检索结果-内蒙古大学图书馆

Uplink radio resource allocation in orthogonal frequency-division multiple access heterogeneous networks with limited feedback

引用

IET COMMUNICATIONS 2014年第18期8卷 3451-3458页

作者： Dashti, Mina Mokari, Nader Abedi, Mohhamad Reza Islamic Azad Univ East Tehran Branch Dept Elect Engn Tehran *** Iran Tarbiat Modares Dept Elect & Comp Engn Tehran 14115349 Iran

Femtocell networks are expected to offer significant performance improvement with low cost. However, adaptive transmission based on maximising the sum rate of macro and femto networks requires perfect channel quality information (CQI) of the macro and femto links. This assumption requires an infinite resolution feedback link, which is not always practical since it requires an excessive amount of bandwidth. This study considers the problem of maximising average sum rate under the constraint of average maximum power transmission at macro and femto users. A suboptimal iterative algorithm is developed for finding the optimal CQI quantisers as well as the discrete power and rate at macro and femto transmitter for each quantised CQI level so as to maximise the average sum rate of the system. The author's numerical results give the number of bits required to sufficiently represent the CQI to achieve almost the maximum sum rate attained using full knowledge of the CQI.

关键词： resource allocation frequency division multiple access femtocellular radio iterative methods uplink radio resource allocation orthogonal frequency-division multiple access heterogeneous networks femtocell networks adaptive transmission macro networks femto networks channel quality information macro links femto links iterative algorithm CQI quantisers

来源：评论

学校读者我要写书评

暂无评论

iterative dual energy material decomposition from spatial mismatched raw data sets

引用

JOURNAL OF X-RAY SCIENCE AND TECHNOLOGY 2014年第6期22卷 745-762页

作者： Zhao, Xing Hu, Jing-Jing Zhao, Yun-Song Zhang, Hui-Tao Zhang, Peng Capital Normal Univ Sch Math Sci CT Lab Beijing 100048 Peoples R China Beijing Inst Technol Sch Software Beijing 100081 Peoples R China Beijing Ctr Math & Informat Interdisciplinary Sci Beijing Peoples R China

Today's clinical dual energy computed tomography (DECT) scanners generally measure different rays for different energy spectra and acquire spatial mismatched raw data sets. The deficits in clinical DECT technologies suggest that mainly image based material decomposition methods are in use nowadays. However, the image based material decomposition is an approximate technique, and beam hardening artifacts remain in decomposition results. A recently developed image based iterative method for material decomposition from inconsistent rays (MDIR) can achieve much better image quality than the conventional image based methods. Inspired by the MDIR method, this paper proposes an iterative method to indirectly perform raw data based DECT even with completely mismatched raw data sets. The iterative process is initialized by density images that were obtained from an image based material decomposition. Then the density images are iteratively corrected by comparing the estimated polychromatic projections and the measured polychromatic projections. Only three iterations of the method are sufficient to greatly improve the qualitative and quantitative information in material density images. Compared with the MDIR method, the proposed method needs not to perform additional water precorrection. The advantages of the method are verified with numerical experiments from inconsistent noise free and noisy raw data.

关键词： Dual energy computed tomography iterative algorithm basis material decomposition calibration

来源：评论

学校读者我要写书评

暂无评论

Robust beamforming and power allocation in cognitive radio relay networks with imperfect channel state information

引用

IET COMMUNICATIONS 2014年第9期8卷 1560-1569页

作者： Mohammadkhani, Saeideh Kahaei, Mohammad Hossein Razavizadeh, Seyed Mohammad Iran Univ Sci & Technol Sch Elect Engn Tehran Iran

The authors study robust beamforming and power allocation in cognitive relay networks using several relays in the secondary link. The channel state information is imperfect modelled by Gaussian random variables. First, minimisation of the total transmit power of relays and the secondary transmitter is considered with a constraint on the interference in the primary receiver. Also, a constraint is assumed on the received signal-to-interference plus noise ratio (SINR) in the secondary receiver. In the other scenario, maximisation of the SINR in the secondary receiver is investigated with a limit on the maximum transmit power of relays and the secondary transmitter. For each non-convex optimisation problem, an iterative and robust algorithm is derived. It is proved that the first proposed algorithm converges to the global optimum. Simulation results similarly show the convergence of both algorithms with a few number of iterations. The outperformance of the robust algorithms is shown compared with a non-robust design.

关键词： cognitive radio relay networks (telecommunication) array signal processing channel allocation radio links Gaussian processes random processes radio receivers radio transmitters interference suppression minimax techniques concave programming iterative methods convergence robust beamforming algorithm power allocation cognitive radio relay network imperfect channel state information radio link convergence iterative algorithm nonconvex optimisation problem secondary transmitter SINR maximisation secondary receiver SINR signal-to-interference plus noise ratio primary receiver transmit power minimisation Gaussian random variables

来源：评论

学校读者我要写书评

暂无评论

iterative solutions of the inverse problems of frequency sounding and electrical prospecting of layered media

引用

INVERSE PROBLEMS IN SCIENCE AND ENGINEERING 2014年第8期22卷 1329-1344页

作者： Timonov, A. Univ South Carolina Upstate Div Math & Comp Sci Spartanburg SC 29303 USA

The paper presents the iterative solutions of two coefficient inverse problems (CIPs) arising in frequency sounding and electrical prospecting. An iterative algorithm is constructed to obtain such solutions. Exploiting the Beilina-Klibanov approach to CIPs, this algorithm possesses the new iterative and refinement procedures. These features enhance significantly both the spatial and contrast resolutions of reconstructed coefficients. The computational effectiveness of the proposed numerical technique is demonstrated in computational experiments with two applied CIPs: electromagnetic or acoustic frequency sounding and electrical prospecting of layered media. The Slichter-Langer-Tikhonov formulation is exploited as a mathematical model of the latter.

关键词： coefficient inverse problem iterative algorithm boundary and internal data

来源：评论

学校读者我要写书评

暂无评论

Energy Efficient Multi-Pair Transmission in Large-Scale Multi-Antenna Relay Systems

Energy Efficient Multi-Pair Transmission in Large-Scale Mult...

引用

International Conference on Wireless Communications and Signal Processing

作者： Yi Wang Chunguo Li Yongming Huang Haibo Dai Shidang Li Luxi Yang Sch. of Inf. Sci. & Eng. Southeast Univ. Nanjing China

ISBN: (纸本)9781467376884

A multi-pair large-scale multi-antenna relaying system is considered in this paper. We investigate the energy efficiency (EE) performance by taking the circuit power consumption into account when maximum ratio combining/maximum ratio transmission is explored at the relay station (RS). By utilizing the law of large numbers, an analytical expression of EE is derived. Based on this, we characterize the trend of EE with regard to the transmit power of the users and the RS, and the number of RS antennas. Regarding to the transmit power at users and RS, it is shown that the optimal EE can be always achieved by an unique globally transmit power set. Furthermore, an iterative algorithm is proposed to obtain the globally optimal solution. The analysis also demonstrates that the EE function is quasiconcave with respect to the RS antenna number when the circuit power is comparable to the transmit power, based on which we obtain the optimal solution in closed form to the number of antennas for RS. When the circuit power is negligible compared with high transmit power, the EE has a nearly logarithmic increase with the number of RS antennas. All the analytical results are verified by the numerical simulations.

关键词： antenna arrays energy conservation iterative methods relay networks (telecommunication) telecommunication power management energy efficiency energy efficient multi-pair transmission iterative algorithm large-scale multi-antenna relay systems maximum ratio combining maximum ratio transmission multi-pair large-scale multiantenna relaying system numerical simulations relay station Approximation methods Integrated circuit modeling Interference MIMO Power demand Relays Transmitting antennas

来源：评论

学校读者我要写书评

暂无评论

Two-Impulse Cotangent Rendezvous Between Coplanar Elliptic and Hyperbolic Orbits

引用

JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2014年第3期37卷 964-970页

作者： Zhang, Gang Cao, Xibin Zhou, Di Harbin Inst Technol Res Ctr Satellite Technol Harbin 150001 Peoples R China Harbin Inst Technol Dept Control Sci & Engn Harbin 150001 Peoples R China

No abstract available.

关键词： Patched Conic Approximation Hohmann Transfer Earth Orbital Rendezvous Secant Method Orbital Period iterative algorithm Flight Path Angle Kepler's Equation Planetary Flyby

来源：评论

学校读者我要写书评

暂无评论

Soft-Decision-Aided Channel Estimation Over the Flat-Fading Channel, and an Application to iterative Decoding Using an Example LTE Turbo Code

引用

IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2014年第11期13卷 6027-6040页

作者： Yuan, Haifeng Kam, Pooi-Yuen Natl Univ Singapore Dept Elect & Comp Engn Singapore 117576 Singapore

We consider transmissions over the frequency-nonselective time-selective fading channel and derive the soft-decision-aided maximum a posteriori probability (SDA-MAP) channel estimator that utilizes the entire received signal sequence, including both pilot signals and data signals, and the a priori statistical information of the transmitted data symbols. This paper theoretically demonstrates how the soft data decisions should be incorporated into the channel estimation process. An iterative implementation of the SDA-MAP estimator is proposed, which uses the feedback of earlier soft decisions and the feedforward of later soft decisions to estimate the current channel gain. This approximate SDA-MAP implementation is similar in structure to the expectation-maximization algorithm. Simulation results show that the receiver using this iterative SDA-MAP estimator outperforms the conventional pilot-symbol-assisted modulation receiver in which the channel estimates are obtained from only the pilot signals. An application to iterative decoding using the LTE turbo code is also provided.

关键词： Soft decision maximum a posteriori probability channel estimation fading channel iterative algorithm LTE turbo code

来源：评论

学校读者我要写书评

暂无评论

Mixed H₂/H_∞ control of time-varying stochastic discrete-time systems under uniform detectability

引用

IET CONTROL THEORY AND APPLICATIONS 2014年第17期8卷 1866-1874页

作者： Sheng, Li Zhang, Weihai Gao, Ming China Univ Petr East China Coll Informat & Control Engn Qingdao 266580 Peoples R China Shandong Univ Sci & Technol Coll Elect Engn & Automat Qingdao 266590 Peoples R China

This study is concerned with the infinite horizon H-2/H control of time-varying stochastic discrete-time systems with state and disturbance dependent noise. The notion of uniform detectability for time-varying stochastic discrete-time systems is introduced, and some good properties are derived. Under uniform detectability, a necessary and sufficient condition for the existence of time-varying stochastic H-2/H control is presented, which transforms the design of H-2/H control into the solvability of coupled time-varying matrix-valued equations. Finally, an iterative algorithm is proposed to solve the coupled time-varying matrix-valued equations, and a numerical example is provided to show the effectiveness of the obtained results.

关键词： H control H-2 control control system synthesis time-varying systems discrete time systems stochastic systems infinite horizon matrix algebra iterative methods mixed H-2-H control design time-varying stochastic discrete-time systems uniform detectability infinite horizon H-2-H control disturbance dependent noise state dependent noise sufficient condition necessary condition coupled time-varying matrix-valued equations time-varying stochastic H-2-H control iterative algorithm

来源：评论

学校读者我要写书评

暂无评论

A novel iterative reconstruction method for dual-energy computed tomography based on polychromatic forward-projection calibration

引用

INSIGHT 2014年第10期56卷 541-548页

作者： Zhao, Xing Hu, Jing-jing Zhao, Yun-song Zhang, Hui-tao Capital Normal Univ Sch Math Sci CT Lab Beijing 100048 Peoples R China Capital Normal Univ Beijing Ctr Math & Informat Interdisciplinary Sci Beijing 100048 Peoples R China Beijing Inst Technol Sch Software Beijing 100081 Peoples R China

Dual-energy computed tomography (DECT) scans the measured object using two different detected X-ray spectra. The acquired polychromatic projections can be used to calculate the density and composition distribution of the scanned object. Due to the non-linear relationship between the polychromatic projections and the images to be reconstructed, precise DECT image reconstruction is generally a difficult task. This paper proposes an iterative reconstruction method for DECT based on polychromatic forward-projection calibration. The method has a fast convergence rate and fits for any scanning configurations commonly used, including both geometrically consistent and inconsistent measurements for different spectra. In contrast to other iterative reconstruction algorithms, the proposed method requires neither knowledge of the X-ray spectrum nor of the attenuation coefficients. The proposed method also has a high degree of parallelism and is suitable for acceleration on graphic processing units (GPUs). The method is validated with numerical experiments from the simulated noise-free and noisy, consistent and inconsistent polychromatic projection data of a FORBILD thorax phantom. The reconstructed linear attenuation coefficients of the test phantom are in excellent agreement with the theoretical ones, and beam hardening artefacts can be completely eliminated.

关键词： dual-energy computed tomography iterative algorithm basis material decomposition calibration

来源：评论

学校读者我要写书评

暂无评论

An iterative updating method for damped structural systems using symmetric eigenstructure assignment

引用

JOURNAL OF COMPUTATIONAL AND APPLIED MATHEMATICS 2014年 256卷 268-277页

作者： Yuan, Yongxin Liu, Hao Jiangsu Univ Sci & Technol Sch Math & Phys Zhenjiang 212003 Peoples R China Nanjing Univ Aeronaut & Astronaut Dept Math Nanjing 210016 Jiangsu Peoples R China

An iterative method for updating finite element models with measured modal results using a symmetric eigenstructure assignment technique is developed. By the method, the updated symmetric damping and stiffness matrices can be obtained within finite iteration steps in the absence of roundoff errors by choosing a special kind of initial matrices and the measured data are embedded in the updated model. The numerical results show that the proposed method is reliable and attractive. (C) 2013 Elsevier B.V. All rights reserved.

关键词： Model updating iterative algorithm Eigenstructure assignment Partially prescribed spectral data Optimal approximation

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：