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IEEE Conference and Exhibition on Global Telecommunications (GLOBECOM)

作者： Jinwen Ma Hongya Ge Center for Communications and Signal Processing Department of Electrical and Computer Engineering New Jersey Institute of Technology Newark NJ USA

Linear space-time multiuser detectors are proposed for CDMA systems which support users transmitting at different bit rates. The performance of the LMMSE space-time dual-rate receiver is studied in the context of two multi-rate access methods: multi-code (MC) access where high data rate users multiplex information streams onto multiple codes, and variable spreading length (VSL) access where signature sequences of different lengths are assigned to users with different data rates. Simulation results show that the proposed LMMSE space-time dual-rate receiver can significantly enhance the multimedia services that can be provided by multi-rate CDMA systems, and the VSL access system offers a distinct advantage over the MC system.

关键词： Multiaccess communication Detectors Fading Multiple access interference Multimedia systems Data communication Multipath channels Receiving antennas signal processing Space technology

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Adaptive multishot canceler for wideband CDMA systems

Adaptive multishot canceler for wideband CDMA systems

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IEEE Conference on Vehicular Technology (VTC)

作者： Xin Tang Y. Bar-Ness N.J.M. Van Waes Center for Communications and Signal Processing Department of Electrical and Computer Engineering New Jersey Institute of Technology Newark NJ USA

With the demand for high capacity (multimedia) services, wideband CDMA (WCDMA) has become an attractive multiple access scheme for 3rd generation wireless systems. Coming with higher data rate, the application of WCDMA brings with it new challenges in terms of multiple access interference (MAI) and intersymbol interference (ISI) suppression due to the fact that compared to the "regular" CDMA, the delay spread is no longer only a few chips. Most of the literature on multiuser detection so far focused on algorithms which, due to high computational/hardware complexity, are unsuitable for large delay spread channels. We present an adaptive symbol-based signal separator based on multishot matched filtering which is suitable for the asynchronous large delay spread fading channels characteristics.

关键词： Wideband Multiaccess communication Delay Multiple access interference Intersymbol interference Multimedia systems Multiuser detection Hardware Particle separators Adaptive filters

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Channel equalization by feedforward neural networks

Channel equalization by feedforward neural networks

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IEEE International Symposium on Circuits and Systems (ISCAS)

作者： B. Lu B.L. Evans Embedded Signal Processing Laboratory Department of Electrical and Computer Engineering University of Technology Austin TX USA

A signal suffers from nonlinear, linear, and additive distortion when transmitted through a channel. Linear equalizers are commonly used in receivers to compensate for linear channel distortion. As an alternative, nonlinear equalizers have the potential to compensate for all three sources of channel distortion. Previous authors have shown that nonlinear feedforward equalizers based on either multilayer perceptron (MLP) or radial basis function (RBF) neural networks can outperform linear equalizers. In this paper, we compare the performance of MLP vs. RBF equalizers in terms of symbol error rate vs. SNR. We design a reduced complexity neural network equalizer by cascading an MLP and a RBF network. In simulation, the new MLP-RBF equalizer outperforms MLP equalizers and RBF equalizers.

关键词： Neural networks Feedforward neural networks Equalizers Neurons Backpropagation algorithms Least squares approximation Convergence Simulated annealing Bayesian methods Finite impulse response filter

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L/sub p/ norm design of stack filters

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IEEE Transactions on Image processing 1999年第12期8卷 1730-1743页

作者： C.E. Savin M.O. Ahmad M.N.S. Swamy Centre for Signal Processing and Communications Department of Electrical and Computer Engineering Concordia University Montreal QUE Canada Nortel Networks Wireless Technology Laboratories Nepean ONT Canada

Addresses the problem of designing optimal stack filters by employing an L/sub p/ norm of the error between the desired signal and the estimated one. It is shown that the L/sub p/ norm can be expressed as a linear function of the decision errors at the binary levels of the filter. Thus, an L/sub p/-optimal stack filter can be determined as the solution of a linear program. The conventional design of using the mean absolute error (MAE), therefore, becomes a special ease of the general L/sub p/ norm-based design developed here. Other special cases of the proposed approach, of particular interest in signal processing, are the problems of optimal mean square error (p=2) and minimax (p/spl rarr//spl infin/) stack filtering. Since an L/spl infin/ optimization is a combinatorial problem, with its complexity increasing faster than exponentially with the filter size, the proposed L/sub p/ norm approach to stack filter design offers an additional benefit of a sound mathematical framework to obtain a practical engineering approximation to the solution of the minimax optimization problem. The conventional MAE design of an important subclass of stack filters, the weighted order statistic filters, is also extended to the L/sub p/ norm-based design. By considering a typical application of restoring images corrupted with impulsive noise, several design examples are presented, to illustrate the performance of the L/sub p/-optimal stack filters with different values of p. Simulation results show that the L/sub p/-optimal stack filters with p/spl ges/2 provide a better performance in terms of their capability in removing impulsive noise, compared to that achieved by using the conventional minimum MAE stack filters.

关键词： Nonlinear filters Minimax techniques Design optimization Acoustic noise signal design signal processing Mean square error methods Filtering Acoustical engineering Design engineering

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Convergence and stability analysis of the adaptive "Bootstrap" CDMA multi-user detector

Convergence and stability analysis of the adaptive "Bootstra...

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Communication Theory Mini-Conference

作者： Cheng-Chou Lee Y. Bar-Ness Center for Communications and Signal Processing Research Department of Electrical and Computer Engineering New Jersey Institute of Technology Newark NJ USA

The "Bootstrap" algorithm provides an efficient adaptive mult-user detection approach to solve the near-far problem in CDMA communication systems. The weight vectors are controlled by a simple decorrelation scheme which minimizes the correlation between their outputs and the hard limited version of the other outputs, respectively. It has been shown that the "Bootstrap" algorithm provides performance similar to that of MMSE with low complexity. In this article, the convergence and stability of the "Bootstrap" algorithm is considered. Sufficient conditions for the code cross-correlation and the step size are provided.

关键词： Convergence Stability analysis Multiaccess communication signal processing algorithms Detectors Matched filters Adaptive signal detection Multiuser detection Decorrelation Propagation delay

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Joint transcoding of multiple MPEG video bitstreams

Joint transcoding of multiple MPEG video bitstreams

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IEEE International Symposium on Circuits and Systems (ISCAS)

作者： H.Z. Sorial W.E. Lynch A. Vincent Centre for Signal Processing and Communications Department of Electrical & Computer Engineering Concordia University Montreal QUE Canada Communications Research Center Ottawa ONT Canada

This paper addresses the problem of bit-rate conversion of a previously compressed video. We provide an MPEG joint transcoder for transcoding several video bitstreams simultaneously. We show that joint transcoding reduces the quality variation between multiple video sequences, as compared to independently transcoding each sequence at a fixed bit rate. Hence, joint transcoding results in a better utilization of the channel capacity. The joint transcoder can be used in a congested communication network as an alternative to data/packet dropping, and in applications which require multiplexing video signals onto a fixed communication channel such as video servers providing video on demand (VOD) service.

关键词： Transcoding Video compression Video on demand Transform coding Video sequences Bit rate Channel capacity Communication networks Communication channels Network servers

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Underground imaging based on edge-preserving regularization

Underground imaging based on edge-preserving regularization

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International Conference on Information Intelligence and Systems

作者： H. Feng D.A. Castanon W.C. Karl Multi-Dimensional Signal Processing Laboratory Department of Electrical and Computer Engineering Boston University Boston MA USA

Develops approaches for imaging weak-contrast buried objects using data from a ground penetrating radar array. An approximate physical model relating the collected data to the underground objects is developed. This model uses ray optics to represent the air/soil interface, and a Born approximation to model the weak contrast backscattering from buried objects. In order to address both modeling errors and ill-posedness, the proposed image reconstruction algorithms use regularization based on a total variation norm with orientation preference. The algorithms are tested on data generated by nonlinear finite difference time domain electromagnetic simulations.

关键词： Buried object detection Optical imaging Ground penetrating radar Nonlinear optics Soil Scattering Approximation methods Backscatter Image reconstruction Testing

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Optimal design of real and complex minimum phase digital FIR filters

Optimal design of real and complex minimum phase digital FIR...

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International Conference on Acoustics, Speech, and signal processing (ICASSP)

作者： N. Damera-Venkata B.L. Evans Embedded Signal Processing Laboratory Department of Electrical and Computer Engineering University of Texas Austin Austin TX USA

We present a generalized optimal minimum phase digital FIR filter design algorithm that supports (1) arbitrary magnitude response specifications, (2) high coefficient accuracy, and (3) real and complex filters. The algorithm uses the discrete Hilbert transform relationship between the magnitude spectrum of a causal real sequence and its minimum phase delay phase spectrum given by Cizek (1970). We extend the transform pair to the complex case and show that the algorithm gives arbitrary coefficient accuracy. We present design examples that exceed the coefficient accuracy of the optimal real minimum phase filters reported by Chen and Parks (1986) and reduce the length of the optimal complex linear phase filters designed by Karam and McClellan (1995).

关键词： Finite impulse response filter Digital filters Nonlinear filters Algorithm design and analysis Polynomials signal processing algorithms Delay Discrete transforms Chebyshev approximation Cepstrum

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Analysis of stochastic gradient identification of polynomial nonlinear systems with memory

Analysis of stochastic gradient identification of polynomial...

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International Conference on Acoustics, Speech, and signal processing (ICASSP)

作者： P. Celka N.J. Bershad J.M. Vesin Department of Electrical Engineering Signal Processing Laboratory Swiss Federal Institute of Technology Switzerland Electrical and Computer Engineering Department University of California Irvine USA

This paper presents analytical, numerical and experimental results for a stochastic gradient adaptive scheme which identifies a polynomial-type nonlinear system with memory for noisy output observations. The analysis includes the computation of the stationary points, the mean square error surface, and the mean behaviour of the algorithm for Gaussian data. Monte Carlo simulations confirm the theoretical predictions which show a small sensitivity to the observation noise.

关键词： Stochastic systems Polynomials Nonlinear systems Nonlinear filters Least squares approximation signal analysis Algorithm design and analysis signal processing algorithms Mean square error methods signal to noise ratio

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Scheduling of DSP data flow graphs onto multiprocessors for maximum throughput

Scheduling of DSP data flow graphs onto multiprocessors for ...

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IEEE International Symposium on Circuits and Systems (ISCAS)

作者： A. Shatnawi M.O. Ahmad M.N.S. Swamy Department of Computer Engineering Jordan University of Science and Technology Irbid Jordan Center for Signal Processing and Communications Department of Electrical and Computer Engineering Concordia University Montreal QUE Canada

A novel technique to obtain a rate- and processor-optimal schedule for a fully-static data flow graph (DFG) onto a multiprocessor system is presented. In this technique, Floyd-Warshall's shortest path algorithm is used to evaluate the relative firing times of the nodes of the given DFG. Despite its implementation simplicity, the proposed technique has a lower time complexity than all the previously proposed techniques. The technique is tested on various benchmark problems to demonstrate its optimal performance.

关键词： Digital signal processing Flow graphs Throughput Processor scheduling signal processing algorithms Circuits Data flow computing Scheduling algorithm Polynomials Delay effects

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