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IEEE Global communications conference (GLOBEcOM)

作者： Kha, Ha H. Tuan, H. d. Nguyen, Ha H. Pham, Tung T. Univ Technol Sydney Fac Engn & Informat Technol Sydney NSW 2007 Australia

ISBN: (纸本)9781467309219;9781467309202

We are concerned with a cooperative beamforming design for multi-user multi-relay wireless networks in which the single-carrier frequency division multiple access (Sc-FdMA) technique is employed at the terminals. The problem of interest is to find the beamforming weights across relays to maximize the minimum signal-to-interference-plus-noise ratio (SINR) among users subject to individual power constraints at each relay. Such a beamforming design is shown to be a hard nonconvex program and therefore it is mathematically challenging to find the optimal solution. By exploring its partial convex structures, we recast the design problem as minimization of a d.c. (difference of two convex) objective function subject to convex constraints and develop an effective iterative algorithm of low complexity to solve it. Simulation results show that our optimal cooperative beamforming scheme realizes the inherent diversity order of the relay network and it performs significantly better than the equal-power beamforming weights.

关键词： cooperative beamforming power allocation Sc-FdMA frequency-domain equalization wireless relay networks d.c. programming maximin optimization

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Joint design of User Power Allocation and Relay Beamforming in Two-Way MIMO Relay Networks

Joint Design of User Power Allocation and Relay Beamforming ...

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7th International conference on Signal Processing and.c.mmunication Systems (IcSPcS)

作者： Kha, Ha H. Tuan, H. d. Nguyen, Ha H. Tam, H. H. M. Ho Chi Minh City Univ Technol Dept Telecommun Engn Ho Chi Minh City Vietnam Univ Technol Sydney Fac Engn & Informat Technol Sydney NSW Australia Univ Saskatchewan Dept Elect & Comp Engn Saskatoon SK Canada

ISBN: (纸本)9781479913190

This paper is concerned with the joint optimization of user power allocation and distributed relay beamforming in two-way wireless relay networks in which multiple multi-antenna relays assist multiple single-antenna users. The design aims at maximizing the minimum information rate among user pairs subject to various practical power constraints at the users and relays. Since the nonconvex structure of the problem is highly complicated, the existing approaches to relax the design problem into a convex program do not appear to be applicable. To solve this challenging nonconvex optimization problem, we introd.c. auxiliary variables and.c.st the design problem into a d.c.(difference of convex functions) program. Then, we develop an efficient iterative algorithm of sequential convex optimization to obtain the optimized solutions. Extensive simulation results demonstrate that our proposed joint design outperforms the only relay beamforming design.

关键词： distributed beamforming power allocation MIMO relay networks joint optimization d.c. programming

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The hill detouring method for minimizing hinging hyperplanes functions

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cOMPUTERS & OPERATIONS RESEARcH 2012年第7期39卷 1763-1770页

作者： Huang, Xiaolin Xu, Jun Mu, Xiaomu Wang, Shuning Tsinghua Univ Tsinghua Natl Lab Informat Sci & Technol TNList Dept Automat Beijing 100084 Peoples R China

This paper studies the problem of minimizing hinging hyperplanes (HH) which is a widely applied nonlinear model. To deal with HH minimization, we transform it into a d.c. (difference of convex functions) programming and a concave minimization on a polyhedron, then some mature techniques are applicable. More importantly, HH is a continuous piecewise linear function and for concave HH, the super-level sets are polyhedra. Inspired by this property, we establish a method which searches on the counter map in order to escape a local optimum. Intuitively, this method bypasses the super-level set and is hence called hill detouring method, following the name of hill climbing. In numerical experiments, the proposed algorithm is compared with cPLEX and a heuristic algorithm showing its effectiveness. (c) 2011 Elsevier Ltd. All rights reserved.

关键词： Hinging hyperplanes continuous piecewise linear Global optimum d.c. programming concave minimization

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RELAY SELEcTION IN MULTI-USER AMPLIFY-FORWARd WIRELESS RELAY NETWORKS

RELAY SELECTION IN MULTI-USER AMPLIFY-FORWARD WIRELESS RELAY...

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IEEE International conference on Acoustics, Speech and Signal Processing

作者： che, Enlong Tuan, H. d. Nguyen, H. H. Univ Technol Sydney Fac Engn & Informat Technol Sydney NSW 2007 Australia Univ Saskatchewan Dept Elect & Comp Engn Saskatoon SK S7N 0W0 Canada

ISBN: (纸本)9781467300469

For multi-user (MU) amplify-and-forward (AF) cooperative networks, their spectral efficiency can be upgraded within the orthogonal transmission of each source node to an assigned subset of all available relays while their information throughput can be improved through optimized power allocation. We consider the joint optimization in both relay assignment for each source-destination pair and power allocation, which is in fact among the hardest problems in optimization. This is the minimization of a nonconvex objective function subject to mixed integer constraints. The existing numerical algorithms could rarely address to its solutions through computationally affordable procedures. Even the conventional relaxation of the integer constraints by linear constraints does not lead to convex optimization, so the standard.c.nvexification does not work either. Nevertheless, we show that it can be effectively solved in the d.c. (difference of two convex) programming context. Numerical simulation confirms the effectiveness of our setting.

关键词： Amplify-and-Forward relay relay selection power allocation maxmin SNR d.c. programming

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Bregman divergence Based Sensor Selections for Spectrum Sensing

Bregman Divergence Based Sensor Selections for Spectrum Sens...

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IEEE Wireless communications and Networking conference (WcNc)

作者： che, Enlong Tuan, H. d. Kha, H. H. Ngo, H. Q. Univ Technol Sydney Fac Engn & Informat Technol Sydney NSW 2007 Australia

ISBN: (纸本)9781467304375;9781467304368

Sensor selection is to pick out an appropriate subset of active sensors for reliable collaborative sensing. Naturally, the selected sensors should be as uncorrelated as possible to have more independent sensing outputs for information fusion. In this paper, various uncorrelation metrics are unified by the concept of Bregman divergence. The sensor selections are then systematically formulated as NP-hard integer programs. Unlike commonly used exhaustive enumeration, heuristic searches or simple relaxation of discrete constraints with inherent drawbacks, this paper recasts them into a continuous d.c. (difference of two convex functions) program under convex constraints. Accordingly, an efficient iterative optimization procedure is tailored for locating the optimal solution. Simulation results show its superior performances in comparison with other existing sensor selections.

关键词： Sensor selection d.c. programming nonsmooth optimization correlation metric integer programming

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Joint design of Source Power Allocation and Relay Beamforming in Multi-User Wireless Networks

Joint Design of Source Power Allocation and Relay Beamformin...

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6th International conference on Signal Processing and.c.mmunication Systems (IcSPcS)

作者： Rashid, Umar Kha, H. H. Tuan, H. d. Nguyen, H. H. Univ Technol Sydney Fac Engn & Informat Technol Sydney NSW 2007 Australia Univ Saskatchewan Dept Elect & Comp Engn Saskatoon SK Canada

ISBN: (纸本)9781467323932;9781467323925

This paper presents joint design of source power allocation and relay beamforming for multi-user multi-relay wireless networks. The problem is formulated as maximization of the worst signal-to-inference-plus-noise ratio (SINR) among users subject to various power constraints. An equivalent d.c. (difference of two convex functions) programming based method is then used to develop an iterative algorithm with low computational complexity to obtain the optimal solution. Simulation results demonstrate that our optimal solutions of the joint optimization problem significantly outperform the solution obtained by separate designs of source power and relay beamforming.

关键词： Wireless networks relay networks amplify-and-forward beamforming power allocation d.c. programming

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A branch and red.c. approach for solving a class of low rank d.c. programs

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JOURNAL OF cOMPUTATIONAL ANd APPLIEd MATHEMATIcS 2009年第2期233卷 492-501页

作者： cambini, Riccardo Salvi, Francesca Univ Pisa Fac Econ Dept Appl Math & Stat I-56124 Pisa Italy

Various classes of d.c. programs have been studied in the recent literature due to their importance in applicative problems. In this paper we consider a branch and red.c. approach for solving a class of d.c. problems. Seven partitioning rules are analyzed and some techniques aimed at improving the overall performance of the algorithm are proposed. The results of a computational experience are provided in order to point Out the performance effectiveness of the proposed techniques. (c) 2009 Elsevier B.V. All rights reserved.

关键词： d.c. programming Branch and red.c.

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Existence of solutions to weak nonlinear bilevel problems via MinSup and d.c. problems

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RAIRO-OPERATIONS RESEARcH 2008年第2期42卷 87-102页

作者： Aboussoror, Abdelmalek Mansouri, Abdelatif Univ Cadi Ayyade Fac Polydisciplinaire Safi Safi Morocco Univ Cadi Ayyade Fac Sci Semlalia Dept Math Marrakech Morocco

In this paper, which is an extension of [4], we first show the existence of solutions to a class of Min Sup problems with linked.c.nstraints, which satisfy a certain property. Then, we apply our result to a class of weak nonlinear bilevel problems. Furthermore, for such a class of bilevel problems, we give a relationship with appropriate d.c. problems concerning the existence of solutions.

关键词： Min Sup problems variational convergence bilevel programming d.c. programming

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Optimal spatial correlations for the noncoherent MIMO Rayleigh fading channel

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IEEE TRANSAcTIONS ON WIRELESS cOMMUNIcATIONS 2007年第10期6卷 3760-3769页

作者： Srinivasan, Shivratna Giri Varanasi, Mahesh K. Univ Colorado Dept Elect & Comp Engn Boulder CO 80309 USA

The behavior in terms of information theoretic metrics of the discrete-input, continuous-output noncoherent MIMO Rayleigh fading channel is studied as a function of spatial correlations. In the low SNR regime, the mutual information metric is considered, while at higher SNR regimes the cutoff rate expression is employed. For any fixed input constellation and at sufficiently low SNR, a fully correlated.c.annel matrix is shown to maximize the mutual information. In contrast, at high SNR, a fully uncorrelated.c.annel matrix (with independent identically distributed elements) is shown to be optimal, under a condition on the constellation which ensures full diversity. In the special case of the separable correlation model, it is shown that as a function of the receive correlation eigenvalues, the cutoff rate expression is a Schur-convex function at low SNR and a Schur-concave function at high SNR, and as a function of transmit correlation eigenvalues, the cutoff rate expression is Schur-concave at high SNR for full diversity constellations. Moreover, at sufficiently low SNR, the fully correlated transmit correlation matrix is optimal. Finally, for the general model, it is shown that the optimal correlation matrices at a general SNR can be obtained using a difference of convex programming formulation.

关键词： block fading channels concave minimization cutoff rate expression d.c. programming general SNR global optimization MIMO mutual information noncoherent schurconcavity schur-convexity spatial correlation

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Solving an inverse problem for an elliptic equation by d.c. programming

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JOURNAL OF GLOBAL OPTIMIZATION 2003年第4期25卷 407-423页

作者： An, LTH Tao, Pd Hào, dN Inst Natl Sci Appl Rouen Lab Modelisat & Optimisat Rech Operat F-76131 Mont St Aignan France Inst Math Hanoi 10000 Vietnam

An inverse problem of determination of a coefficient in an elliptic equation is considered. This problem is ill-posed in the sense of Hadamard and Tikhonov's regularization method is used for solving it in a stable way. This method requires globally solving nonconvex optimization problems, the solution methods for which have been very little studied in the inverse problems community. It is proved that the objective function of the corresponding optimization problem for our inverse problem can be represented as the difference of two convex functions (d.c. functions), and the difference of convex functions algorithm (dcA) in combination with a branch-and-bound technique can be used to globally solve it. Numerical examples are presented which show the efficiency of the method.

关键词： branch-and-bound technique dcA d.c. programming ill-posed problem inverse problem Tikhonov regularization

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