• Journal of Communications and Networks
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• 제7권4호
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• pp.471-477
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• 2005

This paper proposes an efficient constraint-based optimization model for the design of 3G mobile networks, such as universal mobile telecommunications system (UMTS). The model concerns about finding a set of sites for locating radio network controllers (RNCs) from a set of pre-defined candidate sites, and at the same time optimally assigning node Bs to the selected RNCs. All these choices must satisfy a set of constraints and optimize an objective function. This problem is NP-hard and consequently cannot be practically solved by exact methods for real size networks. Thus, this paper proposes a hybrid search strategy for tackling this complex and combinatorial optimization problem. The proposed hybrid search strategy is composed of three phases: A constraint satisfaction method with an embedded problem-specific goal which guides the search for a good initial solution, an optimization phase using local search algorithms, such as tabu algorithm, and a post­optimization phase to improve solutions from the second phase by using a constraint optimization procedure. Computational results show that the proposed search strategy and the model are highly efficient. Optimal solutions are always obtained for small or medium sized problems. For large sized problems, the final results are on average within $5.77\%$ to $7.48\%$ of the lower bounds.

• ETRI Journal
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• 제39권2호
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• pp.222-233
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• 2017

Debugging in distributed environments, such as wireless sensor networks (WSNs), which consist of sensor nodes with limited resources, is an iterative and occasionally laborious process for programmers. In sensor networks, it is not easy to find unintended bugs that arise during development and deployment, and that are due to a lack of visibility into the nodes and a dearth of effective debugging tools. Most sensor network debugging tools are not provided with effective facilities such as real-time tracing, remote debugging, or a GUI environment. In this paper, we present a hybrid debugging framework (HDF) that works on WSNs. This framework supports query-based monitoring and real-time tracing on sensor nodes. The monitoring supports commands to manage/control the deployed nodes, and provides new debug commands. To do so, we devised a debugging device called a Docking Debug-Box (D2-Box), and two program agents. In addition, we provide a scalable node monitor to enable all deployed nodes for viewing. To transmit and collect their data or information reliably, all nodes are connected using a scalable node monitor applied through the Internet. Therefore, the suggested framework in theory does not increase the network traffic for debugging on WSNs, and the traffic complexity is nearly O(1).

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2002년도 춘계학술대회 및 임시총회
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• pp.1-5
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• 2002

본 논문은 수족이 불편한 장애인의 편리성을 위해 휠체어에 음성인식 모듈을 개발하는데 목표로 하고 있다. 본 시스템의 주프로세서는 TMS320C32를 이용하였고, 전처리단계에서 잡음환경의 특성을 고려하여 Winer 필터를 적용해서 잡음을 제거하였고 특징추출과정에서는 LPC&Cepstrum을 이용하여 프레임당 12차의 특징패턴을 추출하였다. 그 후 인식부에서는 기존의 알고리즘 중 고립단어에서 흔히 사용하는 DTW(Dynamic Time Warping)과 오인식률 발생을 방지하기 위해 NN(Neural Network)를 결합한 Hybrid 형태로 구현하였다. 본 연구에서는 DTW와 Hybrid형태를 각각 실험한 결과 잡음환경에서 고립단어 인식률이 평균 96%이상 나타났다.

• 한국산업정보학회논문지
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• 제26권3호
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• pp.9-22
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• 2021

본 연구에서는 조립산업의 공급망(Supply chain)에서의 발생할 수 있는 공급붕괴(Supply disruption)를 고려한 공급망 네트워크(Supply chain network: SCN) 모델이 제안된다. 공급붕괴를 위해 공급자 붕괴(Supplier disruption)와 경로 붕괴(Route disruption)가 함께 SCN 모델에서 고려되며, 이러한 두 가지의 붕괴 현상을 함께 고려한 SCN 모델은 유연성(Flexibility)과 효율성(Efficiency)을 성취할 수 있게 된다. SCN 모델은 수리모형으로 표현되며, 혼합유전알고리즘(Proposed hybrid genetic algorithm: pro-HGA) 접근법을 이용해 이행된다. 수치실험에서는 몇몇 상이한 규모를 가진 SCN 모델을 이용해 제안된 pro-HGA 접근법의 수행도와 기존 접근법의 수행도를 비교분석하였으며, 공급자 수와 백업경로(Backup route) 수의 변화를 통한 민감도 분석을 실시하였다. 실험 결과, 제안된 pro-HGA 접근법의 효율성을 입증하였고, SCN 모델의 유연성과 효용성을 검증하였다. 마지막으로 본 연구 수행의 의의 및 향후 개선방향에 대해 논하였다.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1996년도 International Conference on Agricultural Machinery Engineering Proceedings
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• pp.780-791
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• 1996

A hybrid image processing system which automatically distinguished lean tissues in the image of a complex beef cut surface and generated the lean tissue contour has been developed. Because of the in homegeneous distribution and fuzzy pattern of fat and lean tissue on the beef cut, conventional image segmentation and contour generation algorithm suffer from a heavy computing requirement, algorithm complexity and poor robustness. The proposed system utilizes an artificial neural network enhance the robustness of processing. The system is composed of pre-network , network and post-network processing stages. At the pre-network stage, gray level images of beef cuts were segmented and resized to be adequate to the network input. Features such as fat and bone were enhanced and the enhanced input image was converted tot he grid pattern image, whose grid was formed as 4 X4 pixel size. at the network stage, the normalized gray value of each grid image was taken as the network input. Th pre-trained network generated the grid image output of the isolated lean tissue. A training scheme of the network and the separating performance were presented and analyzed. The developed hybrid system showed the feasibility of the human like robust object segmentation and contour generation for the complex , fuzzy and irregular image.

• 한국산업정보학회논문지
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• 제24권5호
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• pp.53-64
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• 2019

본 연구에서는 재사용 가능한 제품을 대상으로 순방향물류(Forward logistics)에서 부터 역방향물류(Reverse logistics)에 이르기까지 전체 물류비용과 수요와 회수에 따른 제조업자에서의 재고관리, 재사용을 위한 과정에서 발생하는 청소공정비용 및 폐기비용을 고려한 재사용 네트워크 모델(Reusable network model)을 제안한다. 제안 모델의 유효성을 검증하기 위하여 최적화 기법 중 하나인 유전자 알고리즘(Genetic algorithm: GA)을 이용한다. 파라미터가 해(Solution)에 미치는 영향을 알아보기 위해서 세 가지 파라미터 조건에서 우선 순위형 GA(Priority-based GA: priGA)와, 각 세대(Generation)마다 파라미터가 조정되는 개량형 하이브리드 GA(Modified hybrid genetic algorithm: mhGA)를 사이즈가 다른 4가지 예제에 적용하여 시뮬레이션을 실시한다.

• 방송공학회논문지
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• 제17권1호
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• pp.95-107
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• 2012

네트워크 코딩은 멀티캐스트 네트워크에서 전송량을 증가시키기 위해 제안된 기법으로 최근에는 다수의 사용자가 성능 향상을 위해서로의 자원을 공유하는 협력통신에 네트워크 코딩을 적용하는 연구가 활발히 진행 중이다. 네트워크 코딩 기반의 협력통신에서 사용자는 자기 자신의 데이터와 다른 사용자의 데이터를 네트워크 코딩 연산을 통해 결합하여 전송한다. 기존의 연구에서는 네트워크 코딩을 기반으로 한 적응형 복호 후 전송(Network-Coding-based Adaptive Decode-and-Forward, NC-ADF) 방식이 다이버시티(diversity) 이득과 추가적인 전송량 증대를 가져올 수 있음을 보였다. 본 논문에서는 기존 프로토콜의 성능 증대와 네트워크 코딩의 이득을 극대화 하기 위해 사용자간 채널의 상태에 따라 증폭 후 전송(Amplify-and-Forward, AF) 방식과 복호 후 전송(Decode-and-Forward, DF) 방식을 적응적으로 적용한 새로운 네트워크 코딩 기반의 협력통신 기법을 제안하였다. 또한 제안한 기법의 아웃티지 확률을 구하고 높은 SNR 영역에서 최대 다이버시티 차수(full diversity order)를 가짐을 보였다. 나아가 추가적인 성능 향상을 위해 본 논문에서 제안된 기법에 의한 아웃티지 확률을 기반으로 최적의 전송 파워 비율을 구하였다.

• International Journal of Computer Science & Network Security
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• 제24권6호
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• pp.23-32
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• 2024

Mobile Ad hoc Network is a network of multiple wireless nodes which communicate and exchange information together without any fixed and centralized infrastructure. The core objective for the development of MANET is to provide movability, portability and extensibility. Due to infrastructure less network topology of the network changes frequently this causes many challenges for designing routing algorithms. Many routing protocols for MANET have been suggested for last few years and research is still going on. In this paper we review three main routing protocols namely Proactive, Reactive and Hybrid, performance comparison of Proactive such as DSDV, Reactive as AODV, DSR, TORA and Hybrid as ZRP in different network scenarios including dynamic network size, changing number of nodes, changing movability of nodes, in high movability and denser network and low movability and low traffic. This paper analyzes these scenarios on the performance evaluation metrics e.g. Throughput, Packet Delivery Ratio (PDR), Normalized Routing Load(NRL) and End To-End delay(ETE).This paper also reviews various network layer security attacks challenge by routing protocols, detection mechanism proposes to detect these attacks and compare performance of these attacks on evaluation metrics such as Routing Overhead, Transmission Delay and packet drop rates.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2003년도 ISIS 2003
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• pp.195-204
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• 2003

Network optimization is being increasingly important and fundamental issue in the fields such as engineering, computer science, operations research, transportation, telecommunication, decision support systems, manufacturing, and airline scheduling. Networks provide a useful way to modeling real world problems and are extensively used in practice. Many real world applications impose on more complex issues, such as, complex structure, complex constraints, and multiple objects to be handled simultaneously and make the problem intractable to the traditional approaches. Recent advances in evolutionary computation have made it possible to solve such practical network optimization problems. The invited talk introduces a thorough treatment of evolutionary approaches, i.e., hybrid genetic algorithms approach to network optimization problems, such as, fixed charge transportation problem, minimum cost and maximum flow problem, minimum spanning tree problem, multiple project scheduling problems, scheduling problem in FMS.

• ETRI Journal
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• 제33권5호
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• pp.704-711
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• 2011

This paper proposes hybrid distributed stochastic addressing (HDSA), which combines the advantages of distributed addressing and stochastic addressing, to solve the problems encountered when constructing a network in a ZigBee-based wireless sensor network. HDSA can assign all the addresses for ZigBee beyond the limit of addresses assigned by the existing distributed address assignment mechanism. Thus, it can make the network scalable and can also utilize the advantages of tree routing. The simulation results reveal that HDSA has better addressing performance than distributed addressing and better routing performance than other on-demand routing methods.