• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권10호
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• pp.4804-4822
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• 2017

Coverage problem is a research hot spot in directional sensor networks (DSNs). However, the major problem affecting the performance of the current coverage-enhancing strategies is that they just optimize the coverage of networks, but ignore the maximum number of sleep sensors to save more energy. Aiming to find an approximate optimal method that can cover maximum area with minimum number of active sensors, in this paper, a new scheduling algorithm based on learning automata is proposed to enhance area coverage, and shut off redundant sensors as many as possible. To evaluate the performance of the proposed algorithm, several experiments are conducted. Simulation results indicate that the proposed algorithm have effective performance in terms of coverage enhancement and sleeping sensors compared to the existing algorithms.

• Journal of Communications and Networks
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• 제11권1호
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• pp.57-71
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• 2009

Networking together hundreds or thousands of cheap sensor nodes allows users to accurately monitor a remote environment by intelligently combining the data from the individual nodes. As sensor nodes are typically battery operated, it is important to efficiently use the limited energy of the nodes to extend the lifetime of the wireless sensor network (WSN). One of the fundamental issues in WSNs is the coverage problem. In this paper, the border coverage problem in WSNs is rigorously analyzed. Most existing results related to the coverage problem in wireless sensor networks focused on planar networks; however, three dimensional (3D) modeling of the sensor network would reflect more accurately real-life situations. Unlike previous works in this area, we provide distributed algorithms that allow the selection and activation of an optimal border cover for both 2D and 3D regions of interest. We also provide self-healing algorithms as an optimization to our border coverage algorithms which allow the sensor network to adaptively reconfigure and repair itself in order to improve its own performance. Border coverage is crucial for optimizing sensor placement for intrusion detection and a number of other practical applications.

• Journal of Communications and Networks
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• 제16권5호
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• pp.493-501
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• 2014

Coverage completeness is an important indicator for quality of service in wireless sensor networks (WSN). Due to limited energy and diverse working conditions, the sensor nodes have different lifetimes which often cause network holes. Most of the existing methods expose large limitation and one-sidedness because they generally consider only one aspect, either coverage rate or energy issue. This paper presents a novel method for coverage hole detection with residual energy in randomly deployed wireless sensor networks. By calculating the life expectancy of working nodes through residual energy, we make a trade-off between network repair cost and energy waste. The working nodes with short lifetime are screened out according to a proper ratio. After that, the locations of coverage holes can be determined by calculating the joint coverage probability and the evaluation criteria. Simulation result shows that compared to those traditional algorithms without consideration of energy problem, our method can effectively maintain the coverage quality of repaired WSN while enhancing the life span of WSN at the same time.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권10호
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• pp.5014-5034
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• 2016

This paper discusses how to effectively guarantee the coverage and connectivity quality of wireless sensor networks when joint perception model is used for the nodes whose communication ranges are multi-level adjustable in the absence of position information. A Connect Coverage Algorithm Based on Joint Sensing model (CCAJS) is proposed, with which least working nodes are chosen based on probability model ensuring the coverage quality of the network. The algorithm can balance the position distribution of selected working nodes as far as possible, as well as reduce the overall energy consumption of the whole network. The simulation results show that, less working nodes are needed to ensure the coverage quality of networks using joint perception model than using the binary perception model. CCAJS can not only satisfy expected coverage quality and connectivity, but also decrease the energy consumption, thereby prolonging the network lifetime.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2011년도 추계학술발표대회
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• pp.662-664
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• 2011

무선 센서 네트워크에서 관심지역이 각 센서에 의하여 얼마나 잘 센싱되는지의 정도에 대한 커버리지(coverage)와 센서에 의하여 센싱된 데이터를 싱크노드까지 얼마나 잘 전달될 수 있는지의 정도에 관한 연결성(connectivity)은 중요한 연구 분야이다. 이와 관련하여 본 논문에서는 센서 네트워크에서 p-coverage와 q-connectivity ($q{\leq}6$)를 만족하는 최적의 센서 배치패턴 문제에 관한 연구 결과를 기술한다. 특히, 1-coverage의 경우 최적이라 알려진 삼각 격자 패턴에 대하여 p-coverage와 6-connectivity을 만족하도록 하는 배치 방법을 제시한다.

• 한국통신학회논문지
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• 제38B권1호
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• pp.18-25
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• 2013

본 논문에서는 차세대 이종망 환경에서 펨토셀이 자율적으로 커버리지를 조절하는 방안을 제안한다. 펨토셀의 커버리지가 펨토셀이 설치된 실내 영역보다 큰 경우 펨토셀 커버리지를 통과하는 실외 단말에 의해 핸드오버 요청이 발생하여 불필요한 signaling을 증가시키고 이에 따라 overhead가 커지게 된다. 펨토셀의 커버리지가 펨토셀이 설치된 실내 영역보다 작은 경우 실내에 위치한 단말이 펨토셀에 연결되지 못하는 문제가 발생한다. 따라서 본 논문에서는 펨토셀 커버리지가 실내영역과 일치하도록 자율적으로 전송 전력을 조절하는 방법을 제안한다. 제안 기법은 펨토셀이 스스로 얻을 수 있는 정보인 핸드오버 요청 및 단말의 펨토셀에 대한 결합등록(membership) 여부를 이용함으로써 자율적인 커버리지 조절을 가능 하게 한다. 제안 기법의 성능 분석을 위해 먼저 커버리지를 실내영역과 일치시키는 펨토셀 전송 전력의 이론값을 도출한다. 이후 제안 기법을 모의실험에 적용하여 분석한 결과에서 펨토셀의 전송 전력이 자율적으로 조절되어 이론값으로 수렴함을 보인다.

• Journal of Communications and Networks
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• 제17권1호
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• pp.84-92
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• 2015

Multi-hop relay networks have been widely considered as a promising solution to extend the coverage area and to reduce the deployment cost by deploying the relay stations (RSs) in mobile communication systems. Suitable deployment for the RSs is one of the most important features of the demand nodes (DNs) to obtain a high data transmission rate in such systems. Considering a tradeoff among the network throughput, the deployment budget, and the overall coverage of the systems, efficient RS deployment schemes and corresponding algorithms must be developed and designed. A novel cluster-based RS deployment scheme is proposed in this paper to select the appropriate deployment locations for the relay stations from the candidate positions. To make an ideal cluster distribution, the distances between the DNs are calculated when deploying the RSs. We take into account the traffic demands and adopt a uniform cluster concept to reduce the data transmission distances of the DNs. On the basis of the different candidate positions, the proposed scheme makes an adaptive decision for selecting the deployment sites of the RSs. A better network throughput and coverage ratio can be obtained by balancing the network load among the clusters. Simulation results show that the proposed scheme outperforms the previously known schemes in terms of the network throughput and the coverage ratio. Additionally, a suitable deployment budget can be implemented in multi-hop relay networks.

• Journal of Information Processing Systems
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• 제11권4호
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• pp.509-527
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• 2015

Wireless Video Sensor Networks (WVSNs) have become a leading solution in many important applications, such as disaster recovery. By using WVSNs in disaster scenarios, the main goal is achieving a successful immediate response including search, location, and rescue operations. The achievement of such an objective in the presence of obstacles and the risk of sensor damage being caused by disasters is a challenging task. In this paper, we propose a fault tolerance model of WVSN for efficient post-disaster management in order to assist rescue and preparedness operations. To get an overview of the monitored area, we used video sensors with a rotation capability that enables them to switch to the best direction for getting better multimedia coverage of the disaster area, while minimizing the effect of occlusions. By constructing different cover sets based on the field of view redundancy, we can provide a robust fault tolerance to the network. We demonstrate by simulating the benefits of our proposal in terms of reliability and high coverage.

• 한국통신학회논문지
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• 제41권12호
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• pp.1721-1735
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• 2016

Power-efficient base station (BS) operation is one of the important issues in future green cellular networks. Previously well-known BS operation schemes, the cell zooming scheme and the cell wilting and blossoming scheme, require tight cooperation between cells in cellular networks. With the previous schemes, the non-cooperative BSs of a serving cell and neighboring cells could cause coverage holes between the cells, thereby seriously degrading the quality of service as well as the power saving efficiency of the cellular networks. In this paper, we propose a novel power-efficient BS operation scheme for green downlink heterogeneous cellular networks, in which the networks virtually adjust the coverage of a serving macrocell (SM) and neighboring macrocells (NMs) without adjusting the transmission power of the BSs when the SM is lightly loaded, and the networks turn off the BS of the SM when none of active users are associated with the SM. Simulation results show that our proposed scheme significantly improves the power saving efficiency without degrading the quality of service (e.g., system throughput) of a downlink heterogeneous LTE network and outperforms the previous schemes in terms of system throughput and power saving efficiency. In particular, with the proposed scheme, macrocells are able to operate independently without the cooperation of a SM and NMs for green heterogeneous cellular networks.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2014년도 추계학술대회
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• pp.848-850
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• 2014

본 논문에서는 이동 에드혹 네트워크(Mobile Ad hoc network: MANET)에서의 상황인식 기반의 스케쥴링 기법인 CSWC(Coverage Scheduling Weight-value Control) 알고리즘을 제안한다. 기존의 LEACH 알고리즘은 확률적 분포 함수에 의해 커버리지 영역 안에 존재 하는 클러스터 헤드노드를 선택하여 중계노드로 통신한다. 하지만 확률적 분포함수에 의해 선택된 헤드 노드가 커버리지 영역에서 전송거리 비율이 비균형으로 나뉘어 전송할 경우, 노드의 에너지 소모가 일정하지 않아 효율적으로 사용하지 못하는 경우가 발생한다. 따라서 본 논문에서는 최적의 커버리지 영역을 설정하여 유지하는 CSWC알고리즘을 제안한다. 본 논문에서 제안하는 알고리즘은 커버리지 영역이 비균형으로 설정되어 있을 경우, 커버러지 영역을 결정하는 홉 수를 증가시켜 최적의 커버리지 영역을 제공하는 알고리즘이다. 주어진 모의실험 환경에서 노드의 효율적인 커버리지 영역을 설정하여 네트워크의 최적화된 에너지 소모를 보여주고 있다.