• Proceedings of the Korean Information Science Society Conference
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• 2003.10c
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• pp.229-231
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• 2003

기존에 제시된 ad hoc 라우팅 프로토콜에는 안정성에 대한 부분이 고려되어 있지 않다. 본 논문에서는 기존의 DSR ad hoc 라우팅 프로토콜에 안정성을 접목한 SDSR 라우팅 프로토콜을 제시한다. SDSR은 DSR에 안정성 제공을 위해 abnormal node detector와 neighbor table이라는 것을 추가한다. abnormal node detector는 네트워크 내에 abnormal 노드를 탐지해 네트워크에서 고립시켜 네트워크에 안정성을 제공하고 neighbor table에 있는 priority를 값에 따라 이웃 노드에서 들어온 패킷을 처리함으로써 효율적인 처리 능력을 제공한다. 본 논문에서는 abnormal node detector와 neighbor table을 통해 어떤 방식으로 네트워크에 안정성을 제공하는지 살펴보도록 하겠다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.3
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• pp.815-834
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• 2012

Recently, along with the innovative development of wireless communication techniques and mobile devices, mobile P2P services in mobile wireless networks have gained a lot of attention. In this paper, we propose a resource discovery scheme with data dissemination over mobile P2P networks. In the proposed scheme, each peer manages a local information table, a resource index table, and a routing table in a local database to enhance the accuracy and cost of resource discovery. The local information table stores the status of a mobile peer, and the resource index table stores the resource information of the neighbor peers via the ranking function. The routing table is used to communicate with the neighbor peers. We use a timestamp message to determine whether or not the resource index table will be changed before the resource information is exchanged. Our ranking function considers the interest and mobility of the mobile peer and prioritizes the resource information transmitted from the neighbor peers. It is shown via various experiments that the proposed scheme outperforms the existing scheme.

• IEMEK Journal of Embedded Systems and Applications
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• v.1 no.2
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• pp.104-112
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• 2006

ZigBee is the emerging industrial standard for ad hoc networks based on IEEE 802.15.4. It is used for low data rate and low power wireless network applications. Expected applications of ZigBee include wireless sensor networks for remote monitoring, home control, and industrial automation. Since one of the most important design goals of ZigBee is to reduce the installation and running costs, the ZigBee stack is embedded in the cheap and small micro-controller unit. The hierarchical routing algorithm is used for ZigBee end devices which have very limited resources. Using the block addressing scheme, end devices can send data to the destination without a routing table. However, hierarchical routing has the problem that the packets follow the tree hierarchy to the destination even if the destination is located nearby. In this paper, we propose a scheme to improve the hierarchical routing algorithm in ZigBee networks by employing the neighbor table that is originally used together with the routing table. We suggest selecting the neighbor node that has the minimum remaining hops to the destination as the next hop node. Simulation result shows that the proposed scheme saves more than 30% of the hop counts compared with the original hierarchical routing.

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.6
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• pp.721-729
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• 2016

CCN(Content-Centric Network) enables users to retrieve content using the content's name. Researchers face critical challenges in terms of mobility. Since the routing information is part of the content name, when the provider moves, it is necessary to update all the routers routing information. However, this requires significant costs. In this paper, we propose PNPCCN(Proactive Neighbor Pushing CCN), considering the popularity and rarity of mobility support, for providers in CCN environments. Via simulation studies, we demonstrate that our solutions are effective in terms of shorter numbers of retransmitted Interest packets, and average download times and higher delivery ratios during mobility.

• The Journal of the Korea Contents Association
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• v.10 no.9
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• pp.26-35
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• 2010

In this paper, we propose the peer indexing scheme using data dissemination considering content and mobility. The proposed scheme consists of an index table, a buddy table, a routing table to support the cost of data dissemination, the search accuracy and cost. In this proposed scheme, a neighbor peer is recognized through a signal function and the cost of data dissemination is reduced by timestamp message. The transmitted messages are stored in the index structure considering timestamp and weight of interests which improves search accuracy and reduces the cost of search.

• Journal of Korea Society of Industrial Information Systems
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• v.20 no.5
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• pp.25-35
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• 2015

Handoff is a critical issue for seamless roaming in IEEE 802.11-based wireless networks. In order to provide real-time services, handoff mechanism must be provided. However, the IEEE 802.11 standard handoff is not appropriate to provide the services, because it is based on the full-scanning approach which spends too much time searching Access Point (AP). In this paper, we propose a new scheme, which can reduce the scanning latency. A station performs full-scanning operation for finding APs when it enters wireless networks for the first time. The station sends the scanned channel information to AP. AP maintains the neighbor channel table based on the information received from stations. A station performs the partial-scanning by using the table. Therefore, the proposed scheme can reduce the scanning latency.

• Proceedings of the Korea Water Resources Association Conference
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• 1988.07a
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• pp.85-92
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• 1988

A model for the transient one-dimensional moisture movement in the saturated-unsaturated zone using a finite difference method is developed. Hysteresis in the soil water retention is incorporated. The model considers layered geologic formations. Monte Carlo simulation, together with the nearest neighbor model is used. Outputs of the model include pressure head, water content, and the water table elevation. Two Monte Carlo simulations of 100 realizations each are made for a 12-day simulation period with different input values. The simulation results show that the S.D. of the outputs increases with an increase in the input, the S.D. of the log K$$. The model is applied to predict a long term water table fluctuation, and the predicted water table agress well with the observed one.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.857-860
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• 2008

In this paper, we proposed cooperative based localization algorithm for wireless sensor networks, which can estimate to unknown node position using received signal strength table set. The unknown nodes are monitor to RSS from neighbor nodes and exclude existence possibility area of sensor node in sensor field. Finally, we can calculate the centroid position for each unknown node with cooperative localization algorithm. Furthermore, these processes are applied iteratively about all nodes which is recorded to RSS table and can estimate for unknown nodes.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.11 s.353
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• pp.44-53
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• 2006

In this paper, we propose a new Active Channel Scanning scheme by scanning active channels employed by neighbor APs' with the handover counts and non overlap channel information for fast handover. Under the proposed scheme, the mobile which has finished handover to connect a new APsends the neighbor AP's channel information learned by itself during handover to the new AP. And then, the new AP relays the neighbor channel information to the old AP. It decides a priority by handover counts and non overlap channel information for building a Neighbor Channel Table(NCT), and also sends the table information to its associated mobile nodes, periodically. As a result each mobile can scan only active neighbor APs' channels when performs handover based on the referring to NCT information. Using NS-2 Simulator, we applied to supposed ACS that the result of simulation decides to sort by handover counts and non overlap channel information. we evaluate our proposed ACS scheme based on NCT along with the full scanning scheme and the selective scanning scheme. From simulation results, we show that the proposed scheme is advantageous over the other two schemes in terms of the number of scanning channels and the scanning latency.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.4
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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.