Institute for Systems Research Technical Reports

Permanent URI for this collectionhttp://hdl.handle.net/1903/4376

This archive contains a collection of reports generated by the faculty and students of the Institute for Systems Research (ISR), a permanent, interdisciplinary research unit in the A. James Clark School of Engineering at the University of Maryland. ISR-based projects are conducted through partnerships with industry and government, bringing together faculty and students from multiple academic departments and colleges across the university.

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Subject: search.filters.subject.Systems Integration

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Now showing 1 - 10 of 176
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    A System Design for a Hybrid Network Data Communications Terminal Using Asymmetric TCP/IP to Support Internet Applications
    (1994) Falk, Aaron D.; Baras, John S.; ISR; CSHCN
    Access to the Internet is either too slow (e.g. dial-up SLIP) or too expensive (e.g. switched 56 kbps, frame relay) for the home user or small enterprise. The Center for Satellite and Hybrid Communication Networks and Hughes Network Systems have collaborated using system integration principles to develop a prototype of a low-cost hybrid (dial-up and satellite) network terminal which can deliver data from the Internet to the user at rates up to 160 kbps. An asymmetric TCP/IP connection is used breaking the network link into two physical channels: a terrestrial dial-up link for carrying data from the terminal into the Internet and a receiver-only satellite link carrying IP packets from the Internet to the user. With a goal of supporting bandwidth hungry Internet applications such as Mosaic Gopher, and FTP, this system has been designed to support any Intel 80386/486 PC, any commercial TCP/IP package, any unmodified host on the Internet, and any of the routers, etc. within the Internet. The design exploits the following three observations: 1) satellites are able to offer high bandwidth connections to a large geographical area, 2) a receiver-only VSAT is cheap to manufacture and easier to install than one which can also transmit, and 3) most computer users, especially those in a home environment, will want to consume much more data than they generate. IP encapsulation, or tunneling, is used to manipulate the TCP/IP protocols to route packets asymmetrically.
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    Image Browsers: Taxonomy, Guidelines, and Informal Specifications
    (1994) Plaisant, Catherine; Carr, David A.; Shneiderman, Ben; ISR; CSHCN
    Image browsing is necessary in numerous applications. Designers have merely used two one-dimensional scroll bars or they have made ad hoc designs for a two-dimensional scroll bar. However, the complexity of two-dimensional browsing suggests that more careful analysis, design, and evaluation might lead to significant improvements. We present a task taxonomy for image browsing, suggest design features and guidelines, assess existing strategies, and introduce an informal specification
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    Existence and Construction of Optimal Wavelet Basis for Signal Representation
    (1994) Zhuang, Y.; Baras, John S.; ISR; CSHCN
    We study the problem of choosing the optimal wavelet basis with compact support for signal representation and provide a general algorithm for computing the optimal wavelet basis. We first briefly review the multiresolution property of wavelet decomposition and the conditions for generating a basis of compactly supported discrete wavelets in terms of properties of quadrature mirror filter (QMF) banks. We then parametrize the mother wavelet and scaling function through a set of real coefficients. We further introduce the concept of decomposition entropy as an information measure to describe the distance between the given signal and its projection onto the subspace spanned by the wavelet basis in which the signal is to be reconstructed. The optimal basis for a given signal is obtained through minimizing this information measure. We have obtained explicitly the sensitivity of dilations and shifts of the mother wavelet with respect to the coefficient set. A systematic approach is developed in this paper to derive the information gradient with respect to the parameter set from a given square integrable signal and a discrete basis of wavelets. The existence of the optimal basis for the wavelets has been proven in this paper. a gradient based optimization algorithm is developed for computing the optimal wavelet basis.
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    Optimal Wavelet Basis Selection for Signal Representation
    (1994) Zhuang, Y.; Baras, John S.; ISR; CSHCN
    We study the problem of choosing the optimal wavelet basis with compact support for signal representation and provide a general algorithm for computing the optimal wavelet basis. We first briefly review the multiresolution property of wavelet decomposition and the conditions for generating a basis of compactly supported discrete wavelets in terms of properties of quadrature mirror filter (QMF) banks. We then parametrize the mother wavelet and scaling function through a set of real coefficients. We further introduce the concept of information measure as a distance measure between the signal and its projection onto the subspace spanned by the wavelet basis in which the signal is to be reconstructed. The optimal basis for a given signal is obtained through minimizing this information measure. We have obtained explicitly the sensitivity of dilations and shifts of the mother wavelet with respect to the coefficient set. A systematic approach is developed here to derive the information gradient with respect to the parameter set for a given square integrable signal and the optimal wavelet basis. A gradient based optimazation algorithm is developed in this paper for computing the optimal wavelet basis.
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    Object Oriented Hybrid Network Simulation
    (1994) Baras, John S.; Atallah, George C.; Karne, Ramesh K.; Murad, A.; Jang, Kap D.; ISR; CSHCN
    As the complexity and diversity of networks have grown, simulation has proved an important tool in their design, analysis, testing and performance estimation of networks. Hybrid networks involve a variety of network elements - both mobile (e.g., satellites, mobile radio) and fixed nodes (e.g., switches, hubs, network gateways) linked via varied broadcast, multicast and point-to-point communication channels. Because of their complex nature, design and evaluation of hybrid networks is a particularly complicated task. Major requirements of a hybrid network simulation tool are (i) Flexibility and Adaptability - to accommodate all kinds of hybrid networks and protocols, (ii) Advanced Network Visualization Techniques - to clearly visualize complex communication network systems, (iii) Data Management - to organize and analyze the vast quantities of data generated in a typical simulation run, and (iv) Distributed Implementation - to fully utilize available computing resources to speed up simulation. This paper describes the design and functional description of an Object-Oriented Hybrid Network Simulation tool. Its object oriented design and implementation (in C++) allows flexibility through incorporation of new, user specified network elements, protocols and functional blocks. Advanced visualization techniques are combined with the graphical user interface to allow better visualization of complex network structures. A sophisticated geographical database is also incorporated to aid terrestrial mobile, and satellite network systems. To handle and effectively analyze the vast quantities of data generated, an object-oriented database is incorporated into the simulation. In addition to network simulation, the tool is also designed to serve other needs. An interface is provided to allow the user to run real network applications over the simulated network, allowing network application designers to judge the performance of their applications over various network configurations. Incorporation of a database allows computation of network performance dynamically. A network management tool receiving network performance data both from the actual and the simulated network may use the simulation data to make a long term prediction of the actual network behavior to perform long-term network management.
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    ASIC Design of Bit-Serial and Bit-Parallel Discrete Cosine Transform Processors
    (1994) Karunakaran, Vignarajah; Liu, K.J.R.; ISR
    Designs of the bit-serial and bit-parallel versions of the Discrete Cosine Transform Processor using the universal IIR filter module are presented, with emphasis on the bit-serial design. A bit-serial cell mini-library was created. The designs were performed with the AlliedSignal Aerospace Microelectronics Center's 1.2 micro double metal p-well CMOS standard cell library. The core of the bit-serial design is the 18-bit data x 8-bit coefficient bit-serial multiplier, whose design is also presented in detail; the multiplier is capable of handling negative data and negative coefficients, and has an accuracy of o(2-16), The 8-point 18-bit bit-serial DCT has a maximum clock speed of 139.0 MHz and 55.6 MHz under best and worst case conditions respectively. Two bit-parallel design implementations are presented, one with straight bit-parallel multiplier cells and the other with ROM multipliers using distributed arithmetic. The bit-parallel designs are also 8-point, but have an 8-bit wide input and a 12-bit wide output, thereby calculating with much less precision. The parallel multiplier chip's maximum speed under best and worst case conditions is 28.4 MHz and 11.4 MHz respectively, whereas the ROM multiplier chip's is 36.3 MHz and 14.5 MHz respectively. All three designs have a throughput of one clock cycle, with respect to their data input rates. The latencies for the bit-serial and bit-parallel designs are 38 and 5 cycles respectively.
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    Systolic Architectures for Signal Compression and Discrimination
    (1994) Yu, S-S.; JaJa, J.F.; ISR
    In this dissertation we propose systolic architectures for several classes of signal processing computations including schemes based on vector quantization and high order crossings techniques. The systolic concept is adapted to design architectures that are simple, regular, and that achieve high concurrency, local communication, and high throughput. Our tree- structured vector quantization (TSVQ) architecture is composed of a linear array of processors, each processor performing the computations required at one level of the binary tree. Encoding is performed in a pipelined fashion with each processor contributing a portion of the path decision through the tree until the final processor is reached to get the complete index. The predictive TSVQ (PTSVQ) architecture for real-time video coding applications uses pipelined arithmetic components to speed up the computation and to provide for regularity in design. This high throughput architecture is suitable for implementing a fully pipelined real-time PTSVQ system. Data and control flow in both architectures flow in a pipelined fashion and no global control signals are needed. We also present a class of architectures for performing signal discrimination and classification based on higher order crossing (HOC) methods. We also present a detailed design of a prototype HOC PCB system using off-the shelf components that can be used for non-destructive testing.
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    Analysis and Synthesis of Distributed Systems
    (1994) Zhuang, Y.; Baras, J.S.; ISR
    We first model and analyze distributed systems including distributed sensors and actuators. We then consider identification of distributed systems via adaptive wavelet neural networks (AWNNs) by taking advantage of the multiresolution property of wavelet transforms and the parallel computational structure of neural networks. A new systematic approach is developed in this dissertation to construct an optimal discrete orthonormal wavelet basis with compact support for spanning the subspaces employed for system identification and signal representation. We then apply a backpropagation algorithm to train the network to approximate the system. Filter banks for parameterizing wavelet systems are studied. An analog VLSI implementation architecture of the AWNN is also given in this dissertation. This work is applicable to signal representation and compression under optimal orthonormal wavelet bases in addition to progressive system identification and modeling. We anticipate that this work will find future applications in signal processing and intelligent systems.
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    Robust H-infinity Output Feedback Control for Nonlinear Systems
    (1994) Teolis, C.A.; J.S.Baras; ISR
    The study of robust nonlinear control has attracted increasing interest over the last few years. Progress has been aided by the recent extension of the linear quadratic results which links the theories of L2 gain control (nonlinear H∞ control), differential games, and stochastic risk sensitive control. In fact, significant advances in both linear and nonlinear H∞ theory have drawn upon results from the theories of differential games and stochastic risk sensitive control. Despite these advances in H∞ control theory, practical controllers for complex nonlinear systems which operate on basic H∞ principles have not been realized to date. Issues of importance to the design of a practical controller include (i) computational complexity, (ii) operation solely with observable quantities, and (iii) implementability in finite time. In this dissertation we offer a design procedure which yields, practical and implementable H∞ controllers and meets the, mandate of the above issues for general nonlinear systems. In particular, we develop a well defined and realistically implementable procedure for designing robust output feedback controllers for a large class of nonlinear systems. We analyze this problem in both continuous time and discrete time settings. The robust output feedback control problem is formulated as a dynamic game problem. The solution to the game is obtained by transforming the problem into an equivalent full state feedback problem where the new state is called the information state. The information state method provides a separated control policy which involves the solution of a forward and a backward dynamic programming equation. Obtained from the forward equation is the information state, and from the backward equation is the value function of the game and the optimal information state control. The computer implementation of the information state controller is addressed and several approximations are introduced. The approximations are designed to decrease the online computational complexity of controller.
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    Using Treemaps to Visualize the Analytic Hierarchy Process
    (1994) Asahi, Toshiyuki; Turo, D.; Shneiderman, B.; ISR
    Treemaps, a visualization method for large hierarchical data spaces, are used to augment the capabilities of the Analytic Hierarchy Process (AHP) for decision-making. Two direct manipulation tools, presented metamorphically as a "pump" and a "hook", were developed and applied to the treemap to support AHP sensitivity analysis. A usability study was conducted using a prototype AHP application; results showed that treemap representation of decision-support tools was acceptable for AHP users from both a visualization and data operation standpoint. Subjective preferences were high for AHP treemaps.