• 제목/요약/키워드: Iteration scheme

검색결과 243건 처리시간 0.02초

Hybrid combiner design for downlink massive MIMO systems

  • Seo, Bangwon
    • ETRI Journal
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    • 제42권3호
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    • pp.333-340
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    • 2020
  • We consider a hybrid combiner design for downlink massive multiple-input multiple-output systems when there is residual inter-user interference and each user is equipped with a limited number of radio frequency (RF) chains (less than the number of receive antennas). We propose a hybrid combiner that minimizes the mean-squared error (MSE) between the information symbols and the ones estimated with a constant amplitude constraint on the RF combiner. In the proposed scheme, an iterative alternating optimization method is utilized. At each iteration, one of the analog RF and digital baseband combining matrices is updated to minimize the MSE by fixing the other matrix without considering the constant amplitude constraint. Then, the other matrix is updated by changing the roles of the two matrices. Each element in the RF combining matrix is obtained from the phase component of the solution matrix of the optimization problem for the RF combining matrix. Simulation results show that the proposed scheme performs better than conventional matrix-decomposition schemes.

비선형 시스템에 적용가능한 피드백 사용형 2차 반복 학습제어 알고리즘 (A Second-Order Iterative Learning Algorithm with Feedback Applicable to Nonlinear Systems)

  • 허경무;우광준
    • 제어로봇시스템학회논문지
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    • 제4권5호
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    • pp.608-615
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    • 1998
  • In this paper a second-order iterative learning control algorithm with feedback is proposed for the trajectory-tracking control of nonlinear dynamic systems with unidentified parameters. In contrast to other known methods, the proposed teaming control scheme utilize more than one past error history contained in the trajectories generated at prior iterations, and a feedback term is added in the learning control scheme for the enhancement of convergence speed and robustness to disturbances or system parameter variations. The convergence proof of the proposed algorithm is given in detail, and the sufficient condition for the convergence of the algorithm is provided. We also discuss the convergence performance of the algorithm when the initial condition at the beginning of each iteration differs from the previous value of the initial condition. The effectiveness of the proposed algorithm is shown by computer simulation result. It is shown that, by adding a feedback term in teaming control algorithm, convergence speed, robustness to disturbances and robustness to unmatched initial conditions can be improved.

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불변 및 가변 종속거리를 갖는 루프의 병렬처리를 위한 새로운 동기화 기법 (A New Synchronization Scheme for Parallel Processing of Loop with Constant and Variable Dependence Distance)

  • 이광형;황종선;박두순
    • 전자공학회논문지B
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    • 제32B권5호
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    • pp.693-701
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    • 1995
  • In most application programs, loops usually comprise most of the computation in a program and are the most important source of parallelism. When loops are executed on multiprocessors, the cross iteration data dependences need to be enforced by synchronization between processors. Existing synchronization schemes have been studied mainly on the loop with constant dependence distance. When these schemes are applied to the loop with variable dependence distance, there exists lots of overhead by the use of unnecessary synchronization variables and execution of unuseful synchronization instructions. Even though there exist various variable synchronization schemes, they have a lot of run-time overhead to compute synchronization information. In this paper, we present a new synchronization scheme, Synch-Free/Synch-Hold for managing synchronization efficiently on the loop with constant and variable dependence distance.

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STRONG CONVERGENCE FOR THREE CLASSES OF UNIFORMLY EQUI-CONTINUOUS AND ASYMPTOTICALLY QUASI-NONEXPANSIVE MAPPINGS

  • Qin, Xiaolong;Su, Yongfu;Shang, Meijuan
    • 대한수학회지
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    • 제45권1호
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    • pp.29-40
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    • 2008
  • In this paper, we introduce a modified three-step iteration scheme with errors for three classes of uniformly equi-continuous and asymptotically quasi-nonexpansive mappings in the framework of uniformly convex Banach spaces. We then use this scheme to approximate a common fixed point of these mappings. The results obtained in this paper extend and improve the recent ones announced by Khan, Fukhar-ud-di, Zhou, Cho, Noor and some others.

비대선 모형에 대한 점성유동의 수치해석연구 (A Study on the Numerical Analysis of the Viscous Flow for a Full Ship Model)

  • 박명규;강국진
    • 한국항해학회지
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    • 제19권2호
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    • pp.13-22
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    • 1995
  • This paper presents the numerical analysis results of the viscous flow for a full ship model. The mass and momentum conservation equations are used for governing equations, and the flow field is discretized by the Finite-Volume Method for the numerical calculation. An algebraic grid and elliptic grid generation techniques are adopted for generation of the body-fitted coordinates system, which is suitable to ship's hull forms. Time-marching procedure is used to solve the three-dimensional unsteady problem, where the convection terms are approximated by the QUICK scheme and the 2nd-order central differencing scheme is used for other spatial derivatives. A Sub-Grid Scale turbulence model is used to approximate the turbulence, and the wall function is used at the body surface. Pressure and velocity fields are calculated by the simultaneous iteration method. Numerical calculations were accomplished for the Crude Oil Tanker(DWT 95,000tons, Cb=0.805) model. Calculation results are compared to the experimental results and show good agreements.

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Acceleration of the AFEN Method by Two-Node Nonlinear Iteration

  • Moon, Kap-Suk;Cho, Nam-Zin;Noh, Jae-Man;Hong, Ser-Gi
    • 한국원자력학회:학술대회논문집
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    • 한국원자력학회 1998년도 춘계학술발표회논문집(1)
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    • pp.87-92
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    • 1998
  • A nonlinear iterative scheme developed to reduce the computing time of the AFEN method was tested and applied to two benchmark problems. The new nonlinear method for the AFEN method is based on solving two-node problems and use of two nonlinear correction factors at every interface instead of one factor in the conventional scheme. The use of two correction factors provides higher-order accurate interface noes as well as currents which are used as the boundary conditions of the two-node problem. The numerical results show that this new method gives exactly the same solution as that of the original AEFEN method and the computing time is significantly reduced in comparison with the original AFEN method.

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MODEL FOR THE CONTAMINATION OF CONFINED AQUIFERS BY POLLUTANTS

  • Bestman, A.R.;Odigi, M.I.
    • 한국수학교육학회지시리즈B:순수및응용수학
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    • 제6권2호
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    • pp.113-120
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    • 1999
  • This paper studies the problem of an infinite confined aquifer which at time t < 0 is assumed motionless. At time t = 0 crude oil seeps into the aquifer, thereby contaminating the valuable drinking water. Since the crude oil and water are im-miscible, the problem is posed as a one-dimensional two-phase unsteady moving boundary problem. A similarity solution is developed in which the moving front parameter is obtained by Newton-Ralphson iteration. A numerical scheme, involving the front tracking method, is devised employing the fourth order Runge-Kutta method. Comparison of the exact and numerical schemes shows an error of only 3%. Thus the developed numerical scheme is quite accurate in tackling more realistic problems where exact solutions are not possible.

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전역 최적화를 위한 B-스플라인 기반의 Branch & Bound알고리즘 (A B-spline based Branch & Bound Algorithm for Global Optimization)

  • 박상근
    • 한국CDE학회논문집
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    • 제15권1호
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    • pp.24-32
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    • 2010
  • This paper introduces a B-spline based branch & bound algorithm for global optimization. The branch & bound is a well-known algorithm paradigm for global optimization, of which key components are the subdivision scheme and the bound calculation scheme. For this, we consider the B-spline hypervolume to approximate an objective function defined in a design space. This model enables us to subdivide the design space, and to compute the upper & lower bound of each subspace where the bound calculation is based on the LHS sampling points. We also describe a search tree to represent the searching process for optimal solution, and explain iteration steps and some conditions necessary to carry out the algorithm. Finally, the performance of the proposed algorithm is examined on some test problems which would cover most difficulties faced in global optimization area. It shows that the proposed algorithm is complete algorithm not using heuristics, provides an approximate global solution within prescribed tolerances, and has the good possibility for large scale NP-hard optimization.

로봇 비젼시스템을 이용한 강체 배치 실험에 대한 연구 (A Study on Rigid body Placement Task of based on Robot Vision System)

  • 장완식;신광수;안철봉
    • 한국정밀공학회지
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    • 제15권11호
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    • pp.100-107
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    • 1998
  • This paper presents the development of estimation model and control method based on the new robot vision. This proposed control method is accomplished using the sequential estimation scheme that permits placement of the rigid body in each of the two-dimensional image planes of monitoring cameras. Estimation model with six parameters is developed based on the model that generalizes known 4-axis scara robot kinematics to accommodate unknown relative camera position and orientation, etc. Based on the estimated parameters, depending on each camera the joint angle of robot is estimated by the iteration method. The method is experimentally tested in two ways, the estimation model test and a three-dimensional rigid body placement task. Three results show that control scheme used is precise and robust. This feature can open the door to a range of application of multi-axis robot such as assembly and welding.

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Fitting to Panchromatic Image for Pansharpening Combining Point-Jacobian MAP Estimation

  • Lee, Sang-Hoon
    • 대한원격탐사학회지
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    • 제24권5호
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    • pp.525-533
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    • 2008
  • This study presents a pansharpening method, so called FitPAN, to synthesize multispectral images at a higher resolution by exploiting a high-resolution image acquired in panchromatic modality. FitPAN is a modified version of the quadratic programming approach proposed in (Lee, 2008), which is designed to generate synthesized multispectral images similar to the multispectral images that would have been observed by the corresponding sensor at the same high resolution. The proposed scheme aims at reconstructing the multispectral images at the higher resolution with as less spectral distortion as possible. This study also proposes a sharpening process to eliminate some distortions appeared in the fused image of the higher resolution. It employs the Point-Jacobian MAP iteration utilizing the contextual information of the original panchromatic image. In this study, the new method was applied to the IKONOS 1m panchromatic and 4m multispectral data, and the results were compared with them of several current approaches. Experimental results demonstrate that the proposed scheme can achieve significant improvement in both spectral and block distortion.