检索结果-内蒙古大学图书馆

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

引用

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.

关键词：

来源：评论

学校读者我要写书评

暂无评论

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

Bootstrapped decorrelating algorithm for adaptive interferen...

引用

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

来源：评论

学校读者我要写书评

暂无评论

Error feedback loops linearize direct digital synthesizers

Error feedback loops linearize direct digital synthesizers

引用

1994 Second International Conference on Advanced A-D and D-A Conversion Techniques and their Applications

作者： F. Harris B. McKnight Electrical and Computer Engineering Department San Diego State University USA Naval command Control Research & Test and Evaluation Division Ocean Surveillance Center USA

The fidelity of a signal formed by the sequence of recalling stored digital samples from a look-up table and then converting these sample amplitudes to a waveform in a digital-to-analog converter (DAC) is affected by the time and amplitude quantization of the process. The size of the look-up table, hence the number of bits in the addressing scheme, affects the signal's time resolution and results in time-base jitter while the number of bits in the DAC affects amplitude quantization. These errors can be reduced by using noise feedback to spectrally shape the quantization noise formed by the table's address generator and of the quantization noise of the sample values presented to the DAC.< >

关键词： Feedback circuits Digital-analog conversion Frequency synthesizers Quantization Table lookup

来源：评论

学校读者我要写书评

暂无评论

A network approach to integrity maintenance of active object bases

A network approach to integrity maintenance of active object...

引用

Workshop on Object-Oriented Real-Time Dependable Systems (WORDS)

作者： S.T. Chang P.C.-Y. Sheu L.J. Peterson Department of Electrical and Computer Engineering University of California Irvine CA USA RDT&E Division Naval Command Control and Ocean Surveillance Center San Diego CA USA

The paper describes an asynchronous, network based algorithm to enforce integrity control on top of active objects. It proposes that the control of each active object be expressed as production rules, and the production rules associated with the objects be compiled into a network so that they can be evaluated collectively using databased operations. To maintain correctness and exploit all possible parallelism, each token is time stamped and can be processed asynchronously. To handle rollbacks, a lazy cancellation approach is used. It is shown that, in most cases, the performance of the network approach is superior to that of the fully distributed object oriented approach.

关键词： Object oriented modeling Dynamic programming control systems Continuous production Object oriented databases Parallel processing computational modeling Real time systems control system synthesis Oceans

来源：评论

学校读者我要写书评

暂无评论

Adaptive interference suppression for CDMA overlay systems

Adaptive interference suppression for CDMA overlay systems

引用

MILCOM, Military Communications Conference

作者： P. Wei J.R. Zeidler W.H. Ku Department of Electrical and Computer Engineering University of California San Diego La Jolla CA USA RDT & E Division Naval Command Control and Ocean Surveillance Center San Diego CA USA

It has been proposed that CDMA systems can be assigned to spectral bands which are presently occupied by narrowband users to further increase spectral capacity. Such CDMA overlay systems could provide new options for efficient utilization of the spectrum with minimal disruption to existing narrowband users, especially if adaptive interference suppression techniques are utilized in the spread spectrum receiver. The bit error rate (BER) performance of the mobile-to-base link of a CDMA system for a single narrowband user which occupies a significant portion of the CDMA bandwidth is considered to evaluate the performance of the adaptive filtering. It is shown that adaptive filtering provides a significant improvement when the CDMA and narrowband powers are of the same order. The dependence of the BER on the filter order, the bandwidth of the interference, and its center frequency relative to the CDMA carrier frequency are demonstrated.< >

关键词： Interference suppression Multiaccess communication Frequency Binary phase shift keying Filters Bit error rate Bandwidth Narrowband Phase modulation Fading

来源：评论

学校读者我要写书评

暂无评论

Error performance of the blind decision feedback equalizer using decorrelation

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

引用

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

来源：评论

学校读者我要写书评

暂无评论

Compliance control of an EMG-controlled prosthetic forearm using ultrasonic motors

Compliance control of an EMG-controlled prosthetic forearm u...

引用

Proceedings of IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS'94)

作者： K. Ito M. Pecson Zhi-Wei Luo M. Yamakita A. Kato T. Aoya M. Ito Bio-Mimetic Control Research Center RIKEN Institute of Physical and Chemical Research Nagoya Japan Department of lnformation and Computer Sciences Toyohashi University of Technology Toyohashi Japan Department of Electronics Engineering Aichi Institute of Technology Toyota Saitama Japan Department of Electrical Engineering Chubu University Matsumoto Japan

This paper discusses the compliance control of an ultrasonic motor powered prosthetic forearm which utilizes cutaneously measured electromyogram (EMG) signals sensed with the electrodes over the muscles as means of detecting motor commands sent by the central nervous system (CNS). Compliance control of the artificial limb was studied by implementing the bilinear model of the forearm and hand. This model emphasizes the role of the visco-elastic properties of the musculo-skeletal system of the actual limb in controlling its net configuration and movement. The flexor and extensor muscles extending over a joint influence the total joint impedance and determine the equilibrium position of the joint. Relaxing both flexor and extensor muscles makes the joint compliant to external forces, while activating both muscles increases the impedance of the joint.< >

关键词： Prosthetics Muscles Power system modeling Impedance Centralized control control systems Ultrasonic variables measurement Electromyography Electrodes Central nervous system

来源：评论

学校读者我要写书评

暂无评论

Visualization of myocardial perfusion defects in SPECT studies

Visualization of myocardial perfusion defects in SPECT studi...

引用

Visualization in Biomedical Computing 1994

作者： Jarrett Malone, L. Zeidler, James R. Ku, Walter H. Yeung, David W. C. Department of Electrical and Computer Engineering University of California at San Diego San DiegoCA92093-0407 United States Naval Command Control and Ocean Surveillance Center RDT and E Division Code 804 San DiegoCA92152-5000 United States Nuclear Medicine Service Veterans Affairs Medical Center San DiegoCA92161 United States Nuclear Medicine Division Department of Radiology UC San Diego School of Medicine San DiegoCA United States

In this paper, we present a semi-automatic technique to quantize and to visualize myocardial perfusion defects volumetrically. This involves: (1) differentiating the myocardium from encroaching viscera, (2) determining the mass of myocardium, (3) locating and measuring the perfusion defects, and (4) graphically rendering them. First, to differentiate between myocardium and other thoracic structures, we introduce the concept of Maximum Intensity Surface Segmentation (MISS). By locating local maximums in our cardiac Single Photon Emission computerized Tomography (SPECT) image and connecting ones sufficiently close together, we generate the basic shape of the myocardium and the encroaching structures. Second, with the shape of the myocardium determined, we then measure the thickness at each point of the heart wall. Fitting bicubic splines to the measured myocardial thicknesses, we create smooth epicardial and endocardial boundaries for both normal and abnormal regions. Third, using a thresholding technique based on the maximal myocardial activity, we determine the abnormal regions. Finally, with the abnormal regions and the myocardial mass determined, we can calculate the abnormality's size as a percentage of the total myocardial mass. By providing quantitative measurements, our technique meets the physician's long standing need for a volumetric quantitation of the size of myocardial perfusion abnormalities. © 1994 SPIE. All rights reserved.

关键词： Particle beams

来源：评论

学校读者我要写书评

暂无评论

Automatic target detection in dynamic clutter from incoherent ISAR data

Automatic target detection in dynamic clutter from incoheren...

引用

International Conference on Acoustics, Speech, and Signal Processing (ICASSP)

作者： M. Soumekh M. Pollock R. Dinger Department of Electrical & Computer Engineering State University of New York University at Buffalo Amherst NY USA RDT&E Division Naval Command Control and Ocean Surveillance Center San Diego CA USA

This paper presents a method for automatic detection of targets with nonlinear motion embedded in dynamic clutter. This is achieved via processing the targets' incoherent ISAR data that are less vulnerable to multiplicative noise (phase errors). It is shown that the incoherent ISAR signature of a target scene may be viewed as its baseband ISAR signature. Thus, the magnitude of an ISAR database that is severely contaminated with phase errors, i.e., incoherent ISAR data, may be used for ISAR detection of moving targets. Incoherent ISAR data in the fast-time and slow-time domain are transformed into another two-dimensional domain. The signature of a target in the transformed domain is shown to be localized based on its mid-point range and speed. This localized statistic is suitable for automatic, i.e., machine-based, detection of stationary as well as moving targets in the scene.< >

关键词： Object detection Clutter Layout Baseband Radar detection Additive noise Embedded computing Data engineering Motion detection Phase noise

来源：评论

学校读者我要写书评

暂无评论

Microwave characterization of sub-micron n- and p-channel MOSFETs fabricated with thin film Silicon-on-Sapphire

Microwave characterization of sub-micron n- and p-channel MO...

引用

Microwave, MTT-S International Symposium

作者： C.E. Chang P.M. Asbeck P.R. de la Houssaye G. Imthurn G.A. Garcia I. Lagnado Electrical and Computer Engineering Department University of California La Jolla CA USA Development Test and Evaluation Division (NRaD) 553 Naval Command Control and Ocean Surveillance Center Research San Diego CA USA

Microwave characteristics are reported for n- and p- MOS transistors fabricated with thin-film Silicon-on-Sapphire technology. The gates were defined with I-line optical lithography, and ranged down to 0.5 /spl mu/m (drawn dimension). The f/sub t/ values of the transistors reach 22 GHz for the n-channel structures and 21 GHz for the p-channel devices. The PMOS results are significantly higher than found with other Si or III-V technologies, and can potentially lead to high performance complementary microwave circuits. Small signal transistor models are similar to the ones for GaAs FETs. Dependence of model parameters on gate length were determined.< >

关键词： MOSFETs Microwave technology Microwave transistors Microwave FETs Semiconductor thin films Thin film transistors Lithography III-V semiconductor materials Microwave devices Microwave circuits

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：