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Electrical and Computer Engineering, Canadian Journal of

Issue 1 • Date N/A 1989

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Displaying Results 1 - 12 of 12
  • Canadian Journal of Electrical and Computer Engineering - Front cover

    Page(s): c1
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  • Inside front cover

    Page(s): c2
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  • Table of contents

    Page(s): 1
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  • Guest editorial

    Page(s): 2
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  • Random access systems: ALOHA's progeny

    Page(s): 3 - 10
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    Random access algorithms allow a large number of bursty data sources to share a common transmission medium. Such algorithms are essentially refinements of the distributed algorithm first introduced in the ALOHA system. Unlike techniques such as time division multiple access (TDMA), frequency division multiple access (FDMA) and polling, the performance of random access algorithms is insensitive to the number of stations in the system. The weakness of early random access systems is extreme sensitivity to traffic, resulting in instability. Later implementations of the technique have improved throughput, eliminating instability. This paper discusses the three forms of random access techniques: stable backoff algorithms, tree search algorithms and carrier sensing techniques. Forms of the last of these have been used in an optical-fibre local area network. The particular application of random access techniques to satellite communication systems is also considered. View full abstract»

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  • An interactive simulator for unbalanced systems

    Page(s): 11 - 17
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    Unbalances due to faults and line switching have traditionally been calculated using symmetrical components. By contrast, compensation methods or their mathematical equivalent, the matrix modification lemma (MML), a powerful tool for the solution of modified networks, are still employed primarily for contingency calculations. However, they can be efficiently applied to the calculation of voltages and currents due to faults and/or line switching. In the paper, the MML is applied for closing or opening of a switch which may also represent a fault. For better efficiency, the computations are performed in symmetrical components and sparsity techniques are used. To determine the effect of the switching operations, these are performed interactively and sequentially. Generators and loads are represented by appropriate Norton equivalents. Illustrative results are presented. View full abstract»

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  • Worst-case error analysis of the balanced-matrix method of model reduction

    Page(s): 18 - 23
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    Worst-case error analysis, which was previously obtained for the aggregation method of model reduction, is given for the balanced-matrix method. A worst-case error is constructed for balanced reduced-order models approximating a given linear time-invariant, completely controllable, completely observable balanced system. Also, it is shown that the worst-case error bounds can apply to reduced-order models obtained using other reduction methods. When the model and the full-scale system are balanced, the computations to obtain the error bounds are simplified. Several numerical examples are given. View full abstract»

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  • A new technique for unconstrained and constrained linear LAV parameter estimation

    Page(s): 24 - 30
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    Presents a new technique for least absolute value (LAV) linear parameter estimation. The technique can be applied to unconstrained as well as equality- and/or inequality-constrained problems. The estimation problem is stated first. The least squares (LS) solution of the estimation problem is then presented and compared to the LAV solution. The new LAV technique is offered and compared to the standard LAV algorithm which uses linear programming (LP). Several examples which compare results obtained using the LP and this new technique are presented. The examples provide the basis for the conclusions presented in the final section of the paper. The preliminary application of the new algorithm to the power system state estimation problem is also given. View full abstract»

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  • Digital quasi-impulse shaping for multi-level QAM and QPRS system

    Page(s): 31 - 34
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    Digital quasi-impulse-shaped signals for the transmission of Nyquist-shaped raised-cosine filtered signals and partial response signals are considered. Quasi-impulse signals do not require conventionally used phase-equalized x/sin(x)-shaped aperture equalizers. A simple logic circuit reduces the pulse-width of the conventional NRZ format, binary or multi level input data. The finite pulse-width duration of these signals, as compared with the theoretically infinite impulse duration, permits a practical realization with negligible performance degradation. Experimental and computer simulation results demonstrate that pulse-widths of 25% for 225-QPRS class I, 18.75% for 64-QAM and 12.5% for 256-QAM lead to a performance degradation of only 0.2 dB at a Pe=10-8. View full abstract»

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  • Call for papers

    Page(s): 35 - 36
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  • [Back inside cover]

    Page(s): c3
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  • [Back cover]

    Page(s): c4
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Aims & Scope

The role of the Canadian Journal of Electrical and Computer Engineering is to provide scientific and professional activity for its members in Canada, the CJECE complements international journals and will be of particular interest to anyone involved in research and development activities in the field of electrical and computer engineering.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Dr. Shahram Yousefi
Dept. of Electrical and Computer
     Engineering
Queen's University