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BIT-SERIAL VLSI IMPLEMENTATION OF VECTOR QUANTIZER FOR REAL-TIME IMAGE-CODING

IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS 1989年第10期36卷 1281-1290页

作者： RAMAMOORTHY, PA POTU, B TRAN, T Signal Processing and Communications Group Department of Electrical and Computer Engineering University of Cincinnati Cincinnati OH USA

A practical high-throughput architecture and its implementation for real-time coding of television-quality signals are presented. The architecture is directed toward the implementation of multistage vector quantization (VQ), as the authors' simulation results show that the latter is more suitable for real-time coding. However, the implementation is suitable for both single-stage and multistage VQ. The functional blocks of the VQ encoder system have been designed and implemented in VLSI technology. The VQ encoding scheme designed has an encoding delay of 25 clock cycles and is independent of the codebook size.< >

关键词： Very large scale integration Image coding Speech coding Throughput signal processing algorithms Bit rate Image storage Real time systems Application software Hardware

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ESTIMATION OF MULTIPATH CHANNEL RESPONSE IN FREQUENCY SELECTIVE CHANNELS

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IEEE JOURNAL ON SELECTED AREAS IN communications 1989年第1期7卷 12-19页

作者： HATZINAKOS, D NIKIAS, CL Communications and Digital Signal Processing (CDSP) Department of Electrical and Computer Engineering Northeastern University Boston MA USA

A novel discrete-time method is proposed for estimating the impulse response of a frequency-selective digitally modulated communication channel. The received signal is first demodulated and sampled and then the fourth-order cumulants of the resulting discrete-time sequence are estimated. The method estimates the channel impulse response from the complex cepstrum of the aforementioned fourth-order cumulants (i.e. tricepstrum). The method depends only on the second- and fourth-order statistics of the transmitted sequence and is capable of reconstructing nonminimum-phase impulse responses. Monte Carlo simulation results demonstrate the effectiveness of the method, its low sensitivity to observation noise, and its improved performance in terms of probability of error or the reconstructed transmitted sequence.< >

关键词： Frequency estimation Multipath channels signal processing algorithms Decision feedback equalizers Working environment noise Intersymbol interference Data communication Adaptive equalizers Fading Maximum likelihood estimation

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Primitive-based teleconference image coding technique

Primitive-based teleconference image coding technique

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

作者： A.M. Alattar S.A. Rajala Department of Electrical and Computer Engineering Center for Communications and Signal Processing North Carolina State University Raleigh NC USA

An image coding technique with the capability of producing good image quality at a compression ratio over 1000:1 is described. The main idea is to break the image into complicated primitives using a priori knowledge. Usually these primitives are not coded and transmitted, but are matched to a previously created database, and the necessary information about the best match is coded and transmitted. This information is used at the receiver to retrieve a replica of the original primitive from a duplicate database. The primitives are assembled as in computer animation to produce a faithful reconstruction of the original image. The proposed technique allow real-time transmission of video signals over low-bit-rate channels (less than 64 kb/s). The application of this technique to teleconference and picture phone images is discussed.< >

关键词： Teleconferencing Image coding Image segmentation Image databases Head Mouth signal processing Image quality Information retrieval Assembly

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Primitive-based image coding technique for still pictures

Primitive-based image coding technique for still pictures

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IEEE International Symposium on Circuits and Systems (ISCAS)

作者： A.M. Alattar S.A. Rajala Department of Electrical and Computer Engineering and Center for Communications and Signal Processing North Carolina State University Raleigh NC USA

A new image coding technique for achieving an extremely high compression ratio while producing good image quality is described. The idea is analogous to that used in forensic applications when constructing a composite image of a criminal from a collection of images of facial features. The imput image is segmented into complicated primitives that are coded using previously constructed database of primitives. A duplicate database is used at the receiver to decode the primitives. The decoded primitives are assembled as in computer animation to produce a faithful reconstruction of the original image. The technique has been applied to head-and-shoulders images and compression ratios over 1000:1 have been achieved.< >

关键词： Image coding Image databases Spatial databases Decoding Image quality Forensics Facial features Image segmentation Assembly Animation

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Derivation of voltage and current transfer functions for multiconductor transmission lines

Derivation of voltage and current transfer functions for mul...

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IEEE International Symposium on Circuits and Systems (ISCAS)

作者： M. Riddle S. Ardalan J. Suh Center for Communications and Signal Processing Department of Electrical and Computer Engineering North Carolina State University Raleigh NC USA

A set of compact equations is derived for a system of multiconductor transmission lines with arbitrary source and load termination networks. The derivations are based on defining the reflection coefficient matrix for multiconductor transmission lines. Expressions for the voltage and current transfer functions are derived. For the two-conductor case, the equations reduce to well known results. The expressions are very suitable for straightforward coding on a computer. The validity of the derived equations is checked with published experimental and computer models for three- and four-conductor transmission line systems.< >

关键词： Voltage Transfer functions Multiconductor transmission lines Transmission line matrix methods Conductors Reflection Power transmission lines Differential equations Impedance Crosstalk

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Partial shape recognition: a landmark-based approach

Partial shape recognition: a landmark-based approach

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IEEE International Conference on Systems, Man and Cybernetics

作者： N. Ansari E.J. Delp Center for Communications and Signal Processing Electrical and Computer Engineering Department New Jersey Institute of Technology Newark NJ USA Computer Vision and Image Processing Laboratory School of Electrical Engineering Purdue University IN USA

A technique to guide landmark matching known as hopping dynamic programming is described. The location of the model in the scene is estimated with a least-squares fit. A heuristic measure is then computed to decide if the model is in the scene. The shape features of an object are the landmarks associated with the object. The landmarks of an object are defined as the points of interest of the object that have important shape attributes. Examples of landmarks are corners, holes, protrusions, and high-curvature points.< >

关键词： Shape measurement Layout computer vision Pattern recognition signal processing Image processing Laboratories Performance evaluation Least squares approximation Feature extraction

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Parameter extraction of microwave transistors using tree annealing

Parameter extraction of microwave transistors using tree ann...

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IEEE/Cornell Conference on Advanced Concepts in High Speed Semiconductor Devices and Circuits

作者： M.B. Steer G.L. Bilbro R.J. Trew S.G. Skaggs High Frequency Electronics Laboratory and the Center for Communications and Signal Processing Department of Electrical and Computer Engineering North Carolina State University Raleigh NC USA

The authors have developed an alternative formulation of simulated annealing using a tree-based Metropolis procedure called tree annealing. Tree annealing is suited to continuous optimization problems and, in particular, to transistor parameter extraction. The tree annealing optimization algorithm was used to extract the parameters of the HBT (heterojunction bipolar transistor) of U.K. Mishra et al. (IEDM Tech. Dig., p.180-3, Dec. 1988) using a physically based equivalent circuit and deembedded scattering parameter measurements from 45 MHz to 26.5 GHz. Good results were obtained from the parameter extraction technique, and the ability of MFA not to be locked in local minima enabled a physically based equivalent circuit model to be used. Tree annealing is essentially a smart random search technique and so requires many more functional evaluations than do gradient-based minimization algorithms. However, no startling guess is required, and the bounds on parameter values can be widely separated with little effect on optimization time.< >

关键词： Parameter extraction Microwave transistors Simulated annealing Equivalent circuits Combinatorial mathematics Robustness Frequency Laboratories Microwave communication signal processing

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On improving the computational efficiency of digital lightwave link simulation

On improving the computational efficiency of digital lightwa...

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IEEE International Conference on communications (ICC)

作者： J.K. Townsend K.S. Shanmugan Center of Communications and Signal Processing Department of Electrical & Computer Engineering North Carolina State University Raleigh NC USA University of Kansas Lawrence KS USA

It is noted that although bit error rate (BER) analysis of an end-to-end digital lightwave link using simulation is feasible, further reduction in execution time is needed when the link includes an APD (avalanche photodetector) receiver. The authors present techniques that reduce the computational resources required to estimate the BER for these systems by at least two orders of magnitude. They achieve the speedup by developing a more efficient random number generation algorithm for APD shot noise and applying a tail extrapolation technique to the BER conditional distributions. Receiver thermal noise is handled analytically. Simulation results are presented which demonstrate that accurate estimates of the BER for a typical lightwave communications link can be obtained in approximately 1.5 CPU hours on a VAXstation II using a combination of these approaches.< >

关键词： Computational efficiency Bit error rate Error analysis Computational modeling Analytical models Photodetectors Random number generation Noise generators Probability distribution Extrapolation

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An algorithm for computer modeling of coupled multiconductor transmission line networks

An algorithm for computer modeling of coupled multiconductor...

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IEEE International Conference on communications (ICC)

作者： R.A. Nobakht S.H. Ardalan K. Shuey Center of Communications and Signal Processing Department of Electrical and Computer Engineering North Carolina State University Raleigh NC USA Westinghouse Electronic Corporation Raleigh NC USA

A technique for computer modeling and analysis of coupled transmission line networks is presented. The method is based on representing the coupled transmission line network as a coupled tree data structure. By using recursive tree transversal techniques, the network is solved in two passes. In the first pass, the impedances at all nodes are computed and stored in the data structure for that node. For cases where the coupled lines are connected to uncoupled lines, the impedance looking into the uncoupled line subtree must also be computed and stored. In the second pass, starting at the source the voltages and currents are computed by transversing the tree and using the impedances calculated in the first pass. The technique was applied to a particular coupled system, and the effects of coupling calculated using the technique agreed well with the results one would expect from the network. The technique is especially useful in the analysis of coupling in multiconductor transmission line networks with many branches and mixed transmission line characteristics.< >

关键词： computer networks Couplings Multiconductor transmission lines Transmission line matrix methods Conductors Equations Voltage Transmission line theory Distributed parameter circuits Reflection

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Sensitivity analysis of transversal RLS algorithms with correlated inputs

Sensitivity analysis of transversal RLS algorithms with corr...

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IEEE International Symposium on Circuits and Systems (ISCAS)

作者： S.H. Ardalan T. Adali Center for Communication and Signal Processing Department of Electrical and Computer Engineering North Carolina State University Raleigh NC USA

The effects of input signal correlation on the performance on finite-precision RLS (recursive-least-squares) algorithms we presented. It is shown that one way to analyze finite-precision effects is indirectly through the study of the sensitivity of the RLS algorithm to perturbations in the filter coefficients. The authors show that the mean deviation of the optimum error power grows linearly with time and is the same for both correlated and uncorrelated input samples. However, the variance of the deviation from the optimum increases with signal correlation. Upper and lower bounds are derived in terms of the ratio of the maximum eigenvalue of the sample autocorrelation matrix to the signal variance. (The deviation increases as the signal dynamic range increases.) Simulations are presented to verify the theory. A stable finite-precision RLS algorithm is derived by modeling roundoff errors and incorporating their effects into the algorithm.< >

关键词： Sensitivity analysis Resonance light scattering signal processing algorithms Filters Algorithm design and analysis Roundoff errors Least squares methods signal processing Eigenvalues and eigenfunctions Autocorrelation

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