• Journal of the Institute of Electronics Engineers of Korea CI
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• v.44 no.1
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• pp.41-48
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• 2007

In this paper, we propose an optimal placement of sensor nodes with 2.4GHz wireless channel characteristics. The proposed method determines optimal transmission range based on log-normal path loss model, and optimal number of sensor nodes calculating the density of sensor nodes. For the lossless data transmission, we search the optimal locations with self-organizing feature maps(SOM) using transmission range, and number of sensor nodes. We demonstrate that optimal transmission range is 20m, and optimal number of sensor nodes is 8. We performed simulations on the searching for optimal locations and confirmed the link condition of sensor nodes.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.11a
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• pp.587-590
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• 2011

고정형 센서노드들로 구성된 기존의 무선 센서 네트워크는 다양한 응용분야에서 사용되고 있다. 하지만, 센서노드에 이동기능이 추가되면 적절한 움직임을 통해 센싱 영역을 최대화 할 수 있다. 이러한 측면에서 최근 센서의 자율배치에 관련한 연구가 활발하게 진행 중이다. 기존 연구에서의 센서 이동은 대부분 2차원에서의 자율배치에 관하여 연구가 되어 왔다. 본 논문에서는 2차원에서의 자율배치가 아닌 3차원 공간에서의 센서노드의 자율배치에 대한 알고리즘과 이의 결과를 제시한다.

• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.345-348
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• 2005

본 논문은 무선 센서 네트워크에서 SOFM을 이용하여 센서 노드를 배치하는 방법을 제안한다. 제안한 방식은 특정 공간에서 센서 노드의 밀도가 일정하도록 SOFM을 이용하여 센서 노드를 배치시킨다. 시뮬레이션으로 최적의 위치를 탐색하고, 그 위치에 무선 센서 노드를 설치하여 제안한 방식의 성능을 검토하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6A
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• pp.594-599
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• 2010

This paper studies the effect of the deployment position of the relay stations on the downlink signal-to-interference-noise-ratio (SINR) in multihop cellular networks. Two different relay deployment scenarios are considered where relay stations are located either inside cells or on the boundary among adjacent cells. The fundamental contribution is to compare fairly the average SINR between two scenarios with the proposed relay modeling framework that includes multi-cell geometries and inter-cell interferences. The mathematical results show that the SINR increases when relay stations are located inside cells because of higher received signal power.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10d
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• pp.431-434
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• 2006

센서 네트워크(Sensor Network)는 항공기(Aircraft)로 살포되는 센서 노드(Sensor Node)들로 구성된다. 자연적인 장애물 즉, 바람, 나무 등이나 빌딩과 같은 조형물로 인해 적절한 위치에 센서 노드들이 배치되지 못하여 불필요한 에너지 소비와 전송 지연 등이 발생하게 된다. 본 논문에서는 기존 논문에서 사용하던 고정 노드(Static Node) 뿐만 아니라 이동 노드(Mobile Node)를 센서 필드(Sensor Field)에 배치 할 것이다. 각 센서 노드의 정보를 싱크(Sink)노드가 수집 분석 후 본 논문에서 제시한 제안에 따라 이동 노드 위치 변경하여 센서 네트워크 라우팅(Routing)의 성능을 향상시키는 방법을 제안한다.

• KIPS Transactions on Computer and Communication Systems
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• v.9 no.11
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• pp.250-255
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• 2020

For the resolution of the latency problem of the cloud center-based cloud computing, fog computing was proposed that allows end devices to offload computations to nearby fog nodes. In the fog computing, virtualized service images are placed on fog nodes and, if service images are placed close to end devices, the duplicate service image placement problem may occur. Therefore, in this paper, we propose a service image placement mechanism based on the logical fog network that reduces duplicate service images by considering the pattern of collected service requests. For the performance evaluation of the proposed mechanism, through simulations, we compare ours with the on-demand mechanism placing a service image upon the receipt of a service request. We consider the performance factors like the number of service images, the number of non-accommodated service requests, and the network cost.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.6
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• pp.608-618
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• 2000

We consider the problem of placing resources in a distributed computing system so that certain performance requirements may be met while minimizing the number of required resource copies, irrespective of node or link failures. To meet the requirements for high performance and high availability, minimum number of resource copies should be placed in such a way that each node has at least two copies on the node or its neighbor nodes. This is called the fault-tolerant resource placement problem in this paper. The structure of a parallel or a distributed computing system is represented by a graph. The fault-tolerant placement problem is first transformed into the problem of finding the smallest fault-tolerant dominating set in a graph. The dominating set problem is known to be NP-complete. In this paper, searching for the smallest fault-tolerant dominating set is formulated as a state-space search problem, which is then solved optimally with the well-known A* algorithm. To speed up the search, we derive heuristic information by analyzing the properties of fault-tolerant dominating sets. Some experimental results on various regular and random graphs show that the search time can be reduced dramatically using the heuristic information.

• Journal of the Korean Association of Geographic Information Studies
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• v.12 no.4
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• pp.158-168
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• 2009

As nation and society progresses, urban ground facilities and their management system get more complicated and the cost and effort to control the system efficiently grows exponentially. This study suggests to the deployment method of a sensor node by Wireless Sensor Network for controling the Urban Ground Facilities of National Facilities. First, we achieve the management facilities and method using the first analysis and then make the coverage of sensing and then set up the Sensor Node in Urban Ground Facilities. Second, we propose the solution way of repetition by the second analysis. And, we embody the GIS program by Digital Map and this method, we improve the reality by overlapping an aerial photo. Also we make an experience on the sensor node allocation using making program. we can remove the repetition sensor node about 50%, and we can confirm that the sensor nodes are evenly distributed on the road.

• The KIPS Transactions:PartC
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• v.16C no.4
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• pp.535-542
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• 2009

Wireless Sensor Network (WSN) is a wireless network consisting of spatially distributed autonomous devices, using sensors to cooperatively monitor physical or environmental conditions. WSNs face the critical challenge of sustaining long-term operation on limited battery energy. Coverage maintenance has been proposed as a promising approach to prolong network lifetime. Mobile sensors equipped with communication devices can be leveraged to overcome the coverage problem. In this paper, we propose a stepwise movement scheme using perimeter coverage property for the coverage maintenance problem. In our scheme, each sensor monitors neighboring dead nodes, determines vulnerable node (i.e. dead node which makes uncovered area), computes the center of uncovered area HC, and makes a coordinated stepwise movement to compensate the uncovered area. In our experimental results, our scheme shows at least 50 % decrease in the total moving distance which determines the energy efficiency of mobile sensor.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06d
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• pp.179-182
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• 2011

노트북컴퓨터 및 스마트폰을 비롯한 무선랜을 사용하는 이동기기들의 폭발적인 보급에 따라 과도한 무선 트래픽을 처리하기 위한 기술개발이 절실하다. 본 논문에서는 MIM기능이 구현된 무선인터페이스를 가지는 노드들의 적절한 배치를 통해 시스템성능을 향상시키는 방법에 대해서 소개한다. 두 노드간의 거리에 기반한 간단한 MIM캡쳐 확률 모델을 바탕으로 무선 메시노드를 배치하면 동시전송이 가능해져서 기존의 IEEE802.11 DCF를 기반으로 동작하는 무선메시망에 비해 데이터 처리율이 크게 향상될 수 있다. 우리는 시물레이션을 통한 성능검증을 통해 MIM캡쳐를 활용하는 무선메시망 배치구조가 DCF에 기초해서 동작하는 망에 비해서 약 60% 정도의 처리량 향상이 있는 것을 확인하였다.