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Robust adaptive beamforming using beam-space steering vector estimation

ELECTRONICS LETTERS 2013年第19期49卷 1201-+页

作者： Yang, T. Su, T. Zhu, W. T. Zhang, L. Xidian Univ Natl Key Lab Radar Signal Proc Xian 710071 Peoples R China

To solve the problem of performance degradation owing to imprecise knowledge of the array steering vector and inaccurate estimation of the sample covariance matrix, a novel algorithm based on beam-space steering vector estimation for robust adaptive beamforming is presented. By using the complementary set of the spatial sector in which the actual steering vector lies, a beam-space transformation matrix can be constructed to remove the signal of interest from the sampling covariance matrix. The beam-space steering vector is estimated by solving a non-convex quadratically constrained quadratic optimisation problem. The effectiveness and robustness of the proposed algorithm is verified by the simulations.

关键词： adaptive signal processing array signal processing beam steering concave programming covariance matrices quadratic programming signal sampling robust adaptive beamforming beam space steering vector estimation array steering vector spatial sector beam space transformation matrix sampling covariance matrix nonconvex quadratically constrained quadratic optimisation problem

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Proportional fair-based joint subcarrier and power allocation in relay-enhanced orthogonal frequency division multiplexing systems

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IET COMMUNICATIONS 2010年第10期4卷 1143-1152页

作者： Fan, B. Wu, W. Zheng, K. Wang, W. Beijing Univ Posts & Telecommun Wireless Signal Proc & Network Lab Key Lab Universal Wireless Commun Minist Educ Beijing 100876 Peoples R China

There has emerged lots of interests in the resource allocation of the relay-enhanced orthogonal frequency division multiplexing (OFDM) system. Most of the existing research works are with the aim to maximise the transmit rate of the system. However, few of them have taken into account the fairness requirements. In order to achieve the trade-off between the system transmit rate and user fairness, this study originally studies the optimality of proportional fairness (PF) in a downlink relay-enhanced OFDM system, where one source communicates with multiple destinations by the aid of one or many relays. We investigate the joint subcarrier and power allocation problem with PF constraint. Firstly, the resource allocation problem is formulated. Then, the problem is studied in the framework of concave maximisation. By using mathematical decomposition techniques, the optimisation problem is decomposed into multiple-layer subproblems which can be resolved efficiently. With this method, a cross-layer algorithm is derived to achieve the near optimal solution. Finally, numerical results are illustrated. Compared to the existing schemes, our proposed algorithm can both maximise the sum of logarithmic per user average transmit rate and enhance the system transmit rate.

关键词： optimisation problem Optimisation techniques concave maximisation proportional fair-based joint subcarrier proportional fairness multiple-layer subproblems Modulation and coding methods relays OFDM modulation mathematical decomposition techniques resource allocation concave programming multiple destinations cross-layer algorithm power allocation problem Radio links and equipment relay-enhanced orthogonal frequency division multiplexing systems PF constraint radio networks downlink relay-enhanced OFDM system fairness requirements

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Accurate DC offset calibration of Doppler radar via non-convex optimisation

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ELECTRONICS LETTERS 2015年第16期51卷 1282-1283页

作者： Zhao, Heng Hong, Hong Sun, Li Xi, Feng Li, Changzhi Zhu, Xiaohua Nanjing Univ Sci & Technol Sch Elect & Opt Engn Nanjing 210094 Jiangsu Peoples R China Texas Tech Univ Dept Elect & Comp Engn Lubbock TX 79409 USA

Continuous-wave Doppler radar has attracted a lot of attention for non-contact vital sign detection. In the typical quadrature homotype architecture, the DC offset is a tough issue in that it seriously deteriorates the demodulated results. However, existing methods for DC offset calibration can hardly obtain accurate compensation, especially when the sparsity of measurement outliers is relatively large. Proposed is a novel iteratively reweighed l(1) algorithm-based error correction method. Simulated and experimental results demonstrate the advantages of the method for accurate DC offset calibration.

关键词： CW radar Doppler radar calibration concave programming iterative methods medical signal detection medical signal processing patient monitoring radar detection IRL1 algorithm-based error correction method accurate DC offset calibration continuous wave Doppler radar iteratively reweighed ℓ 1 algorithm-based error correction method measurement outlier sparsity noncontact vital sign detection nonconvex optimisation quadrature homotype architecture

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Incorporating variable lifetime and self-discharge into optimal sizing and technology selection of energy storage systems

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IET SMART GRID 2018年第1期1卷 11-18页

作者： Sayfutdinov, Timur Patsios, Charalampos Bialek, Janusz W. Greenwood, David M. Taylor, Phil C. Skolkovo Inst Sci & Technol Ctr Energy Syst Moscow Russia Newcastle Univ Sch Engn Newcastle Upon Tyne Tyne & Wear England

Technology selection and sizing are key aspects of the design procedure for energy storage systems (ESSs) for power system applications. Here, the authors extended existing methodologies for optimal sizing and technology selection by introducing self-discharge effects, and variable ESS lifetime as a function of energy throughput, which results in a non-convex optimisation problem. Simulation results confirmed that making operational lifetime a variable has a significant impact on the results of the optimal sizing and technology selection problem. More specifically, considering the variable ESS lifetime as a function of energy throughput showed that ESSs of various technologies tend to operate such that their operational lifetimes would far exceed their calendar lifetimes. This has confirmed the importance of considering operational lifetime as a variable rather than a fixed value, as without doing this could result to underutilised and/or oversized systems. Taking into account, the self-discharge effect showed that the electrochemical technologies considered here, with the exception of supercapacitors, have low levels of self-discharge, which are largely obscured by the significant impact of the roundtrip efficiency characteristic.

关键词： energy storage concave programming energy storage systems power system applications self-discharge effect variable ESS lifetime nonconvex optimisation problem technology selection problem electrochemical technologies supercapacitors

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A finite algorithm for global minimization of separable concave programs

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JOURNAL OF GLOBAL OPTIMIZATION 1998年第1期12卷 1-35页

作者： Shectman, JP Sahinidis, NV Univ Illinois Dept Chem Engn Urbana IL 61801 USA Univ Illinois Dept Mech & Ind Engn Urbana IL 61801 USA

first examined the problem of separable concave programming more than thirty years ago, making it one of the earliest branches of nonlinear programming to be explored. This paper proposes a new algorithm that finds the exact global minimum of this problem in a finite number of iterations. In addition to proving that our algorithm terminates finitely, the paper extends a guarantee of finiteness to all branch and-bound algorithms for concave programming that (1) partition exhaustively using rectangular subdivisions and (2) branch on the incumbent solution when possible. The algorithm uses domain reduction techniques to accelerate convergence;it solves problems with as many as 100 nonlinear variables, 400 linear variables and 50 constraints in about five minutes on an IBM RS/6000 Power PC. An industrial application with 152 nonlinear variables, 593 linear variables, and 417 constraints is also solved in about ten minutes.

关键词： global optimization concave programming branch-and-bound domain reduction

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A METHOD FOR GLOBALLY MINIMIZING concave FUNCTIONS OVER CONVEX-SETS

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MATHEMATICAL programming 1981年第1期20卷 22-32页

作者： HOFFMAN, KL The National Bureau of Standards Washington DC USA

A method is described for globally minimizing concave functions over convex sets whose defining constraints may be nonlinear. The algorithm generates linear programs whose solutions minimize the convex envelope of the original function over successively tighter polytopes enclosing the feasible region. The algorithm does not involve cuts of the feasible region, requires only simplex pivot operations and univariate search computations to be performed, allows the objective function to be lower semicontinuous and nonseparable, and is guaranteed to converge to the global solution. Computational aspects of the algorithm are discussed.

关键词： concave programming Extreme Point Solutions Global Optimization Nonconvex programming Nonlinear programming

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A novel approach for nonconvex optimal control problems

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OPTIMIZATION 2009年第7期58卷 781-789页

作者： Chinchuluun, Altannar Enkhbat, Rentsen Pardalos, Panos M. Univ Florida Dept Ind & Syst Engn Gainesville FL 32611 USA Natl Univ Mongolia Sch Econ Studies Ulaanbaatar Mongolia

The nonconvex optimal control problem with the concave terminal objective function has been considered. First, the problem reduces to the concave minimization problem and then we apply the global optimality condition given by Strekalovsky [On the global extremum problem, Soviet Math. Doklady 292 (1987), pp. 1062-1066.] to the problem. Based on the global optimality condition, we propose a method for improving a current stationary process in the problem. The proposed method has been tested on some example problems.

关键词： approximation set concave programming global optimization level set nonconvex optimal control problem

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Generalized linearly homogeneous production functions

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CYBERNETICS AND SYSTEMS ANALYSIS 1999年第5期35卷 789-796页

作者： Grigorkiv, VS Taras Shevchenko Univ Kiev Ukraine

The production functions are considered as functions of values of concave programming problems. Some properties of the functions, in particular, the property of homogeneity and linear homogeneity, are investigated. Ex... 详细信息

关键词： mathematical economics mathematical programming concave programming optimization methods production functions properties of production functions linearly homogeneous production functions

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Energy-efficient resource allocation in heterogeneous networks with cell range expansion

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IET NETWORKS 2015年第4期4卷 209-219页

作者： Jiang, Jiamo Peng, Mugen Li, Lei Wang, Wenbo China Acad Telecommun Res Commun Stand Res Inst Beijing Peoples R China Beijing Univ Posts & Telecommun Key Lab Univ Wireless Commun Minist Educ Beijing Peoples R China

Cell range expansion (CRE) has emerged as a promising technique to improve spectral and energy efficiency (EE) in heterogeneous networks (HetNets). In this study, a resource allocation (RA) problem for maximising the EE is formulated with the considerations on CRE and cross-tier interference coordination (CTIC). Owing to the forms of the objective function and the constraints, the optimisation problem is non-convex and intractable. To solve this problem efficiently, we convert the original problem into an equivalent problem. Then, an efficient iterative algorithm is proposed, where the closed-form expressions of power and resource block allocations are derived by Lagrange dual decomposition method in each iteration. It has been revealed that the proposed iterative algorithm converges to the energy-efficient RA solutions. Compared with the algorithm without CTIC, the simulation results present that the proposed algorithm can achieve the EE gains by 70 percents when the number of the expanded-range users is large and the quality of service requirement is high.

关键词： cellular radio resource allocation energy conservation radiofrequency interference concave programming iterative methods decomposition quality of service energy-efficient resource block allocation heterogeneous network cell range expansion spectral efflciency HetNets RA problem CRE EE cross-tier interference coordination CTIC nonconvex optimisation problem closed-form expression power allocation Lagrange dual decomposition method iterative algorithm quality of service

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Secure resource allocation for green two-way relay networks with mutually untrusted relay and mobile users

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IET NETWORKS 2020年第1期9卷 1-6页

作者： Wang, Fei Qin, Changchun Southwest Univ Coll Elect & Informat Engn Chongqing Key Lab Nonlinear Circuit & Intelligent Chongqing 400715 Peoples R China Chongqing Coll Elect Engn Dept Artificial Intelligence & Big Data Chongqing 401331 Peoples R China

The authors investigate secure resource allocation for an orthogonal frequency division multiple access two-way relay network, which has several pairs of mobile users (MUs) and one energy harvesting (EH) relay. In this network, the relay is untrusted and each MU pair may also overhear the other MU pairs' confidential information. In particular, to forward information for each MU, the relay adopts power splitting technique to harvest energy from radio frequency signals emitted by each MU. For this scenario, which has hardly been considered, the joint problem of subcarrier allocation, power control, and power splitting ratio selection is formulated, with the aim to maximise the total secrecy rate of all MUs. A suboptimal algorithm with low complexity and satisfactory performance is proposed to solve the formulated non-convex problem.

关键词： concave programming power control resource allocation relay networks (telecommunication) OFDM modulation energy harvesting telecommunication security frequency division multiple access telecommunication control telecommunication power management secure resource allocation mutually untrusted relay mobile users energy harvesting relay power splitting technique radio frequency signals subcarrier allocation power splitting ratio selection green two-way relay networks orthogonal frequency division multiple access two-way relay network MU pair confidential information power control suboptimal algorithm nonconvex problem

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