• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.765-766
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• 2008

In this paper, It has been emphasized of important path access during transmit of node when each node transmit broadcast service which one's of new MANET (Mobile Ad hoc Networks) of autonomy and mobility network structures. It has proposed analysis methods are hierarchical path structure of transmit which experience context aware through confidence to network connectivity alone as issue which can be reduce duplicate of beam forming on networks and maintenance one's of method got to optimized of transmission network that status information of context awareness using ad hoc ODDMRP(Ontology Doppler effect Dynamic Multicast Routing Protocol) path method.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.9
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• pp.31-40
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• 1997

This paper presents a hybrid WDM/TDM channel acess protocol for high speed WDM networks based on passive double star topology. In the proposed scheme, all nodes in a network are splitted into groups forming passive double star topology and each node has a tunable transmitter and a fixed receiver. WDM channels are allocated to the groups, which are used as home channels to transmit or receive packets. TDM frames of the WDM channel are composed of the same number of slots as that of groups, and all nodes in a group transmit packets simultaneously at each slot. The proposed scheme reduces the system complexity and the number of the required WDM channels. It was proved that the proposed protocol is less sensitive to the propagation delay and maintaining its superior transmission performance by employing the efficient transmission schedule based on passive double star topology.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.05a
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• pp.1461-1464
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• 2005

In contrast with conventional networks, mobile ad hoc networks usually do not provide online access to trusted authorities or to centralized servers, and they exhibit frequent partitioning due to link and node failures and node mobility. For these reasons, traditional security solutions that require online trusted authorities or certificate repositories, but those are not well-suited for securing ad hoc networks. Moreover, a fundamental issue of securing mobile ad hoc networks is to ensure mobile nodes can authenticate each other. Because of its strength and efficiency, public key and digital signature is an ideal mechanism to construct the authentication service. Although this is already mature in the internet application, providing public key based authentication is still very challenging in mobile ad hoc networks. In this paper I propose a secure public key authentication service based on clustering model and trust model to protect nodes from getting false public keys of the others efficiently when there are malicious nodes in the network.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.11
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• pp.5290-5304
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• 2016

With the growth of the massive amount of data, the failure probability of the cloud storage node is becoming more and more big. A single fault tolerance strategy, such as replication and erasure codes, has some unavoidable disadvantages, which can not meet the needs of the today's fault tolerance. Therefore, according to the file access frequency and size, an adaptive hybrid redundant fault tolerance strategy is proposed, which can dynamically change between the replication scheme and erasure codes scheme throughout the lifecycle. The experimental results show that the proposed scheme can not only save the storage space(reduced by 32% compared with replication), but also ensure the fast recovery of the node failures(increased by 42% compared with erasure codes).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.3A
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• pp.287-295
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• 2011

Cognitive radio (CR) features opportunistic access to spectrum when licensed users (LU) are not operating. To avoid interference to LU, cognitive users (CU) need to perform spectrum sensing. Because of local shadowing, fading, or limited sensing capability, it is suggested that multiple CUs cooperate to detect LU. In cooperative spectrum sensing, CUs should exchange their sensing data with minimum bandwidth and delay. In this paper, we introduce a novel method to efficiently report sensing data to the central node in an infrastructured OFDM-based CR network. All CUs simultaneously report their sensing data over unique and orthogonal signals on locally available subcarriers. By detecting the signals, the central node can determine subcarrier availability for each CU. Implementation challenges are identified and then their solutions are suggested. The proposed method is evaluated through simulation on a realistic channel model. The results show that the proposed method is feasible and efficient.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.1417-1420
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• 2004

The combination of Fast-Handoff and Hierarchical Mobile IPv6 (F-HMIPv6) allows the anticipation of the layer3 handoff such that data traffic can be efficiently redirected to the mobile node's new location before it moves there. However, after moving to the new Access Router (NAR), if the mobile node (MN) sends the Local Binding Update (LBU) to the Mobility Anchor Point (MAP) before receiving all of the buffered packet from the NAR, the MN may receive the general packet from the MAP. That is, the MN may simultaneously receive two types of packet which has different sequence number. These cause the confusion in packet order, and the MN sends the dup ack for the packet retransmission to the CN. It results in the degradation of the TCP performance. Therefore, we propose the scheme for minimizing the out-of-sequence packet in F-HMIPv6.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.04a
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• pp.594-596
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• 2011

PMIPv6 (Proxy Mobile IPv6)은 MN (Mobile Node)를 대신하여 액세스 망에서 MN의 이동성을 지원하는 네트워크 기반의 이동성 관리 프로토콜이다. 기존의 PMIPv6는 MN과 Corespondent Node (CN) 간 통신을 할 때, 교환하는 데이터 패킷은 LMA (Local Mobility Anchor)를 경유하고 MAG (Mobile Access Gateway)를 경유해서 전송하기 때문에 시그널링 코스트가 증가하고 전송 지연 문제가 발생한다. 따라서 본 논문은 MN이 도메인 내 핸드오버를 했을 시, LMA에서 MAG를 경유하지 않는 경로 최적화를 제시한다.

• Journal of IKEEE
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• v.26 no.1
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• pp.67-76
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• 2022

In this paper, we propose a new algorithm to improve the accuracy of the Wi-Fi access point (AP) positioning technique. The proposed algorithm based on evaluating the trustworthiness of the signal strength quality of each measurement node is superior to other existing AP positioning algorithms, such as the centroid, weighted centroid, multilateration, and radio distance ratio methods, owing to advantages such as reduction of distance errors during positioning, reduction of complexity, and ease of implementation. To validate the performance of the proposed algorithm, we conducted experiments in a complex indoor environment with multiple walls and obstacles, multiple office rooms, corridors, and lobby, and measured the corresponding AP signal strength value at several specific points based on their coordinates. Using the proposed algorithm, we can obtain more accurate positioning results of the APs for use in research or industrial applications, such as finding rogue APs, creating radio maps, or estimating the radio frequency propagation properties in an area.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.2
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• pp.287-293
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• 2013

Cognitive radio has been recently proposed to dynamically access unused-spectrum. The CR users can share the same frequency band with the primary user without interference to each other. Usually each CR user needs to determine spectrum availability by itself depending only on its local observations. But uncertainty communication environment effects can be mitigated so that the detection probability is improved in a heavily shadowed environment. Soft detection is a primary user detection method of cooperative cognitive radio networks. In our research, we will improve system detection probability by using optimal cooperative node selection algorithm. New algorithm can find optimal number of cooperative sensing nodes for cooperative soft detection by using maximum ratio combining (MRC) method. Through analysis, proposed cooperative node selection algorithm can select optimal node for cooperative sensing according to the system requirement and improve the system detection probability.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.6
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• pp.169-174
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• 2014

Practical deployment methods for sensor nodes are demanding as applications using sensor nodes increase. In particular, node connectivity is crucial not only for the network longevity but also for direct impacts on sensing and data collection capability. Economic requirement at building sensor networks and often limited access for sensor fields due to hostile environment force to remain at random deployment from air. However, random deployment often result in lost connection problem and inefficient network topology issue due to node irregularity. In this paper, mixed deployment of key nodes that have better communication capability is proposed to support the original deployment into working in an efficient way. Node irregularity is improved by introducing mixed nodes and an efficient mixed node density is also analyzed. Simulation results show that the mixed deployment method has better performance than the existing deployment methods.