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ERROR PERFORMANCE OF SYNCHRONOUS MULTIUSER CODE-DIVISION MULTIPLE-ACCESS DETECTOR WITH MULTIDIMENSIONAL ADAPTIVE CANCELER

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EUROPEAN TRANSACTIONS ON TELEcommunications 1994年第6期5卷 719-724页

作者： SIVESKI, Z BARNESS, Y CHEN, DW Center for Communications and Signal Processing Electrical and Computer Engineering Department New Jersey Institute of Technology University Heights Newark NJ 07102 - USA Was on sabbatical with Delft University of Technology Faculty of Electrical Engineering Telecommunications and Traffic-Control Systems Group Delft - The Netherlands.

A code division multiple access detector that employs a combination of a decorrelator and a multidimensional interference canceler is considered. The weights of the canceler are adaptively controlled using a steepest descent algorithm. The probability of error is evaluated and compared to those of the decorrelating detector and a similar, fixed-weights scheme that requires an estimation of received signal energies. It is shown that the proposed two-stage detector provides substantial improvement over the decorrelating detector, particularly in the presence of strong interfering signals. This is especially noticeable in the high bandwidth efficiency cases. It is also observed that in the presence of weak interferers, the proposed scheme performs better than its fixed-weights counterpart.

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Bootstrapped decorrelating algorithm for adaptive interference cancelation in synchronous CDMA communications systems

Bootstrapped decorrelating algorithm for adaptive interferen...

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IEEE International Symposium on Spread Spectrum Techniques and Applications

作者： Y. Bar-Ness Z. Siveski D.W. Chen Faculty of Electrical Engineering Telecommunications and Traffic-Control Systems Group Delft University of Technnology Delft Netherlands Center for Communications and Signal Processing Electrical and Computer Engineering Department New Jersey Institute of Technology Newark NJ USA

A code division multiple access detector that employs a combination of a correlation detector and a multiuser adaptive interference canceler was previously proposed by the authors. The weights of the canceler are adaptively controlled by the steepest descent algorithm using the minimum power criterion of the canceler outputs. It was shown that such a canceler substantially outperforms the decorrelating detector and has almost the same error probability as a canceler that uses reliable estimates of the received signal energies. In this paper, a different weight control criterion based on minimizing the correlation between the signals at the outputs of the canceler is used, and its performance is compared to that obtained with the minimum power criterion. It is shown that both cancelers have almost the same performance, particularly when SNR is modestly high. Although it is not shown in this paper, we believe that minimizing correlation rather than power outputs is a more suitable criterion when dealing with highly dispersive channels.< >

关键词： Decorrelation Interference cancellation Code division multiplexing Multiaccess communication Detectors signal processing algorithms Filters Impedance matching Communication system traffic Telecommunication traffic

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Importance sampling for the efficient simulation of adaptive systems in frequency nonselective slow Rayleigh fading

Importance sampling for the efficient simulation of adaptive...

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1994 IEEE GLOBECOM. communications: The Global Bridge

作者： W.A. Al-Qaq J.K. Townsend Compact Software Inc. Paterson NJ USA Center for Communications and Signal Processing Department of Electrical & Computer Engineering North Carolina Agriculture and Technical State University Raleigh NC USA

Importance sampling (IS) is recognized as an efficient technique in reducing the simulation run time needed to estimate low bit error rates (BERs) in digital communication systems. In this paper. We present an IS stochastic gradient descent technique for the efficient simulation of adaptive systems which employ diversity in the presence of frequency nonselective slow Rayleigh fading and AWGN. After accounting for the overhead of the optimization algorithm, average speed-up factors of up to 6 orders of magnitude (over conventional Monte Carlo (MC)) were attained for error probabilities as low as 10/sup -11/.

关键词： Monte Carlo methods Adaptive systems Frequency Rayleigh channels AWGN Fading Bit error rate signal processing algorithms Computational modeling Error probability

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Error performance of the blind decision feedback equalizer using decorrelation

Error performance of the blind decision feedback equalizer u...

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MILCOM, Military communications Conference

作者： R.E. Kamel Y. Bar-Ness Center for Communications and Signal Processing Department of Electrical and Computer Engineering New Jersey Institute of Technology Newark NJ USA Telecommunications & Traffic-Control Systems Group Delft University of Technnology Delft Netherlands

The decision feedback equalizer has the advantage of compensating for channel amplitude distortion without enhancing noise. Conventional decision feedback equalizers require a training sequence to help them adapt to unknown channel characteristics. Training sequences are not always appropriate. In such situations blind equalizers are more suitable. The blind decision feedback equalizer inherits from the conventional the advantage of not enhancing noise, while compensating for severe ISI. It is thus superior over the blind linear equalizer. On the other hand the blind decision feedback equalizer also suffers from error propagation. In this paper we study the transient behavior of the blind DFE. This is done by deriving an upper bound on the probability of error due to residual ISI and show that it vanishes for the noiseless case. We also determine lower and upper bounds on the probability of error for the additive white Gaussian noise case. The upper bound obtained is the same as that of Duttweiler, et al. (1974). Using a different approach from that of Duttweiler, et al., we derive a lower bound. This bound is tighter than tile "no ISI" lower bound.< >

关键词： Decision feedback equalizers Decorrelation Upper bound Blind equalizers Intersymbol interference Additive white noise Steady-state Convergence Gaussian noise AWGN

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Efficient techniques for two-layer coding of video sequences

Efficient techniques for two-layer coding of video sequences

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The 1994 1st IEEE International Conference on Image processing

作者： Blake, S.L. Rajala, S.A. Gong, Fengmin Mitchell, T.L. Center for Communications and Signal Processing North Carolina State University RaleighNC27695-7914 United States MCNC Information Technologies 3021 Cornwallis Road Research Triangle ParkNC27707-2889 United States Department of Electrical Engineering NC A and T State Univsrsity GreensboroNC27411 United States

Two-layer encoding of packet video may be a useful way to minimize network resource usage while coping with potential packet loss. A two-layer codec architecture modeled after the H.261 RM8 algorithm is proposed, and is shown to be a generalization of the requantization and spectral separation encoding techniques. Experiments were performed using two ten-second video sequences to examine the efficiency of two-layer encoding algorithms. Three techniques: periodic group of blocks (GOB) replenishment, conditional macroblock replenishment, and block error thresholding, are shown to improve the efficiency of two-layer encoding. A hybrid encoding method utilizing both spectral separation and requantization is shown to provide the best results. © 1994 IEEE.

关键词： Efficiency

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Design of limit-cycle-free recursive transfer functions for fixed-point direct form implementation

Design of limit-cycle-free recursive transfer functions for ...

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IEEE International Symposium on Circuits and Systems (ISCAS)

作者： T.I. Laakso M. Lang T. Saramaki Nokia Research Center Helsinki Finland Electrical and Computer Engineering Department Rice University TX USA Signal Processing Laboratory Tampere University of Technology Tampere Finland

An approach for the design of limit-cycle-free digital fixed-point filters is proposed. By constraining the transfer function already in the design phase, it is guaranteed that the filter will be free from limit cycles and overflow oscillations in the direct form implementation. The design strategy also guarantees low roundoff noise. The proposed approach is illustrated with design examples. The examples show that typically a 50-100% increase in the filter order (as compared to standard elliptic design) is needed for the limit-cycle-free implementation of a lowpass filter with the direct form (DF) structure. Since the DF structure is very efficient to implement in signal processors, the proposed filters are very attractive for such environment, whereas dedicated filter structures (wave digital, state-space, etc.) easily result in a 3 to 4-fold implementation complexity.< >

关键词： Transfer functions Limit-cycles Electronic mail Digital filters Stability criteria Algorithm design and analysis Design engineering Laboratories Elliptic design signal processing

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Maximizing data throughput in an integrated TDMA communication system using mean field annealing

Maximizing data throughput in an integrated TDMA communicati...

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IEEE Conference and Exhibition on Global Telecommunications (GLOBECOM)

作者： Gangsheng Wang N. Ansari Center for Communications Signal Procewing Research Department of Electrical and Computer Engineering New Jersey Institute of Technology New Jersey of Technology University Heights Newark NJ USA

In an integrated TDMA communication system, voice and data are multiplexed in time to share a common transmission link. The system operates in a frame format in which time is divided into slots. A certain number of time slots in a frame are allocated to voice and the rest are used to transmit data, Maximum data throughput can be achieved by searching for the optimal configuration of relative positions of voice and data transmission in a frame. This is a NP-complete constrained optimisation problem. In the paper, mean field annealing is used to solve this problem. The determination of the Lagrange parameters, estimation of critical temperature and convergence criterion are addressed. Simulation results show that this approach is a good tradeoff between performance and computational complexity.

关键词： Throughput Time division multiple access Data communication Constraint optimization Annealing Lagrangian functions Parameter estimation Temperature Convergence Computational modeling

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Performance analysis of the multistage CMA adaptive beamformer

Performance analysis of the multistage CMA adaptive beamform...

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MILCOM, Military communications Conference

作者： J.J. Shynk R.P. Gooch Center for Information Processing Research Department of Electrical and Computer Engineering University of California Santa Barbara CA USA Applied Signal Technology Inc. Sunnyvale CA USA

The multistage CMA adaptive beamformer is a blind adaptive antenna system capable of recovering several narrowband cochannel signals. Each stage of the system captures one source (without using a training signal), removes it before processing by subsequent stages, and provides an estimate of its direction of arrival. This system would be useful in frequency reuse applications, such as cellular radio or personal communication networks, where cochannel interference is an important consideration. We present the steady-state convergence properties of the first stage of the multistage CMA adaptive beamformer. computer simulations are presented to verify the analytical results.< >

关键词： Performance analysis Adaptive systems Adaptive arrays Narrowband signal processing Direction of arrival estimation Frequency Application software Land mobile radio cellular systems Personal communication networks

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Efficient techniques for two-layer coding of video sequences

Efficient techniques for two-layer coding of video sequences

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IEEE International Conference on Image processing

作者： S.L. Blake S.A. Rajala Fengmin Gong T.L. Mitchell Center for Communications and Signal Processing North Carolina State University Raleigh NC USA Information Technologies MCNC NC USA Department of Electrical Engineering NC A&T State University Greensboro NC USA

关键词： Video sequences Codecs Encoding Bit rate signal processing algorithms Bandwidth Video coding Video compression Layout Delay

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On the design of a class of 2-D IIR digital filters using a single lattice structure

On the design of a class of 2-D IIR digital filters using a ...

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Canadian Conference on electrical and computer engineering (CCECE)

作者： Qunshan Gu Swany Centre for Signal Processing and Communications Department of Electrical and Computer Engineering Concordia University Montreal QUE Canada Concordia University Montreal QC CA Dept. of Electr. & Comput. Eng. Concordia Univ. Montreal Que. Canada

In this paper, a new approach is presented for the design of a class of 2-D digital filters by employing a single lattice wave digital filter structure. The design procedure is very simple and the resulting filter is extremely efficient for implementation. Moreover, this filter structure provides very desirable properties such as modularity, low sensitivity, high dynamic range and guaranteed stability even under finite arithmetic conditions. Therefore, it is highly suitable for VLSI implementation. An example is given to show the capability of the proposed filter structure in realizing different types of filters.< >

关键词： Wave digital filters IIR digital filters Multidimensional digital filters Stability Very-large-scale integration

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