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Energy-Efficient UAV Backscatter Communication With Joint Trajectory Design and Resource Optimization

IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2021年第2期20卷 926-941页

作者： Yang, Gang Dai, Rao Liang, Ying-Chang Univ Elect Sci & Technol China UESTC Ctr Intelligent Networking & Commun CINC Natl Key Lab Sci & Technol Commun Chengdu 611731 Sichuan Peoples R China Univ Elect Sci & Technol China UESTC Ctr Intelligent Networking & Commun CINC Chengdu 611731 Peoples R China

Backscatter communication which enables wireless-powered backscatter devices (BDs) to transmit information by reflecting incident signals, is an energy- and cost-efficient communication technology for Internet-of-Things. This paper considers an unmanned aerial vehicle (UAV)-assisted backscatter communication network (UBCN) consisting of multiple BDs and carrier emitters (CEs) on the ground as well as a UAV. A communicate-while-fly scheme is first designed, in which the BDs illuminated by their associated CEs transmit information to the flying UAV in a time-division-multiple-access manner. Considering the critical issue of the UAV's limited on-board energy and the CEs' transmission energy, we maximize the energy efficiency (EE) of the UBCN by jointly optimizing the UAV's trajectory, the BDs' scheduling, and the CEs' transmission power, subject to the BDs' throughput constraints and harvested energy constraints, as well as other practical constraints. Furthermore, we propose an iterative algorithm based on the block coordinated decent method to solve the formulated mixed-integer non-convex problem, in each iteration of which the variables are alternatively optimized by leveraging the cutting-plane technique, the Dinkelbach's method and the successive convex approximation technique. Also, the convergence and complexity of the proposed algorithm are analyzed. Finally, simulation results show that the proposed communicate-while-fly scheme achieves significant EE gains compared with the hover-and-fly scheme, the state-of-the-art scheme, and the CE-relay scheme. Useful insights on the optimal trajectory design and resource allocation are also obtained.

关键词： Unmanned aerial vehicles Trajectory Backscatter Wireless communication iterative methods Radio frequency Optimization Backscatter communication UAV communication energy efficiency trajectory design resource optimization iterative algorithm

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A Method for Forming a Single Focused Diffraction Order Using Binary Amplitude Diffractive Elements without a Spatial Carrier

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OPTICS AND SPECTROSCOPY 2021年第5期129卷 511-516页

作者： Krasnov, V. V. Starikov, R. S. Zlokazov, E. Yu Natl Res Nucl Univ MEPhI Moscow 115409 Russia

A method is proposed for the synthesis of self-focusing amplitude diffractive optical elements (DOEs) without a carrier spatial frequency for operation in diverging beams and forming a single focused diffraction order, which can occupy the entire region of the DOE image being reconstructed due to the absence of the need for spatial separation of orders. The synthesis takes place in two stages. The first is carried out by an iterative algorithm similar to the Gerchberg-Saxton algorithm, with the differences that the synthesized DOE is amplitude rather than phase, and the incident wavefront is diverging spherical. Next, the direct search with a random trajectory method is applied. As a result, for a binary amplitude DOE, it was possible to achieve synthesis error values of 6% and a diffraction efficiency of 6%. The results of the experimental implementation of DOE using a digital micromirror device are presented.

关键词： amplitude DOE single diffraction order diverging beam DOE synthesis iterative algorithm digital micromirror device

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Bilayer Distributed Optimization for Robust Microgrid Dispatch With Coupled Individual-Collective Profits

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IEEE TRANSACTIONS ON SUSTAINABLE ENERGY 2021年第3期12卷 1525-1538页

作者： Qiu, Haifeng Gu, Wei You, Fengqi Southeast Univ Sch Elect Engn Nanjing 210096 Peoples R China Cornell Univ Ithaca NY 14853 USA

This paper addresses the economic dispatch problem in microgrids with multi-entities and uncertainties. A novel robust bilayer distributed optimization (BDO) method is put forward to coordinate the individual and collective profits. In the upper-layer of the BDO model, each entity in the microgrids develops a two-stage recourse-based robust dispatch model that minimizes the individual operation cost. This robust model determines the objectives and schemes in both the basic and worst-case scenarios, and provides more practical optimal schedules. According to the generation margin and load curtailment in each entity, a multi-objective bargain dispatch is conducted in the lower-layer coordinating center to co-optimize the tie-line plans, thus getting the lowest collective cost in a cooperative manner through regional power complementarity. An iterative descent algorithm is put forward for the efficient solution of the nonconvex BDO model. Therein a nested column and constraint generation algorithm with equilibrium constraints is developed to tackle the upper-layer robust optimization problems with binary recourses and non-independent uncertainties. The lower-layer bargain model is refined as a mixed-integer linear programming via a complementarity approach for the cooperation of multi-entities. Numerical results of case studies demonstrate the availability and superiority of the robust BDO method and the solution algorithm.

关键词： Optimization Uncertainty Fuels Numerical models Microgrids iterative algorithms Economics Bilayer optimization distributed dispatch iterative algorithm microgrid robust optimization

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Solving second-order nonlinear boundary value problem with nonlinear boundary conditions by an iterative method

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ENGINEERING COMPUTATIONS 2021年第1期38卷 107-130页

作者： Liu, Chein-Shan Chang, Jiang-Ren Hohai Univ Coll Mech & Mat Nanjing Peoples R China Natl Taiwan Ocean Univ Ctr Excellence Ocean Engn Ctr Excellence Oceans Keelung Taiwan Natl Taiwan Ocean Univ Dept Syst Engn & Naval Architecture Keelung Taiwan

Purpose The purpose of this paper is to solve the second-order nonlinear boundary value problem with nonlinear boundary conditions by an iterative numerical method. Design/methodology/approach The authors introduce eigenfunctions as test functions, such that a weak-form integral equation is derived. By expanding the numerical solution in terms of the weighted eigenfunctions and using the orthogonality of eigenfunctions with respect to a weight function, and together with the non-separated/mixed boundary conditions, one can obtain the closed-form expansion coefficients with the aid of Drazin inversion formula. Findings When the authors develop the iterative algorithm, removing the time-varying terms as well as the nonlinear terms to the right-hand sides, to solve the nonlinear boundary value problem, it is convergent very fast and also provides very accurate numerical solutions. Research limitations/implications Basically, the authors' strategy for the iterative numerical algorithm is putting the time-varying terms as well as the nonlinear terms on the right-hand sides. Practical implications Starting from an initial guess with zero value, the authors used the closed-form formula to quickly generate the new solution, until the convergence is satisfied. Originality/value Through the tests by six numerical experiments, the authors have demonstrated that the proposed iterative algorithm is applicable to the highly complex nonlinear boundary value problems with nonlinear boundary conditions. Because the coefficient matrix is set up outside the iterative loop, and due to the property of closed-form expansion coefficients, the presented iterative algorithm is very time saving and converges very fast.

关键词： Nonlinear boundary value problem Nonlinear boundary conditions Eigenfunctions as test functions Closed-form expansion coefficients iterative algorithm

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Reconfigurable Intelligent Surface-Assisted Non-Orthogonal Multiple Access

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2021年第5期20卷 3137-3151页

作者： Yang, Gang Xu, Xinyue Liang, Ying-Chang Di Renzo, Marco Univ Elect Sci & Technol China UESTC Natl Key Lab Sci & Technol Commun Chengdu 611731 Peoples R China Univ Elect Sci & Technol China UESTC Ctr Intelligent Networking & Commun CINC Chengdu 611731 Peoples R China Univ Paris Saclay Lab Signaux & Syst Cent Supelec CNRS F-91192 Gif Sur Yvette France

Reconfigurable intelligent surface (RIS) is a revolutionary technology to achieve spectrum-, energy-, and cost-efficient wireless networks. This paper considers an RIS-assisted downlink non-orthogonal-multiple-access (NOMA) system. To optimize the rate performance and ensure user fairness, we maximize the minimum decoding signal-to-interference-plus-noise-ratio (equivalently the rate) of all users, by jointly optimizing the (active) transmit beamforming at the base station (BS) and the phase shifts (i.e., passive beamforming) at the RIS. A combined-channel-strength based user-ordering scheme for NOMA decoding is first proposed to decouple the user-ordering design and the joint beamforming design. Efficient algorithms are further proposed to solve the non-convex problem, by leveraging the block coordinated descent and semidefinite relaxation (SDR) techniques. For the single-antenna BS setup, the optimal power allocation at the BS and the asymptotically optimal phase shifts at the RIS are obtained in closed forms. For the multiple-antenna BS setup, it is shown that the rank of the SDR solution of the transmit beamforming design is upper bounded by two. Also, the proposed algorithms are analyzed in terms of convergence and complexity. Simulation results show that the RIS-assisted NOMA system can enhance the rate performance significantly, compared to traditional NOMA without RIS and traditional orthogonal multiple access with/without RIS.

关键词： NOMA Array signal processing Downlink Wireless communication Resource management MISO communication Decoding Non-orthogonal multiple access reconfigurable intelligent surface rate optimization user fairness iterative algorithm

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Trajectory design and resource allocation for UAV energy minimization in a rotary-wing UAV-enabled WPCN

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ALEXANDRIA ENGINEERING JOURNAL 2021年第1期60卷 1787-1796页

作者： Wang, Zhen Wen, Miaowen Dang, Shuping Yu, Lisu Wang, Yuhao Beijing Univ Posts & Telecommun Sch Informat & Commun Engn Beijing 100876 Peoples R China Nanchang Univ Sch Informat Engn Nanchang 330031 Jiangxi Peoples R China South China Univ Technol Sch Elect & Informat Engn Guangzhou 510641 Peoples R China King Abdullah Univ Sci & Technol KAUST Comp Elect & Math Sci & Engn Div Thuwal 239556900 Saudi Arabia Chinese Acad Sci Inst Comp Technol State Key Lab Comp Architecture Beijing 100190 Peoples R China

Due to the low efficiency of energy harvest (EH) for the traditional wireless powered communication network (WPCN), we propose a communication scheme based on unmanned aerial vehicle (UAV)-enabled WPCN, which can greatly improve the EH efficiency problem. In this paper, the UAV trajectory, time allocation, transmit power of UAVs, scheduling of wireless information transfer (WIT) and wireless power transfer (WPT) are jointly optimized to minimize the whole energy consumption. To solve the formulated non-convex problem with multiple constraints and attain locally optimal solution, an iterative algorithm is proposed. Simulations show that our proposed algorithm is superior to other benchmark algorithms. (C) 2020 The Authors. Published by Elsevier B.V. on behalf of Faculty of Engineering, Alexandria University. This is an open access article under the CC BY-NC-ND license (http://***/licenses/by-nc-nd/4.0/).

关键词： Energy harvest (EH) Wireless powered communi-cation network (WPCN) Unmanned aerial vehicle (UAV) UAV trajectory Non-convex problem iterative algorithm

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On the reconstruction of material properties of a radially inhomogeneous cylindrical waveguide

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MATHEMATICAL METHODS IN THE APPLIED SCIENCES 2021年第6期44卷 4756-4769页

作者： Vatulyan, Alexandr Ovanesovich Yurov, Victor Olegovich Southern Fed Univ II Vorovich Inst Math Mech & Comp Sci Rostov Na Donu Russia

The scheme of solving the inverse problem (IP) for reconstructing three functions characterizing the radial change in the Lame parameters and in the density in a cylindrical waveguide is presented. The displacement fields corresponding to three types of loading are used as an additional information for solving the IP. An iterative process is constructed, at each step of which a direct problem is solved for the radially inhomogeneous waveguide, and the corrections to the restored functions are determined. The corrections are identified by solving the system of three Fredholm integral equations of the first kind with smooth kernels. The solution is constructed by the A. N. Tikhonov regularization method. A series of computational experiments was carried out. The role of the initial approximation and the frequency range is discussed.

关键词： cylindrical waveguide inhomogeneous properties integral Fourier transform inverse problem iterative algorithm regularization

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A constrained optimization method for blocking artifact compensation in JPEG infrared image

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SIGNAL IMAGE AND VIDEO PROCESSING 2021年第7期15卷 1361-1368页

作者： Pei, Jihong Mo, Wenying Shao, Xuhui Wang, Lixia Shenzhen Univ Sch Elect & Informat Engn Shenzhen 518060 Peoples R China

Aiming to improve the quality of JPEG decompressed infrared images, this paper presents a constrained optimization method for blocking artifact compensation. First, we define the drop value between image blocks and measure the DC component loss by the drop value. Second, a constrained optimization object function is constructed based on the DC component compensation model. Both global and local constraints are used to avoid overcompensation. Finally, the optimal compensation value is obtained using iterative processing. Experimental results show that the proposed algorithm can remove the blocking artifact in JPEG infrared image effectively and outperform the existing methods.

关键词： Blocking artifact removal DC component compensation Constrained optimization objective function iterative algorithm

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Sliding Mode Output Feedback Controller Design of Discrete-Time Markov Jump System Based on Hidden Markov Model Approach

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IEEE ACCESS 2021年 9卷 101089-101096页

作者： Xu, Ming Ma, Longhua Ma, Hongyu Xu, Zhaowen NingboTech Univ Inst Automat & Elect Engn Ningbo 315100 Peoples R China Zhejiang Cybstar Sci & Technol Co Ltd Hangzhou 311121 Peoples R China Shenzhen Polytech Inst Intelligence Sci & Engn Shenzhen 518055 Peoples R China

This paper investigates the problem of sliding mode controller design based on output feedback for discrete-time Markov jump systems. Considering the typical asynchronous phenomenon for jump systems, here we adopt the Hidden Markov Model (HMM) to quantify the asynchronous degree. Based on this, a static output feedback sliding surface is constructed. Sufficient conditions in terms of bilinear matrix inequalities are proposed ensuring the sliding motion dynamic to be stochastically stable and its H-infinity performance for the considered discrete time Markov jump systems. Moreover, the reachability of the sliding mode surface is ensured by a predesigned control law. The whole design scheme is presented by using an iterative algorithm. Finally, simulation results are presented to illustrate the effectiveness of the design methodology.

关键词： Markov processes Hidden Markov models Symmetric matrices Sliding mode control Output feedback Dynamics Licenses Sliding mode control HMM output feedback iterative algorithm

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A comparison of proton stopping power measured with proton CT and x-ray CT in fresh postmortem porcine structures

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MEDICAL PHYSICS 2021年第12期48卷 7998-8009页

作者： DeJongh, Don F. DeJongh, Ethan A. Rykalin, Victor DeFillippo, Greg Pankuch, Mark Best, Andrew W. Coutrakon, George Duffin, Kirk L. Karonis, Nicholas T. Ordonez, Caesar E. Sarosiek, Christina Schulte, Reinhard W. Winans, John R. Block, Alec M. Hentz, Courtney L. Welsh, James S. ProtonVDA LLC Naperville IL 60563 USA Northwestern Med Chicago Proton Ctr Warrenville IL USA Northern Illinois Univ Dept Phys De Kalb IL 60115 USA Northern Illinois Univ Dept Comp Sci De Kalb IL 60115 USA Argonne Natl Lab Data Sci & Learning Div 9700 S Cass Ave Argonne IL 60439 USA Loma Linda Univ Loma Linda CA 92350 USA Edward Hines Jr VA Med Ctr Radiat Oncol Serv Hines IL USA Loyola Univ Stritch Sch Med Dept Radiat Oncol 2160 S 1st Ave Maywood IL 60153 USA

Purpose: Currently, calculations of proton range in proton therapy patients are based on a conversion of CT Hounsfield units of patient tissues into proton relative stopping power. Uncertainties in this conversion necessitate larger proximal and distal planned target volume margins. Proton CT can potentially reduce these uncertainties by directly measuring proton stopping power. We aim to demonstrate proton CT imaging with complex porcine samples, to analyze in detail three-dimensional regions of interest, and to compare proton stopping powers directly measured by proton CT to those determined from x-ray CT scans. Methods: We have used a prototype proton imaging system with single proton tracking to acquire proton radiography and proton CT images of a sample of porcine pectoral girdle and ribs, and a pig's head. We also acquired close in time x-ray CT scans of the same samples and compared proton stopping power measurements from the two modalities. In the case of the pig's head, we obtained x-ray CT scans from two different scanners and compared results from high-dose and low-dose settings. Results: Comparing our reconstructed proton CT images with images derived from x-ray CT scans, we find agreement within 1% to 2% for soft tissues and discrepancies of up to 6% for compact bone. We also observed large discrepancies, up to 40%, for cavitated regions with mixed content of air, soft tissue, and bone, such as sinus cavities or tympanic bullae. Conclusions: Our images and findings from a clinically realistic proton CT scanner demonstrate the potential for proton CT to be used for low-dose treatment planning with reduced margins.

关键词： digitally reconstructed radiograph iterative algorithm proton computed tomography proton imaging proton radiography relative stopping power

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