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Using network fault predictions to enable IP traffic management

Journal of network and systems Management 2001年第3期9卷 327-346页

作者： Thottan, M. Ji, C. Lucent Technologies Bell Laboratories Department of Network and Service Management Holmdel NJ 07733 United States Department of Electrical Computer and Systems Engineering Rensselaer Polytechnic Institute Troy NY 12180 United States Department of Network and Service Management Lucent Technologies Bell Laboratories Rensselaer Polytechnic Institute Troy NY United States

IP traffic management is important for the continued growth of the Internet. Several traffic management algorithms exist today. However, to enable these algorithms it is necessary to provide reliable alarms relating to network performance bottlenecks and failures. In this work we propose an algorithm to obtain reliable predictive alarms for network fault conditions. The algorithm is based on modeling network fault behavior. The algorithm has been successfully tested on two production networks. Predictive alarms were obtained for four different types of failures: file server failures, network access problems, protocol implementation errors, and runaway processes. The potential of using this model to do fault classification is also discussed. In addition, it is shown that the proposed algorithm performs better than the majority-vote scheme. © 2001 Plenum Publishing Corporation.

关键词： Change detection Fault model network health Spatial correlator

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Folded Evanescent-Mode Ridge Waveguide Bandpass Filters

Folded Evanescent-Mode Ridge Waveguide Bandpass Filters

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European Conference on Microwave

作者： Tao Shen Kawthar A. Zaki Hughes Network Systems MD USA Department of Electrical and Computer Engineering University of Maryland College Park MD USA

Modeling and design of folded evanescent-mode ridge waveguide bandpass filters are presented. The filter structure is decomposed into the cascade connection of empty-to-ridge waveguide discontinuities. The generalized scattering matrix of the empty-to-ridge waveguide discontinuity is obtained using mode matching method, from which the filter response can be obtained using cascading procedure. The folded coupling junction is ridged to achieve the required coupling value. A filter example is presented to verify the design approach.

关键词： Band pass filters Resonator filters Waveguide discontinuities Inverters Waveguide junctions Magnetic separation Planar waveguides Impedance Rectangular waveguides Scattering

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Virtual dynamic backbone for mobile ad hoc networks

Virtual dynamic backbone for mobile ad hoc networks

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IEEE International Conference on Communications (ICC)

作者： U.C. Kozat G. Kondylis B. Ryu M.K. Marina Research work in Netwiirk Analysis and Systems Department HRL Laboratories LLC USA Electrical and Computer Engineering Department Institute for Systems Research University of Maryland College Park MD USA Network Analysis and Systems Department HRL Laboratories LLC Malibu CA USA Department of Electrical and Computer Engineering and Computer Science University of Cincinnati Cincinnati OH USA

In this paper, we propose the virtual dynamic backbone protocol (VDBP) for ad hoc networks. VDBP constructs a backbone from a subset of the nodes in the network satisfying these two properties: (i) Any node in the network is either a backbone node or is a neighbor of a backbone node (dominating set property), (ii) any pair of backbone nodes is connected via other backbone nodes (connectivity property). VDBP provides explicit mechanisms to handle the mobility of the nodes and depends on local computations to a large extent. Thus it is highly self-organizing even under highly dynamic topologies. Such a backbone can be potentially used by a routing protocol to disseminate broadcast or multicast messages as well as to handle QoS traffic in mobile ad hoc networks. We present the performance of VDBP in terms of backbone size and connectivity using simulations.

关键词： Spine Mobile ad hoc networks Ad hoc networks network topology Broadcasting Quality of service Routing protocols Multicast protocols Telecommunication traffic Mobile communication

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Error probability performance for coherent DS-CDMA systems in correlated Nakagami fading channels

Error probability performance for coherent DS-CDMA systems i...

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IEEE Conference on Vehicular Technology (VTC)

作者： Jianxia Luo J. Zeidler Department of Electrical & Computer Engineering University of California San Diego CA USA Hughes Network Systems Inc. USA SPAWAR Systems Center San Diego USA

This paper presents the average error probability performance in coherent DS-CDMA systems using a 2D-RAKE receiver with an arbitrary number of antennas and arbitrary number of RAKE fingers. In the analysis, we assume a general frequency selective Nakagami-m fading channel with exponential multipath intensity profile. An analytical expression of the average bit-error-rate (BER) is derived, including the effects of the spatial correlation between antenna elements and non-identical fading for different multipaths. The impacts of the receiver configuration (e.g. the spatial diversity order M, the temporal diversity order L and the antenna separation) and the operating environment parameters (such as fading, maximum number of multipath components, angular spread and MIP power decay factor), on the BER performance and the cell capacity are illustrated.

关键词： Error probability Multiaccess communication Fading Bit error rate Receiving antennas Rayleigh channels Multipath channels RAKE receivers Frequency Antenna arrays

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Error probability performance for WCDMA systems with multiple transmit and receive antennas in correlated Nakagami fading channels

Error probability performance for WCDMA systems with multipl...

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IEEE Conference and Exhibition on Global Telecommunications (GLOBECOM)

作者： Jianxia Luo J.R. Zeidler Department of Electrical & Computer Engineering University of California San Diego CA USA Hughes Network Systems Inc. San Diego CA USA

The bit-error-rate (BER) performance of a 2D-RAKE receiver, in combination with transmit diversity on the downlink of WCDMA system, is presented. The analyses assume correlated fading between receive antenna array elements, and arbitrary number of independent but nonidentical resolvable multipaths; combined by the RAKE receiver, in the general Nakagami-m (1960) fading channel framework. The impacts of the array configuration (e.g. the number of transmit antennas and receive antennas, the antenna element separation) and the operating environment parameters (such as fading severity, angular spread and path delay profile), on the overall space-path diversity gain can be directly evaluated.

关键词： Error probability Multiaccess communication Fading Receiving antennas Antenna arrays Transmitting antennas Bit error rate RAKE receivers Downlink Multipath channels

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Maximum-likelihood tap selection for equalization of land mobile radio channels

Maximum-likelihood tap selection for equalization of land mo...

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GLOBECOM'01. IEEE Global Telecommunications Conference (Cat. No.01CH37270)

作者： Wonjin Sung Dong-Joon Shin In-Kyung Kim Department of Electronic Engineering Sogang University Seoul South Korea Division of Electrical and Computer Engineering Hanyang University Seoul South Korea Hughes Network Systems Germantown MD USA

Mobile radio transmission channels characterized by dominating delay paths can be modelled by the linear intersymbol filter with a few significant taps. For such channels, tap-selectable equalization can be used for the receiver complexity reduction. In this paper, a maximum-likelihood method to select channel taps with significant power is presented and its error performance is analyzed. The scheme performs the CFAR (Constant False Alarm Rate) detection when the receiver noise power level is known. We give an analytic derivation of the error probability that exactly quantifies the the effect of noise power estimation.

关键词： Maximum likelihood detection Maximum likelihood estimation Land mobile radio Delay Nonlinear filters Receivers Error analysis Performance analysis Noise level Error probability

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Simple SNR estimation methods for QPSK modulated short bursts

Simple SNR estimation methods for QPSK modulated short burst...

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GLOBECOM'01. IEEE Global Telecommunications Conference (Cat. No.01CH37270)

作者： Dong-Joon Shin Wonjin Sung In-Kyung Kim Division of Electrical and Computer Engineering Hanyang University Seoul South Korea Department of Electronic Engineering Sogang University Seoul South Korea Hughes Network Systems Inc. Germantown MD USA

An accurate signal-to-noise ratio (SNR) measurement is essential for cellular and satellite communication receivers for various purposes, including the demodulation algorithm adaptation to the time-varying channel conditions. In this paper, computationally simple SNR estimation methods, called the error vector magnitude (EVM) method and the minimum mean-square error estimation (MMSE) method are proposed. Analytic derivations as well as simulation results are presented to demonstrate the performance of the proposed schemes.

关键词： Quadrature phase shift keying Forward error correction Estimation error Signal to noise ratio Satellite communication Demodulation Analytical models computer networks Performance analysis Computational modeling

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Spatio-temporal searcher structure for 3G W-CDMA smart antenna systems

Spatio-temporal searcher structure for 3G W-CDMA smart anten...

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IEEE Conference on Vehicular Technology (VTC)

作者： JeongHo Kim Y.M. Vasavada J.H. Reed Advanced Tcchnology Rcsearch (ATRA) Department Research & Development Center LG Electronics Inc./Information and Communications Anyang Kyunggi South Korea MPRG (Mobile Portable Radio Research Group) Bradley Department of Electrical & Computer Engineering Virginia Polytechnic Institute and State University Blacksburg VA USA Hughes Network Systems Inc. Germantown MD USA

Smart antenna systems have been considered for base station (BS) and mobile station (MS) to improve spectral efficiency and link quality. The newly emerging 3rd generation mobile (W-CDMA and cdma2000) systems are required to support high bit rate services. This type of high bit rate traffic inevitably consumes a significant amount of capacity and causes considerable interference to low data rate users. Under these circumstances, the smart antenna system is a good candidate to mitigate this interference and keep link quality at adequate levels. One of the crucial components, which can be very complex, is the searcher whose functionality is to continuously search for new multipath signals for combining. A spatio-temporal searcher structure is proposed to enhance the detection capability of the multipath traffic channel searcher. This structure basically employs a spatio-temporal signal structure to search for a new signal. The detection and false alarm probabilities of the new and conventional schemes are calculated and numerical examples of mean acquisition time are given.

关键词： Multiaccess communication Signal processing Base stations Interference Research and development Mobile antennas Bit rate Testing Spatial resolution Signal resolution

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A statistical simulation model for correlated Nakagami fading channels

A statistical simulation model for correlated Nakagami fadin...

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International Conference on Communication Technology, ICCT 2000

作者： Luo, Jianxia Zeidler, James R. Electrical and Computer Engineering Department University of California San Diego 9500 Gilman Drive San DiegoCA92093-0407 United States Hughes Network Systems Inc. United States SPA WAR Systems Center San Diego United States

ISBN: (纸本)0780363949

Efficient simulation models for correlated Nakagami-m fading channels are required for the development, performance evaluation and validation of diversity combining systems in general fading channels. We propose a theoretical explanation of the Nakagami-m distribution, as a natural extension of the Rayleigh fading model. In this model, a Nakagami random variable is viewed as the norm of an tridimensional complex random vector. The elements of this m-dimensional random vector are orthogonal to each other, and have Rayleigh-distributed envelopes. Based on this decomposition approach, correlated Nakagami channel gains can be efficiently generated, given the specified correlation coefficients between the underlying Rayleigh processes. © 2000 IEEE.

关键词： Fading channels

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A statistical simulation model for correlated Nakagami fading channels

A statistical simulation model for correlated Nakagami fadin...

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International Conference on Communication Technology (ICCT)

作者： Jianxia Luo J.R. Zeidler Electrical and Computer Engineering Department University of California La Jolla CA USA Hughes Network Systems Inc. SPAWAR Systems Center San Diego USA

Efficient simulation models for correlated Nakagami-m fading channels are required for the development, performance evaluation and validation of diversity combining systems in general fading channels. We propose a theoretical explanation of the Nakagami-m distribution, as a natural extension of the Rayleigh fading model. In this model, a Nakagami random variable is viewed as the norm of an m-dimensional complex random vector. The elements of this m-dimensional random vector are orthogonal to each other, and have Rayleigh-distributed envelopes. Based on this decomposition approach, correlated Nakagami channel gains can be efficiently generated, given the specified correlation coefficients between the underlying Rayleigh processes.

关键词： Fading Rayleigh channels Nakagami distribution Diversity reception Random variables Wireless communication Performance analysis Computational modeling Interchannel interference Diversity methods

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