• 한국통신학회논문지
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• 제38A권4호
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• pp.318-324
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• 2013

블라인드 채널 등화 시 신호 추정의 신뢰도는 등화기의 수렴 속도와 정상상태 성능을 결정한다. 그러므로 신호 추정에 사용되는 비선형 추정기와 기준 신호가 적절히 선택되어야 한다. 이 논문에서는 신호 추정의 신뢰도를 높이기 위해 신호 추정에 성긴 신호점과 촘촘한 신호점을 각각 적용하여 두 오차를 구하고, 두 오차의 상대적 신뢰도를 산출, 이를 활용하여 등화기를 차등적으로 적응시켰다. 이때 두 오차를 번갈아 적용하여 두 동작 모드를 완만하게 결합하였다. 모의실험을 통하여 제안 방식이 기존 방식에 비해 빠른 과도상태 수렴과 낮은 정상상태 오차를 달성하는 것을 보였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권12호
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• pp.3037-3054
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• 2013

Interference between primary user (PU) and secondary user (SU) transceivers should be mitigated in order to implement underlay spectrum sharing in cognitive radio networks (CRN). Considering this scenario, an improved joint subcarrier and bit allocation scheme for cognitive user with primary users' cooperation (PU Coop) in CRN is proposed. In this scheme, the optimization problem is formulated to minimize the average interference power level at the PU receiver via PU Coop, which guarantees a higher primary signal to interference plus noise ratio (SINR) while maintaining the secondary user total rate constraint. The joint optimal scheme is separated into subcarrier allocation and bit assignment in each subcarrier via arith-metric geo-metric (AM-GM) inequality with asymptotical optimization solution. Moreover, the joint subcarrier and bit optimization scheme, which is evaluated by the available SU subcarriers and the allocated bits, is analyzed in the proposed PU Coop model. The performance of cognitive spectral efficiency and the average interference power level are investigated. Numerical analysis indicates that the SU's spectral efficiency increases significantly compared with the PU non-cooperation scenario. Moreover, the interference power level decreases dramatically for the proposed scheme compared with the traditional Hughes-Hartogs bit allocation scheme.

• 한국군사과학기술학회지
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• 제18권1호
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• pp.66-83
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• 2015

Global Positioning System(hereafter; GPS) is recently an essential element in the various navigation and weapon delivery systems of military aircraft. However, GPS is vulnerable to the jamming threats since its signal power is very weak. Therefore, ROK defense has been concerning how to resolve this issue and how to integrate these systems needed, and is trying to acquire the proper anti-jamming GPS system. This study is to provide several schemes against the jamming threats effectively. We propose the several processes to analyze the required capability and demonstrate the result's of modeling and simulations(hereafter; M&S) for this integration of military aircraft, and the mathematical programming model for system optimization of military aircraft anti-jamming GPS system on the basis analysis of M&S results which could be considered available budget and the project characteristic. These schemes will be helpful on proper acquisition of these systems and. We are looking forward to contributing to the integration of anti-jamming GPS system of ROK military aircraft.

• Journal of Information Processing Systems
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• 제17권4호
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• pp.690-706
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• 2021

Classification is a substantial operation in data mining, and each element is distributed taking into account its feature values in the corresponding class. Metaheuristics have been widely used in attempts to solve satellite image classification problems. This article proposes a hybrid approach, the flower pigeons-inspired optimization algorithm (FPIO), and the local search method of the flower pollination algorithm is integrated into the pigeon-inspired algorithm. The efficiency and power of the proposed FPIO approach are displayed with a series of images, supported by computational results that demonstrate the cogency of the proposed classification method on satellite imagery. For this work, the Davies-Bouldin Index is used as an objective function. FPIO is applied to different types of images (synthetic, Alsat-2B, and Sentinel-2). Moreover, a comparative experiment between FPIO and the genetic algorithm genetic algorithm is conducted. Experimental results showed that GA outperformed FPIO in matters of time computing. However, FPIO provided better quality results with less confusion. The overall experimental results demonstrate that the proposed approach is an efficient method for satellite imagery classification.

• 한국음향학회:학술대회논문집
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• 한국음향학회 2000년도 하계학술발표대회 논문집 제19권 1호
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• pp.337-338
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• 2000

The perceptual filter for speech enhancement was analytically derived where the frequency content of the input noisy signal was made the same as that of the estimated clean signal in auditory domain. However, the analytical derivation should rely on the deconvolution associated with the spreading function in the psychoacoustic model, which results in an ill-conditioned problem. In order to cope with the problem associated with the deconvolution, we propose a novel psychoacoustic model based speech enhancement filter whose principle is the same as the perceptual filter, however the filter is derived by a constrained optimization which provides solutions to the ill-conditioned problem.

• 한국정보컨버전스학회논문지
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• 제7권2호
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• pp.7-12
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• 2014

정확한 신호의 검출을 위해서 많은 필터들이 만들어지고 있다. 필터의 성능은 잡음을 효과적으로 제거하는 것으로 평가한다. 필터의 정확한 평가를 위해서 문턱치 값을 효과적으로 결정할 필요가 있다. 본 연구에서는 문턱치 값의 최적화에 대해 연구하였다. 신호는 삼각파와 전원잡음을 이용하였다. 샘플 개수에 따른 SNR 변화를 연구하였다. 샘플 개수가 증가함에 따라 SNR도 안정화가 되었다.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2003년도 추계학술대회 및 정기총회
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• pp.15-18
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• 2003

There are plenty of optimization models for the signal-system of a single intersection and area traffic. Some of those models are adopted for the real traffic signal control system. The simulators for a single crossroad have been developed, so that we could evaluate optimization models and traffic control systems. However, the simulators for the area traffic are still being developed. Therefore, there are many limitations in the analysis and evaluation for area traffic control systems. The area traffic is consist of several intersections interconnected which are very complicated and many traffic strategy are adopted for the control system. This paper features an effective area traffic control system by High Lever Architecture(HLA) which is a new developed simulation tool. In this paper, we discuss the design of HLA-based area traffic control simulation. We describe technical motivations for the HLA, the key elements of the architecture and how they are minimum and essential to the goal of reuse and interoperability.

• 전자공학회논문지A
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• 제33A권7호
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• pp.156-161
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• 1996

Accurate equivalent circuit modeling using multi-circuit optimization has been perfomred for detemining small-signal model of AlGaAs/GaAs HBTs. Three equivalent circuits for a cutoff biasing and two active biasing at different curretns are optimized simultaneously to fit gheir S parameters under the physics-based constrain that current-dependent elements for one of active circuits are connected to those for another circit multiplied by the ratio of two currents. The cutoff mode circuit and the physical constrain give the advantage of extracting physically acceptable parameters, because the number of unknown variables. After this optimization, three ses of optimized model S-parameters agree well with their measured S-parameters from 0.045 GHz to 26.5GHz.

• 한국전자파학회논문지
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• 제25권4호
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• pp.483-486
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• 2014

일반적으로 플립 칩은 와이어 본딩에 비해 신호 무결성을 저해하는 기생 성분이 작지만, 60 GHz 대역에서는 설계하기에 따라서 2 dB 이상의 삽입 손실 차이가 난다. 본 논문에서는 플립 칩 구조의 여러 설계 변수들에 따라 삽입 손실이 어떻게 변하는 지를 분석함으로써 설계를 최적화하는 방법을 제시한다.

• Journal of international Conference on Electrical Machines and Systems
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• 제3권3호
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• pp.248-251
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• 2014

As more vehicles become equipped with advanced electronic control systems, more consideration is needed with regards to automotive safety issues related to the effects of electromagnetic waves. Unwanted electromagnetic waves from the antenna, electricity and other electronic devices cause the performance and safety problem of automotive components. In general, Power Integrity and Signal Integrity analysis have been widely used, but these analyses have stayed PCB level. PCB base analysis is different from radiated emission TEST condition so its results are used just for reference. This paper proposes EMC optimization technology using module level 3-dimensional radiation simulation process closed to fundamental test conditions. If module level EMC analysis, which is proposed in this study, is applied to all automotive electronics systems, unexpected EMC noise will be prevented.