• The KIPS Transactions:PartA
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• v.11A no.5
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• pp.341-346
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• 2004

Recently A Hyper-Star Graph HS(m, k) has been introduced as a new interconnection network of new topology for parallel processing. Hyper-Star Graph has properties of hypercube and star graph, further improve the network cost of a hypercube with the same number of nodes. In this paper, we show that Hyper-Star Graph HS(m, k) is subgraph of hypercube. And we also show that regular graph, Hyper-Star Graph HS(2n, n) is node-symmetric by introduced mapping algorithm. In addition, we introduce an efficient one-to-all broadcasting scheme - takes 2n-1 times - in Hyper-Star Graph HS(2n, n) based on a spanning tree with minimum height.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05a
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• pp.289-292
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• 2003

인터넷이 발전함에 따라 네트워크 시스템의 토폴로지 설계에 관한 여러 가지 문제들에 대한 관심이 증가하고 있다. 이러한 네트워크의 토폴로지 구조는 서비스 센터, 터미널(사용자), 연결 케이블로 이루어져 있다. 근래에 이런 네트워크 시스템들은 사용자들로부터의 요구사항이 많아지고 있기에 주로 광케이블로 구축하는 경우가 점차 늘어나고 있다지만, 광케이블의 비판 비용을 고려하면 네트워크의 구조가 스패닝 트리(spanning tree)로 구축되어 지는 것이 바람직하다고 볼 수 있다. 네트워크 토폴로지 설계 문제들은 연결비용, 평균 메시지 지연, 네트워크 신뢰도 등과 같은 설계 기준들을 최적으로 만족하는 토폴로지를 탐색하는 것으로 정의될 수 있다. 최근에 유전자 알고리즘(GA)은 네트워크 최적화 문제, 조합 최적화 문제, 다목적 최적화 문제 등과 같은 관련된 분야에서 많은 연구들이 이루어지고 있으며 또한, 많은 실세계의 문제를 위한 최적화 기술로서 그 잠재력을 매우 주목 받고 있다. 본 논문에서는 연결비용, 평균 메시지 지연, 네트워크 신뢰도를 고려하여, 광케이블로 구성되어 지는 광대역통신 네트워크의 2목적 네트워크 토폴로지 설계 문제들을 풀기 위한 GA를 제안한다. 또한, 후보 네트워크 토폴로지 구조를 염색체(chromosome)로 표현하기 위해 Prtifer수(PN_와 클러스터 스트링으로 구성되어지는 새로운 엔코딩 방법도 제안한다. 마지막으로 수치예를 통해 제안한 GA의 성능을 평가할 것이다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.3
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• pp.586-597
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• 2004

MAC (Medium Access Control) protocol is necessary for a OLT (Optical Line Termination) to allocate bandwidth to ONUs (Optical Network Units) dynamically in ATM PON (Passive Optical Network) operated in a kind of optical subscriber network having tree topology. The OLT collect information about ONUs and provide all permission with each ONU effectively by means of MAC protocol. Major functions of MAC protocol are composed of the algorism for distributing permission demanded by a ONU dynamically and allocation all permission used in APON properly. Sometimes MAC get to be a element of limiting the whole operation speed and occupy a most frequent operation part of the TC (Transmission Convergence) function module so it have to be designed to guarantee the best quality for each traffic. This paper introduce the way of implementation of a algorism which satisfy all of the upper renditions. This MAC algorism allocate bandwidth according to a number of working ONU and the information of the queue length dynamically and distribute permission for same interval to minimize delay variation of each ONU cell. MAC scheduler for the dynamic bandwidth allocation which is introduced in this paper has look-up table structure that makes programming possible. This structure is very suitable for implementation and operated in high speed because it require very simple and small chip size.

• Journal of Information Processing Systems
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• v.15 no.2
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• pp.440-448
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• 2019

The Internet of Things (IoT) is one of the main enablers for situation awareness needed in accomplishing smart cities. IoT devices, especially for monitoring purposes, have stringent timing requirements which may not be met by cloud computing. This deficiency of cloud computing can be overcome by fog computing for which fog nodes are placed close to IoT devices. Because of low capabilities of fog nodes compared to cloud data centers, fog nodes may not be deployed with all the services required by IoT devices. Thus, in this article, we focus on the issue of fog service placement and present the recent research trends in this issue. Most of the literature on fog service placement deals with determining an appropriate fog node satisfying the various requirements like delay from the perspective of one or more service requests. In this article, we aim to effectively place fog services in accordance with the pre-obtained service demands, which may have been collected during the prior time interval, instead of on-demand service placement for one or more service requests. The concept of the logical fog network is newly presented for the sake of the scalability of fog service placement in a large-scale smart city. The logical fog network is formed in a tree topology rooted at the cloud data center. Based on the logical fog network, a service placement approach is proposed so that services can be placed on fog nodes in a resource-effective way.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.12
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• pp.5819-5840
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• 2018

Considering the topology of hierarchical tree structure, each cluster in WSNs is faced with various attacks launched by malicious nodes, which include network eavesdropping, channel interference and data tampering. The existing intrusion detection algorithm does not take into consideration the resource constraints of cluster heads and sensor nodes. Due to application requirements, sensor nodes in WSNs are deployed with approximately uncorrelated security weights. In our study, a novel and versatile intrusion detection system (IDS) for the optimal defense strategy is primarily introduced. Given the flexibility that wireless communication provides, it is unreasonable to expect malicious nodes will demonstrate a fixed behavior over time. Instead, malicious nodes can dynamically update the attack strategy in response to the IDS in each game stage. Thus, a multi-stage intrusion detection game (MIDG) based on Bayesian rules is proposed. In order to formulate the solution of MIDG, an in-depth analysis on the Bayesian equilibrium is performed iteratively. Depending on the MIDG theoretical analysis, the optimal behaviors of rational attackers and defenders are derived and calculated accurately. The numerical experimental results validate the effectiveness and robustness of the proposed scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8B
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• pp.637-646
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• 2012

Recently, Wireless Sensor Networks (WSNs) are used in many applications. When sensor nodes are deployed on special areas, where humans have any difficulties to get in, the nodes form network topology themselves. By using the sensor nodes, users are able to obtain environmental information. Due to the lack of the battery capability, sensor nodes should be efficiently managed with energy consumption in WSNs. In specific applications (e.g. in intrusion detections), intruders tend to occur unexpectedly. For the energy efficiency in the applications, an appropriate algorithm is strongly required. In this paper, we propose tree-based routing algorithm for the specific applications, which based on the intrusion detection. In addition, In order to decrease traffic density, the proposed algorithm provides enhanced method considering link cost and load balance, and it establishes efficient links amongst the sensor nodes. Simultaneously, by using the proposed scheme, parent and child nodes are (re-)defined. Furthermore, efficient routing table management facilitates to improve energy efficiency especially in the limited power source. In order to apply a realistic military environment, in this paper, we design three scenarios according to an intruder's moving direction; (1) the intruder is passing along a path where sensor nodes have been already deployed. (2) the intruders are crossing the path. (3) the intruders, who are moving as (1)'s scenario, are certainly deviating from the middle of the path. In conclusion, through the simulation results, we obtain the performance results in terms of latency and energy consumption, and analyze them. Finally, we validate our algorithm is highly able to adapt on such the application environments.

• Horticultural Science & Technology
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• v.29 no.6
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• pp.655-658
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• 2011

A new cultivar 'Hongan' was originated from an artificial cross between 'Fuji' and 'Jonathan' carried out at National Institute of Horticultural & Herbal Science in 1993. The cultivar was preliminarily selected among the elite siblings for its high fruit quality in 2002. After regional adaptability test at five districts for subsequent four years as 'Wonkyo Ga-32', it was finally selected in 2006. 'Hongan' is characterized by the following. Optimum harvest time is late September. Shape of the mature fruit at 309 g on mean weight is globosity with a light red skin on a greenish yellow ground and yellowish white flesh. The fruit contains favorable total soluble solids at $13.7^{\circ}Brix$ and an acidity at 0.28%. Safe storage period for the fruit is 3 weeks at room temperature. It is resistant to Bitter rot. 'Hongan' also reveals a physiological cross compatibility with leading cultivars such as 'Gamhong' and 'Tsugaru' in addition to its maternal parent 'Fuji'. Tree topology is semi-spreading with vigorous growth habit.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.1C
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• pp.89-96
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• 2012

Since tactical robots are going to be grown and tactical data communications will be more network-centric, the reliability of wireless tactical data networks is going to be very important in the future. However, the connectivity of such wireless tactical data networks can be extremely uncertain in practical circumstances. In this paper, we propose a searching technique to find out the weak boundary area of the network connectivity using a small UAV(unmanned aerial vehicle) which has a simple polling access function to wireless nodes on the ground in wireless tactical data networks. The UA V calculates the network topology of the wireless tactical data networks and coverts it to the Lapalcian matrix. In the proposed algorithm, we iteratively search the eigenvalues and find a minimum cut in the network resulting in finding the weak boundary of the connectivity for the wireless tactical data networks. If a UAV works as a relay nodes for the weak area, we evaluate that the throughput performance of the proposed algorithm outperforms star connection method and MST(minimum Spanning Tree) connection method. The proposed algorithm can be applied for recovering the connectivity of wireless tactical data networks.

• Horticultural Science & Technology
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• v.33 no.5
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• pp.784-788
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• 2015

A new cultivar 'Picnic' originated from an artificial cross between 'Fuji' and 'Sansa' at National Institute of Horticultural & Herbal Science in 1994. The cultivar was preliminarily selected among the elite siblings for its high fruit quality in 2003. After regional adaptability tests in five districts for four subsequent years as 'Wonkyo Ga-34', it was ultimately selected in 2008. Optimum harvest time is late September. Mature fruit has mean weight of 233 g and is conic with light red skin on a greenish yellow ground and yellowish white flesh. The fruit contains a favorable total soluble solids content at $13.8^{\circ}Brix$ and titratable acidity at 0.43%, which results in gustatory harmony between sugars and acids. It is not resistant to bitter rot or Marssonina blotch. 'Picnic' exhibits a physiological cross compatibility with leading cultivars such as 'Fuji', 'Hongro' and 'Tsugaru'. Tree topology is semi-spreading with a weak growth habit.

• Journal of Internet Computing and Services
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• v.5 no.5
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• pp.27-37
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• 2004

The existing ad hoc network protocols suffer the scalability problem due to the inherent characteristics of node mobility. Cluster-based routing protocols divide the member nodes into a set of clusters and perform a hierarchical routing between these clusters. This hierarchical feature help to improve the scalability of ad hoc network routing. However, previous k-hop cluster-based routing protocols face another problems, that is, control overhead of the cluster headers. This paper proposes a novel k-hop cluster-based routing scheme with delegation functions for mobile ad hoc networks. The scheme employs is based on tree topology to manage cluster members in effectively. The cluster headers do not manage the routing table for whole members, while the header keeps the routing table for its neighbor members and the member list for one hop over nodes within k-hop cluster. Then the in-between leveled nodes manage the nested nodes which is structured in the lower level. Therefore, the proposed mechanism can reduce some control overhead of the cluster leaders.