• 한국산학기술학회논문지
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• 제13권11호
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• pp.5487-5495
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• 2012

무선 센서 네트워크 환경에서 클러스터키 등의 보안키를 적용하기 위한 중요한 고려 사항은 보안키 갱신이 안전하게 이루어져야 하고, 보안키 갱신 시 요구되는 시간과 비용이 적어야 한다는 점이다. 각 센서 노드는 제한된 에너지를 보유하기 때문에 보안키 갱신에 소모되는 에너지가 클 경우 전체 네트워크 수명에 많은 영향을 준다. 따라서 안전하고 에너지 효율적인 보안키 관리 방법이 요구된다. 본 논문에서는 그룹을 기반으로 한 에너지 효율적인 클러스터키 관리 방안을 제안한다. 제안하는 방법에서 대규모 센서 네트워크에서 안전하고 효율적인 키 관리를 위해 5개의 보안키를 사용하고, 섹터, 클러스터 및 그룹 수준의 보안 적합도를 관리하여 보안키 갱신 주기 및 보안에 사용되는 다항식의 차수를 차별화시킨다. 실험을 통해 이전의 보안키 관리 기법보다 네트워크 에너지 효율성이 향상됨을 입증한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권10호
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• pp.2473-2492
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• 2012

Energy conservation is a vital issue in wireless sensor networks. Recently, employing mobile sinks for data gathering become a pervasive trend to deal with this problem. The sink can follow stochastic or pre-defined paths; however the controlled mobility pattern nowadays is taken more into consideration. In this method, the sink moves across the network autonomously and changes its position based on the energy factors. Although the sink mobility would reduce nodes' energy consumption and enhance the network lifetime, the overhead caused by topological changes could waste unnecessary power through the sensor field. In this paper, we proposed EEDARS, an energy-efficient dual-sink algorithm with role switching mechanism which utilizes both static and mobile sinks. The static sink is engaged to avoid any periodic flooding for sink localization, while the mobile sink adaptively moves towards the event region for data collection. Furthermore, a role switching mechanism is applied to the protocol in order to send the nearest sink to the recent event area, hence shorten the path. This algorithm could be employed in event-driven and multi-hop scenarios. Analytical model and extensive simulation results for EEDARS demonstrate a significant improvement on the network metrics especially the lifetime, the load and the end-to-end delay.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제4권4호
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• pp.529-546
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• 2010

Greedy forwarding is the key mechanism of geographic routing and is one of the protocols used most commonly in wireless sensor networks. Greedy forwarding uses 1-hop local information to forward packets to the destination and does not have to maintain the routing table, and thus it takes small overhead and has excellent scalability. However, the signal intensity reduces exponentially with the distance in realistic wireless sensor network, and greedy forwarding consumes a lot of energy, since it forwards the packets to the neighbor node closest to the destination. Previous proposed greedy forwarding protocols are the sender-based greedy forwarding that a sender selects a neighbor node to forward packets as the forwarding node and hence they cannot guarantee energy efficient forwarding in unpredictable wireless environment. In this paper, we propose the receiver-based greedy forwarding called RGF where one of the neighbor nodes that received the packet forwards it by itself. In RGF, sender selects several energy efficient nodes as candidate forwarding nodes and decides forwarding priority of them in order to prevent unnecessary transmissions. The simulation results show that RGF improves delivery rate up to maximum 66.8% and energy efficiency, 60.9% compared with existing sender-based greedy forwarding.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권8호
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• pp.1805-1824
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• 2013

Recently, the use of wireless body area networks (WBAN) has been increasing rapidly in medical healthcare applications. WBANs consist of smart nodes that can be used to sense and transmit vital data such as heart rate, temperature and ECG from a human body to a medical centre. WBANs depend on limited resources such as energy and bandwidth. In order to utilise these resources efficiently, a very well organized medium access control (MAC) protocol must be considered. In this paper, a new, adaptive and energy-efficient MAC protocol, entitled isMAC, is proposed for WBANs. The proposed MAC is based on multi-channel communication and aims to prolong the network lifetime by effectively employing (i) a collision prevention mechanism, (ii) a coordinator node (WCN) selection algorithm and (iii) a transmission power adjustment approach. The isMAC protocol has been developed and modelled, by using OPNET Modeler simulation software. It is based on a networking scenario that requires especially high data rates such as ECG, for performance evaluation purposes. Packet delay, network throughput and energy consumption have been chosen as performance metrics. The comparison between the simulation results of isMAC and classical IEEE 802.15.4 (ZigBee) protocol shows that isMAC significantly outperforms IEEE 802.15.4 in terms of packet delay, throughput and energy consumption.

• ETRI Journal
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• 제33권6호
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• pp.857-863
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• 2011

Due to uncertainties in target motion and randomness of deployed sensor nodes, the problem of imbalance of energy consumption arises from sensor scheduling. This paper presents an energy-efficient adaptive sensor scheduling for a target monitoring algorithm in a local monitoring region of wireless sensor networks. Owing to excessive scheduling of an individual node, one node with a high value generated by a decision function is preferentially selected as a tasking node to balance the local energy consumption of a dynamic clustering, and the node with the highest value is chosen as the cluster head. Others with lower ones are in reserve. In addition, an optimization problem is derived to satisfy the problem of sensor scheduling subject to the joint detection probability for tasking sensors. Particles of the target in particle filter algorithm are resampled for a higher tracking accuracy. Simulation results show this algorithm can improve the required tracking accuracy, and nodes are efficiently scheduled. Hence, there is a 41.67% savings in energy consumption.

• 한국산학기술학회논문지
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• 제11권5호
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• pp.1661-1669
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• 2010

본 논문에서는 센서 네트워크의 수명을 길게 하기 위해 클러스터 헤드에 집중된 에너지 과부하를 클러스터 그룹 헤드와 클러스터 헤드로 분산시켜서 에너지 소모량을 감소시키는 유전 알고리즘 기반의 에너지 효율적인 클러스터링(ECGA: Energy efficient Clustering based on Genetic Algorithm)을 제안한다. ECGA 알고리즘은 예상 에너지 비용 합계, 센서 노드 에너지 잔량의 평균 및 표준 편차를 구하여 이를 적합도 함수에 적용하였다. 이 적합도를 이용하여 최적의 클러스터 그룹 및 클러스터를 형성한다. 실험을 통하여 ECGA 알고리즘이 이전의 클러스터링 기법보다 에너지 소모를 줄이고 네트워크의 수명을 연장시켰음을 보였다.

• 한국컴퓨터정보학회논문지
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• 제24권5호
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• pp.1-9
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• 2019

In this paper, we propose the algorithms which determine 1) the efficient anchor-node visiting route of mobile sink in terms of energy supply and 2) the efficient energy amount to be charged to each anchor node, by using the information of each anchor node and the mobile sink. Wireless sensor networks (WSNs) using mobile sinks can be deployed in more challenging environments such as those that are isolated or dangerous, and can also achieve a balanced energy consumption among sensors which leads to prolong the network lifetime. Most mobile sinks visit only some anchor nodes which store the data collected by the nearby sensor nodes because of their limited energy. The problem of these schemes is that the lifetime of the anchor nodes can be shorten due to the increased energy consumption, which rapidly reduces the overall lifetime of WSN. This study utilizes a mobile sink capable of wireless power transmission to solve this problem, so a mobile sink can gather data from anchor nodes while charging energy to them. Through the performance verification, it is confirmed that the number of blackout nodes and the amount of collected data are greatly improved regardless of the size of the network.

• 한국멀티미디어학회논문지
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• 제19권8호
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• pp.1460-1465
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• 2016

In this paper, we propose an energy efficient and multimedia traffic friendly MAC protocol (EEMF-MAC) that controls sender's wakeup period based on the data packet's transmission urgency and the receiver's wakeup periods based on the received data packet traffic loads. The protocol is useful for applications such as object tracking, real time data gathering, in which priority-based packet transmission is required. The basic idea of EEMF-MAC is that it uses the priority concept with transmission urgency of sender's data packet to reduce the transmission delay of the urgent data and it also uses duty cycling technique in order to achieve energy efficiency. EEMF-MAC showed a better performance in energy efficiency and packet transmission delay compared to existing protocols, RI-MAC and EE-RI-MAC.

• ETRI Journal
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• 제34권6호
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• pp.922-931
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• 2012

With the increasing demands for mobile wireless sensor networks in recent years, designing an energy-efficient clustering and routing protocol has become very important. This paper provides an analytical model to evaluate the power consumption of a mobile sensor node. Based on this, a clustering algorithm is designed to optimize the energy efficiency during cluster head formation. A genetic algorithm technique is employed to find the near-optimal threshold for residual energy below which a node has to give up its role of being the cluster head. This clustering algorithm along with a hybrid routing concept is applied as the near-optimal energy-efficient routing technique to increase the overall efficiency of the network. Compared to the mobile low energy adaptive clustering hierarchy protocol, the simulation studies reveal that the energy-efficient routing technique produces a longer network lifetime and achieves better energy efficiency.

• Journal of Communications and Networks
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• 제14권2호
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• pp.188-194
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• 2012

Cognitive networks (CNs) are capable of enabling dynamic spectrum allocation, and thus constitute a promising technology for future wireless communication. Whereas, the implementation of CN will lead to the requirement of an increased energy-arrival rate, which is a significant parameter in energy harvesting design of a cognitive user (CU) device. A well-designed spectrum-sensing scheme will lower the energy-arrival rate that is required and enable CNs to self-sustain, which will also help alleviate global warming. In this paper, spectrum sensing in a multi-user cognitive ad hoc network with a wide-band spectrum is considered. Based on the prospective spectrum sensing, we classify CN operation into two modes: Distributed and centralized. In a distributed network, each CU conducts spectrum sensing for its own data transmission, while in a centralized network, there is only one cognitive cluster header which performs spectrum sensing and broadcasts its sensing results to other CUs. Thus, a wide-band spectrum that is divided into multiple sub-channels can be sensed simultaneously in a distributed manner or sequentially in a centralized manner. We consider the energy consumption for spectrum sensing only of an analog-to-digital convertor (ADC). By formulating energy consumption for spectrum sensing in terms of the sub-channel sampling rate and whole-band sensing time, the sampling rate and whole-band sensing time that are optimal for minimizing the total energy consumption within sensing reliability constraints are obtained. A power dissipation model of an ADC, which plays an important role in formulating the energy efficiency problem, is presented. Using AD9051 as an ADC example, our numerical results show that the optimal sensing parameters will achieve a reduction in the energy-arrival rate of up to 97.7% and 50% in a distributed and a centralized network, respectively, when comparing the optimal and worst-case energy consumption for given system settings.