Schmidt

All Computer Science and Engineering Research

As computer size continues to decrease and new user interface technologies become more ubiquitous, the conventional keyboard and mouse input interfaces are becoming harder to design into newer machines and less practical for use in some applications. The pen is one input technology more suited for the upcoming generation of smaller computers using direct manipulation interfaces. However, a pen-only user interface relies on continuous gesture and handwriting tecognizers that are often slow, inaccurate, and error prone for command and text entry. Speech recognition is an input modality that can input commands quickly and potentially be a fast text entry mechanism ...


Vaudeville: A High Performance, Voice-Activated Teleconferencing Application, Jyoti K. Parwatikar, T. Paul Mccartney, John D. Dehart, Maynard Engebretson, Kenneth J. Goldman Jan 1996

Vaudeville: A High Performance, Voice-Activated Teleconferencing Application, Jyoti K. Parwatikar, T. Paul Mccartney, John D. Dehart, Maynard Engebretson, Kenneth J. Goldman

All Computer Science and Engineering Research

We present a voice-activated, hands-off, ATM-based video conferencing application. The application, called Vaudeville, features high quality NTSC video, voice-activated audio transmission, audio bridging of two audio streams, and voice-activated video switching. It supports multiple simultaneous multi-party conferences using a scalable multicast mechanism. We describe how Vaudeville was built using a component-based distributed programming environment. We also describe the algorithms used to contorl the audio and video of the applciation. Audio and video are encoded in hardware using an ATM hardware multimedia interface.


End-User Construction And Configuration Of Distributed Multimedia Applications, Terrance Paul Mccartney Jan 1996

End-User Construction And Configuration Of Distributed Multimedia Applications, Terrance Paul Mccartney

All Computer Science and Engineering Research

Distributed multimedia applications supported by a global electronic infrastructure have tremendous potential for providing users with customized communication and computation environments. Since communication and computation requirements vary by context and change dynamically, it is unlikely that off-the-shelf applications will anticipate the needs of all users. Therefore, empowering end-users to create their own customized applications for both communication and computation is an important challenge. This dissertation presents several mechanisms that enable end-users to create and configure distributed multimedia applications, including end-users construction direct manipulation graphical users interface (GUIs) and application management of distributed multimedia applications over the Internet.


Simulator For The Performance Analysis Of Cpm Schemes In An Indoor Wireless Environment, Ronald Chua Jan 1996

Simulator For The Performance Analysis Of Cpm Schemes In An Indoor Wireless Environment, Ronald Chua

Theses : Honours

A software simulator for characterising Continuous Phase Modulation (CPM) schemes in an indoor multipath environment has been developed using SIMULINK and MATLAB. The simulator is capable of simulating a wide range of CPM schemes to determine bandwidth efficiency and robustness to additive white Gaussian noise (AWGN) and Rician fading. Initial trials of the simulator indicate that the simulator is functioning correctly. Eventually, the simulator will be used to determine the most suitable modulation scheme for the development of an actual indoor wireless system.


Analysis Of Background Noise For Wireless Microwave Lan Channels, Jason C. Hislop Jan 1996

Analysis Of Background Noise For Wireless Microwave Lan Channels, Jason C. Hislop

Theses : Honours

Perusal of the details within, should provide the reader with an insight into general wireless indoor communications within the microwave spectrum, with respect to the problems laced, specific to noise corruption of the transmitted signal. Indoor communication systems are difficult to model, due to the largely random nature of the relevant environment, and the compounding factors that degrade system performance. These factors are many and varied, in accordance with the operational topologies of possible application area. However, there exists a common and increasing need to effectively model the communication links in question. Part of this strategy involves having an understanding ...


Ua8 Information Technology Update, Wku Information Technology Jan 1996

Ua8 Information Technology Update, Wku Information Technology

WKU Archives Records

Newsletter created by and about WKU Information Technology.


Automation Of Real-Time X-Ray Scans, Madhusudhan R. Midhe Jan 1996

Automation Of Real-Time X-Ray Scans, Madhusudhan R. Midhe

Retrospective Theses and Dissertations

The present day needs of the commercial market have forced the industry to manufacture materials which are stronger, weigh less and cost less. In other words, it is of prime concern to characterize the material properties. The characterization of a material can be done either at the time of fabrication or while the material is being used. A material can be tested in two ways, destructively or non-destructively. In destructive means of testing materials, a sample is selected randomly from a batch and is inspected thoroughly and the results are extrapolated in a manner so that they represent the whole ...


Performance Characteristics Of The Is-95 Standard For Cdma Spread Spectrum Mobile Communication Systems, Vijayalakshmi R. Raveendran Jan 1996

Performance Characteristics Of The Is-95 Standard For Cdma Spread Spectrum Mobile Communication Systems, Vijayalakshmi R. Raveendran

Retrospective Theses and Dissertations

No abstract provided.


Development Of A Pulsed Eddy Current Instrument For Corrosion Detection, Sunil K. Shaligram Jan 1996

Development Of A Pulsed Eddy Current Instrument For Corrosion Detection, Sunil K. Shaligram

Retrospective Theses and Dissertations

The pulsed eddy current technique has been under development at Iowa State University since 199:3 under the supervision of Mr. John Moulder. It has shown much promise for detecting corrosion and cracks in multi-layered aircraft structures, and has elicited strong interest from the aviation community. The Pulsed Eddy Current Group at the Center for Nondestructive Evaluation, ISU, has built an instrument which utilizes the theory behind pulsed eddy currents and transforms it into a practical field instrument.