Institute for Systems Research

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Author: search.filters.author.Baras, John S.Subject: search.filters.subject.Systems Integration

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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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    Partially Observed Differential Games, Infinite Dimensional HJI Equations, and Nonlinear HControl
    (1994) James, Matthew R.; Baras, John S.; ISR
    This paper presents new results for partially observed nonlinear differential games, which are applied to the nonlinear output feedback Hrobust control problem. Using the concept of information state, we solve these problems in terms of an infinite dimensional partial differential equation, viz., the Hamilton-Jacobi-Isaacs equation for partial observed differential games. We give definitions of smooth and viscosity solutions, and prove that the value function is a viscosity solution of the HJI equation. We prove a verification theorem, which implies that the optimal controls are separated in that they depend on the observations through the information state. This constitutes a separation principle for partially observed differential games. We also present some new results concerning the certainty equivalence principle.
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    Next Generation Network Management Technology
    (1994) Atallah, George C.; Ball, Michael O.; Baras, John S.; Goli, Shravan K.; Karne, Ramesh K.; Kelley, Stephen; Kumar, Harsha P.; Plaisant, Catherine; Roussopoulos, Nick; Shneiderman, Ben; Srinivasarao, Mulugu; Stathatos, Kostas; Teittinen, Marko; Whitefield, David; ISR; CSHCN
    Today's telecommunications networks are becoming increasingly large, complex, mission critical and heterogeneous in several dimensions. For example, the underlying physical transmission facilities of a given network may be ﲭixed media (copper, fiber- optic, radio, and satellite); the sub networks may be acquired from different vendors due to economic, performance, or general availability reasons; the information being transmitted over the network may be ﲭultimedia (video, data, voice, and images) and, finally, varying performance criteria may be imposed e.g. data transfer may require high throughput while the others, whose concern is voice communications, may require low call blocking probability. For these reasons, future telecommunications networks are expected to be highly complex in their services and operations. Due to this growing complexity and the disparity among management systems for individual sub networks, efficient network management systems have become critical to the current and future success of telecommunications companies. This paper addresses a research and development effort which focuses on prototyping configuration management, since that is the central process of network management and all other network management functions must be built upon it. Our prototype incorporates ergonomically designed graphical user interfaces tailored to the network configuration management subsystem and to the proposed advanced object-oriented database structure. The resulting design concept follows open standards such as Open Systems Interconnection (OSI) and incorporates object oriented programming methodology to associate data with functions, permit customization, and provide an open architecture environment.
      A revised version of this technical report has been published in
      The 12th Symposium on Space Nuclear Power and Propulsion/Commercialization, pp. 75-82, Albuquerque, NM, January 8-12, 1995.
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    Comparison Studies of Several Microphone Robustness Techniques
    (1994) Sonmez, M.K.; Kao, Yu-Hung; Rajasekaran, P.K.; Baras, John S.; ISR
    We study the effectiveness of various microphone robustness techniques from the viewpoint of speech recognition, utilizing the ARPA-sponsored Wall Street Journal (WSJ) data base [1]. Two of the techniques considered are being introduced in this paper: two cepstral normalization algorithms utilizing the artificial neural network techniques Self Organizing Map (SOM) and Learning Vector Quantization (LVQ). The algorithms obtained are low- complexity non-parametric counterparts of the parametric approaches Codeword-dependent Cepstral Normalization (CDCN) and Fixed CDCN (FCDCN). The other techniques considered are Cepstral Mean Normalization (CMN), RASTA, SNR-dependent Cepstral Normalization (SDCN), Interpolated SDCN (ISDCN), CDCN, FCDCN; some of these techniques require one or more of the following information: stereo data, SNR estimate, single microphone data for adaptation, and knowledge of the microphone used for the specific data under test. We determine the effectiveness in several ways: (i) scattergram plot of the speech frame parameter vector (usually a cepstral vector), (ii) adjusted deviation ratio, measured from scattergram, and (iii) correctness of classifying a test vector into a vector code book. All these measures have direct correlation with speech recognition performance, which will be measured with experiments to be conducted.
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    A Dynamic Routing Algorithm in Mixed Media Networks with Integrated Voice and Data Traffic
    (1993) Chen, Shih-Wei; Baras, John S.; ISR; CSHCN
    In this paper, we consider mixed media networks with multi-media traffic to find the optimal splitting ratio between satellite network and terrestrial network for data and voice traffic dynamically. We constantly monitor the traffic and measure the arrival rate and occupancy of every link. Based on these data, we optimize data traffic delay in a suitable time-frame under the constraints of voice traffic blocking probabilities of voice transmission links being less than specified value, which is up to system's design or users' requirements. A dynamic routing algorithm is presented.
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    Optimal Routing in Mixed Media Networks with Integrated Voice and Data Traffic
    (1993) Chen, Sujen; Baras, John S.; ISR; CSHCN
    In this paper, we consider a large mixed-media network which consists of a low-delay terrestrial sub-network and a high- bandwidth satellite sub-network. both voice and data traffic are transmitted and routed through the same network. We show how to route both traffic via ground and/or satellite links by means of static, deterministic procedures. Two common voice/data integrated protocols such as fixed boundary and movable boundary schemes for the satellite channel are investigated, and the performance of both schemes is evaluated. The optimal splitting ratios for voice and data at the SIMPs (satellite Interface Message Processors) are found using a powerful numerical optimization package (FSQP).
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    Hybrid (Satellite and Terrestrial) Communication Networks: Object Oriented Generic Tools for Simulation and Management
    (1993) Baras, John S.; Charuhas, Thomas; ISR; CSHCN
    We describe a generic object oriented software environment for the simulation and management of hybrid communication networks (satellite and terrestrial) under development at the University of Maryland, as part of NASA CCDS program. We refer to this environment as a "systems engineering workstation for hybrid networks". It will have the capability to model such networks in a totally object oriented environment and link to network performance evaluation modules. Satellites are treated both as electronic/mechanical systems and as communication nodes. Great flexibility is allowed for defining the various components of the satellite, including its type (i.e. LEO or GEO), on board processing capabilities, bandwidth, multiple access scheme, linkage to terrestrial networks. The satellite link is also treated as an object allowing great flexibility in modeling weather effects, multipath interference and coverage. We show the system's flexibility in studying combined adaptive routing and access for voice-data large hybrid networks.
      A revised version of this technical report has been published in
      Proceedings of the IEEE Conference for MILCOM 92, Vol. II, pp. 0553-0559, San Diego, CA, October 11-14, 1992.
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    Design of the MANDATE MIB
    (1993) Haritsa, Jayant R.; Ball, Michael O.; Roussopoulos, Nicholas; Baras, John S.; Datta, Anindya; ISR; CSHCN
    A management information database is the heart of a network management system -- it provides the interface between all functions of the network management system, and therefore has to provide sophisticated functionality allied with high performance. In this paper, we introduce the design of MANDATE, a database system that is designed to effectively support the management of large enterprise network. MANDATE proposes to use special characteristics of network management data and transactions, together with recent advances in database technology, to efficiently derive its functionality.