• Journal of KIISE:Computing Practices and Letters
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• v.16 no.5
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• pp.561-565
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• 2010

Many methods have been researched to prolong sensor network lifetime using mobile technologies. In the mobile sink research, there are the track based methods and the anchor points based methods as representative operation methods for mobile sinks. However, the existing methods decrease Quality of Service (QoS) and lead the routing hotspot in the vicinity of the mobile sink. The reason is that they use static mobile paths that are not concerned about the network environments such as the query position and the data priority. In this paper, we propose the novel mobile sink operation method that solves the problems of the existing methods. In our method, the probing priority of the mobile sink is determined with the data priorities for increasing the QoS and the mobile features are used for reducing the routing hotspot. The experimental results show that the proposed method reduces query response time and improves network lifetime over the existing methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.6A
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• pp.617-625
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• 2011

In wireless sensor networks, data dissemination protocols have been proposed for mobile sink groups that are characterized by geographically staying closely and collective movement. They usually exploit flooding technology for mobility supporting and data delivery guarantee. However, it causes the excessive energy consumption of all sensor nodes in the group region due to data delivery participation. Moreover, the costs of the flooding would become higher in proportional to the group region. In this paper, we propose an energy efficient data dissemination scheme that resolves these problems. The virtual infrastructure called a 'pipe' is used as a rendezvous area. A source delivers data to the pipe, from which member sinks in the group retrieve it directly. Simulation results showed that this solution has better performance than existing protocols in terms of energy consumption as it reduces the number of regional flooding and eliminates unnecessary data flooding.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.3
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• pp.201-205
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• 2009

This paper addresses issues to efficiently collect and aggregate data of sources within a local and adjacent region in geographic routing for wireless sensor networks. We first introduce the concept of a local sink which collects and aggregates data form source nodes in the region and delivers the aggregated data to a global sink. We also design a model to determine an optimal location of the local sink and propose a mechanism to collect data through the local sink. Simulation results show that the proposed mechanism with the local sink is more efficient in terms of the energy and the data delivery ratio than the existing mechanism without the local sink in a geographic routing.

• Journal of KIISE
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• v.42 no.11
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• pp.1430-1440
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• 2015

In contrast with battery-based wireless sensor networks (WSNs), solar-powered WSNs can operate for a longtime assuming that there is no hardware fault. Meanwhile, a mobile sink can save the energy consumption of WSN, but its ineffective movement may incur so much energy waste of not only itself but also an entire network. To solve this problem, many approaches, in which a mobile sink visits only on clustering-head nodes, have been proposed. But, the clustering scheme also has its own problems such as energy imbalance and data instability. In this study, therefore, a cluster-based energy-aware data-sharing scheme (CE-DSS) is proposed to effectively support a mobile sink in a solar-powered WSN. By utilizing the redundant energy efficiently, CE-DSS shares the gathered data among cluster-heads, while minimizing the unexpected black-out time. The simulation results show that CE-DSS increases the data reliability as well as conserves the energy of the mobile sink.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.5
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• pp.79-85
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• 2009

A sink node and its neighbor nodes spend more energy than other nodes since a stationary sink node collects data from wireless sensor networks(WSNs). For larger WSNs, the unbalanced energy of nodes causes the operation of WSNs to stop rapidly. This paper proposes a data gathering method by adapting the mobile sink to prolong the life time of large WSNs. After partitioning a network into several clusters, a mobile sink visits each cluster and collects data from it. An efficient algorithm is proposed to improve the energy efficiency by delivering the message from the mobile sink to the cluster head as well as to reduce the data gathering delay, which is the disadvantage of the mobile sink. Also, The algorithm is analyzed for the energy consumption and the data gathering delay. The validity of the ananlysis result is confirmed by the simulation.

• Journal of the Korea Society of Computer and Information
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• v.25 no.2
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• pp.105-111
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• 2020

In this paper, we propose a scheme that minimizes the energy imbalance problem of solar-powered wireless sensor network (SP-WSN) using both a mobile sink capable of wireless power transfer and an efficient clustering scheme (including cluster head election). The proposed scheme charges the cluster head using wireless power transfer from a mobile sink and mitigates the energy hotspot of the nodes nearby the head. SP-WSNs can continuously harvest energy, alleviating the energy constraints of battery-based WSN. However, if a fixed sink is used, the energy imbalance problem, which is energy consumption rate of nodes located near the sink is relatively increased, cannot be solved. Thus, recent research approaches the energy imbalance problem by using a mobile sink in SP-WSN. Meanwhile, with the development of wireless power transmission technology, a mobile sink may play a role of energy charging through wireless power transmission as well as data gathering in a WSN. Simulation results demonstrate that increase the amount of collected data by the sink using the proposed scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.1B
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• pp.48-57
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• 2008

Wireless sensor networks are composed of a lot of sensor nodes and they are used to monitor environments. Since many studies on wireless sensor networks have considered a stationary sink node, they cannot provide fully ubiquitous applications based on a mobile sink node. In those applications, routing paths for a mobile sink node should be updated while a sink node moves in order to deliver sensor data without data loss. In this paper, we propose a method to continuously update routing paths for a mobile sink node which can be extended on hierarchical multi-hop routing protocols in wireless sensor networks. The efficiency of the proposed scheme has been validated through comparing existing method using a location based routing protocol by extensive computer simulation.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.1
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• pp.80-84
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• 2010

Data multicasting from a source to multiple sinks in wireless sensor networks is used to achieve both reducing communication costs and energy efficiency. Almost all existing schemes for the multicasting might be effectively performed by optimal construction of a multicasting tree between a source and multiple stationary sinks. However, in practical sensor applications, sinks could move around on the wireless sensor networks for own missions, such as scouting of soldiers and saving lives of victims by firefighters. Unfortunately, the sink mobility causes frequent entire reconstruction of the multicasting tree and thus it leads to exhaustion of battery power of sensors. Hence, we propose an energy-efficient multicast protocol to support multiple mobile sinks by the local multicast tree reconstruction, called Local Update-based geographic Multicasting for Mobile sinks (LUMM) for wireless sensor networks. Our simulation results show that our scheme for mobile sinks is more efficient in terms of energy resource management than other exist works.

• Proceedings of the KAIS Fall Conference
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• 2012.05b
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• pp.680-684
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• 2012

본 연구는 히트싱크의 효율적인 설계를 위하여 히트싱크 휜의 형상을 변화시켜 냉각성능에 대한 연구를 수행하였다. 휜의 형상을 Vertical, Round, S-Curve, Triangle의 네 가지와 휜의 개수를 16개와 64개로 설계해, 총 8가지로 설계 및 해석 하였다. 이와 같이 설계된 히트싱크는 Fluent 6.3.26 으로 수치해석 하였고, 해석 결과 약간의 형상을 변경하는 것 보다는 휜의 개수를 늘리는 것이 냉각성능을 높이는데 더 효과적인 것으로 드러났다. 히트싱크의 온도분포와 열전달계수에 대한 수치해석을 통해 휜의 개수가 64개이고 S-Curve의 형태에서 냉각성능이 가장 우수한 것으로 나타났다.

• Proceedings of the Korean Information Science Society Conference
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• 2008.06d
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• pp.181-184
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• 2008

근래에 센서 네트워크 내의 싱크 노드 이동에 대한 많은 연구가 이루어지고 있다. 이들 연구의 대부분은 싱크 노드의 이동으로 인한 데이터 손실을 최소화하거나 싱크 노드가 소스 노드의 위치를 인식하는 것에 초점을 맞추고 있다. 그러나 센서 네트워크는 그 특성 상 노드의 에너지 공급이 매우 어렵기 때문에 에너지 절약이 데이터 손실 방지 못지 않게 중요하다. 본 논문에서는 모바일 싱크 노드를 가진 센서 네트워크에서 에너지 소모량을 최소화할 수 있는 라우팅 기법을 제안하고, NS2를 이용하여 이 기법을 구현한다. 또한, 이 시뮬레이션을 통해 센서 네트워크의 에너지 소모량을 측정한다. 그 결과, 기존의 에너지 효율적인 라우팅 프로토콜인 Pulse 프로토콜과 에너지 효율 면에서 유사함을 보인다.