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  • Articles  (3,776)
  • Springer  (3,776)
  • American Chemical Society
  • 1995-1999  (3,776)
  • 1997  (3,776)
  • Computer Science  (2,709)
  • Natural Sciences in General  (1,095)
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  • Articles  (3,776)
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  • 1995-1999  (3,776)
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  • 1
    Electronic Resource
    Electronic Resource
    Development of an information model for composites design data (1997)
    Springer
    Engineering with computers 13 (1997), S. 48-64 
    Details
    ISSN: 1435-5663
    Keywords: Composite materials ; Conceptual modeling ; Database design ; Fiber-reinforced plastics ; information modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Material properties data, particularly those of advanced composite materials such as fiber-reinforced plastics, provides a very complex domain which is difficult to computerize. As a foundational activity supporting the development of material property databases, we have examined and modeled the data contained within this large, diverse, and intricate domain. Our primary objective was to gain a better understanding of the data involved in this system and their transformation and use. We examined the life cycle of a fiber-reinforced composite material, from a raw material to a manufactured product, focusing on the various applications which require and/or supply materials data and the types of materials data which must be included. A high-level information model was created to illustrate the overall picture of composite materials data which emerged from this analysis. This model provides a global view of the data encompassed in the domain of composite materials, and forms the basis of a formal conceptual model from which databases may be developed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01201860
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  • 2
    Electronic Resource
    Electronic Resource
    A data management model for collaborative design in a CAD environment (1997)
    Springer
    Engineering with computers 13 (1997), S. 65-86 
    Details
    ISSN: 1435-5663
    Keywords: Collaborative design ; Version control ; Configuration scheme ; Change management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract This paper presents a data management model to support collaborative design. More specifically, it addresses the storing and managing of changes among designers in a multidisciplinary design project. We propose a three-layered model ofversions, assemblies, andconfigurations. Versions maintain evolving descriptions of primitive entities within a single discipline.Assemblies integrate component instances to describe more complex entities, as well as designs within individual disciplines.Configurations provide a framework to represent an overall project design which is composed of designs from the participating disciplines. We apply a concept ofequivalent operations for developing operators that store, detect and manage changes among versions of a primitive design entity. The close coupling of the version, assembly, and configuration layers enables computed version changes to be recursively combined to characterize changes at the assembly and configuration levels. This applies for both project coordination throughasynchronous communication of changes among designers, and project monitoring through systematic tracking of evolving project descriptions. This paper also presents an implementation of the data management model in a CAD paradigm. We use a simple multidisciplinary facility design example to demonstrate the change management capabilities of the proposed model. This example has been tested on a prototype implementation in an AUTOCAD environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01350751
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  • 3
    Electronic Resource
    Electronic Resource
    Using objects to handle complexity in finite element software (1997)
    Springer
    Engineering with computers 13 (1997), S. 99-111 
    Details
    ISSN: 1435-5663
    Keywords: Finite elements ; Object oriented methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Engineering software is becoming ever more complex. Finite element programs have sophisticated graphical input and output facilities, and are increasingly required to be linked to other software such as CAD or databases. The paper shows how an object oriented approach to finite element programming can be used to handle this complexity. This requires an approach that is very different from that adopted in more traditional programming. A foundation finite element class system is developed. This represents the essential data structure of the main finite element classes. It is then shown how this system can be used in a graphical model of two dimensional structures. The finite element system imposed no constraints on the development of the graphical model, yet could still be used easily. An important feature is that the nodes and elements are distributed around the graphical model, rather than being held centrally. For instance nodes may belong to points or lines of the graphical model. This means that the data structure used in the program more closely matches the way that the user of the program is likely to think.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01350753
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  • 4
    Electronic Resource
    Electronic Resource
    Elimination of the adverse effects of small model features by the local modification of automatically generated meshes (1997)
    Springer
    Engineering with computers 13 (1997), S. 134-152 
    Details
    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Issues related to the automated identification and elimination of the adverse influence of small geometric model features on the quality of automatically generated meshes, using local mesh modification operators, are addressed. The definition of mesh validity with respect to the geometric model is extended to include multiple mesh entity classifications. Checks based on mesh topology are used to ensure no dimensional reductions in the locally modified mesh. Example geometric models of varied complexity containing small geometric features are used to demonstrate the ability of presented procedures to improve mesh quality in terms of aspect ratio and small angle metrics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01221211
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  • 5
    Electronic Resource
    Electronic Resource
    Local refinement of three-dimensional finite element meshes (1997)
    Springer
    Engineering with computers 13 (1997), S. 165-174 
    Details
    ISSN: 1435-5663
    Keywords: Mesh refinement ; Mixed element meshes ; Unstructured meshes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Mesh refinement is an important tool for editing finite element meshes in order to increase the accuracy of the solution. Refinement is performed in an iterative procedure in which a solution is found, error estimates are calculated, and elements in regions of high error are refined. This process is repeated until the desired accuracy is obtained. Much research has been done on mesh refinement. Research has been focused on two-dimensional meshes and three-dimensional tetrahedral meshes ([1] Ning et al. (1993) Finite Elements in Analysis and Design, 13, 299–318; [2] Rivara, M. (1991) Journal of Computational and Applied Mathematics 36, 79–89; [3] Kallinderis; Vijayar (1993) AIAA Journal,31, 8, 1440–1447; [4] Finite Element Meshes in Analysis and Design,20, 47–70). Some research has been done on three-dimensional hexahedral meshes ([5] Schneiders; Debye (1995) Proceedings IMA Workshop on Modelling, Mesh Generation and Adaptive Numerical Methods for Partial Differential Equations). However, little if any research has been conducted on a refinement algorithm that is general enough to be used with a mesh composed of any three-dimensional element (hexahedra, wedges, pyramids, and/or retrahedra) or any combination of three-dimensional elements (for example, a mesh composed of part hexahedra and part wedges). This paper presents an algorithm for refinement of three-dimensional finite element meshes that is general enough to refine a mesh composed of any combination of the standard three-dimensional element types.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01221213
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  • 6
    Electronic Resource
    Electronic Resource
    A simple genetic algorithm for the design of reinforced concrete beams (1997)
    Springer
    Engineering with computers 13 (1997), S. 185-196 
    Details
    ISSN: 1435-5663
    Keywords: Artificial intelligence ; Design optimization ; Genetic algorithms ; Structural optimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract We present an optimization model for the design of rectangular reinforced concrete beams subject to a specified set of constraints. Our model is more realistic than previously published models because it minimizes the cost of the beam on strength design procedures, while also considering the costs of concrete, steel and shuttering. Thus our method leads to very practical designs. As there is an infinite number of possible beam dimensions and reinforcement ratios that yield the same moment of resistance, an efficient search technique is preferred over the more traditional iterative methods. We employ a simple genetic algorithm as the search engine, and we compare our results with those obtained via geometric programming. Since the adjustment of parameters in a genetic algorithm (e.g., population size, crossover and mutation rates, and maximum number of generations) is a significant problem for any application, we present our own methodology to deal with this problem. A prototype of this system is currently being tested in México, in order to evaluate its potential as a reliable design tool for real world applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01200046
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  • 7
    Electronic Resource
    Electronic Resource
    Object-oriented analysis of spatial multibody systems based on graph theory (1997)
    Springer
    Engineering with computers 13 (1997), S. 211-221 
    Details
    ISSN: 1435-5663
    Keywords: Graph theory ; Joint coordinate method ; Linked lists of objects ; Object oriented hierarchy ; System matrices
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The purpose of this paper is to illustrate the implementation of efficient methods in the analysis of general multibody systems. The main goal is a total general purpose program which is able to handle the analysis of open as well as closed loop systems. The development of a general purpose program necessitates considerations concerning storing of code and data access facilities of the analysis code. Many of the building blocks for the analysis are supposed to solve the same problems although this is obtained in different ways depending on the specific type of block. These considerations lead to the creation of an object oriented structure of the analysis code. The development of the analysis algorithms is based on the kinematics of the system. The implementation of these schemes is based on graph theory and is presented through an example by the end of the paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01200048
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  • 8
    Electronic Resource
    Electronic Resource
    Design of multi-component structural systems for optimal layout topology and joint locations (1997)
    Springer
    Engineering with computers 13 (1997), S. 235-243 
    Details
    ISSN: 1435-5663
    Keywords: Structural connections ; Structural optimization ; Topology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Present day topology optimization techniques for continuum structures consider the design of single structural components, while most real life engineering design problems involve multiple components or structures. It is therefore necessary to have a methodology that can address the design of multi-component systems and generate designs for the optimal layouts of individual structures and locations for interconnections. The interconnections include supports provided by the ground, joints and rigid connections like rivets, bolts and welds between components. While topology optimization of structures has been extensively researched, relatively little work has been done on optimizing the locations of the interconnections. In this research, a method to model and define domains for the interconnections has been developed. The optimization process redistributes material in the component design domains and locates the connections optimally based on an energy criterion. Some practical design examples are used to illustrate the capability of this method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01200050
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  • 9
    Electronic Resource
    Electronic Resource
    Two remarks on circular arc graphs (1997)
    Springer
    Graphs and combinatorics 13 (1997), S. 65-72 
    Details
    ISSN: 1435-5914
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract In our first remark we observe a property of circular arcs which is similar to the Helly property and is helpful in describing all maximal cliques in circular arc graphs (as well as allowing us to genralize a result of Tucker). Our main result is a new simple characterization of circular arc graphs of clique covering number two. These graphs play a crucial role in recognition algorithms for circular arc graphs, and have been characterized by several authors. Specifically, we show that a graph with clique covering number two is a circular arc graph if and only if its edges can be coloured by two colours so that no induced four-cycle contains two opposite edges of the same colour. Our proof of the characterization depends on the ‘lexicographic method’ we have recently introduced. Both remarks could be useful in designing efficient algorithms for (maximum cliques in, respectively recognition of) circular arc graphs
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01202237
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  • 10
    Electronic Resource
    Electronic Resource
    Cycle-pancyclism in tournaments III (1997)
    Springer
    Graphs and combinatorics 13 (1997), S. 57-63 
    Details
    ISSN: 1435-5914
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract LetT be a hamiltonian tournament withn vertices and γ a hamiltonian cycle ofT. For a cycleC k of lengthk inT we denoteI γ(C k, the number of arcs that γ andC k have in common. Letf(n,k,T,γ)=max{I γ(C k)|C k ⊂T} andf(n, k)=min{f(n, k, T, γ)|T is a hamiltonian tournament withn vertices, and γ a hamiltonian cycle ofT}. In a previous paper [3] we studied the case ofn≥2k−4 and proved that .f(n, 3)=1, f(n, 4)=1 andf(n, 5)=2 ifn≠2k−2; .f(n, k)=k−1 if and only ifn=2k−2; . fork〉5,f(n, k)=k−2 if and only ifn≥2k−4,n≠2k−2 andn≡k (modk−2); . fork〉5,f(n, k)=k−3 if and only ifn≥2k−4 andn≢k (modk−2). In this paper we consider the case ofn≤2k−5 and complete the description off(n, k) by proving thatf(n, k)=k−4 if and only ifn≤2k−5.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01202236
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  • 11
    Electronic Resource
    Electronic Resource
    A new recursive theorem onn-extendibility (1997)
    Springer
    Graphs and combinatorics 13 (1997), S. 79-83 
    Details
    ISSN: 1435-5914
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract A graphG having a 1-factor is calledn-extendible if every matching of sizen extends to a 1-factor. LetG be a 2-connected graph of order 2p. Letr≥0 andn〉0 be integers such thatp−r≥n+1. It is shown that ifG/S isn-extendible for every connected subgraphS of order 2r for whichG/S is connected, thenG isn-extendible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01202239
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  • 12
    Electronic Resource
    Electronic Resource
    d-Cube decompositions ofK n/K m (1997)
    Springer
    Graphs and combinatorics 13 (1997), S. 1-7 
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    ISSN: 1435-5914
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Necessary conditions onn, m andd are given for the existence of an edge-disjoint decomposition ofK n/K m into copies of the graph of ad-dimensional cube. Sufficiency is shown whend=3 and, in some cases, whend=2t. We settle the problem of embedding 3-cube decompositions ofK m into 3-cube decompositions ofK n, wheren≥m.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01202232
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  • 13
    Electronic Resource
    Electronic Resource
    Searching for counterfeit coins (1997)
    Springer
    Graphs and combinatorics 13 (1997), S. 9-20 
    Details
    ISSN: 1435-5914
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract The well-known counterfeit problem asks for the minimum number of weighings necessary to determine all fake coins in a given set ofn coins. We derive a new upper bound when we know that at mostd coins are defective, improving a previous result of L. Pyber.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01202233
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  • 14
    Electronic Resource
    Electronic Resource
    The girth of a thin distance-regular graph (1997)
    Springer
    Graphs and combinatorics 13 (1997), S. 21-30 
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    ISSN: 1435-5914
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Let Γ be a distance-regular graph of diameterd≥3. For each vertexx of Γ, letT(x) denote the Terwilliger algebra for Γ with respect tox. An irreducibleT(x)-moduleW is said to bethin if dimE i * (x)W≤1 for 0≤i≤d, whereE i * (x) is theith dual idempotent for Γ with respect tox. The graph Γ isthin if for each vertexx of Γ, every irreducibleT(x)-module is thin. Aregular generalized quadrangle is a bipartite distance-regular graph with girth 8 and diameter 4. Our main results are as follows: Theorem. Let Γ=(X,R) be a distance-regular graph with diameter d≥3 and valency k≥3. Then the following are equivalent: (i) Γis a regular generalized quadrangle. (ii) Γis thin and c 3=1. Corollary. Let Γ=(X,R) be a thin distance-regular graph with diameter d≥3 and valency k≥3. Then Γ has girth 3, 4, 6, or 8. Then girth of Γ is 8 exactly when Γ is a regular generalized quadrangle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01202234
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  • 15
    Electronic Resource
    Electronic Resource
    Partitions of bipartite numbers (1997)
    Springer
    Graphs and combinatorics 13 (1997), S. 73-78 
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    ISSN: 1435-5914
    Keywords: 11P82 ; 11P81 ; 05A17 ; Partitions ; Bipartite partitions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Letp j(m, n) be the number of partitions of (m, n) into at mostj parts. We prove Landman et al.'s conjecture: for allj andn, p j(x, 2n−x) is a maximum whenx-n. More generally we prove that for all positive integersm, n andj, p j(n, m)=pj(m, n)≥pj(m−1, n+1) ifm≤n.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01202238
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  • 16
    Electronic Resource
    Electronic Resource
    The problem of irregular perfect systems of sets of iterated differences (1997)
    Springer
    Graphs and combinatorics 13 (1997), S. 85-94 
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    ISSN: 1435-5914
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Fors≥2, the set of iterated differences associated with the prescribed integersa(s, j), 1≤j≤s, is the set {a(i, j): 1≤j≤i≤s} wherea(i−1,j)=|a(i, j)−a(i, j+1)|, general problem raised by work of Kreweras and Loeb concerns the existence of partitions of runs of consecutive integers into full sets of iterated differences. In the regular case, where all the sets of iterated differences have the same valencys, it is known that such partitions do not exist at least fors〉8. We find here that the problem is more challenging in the case where the sets have different valencies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01202240
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  • 17
    Electronic Resource
    Electronic Resource
    Design and performance evaluation of an RRA scheme for voice‐data channel access in outdoor microcellular environments (1997)
    Springer
    Mobile networks and applications 2 (1997), S. 31-43 
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    ISSN: 1572-8153
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In PCS networks, the multiple access problem is characterized by spatially dispersed mobile source terminals sharing a radio channel connected to a fixed base station. In this paper, we design and evaluate a reservation random access (RRA) scheme that multiplexes voice traffic at the talkspurt level to efficiently integrate voice and data traffic in outdoor microcellular environments. The scheme involves partitioning the time frame into two request intervals (voice and data) and an information interval. Thus, any potential performance degradation caused by voice and data terminals competing for channel access is eliminated. We consider three random access algorithms for the transmission of voice request packets and one for the transmission of data request packets. We formulate an approximate Markov model and present analytical results for the steady state voice packet dropping probability, mean voice access delay and voice throughput. Simulations are used to investigate the steady state voice packet dropping distribution per talkspurt, and to illustrate preliminary voice-data integration considerations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1013251826537
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  • 18
    Electronic Resource
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    Performance study of access control in wireless LANs – IEEE 802.11 DFWMAC and ETSI RES 10 Hiperlan (1997)
    Springer
    Mobile networks and applications 2 (1997), S. 55-67 
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    ISSN: 1572-8153
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Currently two projects are on their way to standardize physical layer and medium access control for wireless LANs – IEEE 802.11 and ETSI RES 10 Hiperlan. This paper presents an introduction to both projects focussing on the applied access schemes. Further we will present our simulation results, analyzing the performance of both access protocols depending on the number of stations and on the packet size, evaluating them regarding their capability to support QoS parameters, regarding the impact of hidden terminals and their range extension strategy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1013255927445
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  • 19
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    Editorial: Data Management Issues in Mobile Computing (1997)
    Springer
    Mobile networks and applications 2 (1997), S. 113-114 
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    ISSN: 1572-8153
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1013674029263
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  • 20
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    Performance of ARQ Go-Back-N protocol in Markov channels with unreliable feedback (1997)
    Springer
    Mobile networks and applications 2 (1997), S. 183-193 
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    ISSN: 1572-8153
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper, an ARQ Go-Back-N protocol with time-out mechanism is studied. Transmissions on both the forward and the reverse channels are assumed to be subject to Markovian errors. A recently developed approach, based on renewal theory, is further extended and the steady state average number of packets in the ARQ system is evaluated. This allows us to determine analytically both throughput and transmission delay of the system. Simulation results, that confirm the analysis, are also presented. Based on the analysis, the trade-off involved in the choice of the time-out parameter is identified and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1013628616059
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  • 21
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    Link layer retransmission schemes for circuit-mode data over the CDMA physical channel (1997)
    Springer
    Mobile networks and applications 2 (1997), S. 195-211 
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    ISSN: 1572-8153
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In the last few years, wide-area data services over North American digital (TDMA and CDMA) cellular networks have been standardized. The standards were developed under three primary constraints: (i) compatibility with existing land-line standards and systems, (ii) compatibility with existing cellular physical layer standards that are optimized for voice, and (iii) market demands for quick solutions. In particular, the IS-95 CDMA air interface standard permits multiplexing of primary traffic (e.g., voice or circuit data) and secondary traffic (e.g., packet data) or in-band signaling within the same physical layer burst. In this paper, we describe two radio link protocols for circuit-mode data over IS-95. The first protocol, Protocol S, relies on a single level of recovery and uses a flexible segmentation and recovery (FSAR) sublayer to efficiently pack data frames into multiplexed physical layer bursts. We next describe Protocol T, that consists of two levels of recovery. Protocol T has been standardized for CDMA circuit-mode data as IS-99 (Telecommunications Industry Association, 1994). We provide performance comparisons of the two protocols in terms of throughput, delay and recovery from fades. We find that the complexity of the two level recovery mechanism can buy higher throughput through the reduced retransmission data unit size. However, the choice of TCP (and its associated congestion control mechanism) as the upper layer of recovery on the link layer, leads to long fade recovery times for Protocol T. The two approaches also have significant differences with respect to procedures and performance at handoff and connection establishment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1013680600129
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  • 22
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    A formal method for synthesizing optimized protocol converters and its application to mobile data networks (1997)
    Springer
    Mobile networks and applications 2 (1997), S. 259-269 
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    ISSN: 1572-8153
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract As mobile information networks are expanding rapidly, we expect to integrate voice, paging, electronic mail and other wireless information services. Interworking units that perform protocol conversion at the boundaries of different networks will play an important role. In this paper, we propose an efficient algorithm for constructing optimized protocol converters to achieve interoperability between heterogeneous data networks. This algorithm first derives constraints from two given protocols, and apply the constraints to channel specifications, thus removing message sequences that do not contribute to system progress. Then, an optimized converter is generated from a given service specification, the two protocol specifications and the modified channel specifications. A reduction relation is used to compare the service specification and the constructed internetworking system in order to deal with the problem of nondeterministic services. Compared with related works, our method has two advantages: (1) it generates an optimized converter; (2) it can be applied to the case that the service specification is nondeterministic. The application of the method to mobile networks is given by an example.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1013692902855
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  • 23
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    Communication protocol design to facilitate re‐use based on the object‐oriented paradigm (1997)
    Springer
    Mobile networks and applications 2 (1997), S. 285-301 
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    ISSN: 1572-8153
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The main motivation for the present work stems from the wide gap which exists between the research efforts devoted to developing formal descriptions for communication protocols and the effective development methodologies used in industrial implementations. We apply Object-Oriented (OO) modelling principles to networking protocols, exploring the potential for producing re-useable software modules by discovering the underlying generic class structures and behaviour. Petri Nets (PNs) are used to derive re-useable model elements and a slightly modified TTCN notation is used for message sequence encoding. This demonstrates a formal, practical approach to the development of a protocol implementation through OO modelling. Our utilisation of PNs in the context of object based modelling allows for isolation of the behavioural characterisation of objects into a separate design plane, treated as a meta-level object control. This separation permits greater execution flexibility of the underlying object models. It is that very aspect of our modelling approach which can be utilised in software implementations where dynamically determined ‘re-programming’ (i.e., change of procedures) is needed. For example, one of the requirements in wireless networking software is the ability to cope with ever-changing transmission/reception conditions and that, in turn, creates greatly varying error rates. Similarly, handoff procedures create situations where dynamically determined change of operational modes is required. To illustrate the modelling concepts, the paper addresses the problem of inter-layer communication among multiple protocol entities (PEs), assuming the standard ISO/OSI Reference Model. A generalised model called the Inter-Layer Communication (ILC) Model is proposed. An example of a PE based on the Alternating-Bit Protocol (ABP) is also discussed. The final example demonstrates how meta-level object control (PNs) allows for the dynamic selection of different ARQ based algorithms.
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    URL: http://dx.doi.org/10.1023/A:1013697003764
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    An efficient multicast protocol for PCS networks (1997)
    Springer
    Mobile networks and applications 2 (1997), S. 333-344 
    Details
    ISSN: 1572-8153
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In a Personal Communication Services (PCS) network, mobile hosts communicate with other mobile hosts through base stations on a wired (static) network. The mobile hosts connect to different base stations through wireless links and the base stations to which mobile hosts are connected change depending on the current location of the mobile hosts. In this environment, the problem of efficiently delivering a multicast message from one mobile host to a group of other mobile hosts becomes challenging. In this paper, we present a multicast protocol that delivers multicast messages from a mobile host to a group of other mobile hosts without flooding the wired network. The multicast protocol is built on top of a user location strategy that should follow one of the three models of user location described in the paper. The basic multicast protocol proposed guarantees exactly‐once message delivery to all mobile hosts in the multicast group and also ensures that multicast messages are delivered in FIFO order from the point of view of the base station that originates the multicast message (referred to as BS‐FIFO). More importantly, an extension of the basic protocol is provided that, unlike earlier work, delivers multicast messages in FIFO order from the point of view of the mobile host that initiates the multicast message (referred to as MH‐FIFO). The modifications to be made to the multicast protocol to accommodate each of the three models of user location is also described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1013657422419
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    Editorial (1997)
    Springer
    International journal of speech technology 2 (1997), S. 5-6 
    Details
    ISSN: 1572-8110
    Source: Springer Online Journal Archives 1860-2000
    Topics: Linguistics and Literary Studies , Computer Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02215799
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    Keep talking—Performance effectiveness with continuous voice recognition for spreadsheet users (1997)
    Springer
    International journal of speech technology 2 (1997), S. 41-48 
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    ISSN: 1572-8110
    Keywords: voice recognition ; user performance ; spreadsheet ; continuous voice recognition ; decision style ; voice input
    Source: Springer Online Journal Archives 1860-2000
    Topics: Linguistics and Literary Studies , Computer Science
    Notes: Abstract The performance of spreadsheet users was compared for two modes of input to the computer—keyboard and continuous voice recognition (CVR)—for subjects classified by their decision style. In addition, the data for this experiment was compared to results of a similar experiment that used a discrete word recognition system. Dependent measures were task completion time, accuracy, keystroke count, correction count, and user confidence for spreadsheet tasks. Results, using a speaker-dependent continuous voice recognizer, showed that for both simple data input and more complex analytical problems, subjects did not perform more effectively using CVR compared to keyboard. In addition, a subject's decision style was found not to interact with CVR for an effect on performance. Compared to earlier discrete word recognition results, CVR tended to shorten the time to complete a spreadsheet analysis task.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02215803
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    Telephony based speech technology—From laboratory visions to customer applications (1997)
    Springer
    International journal of speech technology 2 (1997), S. 89-99 
    Details
    ISSN: 1572-8110
    Keywords: telephony based speech technology ; speech platforms ; directory automation ; text to speech ; large vocabulary speech recognition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Linguistics and Literary Studies , Computer Science
    Notes: Abstract This paper describes how research into Automatic Speech Recognition (ASR) and Text to Speech Synthesis (TTS) is being widely applied within the UK telephone network. It compares and contrasts telephony based speech technology with that used in non-telephony based applications and describes some of the special problems associated with integrating these into the existing telephone network. In particular, it highlights the main issues concerned with providing flexible, yet robust, multiple channel systems and shows how this has been achieved on a commercial speech platform. Finally, it describes how the platform has been used to deliver a number of advanced services including CallMinderTM and MeterLinkTM and how it is now being used to trial larger vocabulary applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02208821
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    A spoken dialog system for the Dutch public transport information service (1997)
    Springer
    International journal of speech technology 2 (1997), S. 121-131 
    Details
    ISSN: 1572-8110
    Keywords: spoken dialog systems ; public transport information ; continuous speech recognition ; natural language processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Linguistics and Literary Studies , Computer Science
    Notes: Abstract In the Netherlands there is a nationwide premium rate telephone number that can be dialed to obtain information about various forms of public transport. In 1996 this number was called more than twelve million times. Human operators managed to handle only about nine million of these calls. In order to answer more of these calls, a spoken dialog system was developed to automate part of this service. The automation component concerns information about journeys between two train stations. The starting point of our research was an existing German information system. This system was ported to Dutch. A bootstrapping method was used to collect the data, which in turn were used to improve the system itself.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02208824
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    ECHO: A speech recognition package for the design of robust interactive speech-based applications (1997)
    Springer
    International journal of speech technology 2 (1997), S. 133-143 
    Details
    ISSN: 1572-8110
    Keywords: speech recognition ; robustness ; usability ; speech-based applications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Linguistics and Literary Studies , Computer Science
    Notes: Abstract This paper describes speech recognition software called ECHO (Environnement de Communication Homme-Ordinateur) which is devoted to the design of usable interactive speech-based applications. “Usability” refers to the stability of the Speech Recognition system performance under ordinary usage conditions (i.e., different acoustic environments) rather than high performance in a limited set of well-known conditions. In order to reach this objective, the system must be able to anticipate any change in the environment and adapt itself to the different usage conditions. One solution for this problem has been achieved by connecting some specialized modules of speech signal pre-processing and post-processing to the automatic speech recognition engine. These different modules interact as a mirror with the speech engine in order to force it to adapt its runtime parameters, thus improving its performance and its robustness.
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    URL: http://dx.doi.org/10.1007/BF02208825
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    A new model for scheduling packet radio networks (1997)
    Springer
    Wireless networks 3 (1997), S. 71-82 
    Details
    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract Packet radio networks are modeled as arbitrary graphs by most researchers. In this paper we show that an arbitrary graph is an inaccurate model of the radio networks. This is true because there exists a large class of graphs which will not model the radio networks. Radio networks can be modeled accurately by a restricted class of graphs called the planar point graphs. Since the radio networks can accurately be modeled only by a restricted class of graphs, the NP-completeness results for scheduling using an arbitrary graph as the model, do not correctly reflect the complexity of the problem. In this paper we study the broadcast scheduling problem using the restricted class as the model. We show that the problem remains NP-complete even in this restricted domain. We give an O(n log n) algorithm when all the transceivers are located on a line.
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    URL: http://dx.doi.org/10.1023/A:1019128411323
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    Delay analysis for forward signaling channels in wireless cellularnetwork (1997)
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    Wireless networks 3 (1997), S. 53-69 
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    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract We consider connection-oriented wireless cellular networks. Such second generation systems are circuit-switched digital networks which employ dedicated radio channels for the transmission of signaling information. A forward signaling channel is a common signaling channel assigned to carry the multiplexed stream of paging and channel-allocation packets from a base station to the mobile stations. Similarly, for ATM wireless networks, paging and virtual-circuit-allocation packets are multiplexed across the forward signaling channels as part of the virtual-circuit set-up phase. The delay levels experienced by paging and channel-allocation packets are critical factors in determining the efficient utilization of the limited radio channel capacity. A multiplexing scheme operating in a “slotted mode” can lead to reduced power consumption at the handsets, but may in turn induce an increase in packet delays. In this paper, focusing on forward signaling channels, we present schemes for multiplexing paging and channel-allocation packets across these channels, based on channelization plans, access priority assignments and paging group arrangements. For such multiplexing schemes, we develop analytical methods for the calculation of the delay characteristics exhibited by paging and channel-allocation packets. The resulting models and formulas provide for the design and analysis of forward signaling channels for wireless network systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019176327253
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    Using channel state dependent packet scheduling to improve TCPthroughput over wireless LANs (1997)
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    Wireless networks 3 (1997), S. 91-102 
    Details
    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract In recent years, a variety of mobile computers equipped with wireless communication devices have become popular. These computers use applications and protocols, originally developed for wired desktop hosts, to communicate over wireless channels. Unlike wired networks, packets transmitted on wireless channels are often subject to burst errors which cause back to back packet losses. In this paper we study the effect of burst packet errors and error recovery mechanisms employed in wireless MAC protocols on the performance of transport protocols such as TCP. Most wireless LAN link layer protocols recover from packet losses by retransmitting lost segments. When the wireless channel is in a burst error state, most retransmission attempts fail, thereby causing poor utilization of the wireless channel. Furthermore, in the event of multiple sessions sharing a wireless link, FIFO packet scheduling can cause the HOL blocking effect, resulting in unfair sharing of the bandwidth. This observation leads to a new class of packet dispatching methods which explicitly take wireless channel characteristics into consideration in making packet dispatching decisions. We compare a variety of channel state dependent packet (CSDP) scheduling methods with a view towards enhancing the performance of transport layer sessions. Our results indicate that by employing a CSDP scheduler at the wireless LAN device driver level, significant improvement in channel utilization can be achieved in typical wireless LAN configurations.
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    URL: http://dx.doi.org/10.1023/A:1019132612232
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    Cumulated interference power and bit‐error‐rates in mobile packet radio (1997)
    Springer
    Wireless networks 3 (1997), S. 169-172 
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    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract In this paper we determine the probability distribution function of cumulated instantaneous interference power in a mobile radio network, when the positions of interfering stations are distributed according to a one‐ or two‐dimensional Poisson point process, truncated at a finite horizon. The influences of Rice and Rayleigh fading, lognormal shadowing, near far effect and capture are taken into account. From the resulting distribution the probability of successful transmission and corresponding bit‐error‐rates are derived.
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    URL: http://dx.doi.org/10.1023/A:1019149015867
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    Paging strategy optimization in personal communication systems (1997)
    Springer
    Wireless networks 3 (1997), S. 195-204 
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    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract Mobility tracking is concerned with finding a mobile subscriber (MS) within the area serviced by the wireless network. The two basic operations for tracking an MS, location updating and paging, constitute additional load on the wireless network. The total cost of updating and paging can be minimized by optimally dividing the cellular area into location registration (LR) areas. In current systems broadcast paging messages are sent within the LR area to alert the MS of an incoming call. In this paper we propose a selective paging strategy which uses the MS mobility and call patterns to minimize the cost of locating an MS within an LR area subject to a constraint on the delay in locating the MS.
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    URL: http://dx.doi.org/10.1023/A:1019105200845
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    Performance modeling of asynchronous data transfer methods of IEEE 802.11 MAC protocol (1997)
    Springer
    Wireless networks 3 (1997), S. 217-234 
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    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract To satisfy the needs of wireless data networking, study group 802.11 was formed under IEEE project 802 to recommend an international standard for Wireless Local Area Networks (WLANs). A key part of standard are the Medium Access Control (MAC) protocol needed to support asynchronous and time bounded delivery of data frames. It has been proposed that unslotted Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) be the basis for the IEEE 802.11 WLAN MAC protocols. We conduct performance evaluation of the asynchronous data transfer protocols that are a part of the proposed IEEE 802.11 standard taking into account the decentralized nature of communication between stations, the possibility of “capture”, and presence of “hidden” stations. We compute system throughput and evaluate fairness properties of the proposed MAC protocols. Further, the impact of spatial characteristics on the performance of the system and that observed by individual stations is determined. A comprehensive comparison of the access methods provided by the 802.11 MAC protocol is done and observations are made as to when each should be employed. Extensive numerical and simulation results are presented to help understand the issues involved.
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    URL: http://dx.doi.org/10.1023/A:1019109301754
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    A control and management network for wireless ATM systems (1997)
    Springer
    Wireless networks 3 (1997), S. 1-17 
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    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract This paper describes the design of a control and management network (orderwire) for a mobile wireless Asynchronous Transfer Mode (ATM) network. This mobile wireless ATM network is part of the Rapidly Deployable Radio Network (RDRN). The orderwire system consists of a packet radio network which overlays the mobile wireless ATM network. Each network element in this network uses Global Positioning System (GPS) information to control a beamforming antenna subsystem which provides for spatial reuse. This paper also proposes a novel Virtual Network Configuration (VNC) algorithm for predictive network configuration. A mobile ATM Private Network–Network Interface (PNNI) based on VNC is also discussed. Finally, as a prelude to the system implementation, results of a Maisie simulation of the orderwire system are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019117603571
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    A rate‐based overload control method for the radio channel in PCN (1997)
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    Wireless networks 3 (1997), S. 1-9 
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    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract Third‐generation wireless digital communication systems, currently being developed, are intended to integrate all the existing wireless systems and cover a wide range of services, including voice, video and multimedia. A difficult problem towards this direction is the efficient use of the limited available bandwidth. Although considerable improvements have been made recently in transmitter and receiver technology, the capacity of the air interface is still considerably smaller compared to other media such as fiber optics. Accordingly, traffic congestion is an important problem, especially for bandwidth demanding applications (e.g., video), leading to poor quality‐of‐service (QoS). This paper presents an overload control method, for TDMA systems, to temporarily reduce the source rate requirements to a sustainable level, in order to avoid a sudden degradation in QoS. The control is activated when the aggregate rate crosses a predefined threshold that identifies congestion. To ensure fairness, the selection of the sources whose rate will be reduced is performed in co‐operation with a priority‐based scheduling technique. The performance of the system under the proposed method is analyzed and system parameter values are optimized. It is shown that the method attains considerable improvement in the loss probability performance.
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    URL: http://dx.doi.org/10.1023/A:1019165519501
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    Editorial (1997)
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    Wireless networks 3 (1997), S. 309-310 
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    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019125805388
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    Editorial (1997)
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    Formal methods in system design 10 (1997), S. 5-5 
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    ISSN: 1572-8102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008659413372
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    Introduction to the Special Issue on Computer-Aided Verification (CAV93) (1997)
    Springer
    Formal methods in system design 11 (1997), S. 111-112 
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    ISSN: 1572-8102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008603628600
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    Joint Minimization of Code and Data for Synchronous Dataflow Programs (1997)
    Springer
    Formal methods in system design 11 (1997), S. 41-70 
    Details
    ISSN: 1572-8102
    Keywords: dataflow programming ; synchronous dataflow ; memory management ; multirate signal processing algorithms ; SDF compiler ; on-chip memory ; minimum cuts ; dynamic programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper, we formally develop techniques that minimize the memory requirements of a target program when synthesizing software from dataflow descriptions of multirate signal processing algorithms. The dataflow programming model that we consider is the synchronous dataflow (SDF) model [21], which has been used heavily in DSP design environments over the past several years. We first focus on the restricted class of well-ordered SDF graphs. We show that while extremely efficient techniques exist for constructing minimum code size schedules for well-ordered graphs, the number of distinct minimum code size schedules increases combinatorially with the number of vertices in the input SDF graph, and these different schedules can have vastly different data memory requirements. We develop a dynamic programming algorithm that computes the schedule that minimizes the data memory requirement from among the schedules that minimize code size, and we show that the time complexity of this algorithm is cubic in the number of vertices in the given well-ordered SDF graph. We present several extensions to this dynamic programming technique to more general scheduling problems, and we present a heuristic that often computes near-optimal schedules with quadratic time complexity. We then show that finding optimal solutions for arbitrary acyclic graphs is NP-complete, and present heuristic techniques that jointly minimize code and data size requirements. We present a practical example and simulation data that demonstrate the effectiveness of these techniques.
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    URL: http://dx.doi.org/10.1023/A:1008633809454
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    Verification of Real-Time Systems using Linear Relation Analysis (1997)
    Springer
    Formal methods in system design 11 (1997), S. 157-185 
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    ISSN: 1572-8102
    Keywords: abstract interpretation ; convex polyhedra ; real time systems ; synchronous languages ; hybrid systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Linear Relation Analysis [11] is an abstract interpretation devoted to the automatic discovery of invariant linear inequalities among numerical variables of a program. In this paper, we apply such an analysis to the verification of quantitative time properties of two kinds of systems: synchronous programs and linear hybrid systems.
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    URL: http://dx.doi.org/10.1023/A:1008678014487
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    Computing Accumulated Delays in Real-time Systems (1997)
    Springer
    Formal methods in system design 11 (1997), S. 137-155 
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    ISSN: 1572-8102
    Keywords: Formal verification ; model checking ; real-time systems ; duration properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We present a verification algorithm for duration properties of real-time systems. While simple real-time properties constrain the total elapsed time between events, duration properties constrain the accumulated satisfaction time of state predicates. We formalize the concept of durations by introducing duration measures for timed automata. A duration measure assigns to each finite run of a timed automaton a real number —the duration of the run— which may be the accumulated satisfaction time of a state predicate along the run. Given a timed automaton with a duration measure, an initial and a final state, and an arithmetic constraint, the duration-bounded reachability problem asks if there is a run of the automaton from the initial state to the final state such that the duration of the run satisfies the constraint. Our main result is an (optimal) PSPACE decision procedure for the duration-bounded reachability problem.
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    URL: http://dx.doi.org/10.1023/A:1008626013578
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    A Unifying Theoretical Background for Some Bdd-based Data Structures (1997)
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    Formal methods in system design 11 (1997), S. 223-237 
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    ISSN: 1572-8102
    Keywords: OBDD ; data structures for Boolean manipulation ; cube transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In the paper, we propose a general concept (denoted by TBDD) for Boolean functions manipulation that is based on cube transformations. The basic idea is to manipulate a Boolean function by converting it by means of a cube transformation into a function that can be efficiently represented and manipulated in terms of ordered binary decision diagrams (OBDDs). We show that the new concept unifies several BDD–based data structures considerably, and simplifies their manipulation to work with the simple and well–understood data struture of OBDDs. This is especially important for practical applications. Further, to give an example of how TBDDs open new ways in the search for efficient data structures for Boolean functions, we discuss the data structure of typed kFBDDs.
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    URL: http://dx.doi.org/10.1023/A:1008667729897
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    Turn-taking as a design principle for barge-in in Spoken Language Systems (1997)
    Springer
    International journal of speech technology 2 (1997), S. 155-164 
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    ISSN: 1572-8110
    Keywords: spoken language systems ; automatic speech recognition ; barge-in ; telephone interface ; user interface design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Linguistics and Literary Studies , Computer Science
    Notes: Abstract It is widely acknowledged that users of Spoken Language Systems (SLS) want the ability to truncate system prompts by using a barge-in capability (e.g., Basson et al., 1995; Yankelovich et al., 1995). However, little has been published on how barge-in is used or if it adversely affects Automatic Speech Recognition (ASR) and the interface usability. Typically, user requests for barge-in are assumed to be based on the desire to make system interactions faster and therefore more similar to interactions with touch-tone systems. We believe that requests for a barge-in capability are rooted in the notion of discourse as a turn-taking event. Viewed in this way, we believe SLS can be enhanced to develop speech interfaces that are deemed more natural by users, as well as to increase system performance. This study addressed several issues. We found that users new to the system did not need to be informed about the barge-in capability before they attempted barge-in, that they used barge-in during almost half of their interactions with the system, and that they had identifiable patterns of barge-in use consistent with the turn-taking model. Results are presented and consequences for speech interface design as well as algorithm enhancement are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02208827
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    Error control schemes for networks: An overview (1997)
    Springer
    Mobile networks and applications 2 (1997), S. 167-182 
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    ISSN: 1572-8153
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper, we investigate the issue of error control in wireless communication networks. We review the alternative error control schemes available for providing reliable end-to-end communication in wireless environments. Through case studies, the performance and tradeoffs of these schemes are shown. Based on the application environments and QoS requirements, the design issues of error control are discussed to achieve the best solution.
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    URL: http://dx.doi.org/10.1023/A:1013676531988
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    Extending NCP for protocols using public keys (1997)
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    Mobile networks and applications 2 (1997), S. 227-241 
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    ISSN: 1572-8153
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract One of the greatest obstacles to wide-spread deployment of wireless mobile systems is security. Cryptographically strong protocols and algorithms are required to enable secure communication over links that are easy to monitor and control by an attacker. While good cryptographic algorithms exist, it is difficult to design protocols that are immune to malicious attack. Good analysis techniques are lacking. This paper presents extensions to a technique for specifying and analyzing nonmonotonic cryptographic protocols that use asymmetric keys. We introduce new actions and inference rules, as well as slight modifications to the Update function. An important observation is that reasoning about the origin of messages is quite different when dealing with asymmetric key protocols. We also introduce the notion that keys in certificates should be bound to the principals receiving them. We extend the technique to meet the binding requirements and show how the flaw in the Denning and Sacco public key protocol, which was discovered by Abadi and Needham, is revealed. We demonstrate the extended technique using one protocol of our own and the Needham and Schroeder public key protocol. We also introduce and analyze a fix to a known weakness in Needham and Schroeder’s protocol using our extended technique. Finally, we present several applications of these techniques to protocols for mobile computing over wireless networks.
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    URL: http://dx.doi.org/10.1023/A:1013636817876
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  • 48
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    Editorial (1997)
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    Mobile networks and applications 2 (1997), S. 303-304 
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    ISSN: 1572-8153
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1013649120602
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  • 49
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    Performance evaluation of optimum combining and maximal ratio combining in the presence of co‐channel interference and channel correlation for wireless communication systems (1997)
    Springer
    Mobile networks and applications 2 (1997), S. 315-324 
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    ISSN: 1572-8153
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Antenna diversity is an important technique to combat fading and reduce co‐channel interference (CCI). In this paper, we present an analytical approach to derive bit error rate (BER) for Optimum Combining (OC) and Maximal Ratio Combining (MRC) in the presence of CCI. The paper has two parts. In the first part, the analysis of BER for OC with two co‐channel interferers and MRC with an arbitrary number of interferers is presented for M‐array antenna systems under the assumption that the channels of users are independent of each other. In the second part, the analysis of BER for OC and MRC in the presence of one dominant co‐channel interferer is presented for dual antenna systems by assuming that the channels of the desired user or co‐channel interferer are correlated. For DPSK signal, an exact BER expression is derived. The work presented here also yields an upper bound for BPSK or QAM signal based on the results of Foschini and Salz (1983).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1013653321510
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  • 50
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    Zippering: Managing intermittent connectivity in DIANA (1997)
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    Mobile networks and applications 2 (1997), S. 357-364 
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    ISSN: 1572-8153
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper describes an approach for handling intermittent connectivity between mobile clients and network‐resident applications, which we call zippering. When the client connects with the application, communication between the client and the application is synchronous. When the client intermittently connects with the application, communication becomes asynchronous. The DIANA (Device‐Independent, Asynchronous Network Access) approach allows the client to perform a variety of operations while disconnected. Finally, when the client reconnects with the application, the operations performed independently on the client are replayed to the application in the order they were originally done. Zippering allows the user at the client to fix errors detected during reconciliation and continues the transaction gracefully instead of aborting the whole transaction when errors are detected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1013661523328
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  • 51
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    Editorial: Error Control in Wireless Packet Networks (1997)
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    Mobile networks and applications 2 (1997), S. 165-166 
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    ISSN: 1572-8153
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1013624515150
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  • 52
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    Editorial (1997)
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    Mobile networks and applications 2 (1997), S. 225-226 
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    ISSN: 1572-8153
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1013684701038
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  • 53
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    Editorial (1997)
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    International journal of speech technology 1 (1997), S. 89-90 
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    ISSN: 1572-8110
    Source: Springer Online Journal Archives 1860-2000
    Topics: Linguistics and Literary Studies , Computer Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02277189
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  • 54
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    A mobile transaction model that captures both the data and movement behavior (1997)
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    Mobile networks and applications 2 (1997), S. 149-162 
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    ISSN: 1572-8153
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Unlike distributed transactions, mobile transactions do not originate and end at the same site. The implication of the movement of such transactions is that classical atomicity, concurrency and recovery solutions must be revisited to capture the movement behavior. As an effort in this direction, we define a model of mobile transactions by building on the concepts of split transactions and global transactions in a multidatabase environment. Our view of mobile transactions, called Kangaroo Transactions, incorporates the property that transactions in a mobile computing system hop from one base station to another as the mobile unit moves through cells. Our model is the first to capture this movement behavior as well as the data behavior which reflects the access to data located in databases throughout the static network. The mobile behavior is dynamic and is realized in our model via the use of split operations. The data access behavior is captured by using the idea of global and local transactions in a multidatabase system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1013672431080
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  • 55
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    Methods for packet combining in HARQ systems over bursty channels (1997)
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    Mobile networks and applications 2 (1997), S. 213-224 
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    ISSN: 1572-8153
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The performance of ARQ systems can be improved by combining current and prior transmissions at the receiver. Two techniques for combining outputs in a packet-based communication system are presented. In both techniques the fundamental unit of retransmission is a packet, and the fundamental unit of combining is a codeword. The techniques are analyzed for a bursty channel and a system that employs Reed–Solomon coding and bounded-distance errors-and-erasures decoding. Performance results show that the packet-combining schemes provide significant gains in throughput and reductions in error probability when compared with a system that does not employ combining.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1013632716967
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  • 56
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    Deadlock detection in communicating finite state machines by even reachability analysis (1997)
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    Mobile networks and applications 2 (1997), S. 251-257 
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    ISSN: 1572-8153
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A network of communicating finite state machines (CFSM) consists of a set of finite state machines which communicate asynchronously with each other over (potentially) unbounded FIFO channels by sending and receiving typed messages. As a concurrency model, CFSMs has been widely used to specify and validate communications protocols. CFSMs is also powerful and suitable for modeling mobile communication systems – a CFSM can naturally model a mobile station in a wireless communication system. The unbounded FIFO channels are ideal for modeling the communication behavior among mobile stations. Fair reachability is a very useful technique in detecting errors of deadlocks and unspecified receptions in networks of (CFSMs) consisting of two machines. The paper extends the classical fair reachability technique, which is only applicable to the class of two-machine CFSMs, to the general class of CFSMs. For bounded CFSMs, the extended fair reachability technique reduces by more than one half the total number of reachable global states that have to be searched in verifying freedom from deadlocks. The usefulness of the new reachability technique, called even reachability, is demonstrated through two examples.
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    URL: http://dx.doi.org/10.1023/A:1013640918785
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  • 57
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    Protocol discovery in multiprotocol networks (1997)
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    Mobile networks and applications 2 (1997), S. 271-284 
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    ISSN: 1572-8153
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Interoperability requires that communicating systems support compatible protocols. Maintaining compatible protocols is problematic in heterogeneous networks, especially in a wireless infrastructure where hosts can move from one protocol environment to another. It is possible to improve the flexibility of a communication network's operation by deploying systems that support multiple protocols. These multiprotocol systems require support mechanisms that enable users to effectively access the different protocols. Of particular importance is the need to determine which of several protocols to use for a given communication task. In this work, we propose architectures for a protocol discovery system that uses directory services and protocol feedback mechanisms to determine which protocols are supported. We describe the issues related to protocol discovery and present protocol features necessary to support multiprotocol systems.
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    URL: http://dx.doi.org/10.1023/A:1013645019693
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  • 58
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    Editorial (1997)
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    Wireless networks 3 (1997), S. 1-2 
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    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019116108598
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  • 59
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    Hybrid diversity combining techniques for DS‐CDMA over a multipath fading channel (1997)
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    Wireless networks 3 (1997), S. 155-158 
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    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract The combined effect of antenna diversity and spread spectrum (SS) diversity for a direct sequence code division multiple access (DS‐CDMA) system using differential binary phase‐shift keying (DBPSK) modulation is evaluated. Both maximal ratio combining (MRC) and selection diversity (SD) are considered and the bit error rate (BER) performance for four following diversity schemes are compared: (1) SS diversity with MRC and antenna diversity with SD; (2) SS diversity with SD and antenna diversity with MRC; (3) MRC of both SS diversity and antenna diversity; (4) SD of both SS diversity and antenna diversity. It is shown that antenna diversity with MRC and SS diversity with selection has a performance very close to that of antenna diversity and SS diversity both with MRC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019144914958
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  • 60
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    A simplified approach to the performance evaluation of FDMA‐CDMA systems (1997)
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    Wireless networks 3 (1997), S. 173-179 
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    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract This work shows it is possible to apply for the performance evaluation of FDMA‐CDMA cellular mobile systems a simple analytical approximated method, previously successfully proposed by two of the authors with reference to FDMA‐TDMA systems. The distinctive feature of the methodology we describe is that it allows for an immediate determination of both the indexes traditionally employed to define system performance, i.e., average bit error probability $$\bar P$$ e and outage probability P out at a very low computational cost. The hypothesis required to apply the proposed approximation is that the examined spread spectrum system be characterized by a bandwidth occupancy lower than the coherence bandwidth of the transmission channel. This could be the case of a wireless DS‐CDMA system envisioned to provide voice service and exploiting a processing gain of the order of a hundred. We apply our methodology to determine the performance improvements in both $$\bar P$$ e and P out introduced increasing the protection of the transmitted information through error correcting codes and interleaving, in different operating conditions as regards the functioning of the power control loops. A comparison is also satisfyingly carried out with some other approximated analytical methods found in literature. We strongly point out that the corresponding results are achieved at a much more modest computational cost than in traditional approaches.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019101132705
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  • 61
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    Location update optimization in personal communication systems (1997)
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    Wireless networks 3 (1997), S. 205-216 
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    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract Mobility tracking is concerned with finding a mobile subscriber (MS) within the area serviced by the wireless network. The two basic operations for tracking an MS, location updating and paging, constitute additional load on the wireless network. The total cost of updating and paging can be minimized by optimally dividing the service area into location registration (LR) areas. There are various factors affecting this cost, including the mobility and call patterns of the individual MS, the shape, size and orientation of the LR area, and the method of searching for the MS within the LR area. Based on various mobility patterns of users and network architecture, the design of the LR area is formulated as a combinatorial optimization problem. The objective is to minimize the location update cost subject to a constraint on the size of the LR area.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019157217684
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  • 62
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    PHS terminating call control (1997)
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    Wireless networks 3 (1997), S. 1-8 
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    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract This paper describes terminating call control for Personal Handyphone System (PHS), which is achieved by simultaneously forwarding terminating call control messages to multiple interfaces. The Network Assisted Reforwarding (NAR) scheme in which a terminating call control message is reforwarded after a certain period of time to improve the likelihood of its receipt by the personal station (PS), is described. The NAR scheme is modeled and analyzed. This paper also proposes an enhanced NAR (E‐NAR) scheme in which the terminating call control messages are reforwarded only if the response is not received within a certain time‐period. The E‐NAR scheme is modeled, analyzed and compared with the NAR scheme. Finally, a secure control method that prevents fraud for terminating call control is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019121704480
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  • 63
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    Spectrum sharing under the asynchronous UPCS etiquette: The performance of collocated systems under heavy load (1997)
    Springer
    Wireless networks 3 (1997), S. 325-331 
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    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract Recently the FCC opened three 10 MHz bands for unlicensed use. In order to operate in UPCS bands, devices must comply with rules known as the UPCS etiquette (United States Code of Federal Regulations, Title 47, Part 15(d)). In this paper we study channel sharing between two or more collocated systems under the asynchronous UPCS etiquette. In particular we show that under heavy load individual systems have a tendency to hold the channel for hundreds of milliseconds, thus blocking all traffic in other, competing systems. We have calculated the distribution of the blocking time for two versions (or interpretations) of the UPCS etiquette. The impact of the average blocking time on delay sensitive traffic is discussed and possible improvements achieved through a tradeoff between system capacity and average blocking time are investigated.
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    URL: http://dx.doi.org/10.1023/A:1019129906297
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  • 64
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    Dependency sequences and hierarchical clocks: Efficient alternatives to vector clocks for mobile computing systems (1997)
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    Wireless networks 3 (1997), S. 349-360 
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    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract Vector clocks have been used to capture causal dependencies between processes in distributed computing systems. Vector clocks are not suitable for mobile computing systems due to (i) lack of scalability: its size is equal to the number of nodes, and (ii) its inability to cope with fluctuations in the number of nodes. This paper presents two efficient alternatives to vector clock, namely, sets of dependency sequences, and hierarchical clock. Both the alternatives are scalable and are immune to fluctuations in the number of nodes in the system.
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    URL: http://dx.doi.org/10.1023/A:1019134007206
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    Building reliable mobile‐aware applications using the Rover toolkit (1997)
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    Wireless networks 3 (1997), S. 405-419 
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    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract This paper discusses extensions to the Rover toolkit for constructing reliable mobile‐aware applications. The extensions improve upon the existing failure model, which addresses client or communication failures and guarantees reliable message delivery from clients to server, but does not address server failures (e.g., the loss of an incoming message due to server failure) (Joseph et al., 1997). Due to the unpredictable, intermittent communication connectivity typically found in mobile client environments, it is inappropriate to make clients responsible for guaranteeing request completion at servers. The extensions discussed in this paper provide both system‐ and language‐level support for reliable operation in the form of stable logging of each message received by a server, per‐application stable variables, programmer‐supplied failure recovery procedures, server process failure detection, and automatic server process restart. The design and implementation of fault‐tolerance support is optimized for high performance in the normal case (network connectivity provided by a high latency, low bandwidth, wireless link): measurements show a best‐case overhead of less than 7% for a reliable null RPC over wired and cellular dialup links. Experimental results from both micro‐benchmarks and applications, such as the Rover Web Browser proxy, show that support for reliable operation can be provided at an overhead of only a few percent of execution time during normal operation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019142209023
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    Biological aspects of mobile communication fields (1997)
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    Wireless networks 3 (1997), S. 439-453 
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    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract Our knowledge on the biological effects of RF radiation has been increasing for many decades. It has become a focus of attention because of the accelerated use of RF radiation for wireless communication over the past few years. It is fairly well established that at sufficiently high power levels, RF and microwave energy can produce deleterious biological effects. Wireless communication systems use low power modulated forms of RF and microwave radiation that was not investigated extensively in the past. Thresholds and SARs for biological effects both vary widely. Many specific questions must be answered before any consistent, dependable and scientific conclusions can be drawn for the biological effects and safety of wireless mobile communication systems. Nevertheless, available data do not suggest any immediate cause for concern of a impending threat to public health from acute or short term exposure to low level RF and microwave radiation. Investigations to answer some of the questions have already begun. Many of them are designed to study the effects of long term exposure. When considering repeated, low level irradiation, the possibility of cumulative effects have been raised. While there is presently no confirmed evidence for cumulative effect, there is little information to the contrary. Large scale epidemiological investigations should also be undertaken among the two‐way mobile communication and cellular telephone users who may be exposed to varying levels of RF radiation over time. Better understanding is needed of the mechanisms of interaction between RF/microwave radiation and biological systems, and of the significance of any observed effects. Enormous progress has been made in the difficult area of dosimetry. However, measurement of energy distribution in and around a subject for exposure assessment remains a challenge, more so for large numbers of people. This type of quantitative information is also required for extrapolation from animal experimentation to human response.
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    URL: http://dx.doi.org/10.1023/A:1019198426770
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    Scheduling techniques for reducing processor energy use in MacOS (1997)
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    Wireless networks 3 (1997), S. 311-324 
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    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract The CPU is one of the major power consumers in a portable computer, and considerable power can be saved by turning off the CPU when it is not doing useful work. In Apple's MacOS, however, idle time is often converted to busy waiting, and generally it is very hard to tell when no useful computation is occurring. In this paper, we suggest several heuristic techniques for identifying this condition, and for temporarily putting the CPU in a low‐power state. These techniques include turning off the processor when all processes are blocked, turning off the processor when processes appear to be busy waiting, and extending real time process sleep periods. We use trace‐driven simulation, using processor run interval traces, to evaluate the potential energy savings and performance impact. We find that these techniques save considerable amounts of processor energy (as much as 66%), while having very little performance impact (less than 2% increase in run time). Implementing the proposed strategies should increase battery lifetime by approximately 20% relative to Apple's current CPU power management strategy, since the CPU and associated logic are responsible for about 32% of power use; similar techniques should be applicable to operating systems with similar behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019177822227
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    A dynamic load balancing strategy for channel assignment using selective borrowing in cellular mobile environment (1997)
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    Wireless networks 3 (1997), S. 333-347 
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    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract We propose a dynamic load balancing scheme for the channel assignment problem in a cellular mobile environment. As an underlying approach, we start with a fixed assignment scheme where each cell is initially allocated a set of channels, each to be assigned on demand to a user in the cell. A cell is classified as 'hot', if the degree of coldness of a cell (defined as the ratio of the number of available channels to the total number of channels for that cell), is less than or equal to some threshold value. Otherwise the cell is 'cold'. Our load balancing scheme proposes to migrate unused channels from underloaded cells to an overloaded one. This is achieved through borrowing a fixed number of channels from cold cells to a hot one according to a channel borrowing algorithm. A channel assignment strategy is also proposed based on dividing the users in a cell into three broad types – 'new', 'departing', 'others' – and forming different priority classes of channel demands from these three types of users. Assignment of the local and borrowed channels are performed according to the priority classes. Next, a Markov model for an individual cell is developed, where the state is determined by the number of occupied channels in the cell. The probability for a cell being hot and the call blocking probability in a hot cell are derived, and a method to estimate the value of the threshold is also given. Detailed simulation experiments are carried out in order to evaluate our proposed methodology. The performance of our load balancing scheme is compared with the fixed channel assignment, simple borrowing, and two existing strategies with load balancing (e.g., directed retry and CBWL), and a significant improvement of the system behavior is noted in all cases.
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    URL: http://dx.doi.org/10.1023/A:1019181923135
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    Low‐loss TCP/IP header compression for wireless networks (1997)
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    Wireless networks 3 (1997), S. 375-387 
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    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract Wireless is becoming a popular way to connect mobile computers to the Internet and other networks. The bandwidth of wireless links will probably always be limited due to properties of the physical medium and regulatory limits on the use of frequencies for radio communication. Therefore, it is necessary for network protocols to utilize the available bandwidth efficiently. Headers of IP packets are growing and the bandwidth required for transmitting headers is increasing. With the coming of IPv6 the address size increases from 4 to 16 bytes and the basic IP header increases from 20 to 40 bytes. Moreover, most mobility schemes tunnel packets addressed to mobile hosts by adding an extra IP header or extra routing information, typically increasing the size of TCP/IPv4 headers to 60 bytes and TCP/IPv6 headers to 100 bytes. In this paper, we provide new header compression schemes for UDP/IP and TCP/IP protocols. We show how to reduce the size of UDP/IP headers by an order of magnitude, down to four to five bytes. Our method works over simplex links, lossy links, multi‐access links, and supports multicast communication. We also show how to generalize the most commonly used method for header compression for TCP/IPv4, developed by Jacobson, to IPv6 and multiple IP headers. The resulting scheme unfortunately reduces TCP throughput over lossy links due to unfavorable interaction with TCP's congestion control mechanisms. However, by adding two simple mechanisms the potential gain from header compression can be realized over lossy wireless networks as well as point‐to‐point modem links.
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    URL: http://dx.doi.org/10.1023/A:1019138108114
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    Brain tumour development in rats exposed to electromagnetic fields used in wireless cellular communication (1997)
    Springer
    Wireless networks 3 (1997), S. 463-469 
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    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract It has been suggested that electromagnetic fields (EMF) act as promoters late in the carcinogenesis process. To date, however, there is no convincing laboratory evidence that EMFs cause tumour promotion at non‐thermal exposure levels. Therefore the effects of exposure to electromagnetic fields were investigated in a rat brain glioma model. Some of the exposures correspond to electromagnetic fields used in wireless communication. Microwaves at 915 MHz were used both as continuous waves (1 W), and pulse‐modulated at 4, 8, 16 and 217 Hz in 0.57 ms pulses and 50 Hz in 6.67 ms pulses (2 W per pulse). Fischer 344 rats of both sexes were used in the experiments. By stereotaxic technique rat glioma cells (RG2 and N32) were injected into the head of the right caudate nucleus in 154 pairs of rats, exposed and matched controls. Starting on day 5 after inoculation, the animals were exposed for 7 hours a day, 5 days a week during 2–3 weeks. Exposed animals were kept unanaesthetized in well‐ventilated TEM cells producing 915 MHz continuous or modulated microwaves. Their matched controls were kept in identical TEM cells without EMF exposure. All brains were examined histopathologically and the tumour size was estimated as the volume of an ellipsoid. Our study of 154 matched pairs of rats does not show any significant difference in tumour size between animals exposed to 915 MHz, and those not exposed. Thus our results do not support that even an extensive daily exposure to EMF promotes tumour growth when given from the fifth day after the start of tumour growth in the rat brain until the sacrifice of the animal after about 16 days.
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    URL: http://dx.doi.org/10.1023/A:1019102627678
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    Evaluation of electromagnetic power deposition in a spherical multilayer head in the near field of a linear antenna (1997)
    Springer
    Wireless networks 3 (1997), S. 499-510 
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    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract The canonical problem of the radiation of an elementary dipole close to a stratified sphere representing a simplified model of human head is investigated in this paper. The proposed approach is a flexible method of investigation about the influence on Specific Absorption Rate (S.A.R.) evaluation of tissue dielectric parameters and geometry as well as a useful tool to test numerical codes. The solution of the electromagnetic (e.m.) problem is achieved in a closed form; results highlight the position of maximum S.A.R. values and their dependence on frequency: for particular layer thicknesses and dielectric parameters, the maximum absorption can occur in the frequency range of cellular phones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019110829496
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    System Level Hardware/Software Partitioning Based on Simulated Annealing and Tabu Search (1997)
    Springer
    Design automation for embedded systems 2 (1997), S. 5-32 
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    ISSN: 1572-8080
    Keywords: Hardware/software partitioning ; co-synthesis ; iterative improvement heuristics ; simulated annealing ; tabu search
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper presents two heuristics for automatic hardware/software partitioning of system level specifications. Partitioning is performed at the granularity of blocks, loops, subprograms, and processes with the objective of performance optimization with a limited hardware and software cost. We define the metric values for partitioning and develop a cost function that guides partitioning towards the desired objective. We consider minimization of communication cost and improvement of the overall parallelism as essential criteria during partitioning. Two heuristics for hardware/software partitioning, formulated as a graph partitioning problem, are presented: one based on simulated annealing and the other on tabu search. Results of extensive experiments, including real-life examples, show the clear superiority of the tabu search based algorithm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008857008151
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  • 73
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    VLIW Processor Codesign for Video Processing (1997)
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    Design automation for embedded systems 2 (1997), S. 79-119 
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    ISSN: 1572-8080
    Keywords: Embedded system design ; video processing ; VLIW processors ; performance analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A codesign approach for complex video compression systems is presented. The system is based on a flexible and programmable VLIW (Very Long Instruction Word) architecture. The design approach can be subdivided into two phases: a quantitative analysis for deriving the main processor structure and a cosynthesis for generating the processor hardware and the compiler back-end. The analysis results of different video compression algorithms are summarized. This permits to adapt the processor to a set of related applications rather than to a particular task. A compiled instruction-set simulator for analyzing large data sets is presented. An HTML-based codesign framework is shown which documents and organizes the analysis data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008818711786
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  • 74
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    APGAN and RPMC: Complementary Heuristics for Translating DSP Block Diagrams into Efficient Software Implementations (1997)
    Springer
    Design automation for embedded systems 2 (1997), S. 33-60 
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    ISSN: 1572-8080
    Keywords: Dataflow programming ; synchronous dataflow ; memory management ; multirate signal processing algorithms ; SDF compiler ; on-chip memory ; clustering ; minimum cuts ; dynamic programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Dataflow has proven to be an attractive computational model for graphical DSP design environments that support the automatic conversion of hierarchical signal flow diagrams into implementations on programmable processors. The synchronous dataflow (SDF) model is particularly well-suited to dataflow-based graphical programming because its restricted semantics offer strong formal properties and significant compile-time predictability, while capturing the behavior of a large class of important signal processing applications. When synthesizing software for embedded signal processing applications, critical constraints arise due to the limited amounts of memory. In this paper, we propose a solution to the problem of jointly optimizing the code and data size when converting SDF programs into software implementations. We consider two approaches. The first is a customization to acyclic graphs of a bottom-up technique, called pairwise grouping of adjacent nodes (PGAN), that was proposed earlier for general SDF graphs. We show that our customization to acyclic graphs significantly reduces the complexity of the general PGAN algorithm, and we present a formal study of our modified PGAN technique that rigorously establishes its optimality for a certain class of applications. The second approach that we consider is a top-down technique, based on a generalized minimum-cut operation, that was introduced recently in [14]. We present the results of an extensive experimental investigation on the performance of our modified PGAN technique and the top-down approach and on the trade-offs between them. Based on these results, we conclude that these two techniques complement each other, and thus, they should both be incorporated into SDF-based software implementation environments in which the minimization of memory requirements is important. We have implemented these algorithms in the Ptolemy software environment [5] at UC Berkeley.
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    URL: http://dx.doi.org/10.1023/A:1008806425898
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  • 75
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    Compilation Methods for the Address Calculation Units of Embedded Processor Systems (1997)
    Springer
    Design automation for embedded systems 2 (1997), S. 61-77 
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    ISSN: 1572-8080
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract An essential component of today's embedded system is an instruction-set processor running real-time software. All variations of these core components contain at least the minimum data-flow processing capabilities, while a certain class contain specialized units for highly data-intensive operations for Digital Signal Processing (DSP). For the required level of memory interaction, the parallel executing Address Calculation Unit (ACU) is often used to tune the architecture to the memory access characteristics of the application. The design of the ACU is performance critical. In today's typical design flow, this design task is somewhat driven by intuition as the transformation from application algorithm to architecture is complex and the exploration space is immense. Automatic utilities to aid the designer are essential; however, the key compilation techniques which map high-level language constructs onto addressing units have lagged far behind the emergence of these units. This paper presents a new retargetable approach and prototype tool for the analysis of array references and traversals for efficient use of ACUs. In addition to being an enhancement to existing compiler systems, the ArrSyn utility may be used as an aid to architecture exploration. A simple specification of the addressing resources and basic operations drives the available transformations and allows the designer to quickly evaluate the effects on speed and code size of his/her algorithm. Thus, the designer can tune the design of the ACU toward the application constraints. ArrSyn has been successfully used together with a C compiler developed for a VLIW architecture for an MPEG audio decoding application. The combination of these methods with the C compiler showed on average a 39% speedup and 29% code size reduction for a representative set of DSP benchmarks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008862510877
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    An Algorithm for Hardware/Software Partitioning Using Mixed Integer Linear Programming (1997)
    Springer
    Design automation for embedded systems 2 (1997), S. 165-193 
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    ISSN: 1572-8080
    Keywords: hardware/software codesign ; hardware/software partitioning ; embedded systems ; mixed integer linear programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract One of the key problems in hardware/software codesign is hardware/software partitioning. This paper describes a new approach to hardware/software partitioning using integer programming (IP). The advantage of using IP is that optimal results are calculated for a chosen objective function. The partitioning approach works fully automatic and supports multi-processor systems, interfacing and hardware sharing. In contrast to other approaches where special estimators are used, we use compilation and synthesis tools for cost estimation. The increased time for calculating values for the cost metrics is compensated by an improved quality of the values. Therefore, fewer iteration steps for partitioning are needed. The paper presents an algorithm using integer programming for solving the hardware/software partitioning problem leading to promising results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008832202436
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  • 77
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    LYCOS: the Lyngby Co-Synthesis System (1997)
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    Design automation for embedded systems 2 (1997), S. 195-235 
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    ISSN: 1572-8080
    Keywords: codesign ; co-synthesis ; hardware/software partitioning ; analysis ; estimation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper describes the LYCOS system, an experimental co-synthesis environment. We present the motivation and philosophy of LYCOS and after an overview of the entire system, the individual parts are described. We use a single CPU, single ASIC target architecture and we describe the techniques we use to estimate metrics concerning hardware, software and communication in this architecture. Finally we present a novel partitioning technique called PACE, which has shown to produce excellent results, and we demonstrate how partitioning is used to do design space exploration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008884219274
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  • 78
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    The Extended Partitioning Problem: Hardware/Software Mapping, Scheduling, and Implementation-bin Selection (1997)
    Springer
    Design automation for embedded systems 2 (1997), S. 125-163 
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    ISSN: 1572-8080
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In system-level design, applications are represented as task graphs where tasks (called nodes) have moderate to large granularity and each node has several implementation options differing in area and execution time. We define the extended partitioning problem as the joint determination of the mapping (hardware or software), the implementation option (called implementation bin), as well as the schedule, for each node, so that the overall area allocated to nodes in hardware is minimum and a deadline constraint is met. This problem is considerably harder (and richer) than the traditional binary partitioning problem that determines just the best mapping and schedule. Both binary and extended partitioning problems are constrained optimization problems and are NP-hard. We first present an efficient(O(N 2)) heuristic, called GCLP, to solve the binary partitioning problem. The heuristic reduces the greediness associated with traditional list-scheduling algorithms by formulating a global measure, called global criticality (GC). The GC measure also permits an adaptive selection of the optimization objective at each step of the algorithm; since the optimization problem is constrained by a deadline, either area or time is optimized at a given step based on the value of GC. The selected objective is used to determine the mapping of nodes that are “normal”, i.e. nodes that do not exhibit affinity for a particular mapping. To account for nodes that are not “normal”, we define “extremities” and “repellers”. Extremities consume disproportionate amounts of resources in hardware and software. Repellers are inherently unsuitable to either hardware or software based on certain structural properties. The mapping of extremities and repellers is determined jointly by GC and their local preference. We then present an efficient ( O(N 3 + N 2 B), for N nodes and B bins per node) heuristic for extended partitioning, called MIBS, that alternately uses GCLP and an implementation-bin selection procedure. The implementation-bin selection procedure chooses, for a node with already determined mapping, an implementation bin that maximizes the area-reduction gradient of as-yet unmapped nodes. Solutions generated by both heuristics are shown to be reasonably close to optimal. Extended partitioning generates considerably smaller overall hardware as compared to binary partitioning.
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    URL: http://dx.doi.org/10.1023/A:1008872518365
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    Editorial: Special Issue on Hardware/Software Partitioning (1997)
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    Design automation for embedded systems 2 (1997), S. 123-124 
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    ISSN: 1572-8080
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008860423857
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  • 80
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    Editorial (1997)
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    Design automation for embedded systems 2 (1997), S. 265-266 
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    ISSN: 1572-8080
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008856526933
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  • 81
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    Extending the Kernighan/Lin Heuristic for Hardware and Software Functional Partitioning (1997)
    Springer
    Design automation for embedded systems 2 (1997), S. 237-261 
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    ISSN: 1572-8080
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The Kernighan/Lin graph partitioning heuristic, also known as min-cut or group migration, has been extended over several decades very successfully for circuit partitioning. Those extensions customized the heuristic and its associated data structure to rapidly compute the minimum-cut metric central to circuit partitioning; as such, those extensions are not directly applicable to other problems. In this paper, we extend the heuristic for functional partitioning, which in turn can solve the much investigated codesign problem of partitioning a system's coarse-grained functions among hardware and software components. The key extension customizes the heuristic and data structure to rapidly compute execution-time and communication metrics, crucial to hardware and software partitioning, and leads to near-linear time-complexity and excellent resulting quality. Another extension uses a new criteria for terminating the heuristic, eliminating time-consuming and unnecessary fine-tuning of a partition. Our experiments demonstrate extremely fast execution times (just a few seconds) with results matched only by the slower simulated annealing heuristic, meaning that the extended Kernighan/Lin heuristic will likely prove hard to beat for hardware and software functional partitioning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008836303344
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    Virtual Prototyping For Modular And Flexible Hardware-Software Systems (1997)
    Springer
    Design automation for embedded systems 2 (1997), S. 267-282 
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    ISSN: 1572-8080
    Keywords: Hardware/software codesign ; rapid prototyping ; co-synthesis ; co-simulation ; codesign environments ; communication abstraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The goal of this work is to develop a methodology for fast prototyping of highly modular and flexible electronic systems including both, software and hardware. The main contribution of this work is the ability to handle a wide range of architectures. We assume that hardware/software partitioning is already made. This stage of the codesign process starts with a virtual prototype, an heterogeneous architecture composed of a set of distributed modules, represented in VHDL for hardware elements and in C for software elements, communicating through communication modules. This work concentrates on a modelling strategy that allow virtual prototype to be used for both cosynthesis (mapping hardware and software modules onto an architectural platform) and cosimulation (that is the joint simulation of hardware and software components) into an unified environment. The main contribution is the use of a multi-view library concept in order to hide specific hardware/software implementation details and communication schemes. In particular this approach addresses the problem of communication between the hardware and software modules.
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    URL: http://dx.doi.org/10.1023/A:1008829719142
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    Hardware-Software Partitioning for Real-Time Embedded Systems (1997)
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    Design automation for embedded systems 2 (1997), S. 339-358 
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    ISSN: 1572-8080
    Keywords: system-level design ; hardware-software partitioning ; real-time embedded systems ; system architecture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper, we present an approach to hardware-software partitioning for real-time embedded systems. Hardware and software components are modeled at the system level, so that cost and performance tradeoffs can be studied early in the design process and a large design space can be explored. Feasibility factor is introduced to measure the possibility of a real-time system being feasible, and is used as both a constraint and an attribute during the optimization process. An imprecise value function is employed to model the tradeoffs among multiple performance attributes. Optimal partitioning is achieved through the use of an existing computer-aided design tool. We demonstrate the application of our approach through the design of an example embedded system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008891704121
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    Prototyping of Tightly Coupled Hardware/Software-Systems (1997)
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    Design automation for embedded systems 2 (1997), S. 283-317 
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    ISSN: 1572-8080
    Keywords: Description analysis ; Profiling ; Hardware/Software-Partitioning ; Estimation ; Prototyping ; Emulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Verification and test issues raise the need for rapid prototyping of complex systems and especially hardware/software-systems. We tackle this problem by integration of hardware/software-codesign and prototyping. First we define the concept of the entire system architecture. This concept directs the hardware/software-partitioning process. Our prototyping environment reflects the architecture concept as well. In this overview the architecture concept and all important design tasks (hardware/software-partitioning, speed-up estimation before HW-synthesis, and prototyping of the entire hardware/software-system) are presented and compared to several approaches from literature. Thus a substantial overview over the prototyping problem is given. The latter part of this presentation illustrates our approach by a case study and presents the results. Our automated design process generates a tightly coupled hardware/software-system with very good performance characteristics. The case study focus on the prototyping of a ciphering algorithm. The reported approach leads to a reasonable overall system speed-up of 10 percent. Similar results have been found for further examples as well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008887603213
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    Domain–Specific High–Level Modeling and Synthesis for ATM Switch Prototyping (1997)
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    Design automation for embedded systems 2 (1997), S. 319-338 
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    ISSN: 1572-8080
    Keywords: high-level synthesis ; ATM switch ; domain-specific synthesis ; scheduling ; allocation ; RTL synthesis ; VHDL
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract ATM switch, the core technology of an ATM networking system, is one of the major products in Fujitsu telecommunication business. However, current gate–level design methodology can no longer satisfy its stringent time–to–market requirement. It becomes necessary to exploit high–level methodology to specify and synthesize the design at an abstraction level higher than logic gates. This paper presents our prototyping experience on domain–specific high–level modeling and synthesis for Fujitsu ATM switch design. We propose a high–level design methodology using VHDL, where ATM switch architectural features are considered during behavior modeling, and a high–level synthesis compiler, MEBS, is prototyped to synthesize the behavior model down to a gate–level implementation. Since the specific ATM switch architecture is incorporated into both modeling and synthesis phases, a high–quality design is efficiently derived. The synthesis results shows that given the design constraints, the proposed high–level design methodology can produce a gate–level implementation by MEBS with about 15 percent area reduction in shorter design cycle when compared with manual design.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008839720051
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    Hardware/Software Communication and System Integration for Embedded Architectures (1997)
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    Design automation for embedded systems 2 (1997), S. 359-382 
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    ISSN: 1572-8080
    Keywords: Hardware/Software Co-Design ; Interface and Communication Synthesis ; Target Architecture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Embedded system architectures comprising of software programmable components (e.g. DSP, ASIP, and micro-controller cores) and customized hardware co-processors, integrated into a single cost-efficient VLSI chip, are emerging as a key solution to today’s microelectronics design problems. This trend is being driven by new emerging applications in the areas of wireless communication, high-speed optical networking, and multimedia computing, fueled by increasing levels of integration. These applications are often subject to stringent requirements in terms of processing performance, power dissipation, and flexibility. A key problem confronted by embedded system designers today is the rapid prototyping of an application-specific embedded system architecture where different combinations of programmable processor components, library hardware components, and customized hardware components must be integrated together, while ensuring that the hardware and software parts communicate correctly. Designers often spend an enormous time on this highly error proned task. In this paper, we present a solution to this embedded architecture co-synthesis and system integration problem based on an orchestrated combination of architectural strategies, parameterized libraries, and software CAD tools.
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    URL: http://dx.doi.org/10.1023/A:1008843820959
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    Another Look at LTL Model Checking (1997)
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    Formal methods in system design 10 (1997), S. 47-71 
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    ISSN: 1572-8102
    Keywords: automatic verification ; temporal logic ; model checking ; binary decision diagrams
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We show how LTL model checking can be reduced to CTL model checking with fairness constraints. Using this reduction, we also describe how to construct a symbolic LTL model checker that appears to be quite efficient in practice. In particular, we show how the SMV model checking system developed by McMillan [16] can be extended to permit LTL specifications. The results that we have obtained are quite surprising. For the specifications which can be expressed in both CTL and LTL, the LTL model checker required at most twice as much time and space as the CTL model checker. We also succeeded in verifying non-trivial LTL specifications. The amount of time and space that is required is quite reasonable. Based on the examples that we considered, it appears that efficient LTL model checking is possible when the specifications are not excessively complicated.
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    URL: http://dx.doi.org/10.1023/A:1008615614281
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    Formal Verification of a Distributed Computer System (1997)
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    Formal methods in system design 10 (1997), S. 93-125 
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    ISSN: 1572-8102
    Keywords: formal verification ; induction proofs ; formal methods ; homomorphic reduction ; modeling of distributed systems ; L-automata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Modeling distributed computer systems is known to be a challenging enterprise. Typically, distributed systems are comprised of large numbers of components whose coordination may require complex interactions. Modeling such systems more often than not leads to the nominal intractability of the resulting state space. Various formal methods have been proposed to address the modeling of coordination among distributed systems components. For the most part, however, these methods do not support formal verification mechanisms. By way of contrast, the L-automata/L-processes model supports formal verification mechanisms which in many examples can successfully circumvent state space explosion problems, and allow verification proofs to be extended to an arbitrary number of components. After reviewing L-automata/L-processes formalisms, we present here the formal specification of a fault-tolerant algorithm for a distributed computer system. We also expose the L-automata/L-processes verification of the distributed system, demonstrating how various techniques such as homomorphic reduction, induction, and linearization, can be used to overcome various problems which surface as one models large, complex systems.
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    URL: http://dx.doi.org/10.1023/A:1008667631119
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    Factored Edge-Valued Binary Decision Diagrams (1997)
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    Formal methods in system design 10 (1997), S. 243-270 
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    ISSN: 1572-8102
    Keywords: Ordered Binary Decision Diagrams ; Pseudo-Boolean functions ; affine property ; logic verification ; integer linear programming ; matrix operations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Factored Edge-Valued Binary Decision Diagrams form an extension to Edge-Valued Binary Decision Diagrams. By associating both an additive and a multiplicative weight with the edges, FEVBDDs can be used to represent a wider range of functions concisely. As a result, the computational complexity for certain operations can be significantly reduced compared to EVBDDs. Additionally, the introduction of multiplicative edge weights allows us to directly represent the so-called complement edges which are used in OBDDs, thus providing a one to one mapping of all OBDDs to FEVBDDs. Applications such as integer linear programming and logic verification that have been proposed for EVBDDs also benefit from the extension. We also present a complete matrix package based on FEVBDDs and apply the package to the problem of solving the Chapman-Kolmogorov equations.
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    URL: http://dx.doi.org/10.1023/A:1008691605584
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    Arithmetic Boolean Expression Manipulator Using BDDs (1997)
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    Formal methods in system design 10 (1997), S. 221-242 
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    ISSN: 1572-8102
    Keywords: Boolean function ; BDD ; Boolean expression ; LSI CAD ; combinatorial problem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Recently, there has been a lot of works on LSI design systems using Binary Decision Diagrams (BDDs), which are efficient representations of Boolean functions. We previously developed a Boolean expression manipulator, that can quickly calculate Boolean expressions by using BDD techniques. It has greatly assisted us in developing VLSI design systems and solving combinatorial problems. In this paper, we present an Arithmetic Boolean Expression Manipulator (BEM-II), that is also based on BDD techniques. BEM-II calculates Boolean expressions that contain arithmetic operations, such as addition, subtraction, multiplication and comparison, and then displays the results in various formats. It can solve problems represented by a set of equalities and inequalities, which are dealt with in 0-1 linear programming. We discuss the algorithm and data structure used for manipulating arithmetic Boolean expressions and show the formats used for displaying the results. The specifications for BEM-II are described and several application examples are presented. Arithmetic Boolean expressions will be useful for various applications. They perform well in terms of the total time for programming and execution. We expect BEM-II to facilitate research and development of digital systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008643722423
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    A Symbolic Algorithms for Maximum Flow in 0-1 Networks (1997)
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    Formal methods in system design 10 (1997), S. 207-219 
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    ISSN: 1572-8102
    Keywords: symbolic algorithms ; network algorithms ; Binary Decision Diagrams
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We present an algorithm for finding the maximum flow in a 0-1 network. The algorithm is symbolic and does not require explicit enumeration of the nodes and edges of the network. Therefore, it can handle much larger graphs than it was previously possible (more than 1036 edges). The main idea is to trace (implicitly) sets of edge-disjoint augmenting paths. Disjointness is enforced by solving an edge matching problem for each layer of the network with the help of newly defined priority functions.
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    URL: http://dx.doi.org/10.1023/A:1008651924240
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    Stubborn Sets for Real-Time Petri Nets (1997)
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    Formal methods in system design 11 (1997), S. 23-40 
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    ISSN: 1572-8102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The stubborn-set method attempts to reduce the number of states that must be explicitly enumerated during reachability analysis of a concurrent system, while preserving crucial concurrency properties in the reduced state space. Here we extend the method to the analysis of certain timed models. We also prove that timing properties of interest, such as minimum and maximum delays between events, are preserved in the reduced model. Finally, we report on some experimental results that we have obtained with our extension. These results show that real-time stubborn sets can often provide significant reductions in state space size.
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    URL: http://dx.doi.org/10.1023/A:1008629725384
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    Bounded Delay Timing Analysis of a Class of CSP Programs (1997)
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    Formal methods in system design 11 (1997), S. 265-294 
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    ISSN: 1572-8102
    Keywords: Timing analysis ; abstract algebra ; asynchronous systems ; concurrent systems ; time separation of events
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We describe an algebraic technique for performing timing analysis of a class of asynchronous circuits described as CSP programs (including Martin's probe operator) with the restrictions that there is no OR-causality and that guard selection is either completely free or mutually exclusive. Such a description is transformed into a safe Petri net with interval time delays specified on the places of the net. The timing analysis we perform determines the extreme separation in time between two communication actions of the CSP program for all possible timed executions of the system. We formally define this problem, propose an algorithm for its solution, and demonstrate polynomial running time on a non-trivial parameterized example. Petri nets with 3000 nodes and 1016 reachable states have been analyzed using these techniques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008655714875
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  • 94
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    Advances in human-interface engineering for reverse directory assistance (ACNA) services (1997)
    Springer
    International journal of speech technology 1 (1997), S. 91-101 
    Details
    ISSN: 1572-8110
    Keywords: speech synthesis ; synthesis applications ; directory preprocessing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Linguistics and Literary Studies , Computer Science
    Notes: Abstract After years of productive research, speech synthesis is now profitably automating services by answering queries via constrained dialogs, directly accessing individual computer databases, and speaking text created from disparate sources of information. Directory-based services, such as Automated Customer Name and Address (ACNA), requires synthesis with high intelligibility and name pronunciation accuracy. Current synthesis technology achieves those goals. However, even the best of current speech technology is not good enough to mindlessly “drop” into complex services. Customized directory preprocessing is still necessary to transform listing data, which commonly contains unconventional abbreviations, unlabeled acronyms, and scrambled word ordering, into a sentence suitable for synthesis. This article describes state-of-the-art directory preprocessing programs that have led to successful implementations for synthesis services in 2 major U.S. telephone companies (Ameritech and Bell Atlantic). Of course, the basic capabilities of the synthesizer, such as pronuncïation accuracy, speech quality and naturalness, play a large role. Efforts ensured locality terms were pronounced in accordance with local custom. Finally, for prompts and other fixed messages, this article describes experiments that determined whether the naturalness of recorded speech offsets the undesirable discontinuity between recorded and synthesized utterances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02277190
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  • 95
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    Combining concatenation and formant synthesis for improved intelligibility and naturalness in text-to-speech systems (1997)
    Springer
    International journal of speech technology 1 (1997), S. 103-107 
    Details
    ISSN: 1572-8110
    Keywords: formant synthesis ; time-domain concatenation ; hybrid system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Linguistics and Literary Studies , Computer Science
    Notes: Abstract A general method which combines formant synthesis by rule and time-domain concatenation is proposed. This method utilizes the advantages of both techniques by maintaining naturalness while minimizing difficulties such as prosodic modification and spectral discontinuities at the point of concatenation. An integrated sampled natural glottal source (Matsui et al., 1991) and sampled voiceless consonants were incorporated into a real-time text-to-speech formant synthesizer. In special cases, voicing amplitude envelopes and formant transitions dirived from natural speech were also utilized. Several listening tests were performed to evaluate these methods. We obtained a significant overall improvement in intelligibility over our previous formant synthesizer. Such improvements in intelligibility were previously obtained with a Japanese text-to-speech system using a related hybrid system (Kamai and Matsui, 1993), indicating the applicability of this method for multi-lingual synthesis. The results of subjective analyses showed that these methods can alo improve naturalness and listenability factors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02277191
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  • 96
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    Speaker indexing using neural network clustering of vowel spectra (1997)
    Springer
    International journal of speech technology 1 (1997), S. 143-149 
    Details
    ISSN: 1572-8110
    Keywords: speaker indexing ; audio retrieval ; audio skimming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Linguistics and Literary Studies , Computer Science
    Notes: Abstract Speaker indexing refers to the process of separating speakers within a recording and assigning indices to each unique speaker. This paper describes a new speaker indexing algorithm which dynamically generates and trains a neural network to model each postulated speaker found within a recording. Each neural network is trained to differentiate the vowel spectra of one specific speaker from all other speakers. A method for combining speaker indexing and other annotations of a recording in a general framework is also presented. The speaker indexing system is currently being incorporated into several application systems in the Speech Group at the MIT Media Lab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02277195
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  • 97
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    Development and application of an accurate and flexible automatic aligner (1997)
    Springer
    International journal of speech technology 1 (1997), S. 151-160 
    Details
    ISSN: 1572-8110
    Keywords: automatic aligner ; labelling ; recognition ; tools
    Source: Springer Online Journal Archives 1860-2000
    Topics: Linguistics and Literary Studies , Computer Science
    Notes: Abstract Large databases are useful tools for speech technology research. Their usefulness is greatly enhanced if the data is annotated with time aligned labels. This is expensive and time consuming and has lead to the investigation and development of automatic aligners. This paper reports on an automatic aligner developed initially to solve the problem of annotating a large database within a set period of time. While developing the aligner, we investigated the importance of the models, the use of manual labels to bootstrap the system, and the role of the dictionary in the effectiveness of the aligner, and found that each had a contribution to make. The aligner produced was tested on unseen data to gauge its accuracy before being applied as a tool to annotation of a large amount of data. The aligner was developed in a way that facilitates its use in other applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02277196
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  • 98
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    A field evaluation of the Italian “Automated reverse directory assistance” service (1997)
    Springer
    International journal of speech technology 1 (1997), S. 161-169 
    Details
    ISSN: 1572-8110
    Keywords: text-to-speech synthesis evaluation ; field test evaluation ; text-to-speech synthesis in real applications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Linguistics and Literary Studies , Computer Science
    Notes: Abstract The paper describes a field evaluation of the automated ‘reverse directory assistance’ service presently in use in Italy in which information about names and addresses is provided by a TTS system. A simulation of the service using a natural voice was also run to get comparative data. Both services were accessed from an office room and a call-box on the street. Different evaluation metrics, such as intelligibility, task completion, task correctness, transaction success, and user's reactions were used. The aim of the work was to evaluate TTS synthesis in real world use and to make a comparison between laboratory data and data on system performance in a real application. Such a comparison suggested that in laboratory tests more attention should be dedicated to simulate more closely the conditions that can be predicted in real world use, by including important aspects that are generally not taken into consideration in laboratory tests and that are likely to have a large influence on TTS system performance such as environmental noise, prosody, and task complexity. The results also underline the importance of field evaluations to get an overall view of the usability of a service in real applications and with users who are as similar as possible to actual users.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02277197
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  • 99
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    Voter response to computerized campaigning (1997)
    Springer
    International journal of speech technology 2 (1997), S. 33-40 
    Details
    ISSN: 1572-8110
    Keywords: campaign ; election ; voter ; telephone ; computer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Linguistics and Literary Studies , Computer Science
    Notes: Abstract A computer system was designed to telephone voters en masse and play a short campaign message in support of a candidate. The calling program used a new algorithm to detect and leave messages on answering machines, or, when a human answered, to observe telephone etiquette. It was tested in the Raleigh City Council election of 1993. Over 30,000 households were called in both a primary and final election. Immediately after the November election about 600 of the called households were polled by telephone (using human interrogators) to measure the effect of the calling campaign. Among persons reached who actually voted, 52% remembered the candidate's name, and 6.4% said the call had affected their vote.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02215802
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  • 100
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    Preface (1997)
    Springer
    International journal of speech technology 2 (1997), S. 87-88 
    Details
    ISSN: 1572-8110
    Source: Springer Online Journal Archives 1860-2000
    Topics: Linguistics and Literary Studies , Computer Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02208820
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