• The Journal of Korean Institute of Communications and Information Sciences
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• 제25권1A호
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• pp.104-113
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• 2000

In this paper, we propose a protocol that makes use of a concept of a meta-group based on propagation trees to deal with duplicated members of the same multicast group. It is shown that, if multicast tree is composed ofthese meta-groups, the depth of the tree can be shortened and the ordering of the multicast that communicatesbetween multiple senders and receivers can be easier. In the protocol, we assign a Designated Manager(DM) toeach meta-group and make each DM do the role of the representative receiver of the meta group. In this Paper,the DM's are supposed to handle ACK and retransmission for the members in the same meta group. Hence, theDM's distribute the ACK from senders, and they can reduce the burden of senders by shortening commit delaytime. We also show, through a simulation analysis, that the new multicast protocol outperforms the existing onesnot only in message costs but also in commit delay times.

• The Transactions of the Korea Information Processing Society
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• 제6권2호
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• pp.299-306
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• 1999

Considers the problem to update the spanning tree and strongly-connected components in response to topology change of the network. This paper proposes a distributed algorithm that solves such a problem after several processors and links are added and deleted. Its message complexity and its ideal-time complexity are O(n'log n'+ (n'+s+t)) and O(n'logn') respectively where n'is the number of processors in the network after the topology change, s is the number of added links, and t is the total number of links in the strongly connected component (of the network before the topology change) including the deleted links.

• Smart Media Journal
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• 제10권4호
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• pp.15-20
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• 2021

The distributed trigger counting problem is to notify the user when the total number of triggers received from a distributed system consisting of n nodes reaches a predefined value w. The distributed trigger counting problem is used for monitoring and global snapshots in various distributed systems. In this paper, we propose a simple and efficient algorithm for the distributed trigger counting problem. The proposed algorithm operates based on a tree structure of degree $\sqrt{n}$ and height 2. The proposed algorithm operates in three different phases based on the remaining number of triggers. Experimental results show that the proposed algorithm has a smaller message complexity than CoinRand, and MaxRcv also performed better when the number of nodes is not large.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제30권5C호
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• pp.415-421
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• 2005

Passive RFID tag does not have its own power, so it has very poor computation abilities and it can deliver signals in very short range. From the facts, most RFID Tag security schemes assumed that the backward channel from tags to a reader is safe from eavesdropping. However, eavesdroppers near a tag can overhear message from a tag illegally. In this paper, we propose a method to protect the backward channel from eavesdropping by illegal readers. The proposed scheme can overcome the problems of conventional schemes such as randomized tree walking, which have been proposed to secure tag information in tree-walking algorithm as an anti-collision scheme for RFID tags. We showed the efficiency of our proposed method by using an analytical model, and it is also shown that the proposed method can provide the probability of eavesdropping in some standardized RFID tag system such as EPCglobal, ISO, uCode near to '0'.

• Journal of the Korea Computer Industry Society
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• 제6권3호
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• pp.539-550
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• 2005

The spanning tree, which is being used the most widely in indoor wiring network, is chosen for the network topology of the optimal LAN design. To apply a spanning tree to GA, the concept of $Pr\ddot{u}fer$ numbers is used. $Pr\ddot{u}fer$ numbers can express he spanning tree in an efficient and brief way, and also can properly represent the characteristics of spanning trees. This paper uses Pareto Stratum-Niche Cubicle(PS-NC) GA by complementing the defect of the same priority allowance in non-dominated solutions of pareto genetic algorithm(PGA). By applying the PS-NC GA to the LAN design areas, the optimal LAN topology design in terms of minimizing both message delay time and connection-cost could be accomplished in a relatively short time. Numerical analysis has been done for a hypothetical data set. The results show that the proposed algorithm could provide better or good solutions for the multi-objective LAN design problem in a fairly short time.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 한국정보통신학회 2021년도 추계학술대회
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• pp.194-198
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• 2021

LoRa is a physical layer technology that is designed to provide a reliable long-range communication with introducing CSS and with introducing a loco parentis tree network. Since a leaf can utilize multiple parents at the same time with a single transmission, PDR increases logarithmically as the number of gateways increases. Because of the ALOHA-like MAC of LoRa, however, the PDR degrades even under the loco parentis tree topology similarly to the single-gateway environment. Our proposed method is aimed to achieve SDMA approach to reuse the same frequency in different areas. For that purpose, it elaborately controls each TxPower of the senders for each message in concurrent transmission to survive the collision at each different gateway. The gain from this so-called capture effect increases the capacity of resource-hungry LPWAN. Compared to a typical collision-free controlled-access scheme, our method outperforms by 10-35% from the perspective of the total count of the consumed time slots. Also, due to the power control mechanism in our method, the energy consumption reduced by 20-40%.

• Journal of applied mathematics & informatics
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• 제17권1_2_3호
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• pp.1-23
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• 2005

The shortest-paths problem is a fundamental problem in graph theory and finds diverse applications in various fields. This is why shortest path algorithms have been designed more thoroughly than any other algorithm in graph theory. A large number of optimization problems are mathematically equivalent to the problem of finding shortest paths in a graph. The shortest-path between a pair of vertices is defined as the path with shortest length between the pair of vertices. The shortest path from one vertex to another often gives the best way to route a message between the vertices. This paper presents an $O(n^2)$ time sequential algorithm and an $O(n^2/p+logn)$ time parallel algorithm on EREW PRAM model for solving all pairs shortest paths problem on circular-arc graphs, where p and n represent respectively the number of processors and the number of vertices of the circular-arc graph.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제26권5A호
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• pp.889-901
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• 2001

본 논문에서 Multiprotocol Label Switching 시스템을 위한 Label Distribution Protocol의 개발과 분석에 관해서 기술한다. 먼저 Gigabit Switched Router를 만들기 위해서, 상용화시 Carrier Class 제품에 적용하기 위한 LDP의 구현시 고려해야 될 사항에 대해 살피고, 상세 설계를 제안한다. IETF 표준에 의거한 LDP의 구현을 위한 상세 설계는 프로토콜 상태기계의 유도 트리와 프로세스 대수를 사용한 형식적 명세를 사용하여 제시한다. 본 논문에서는 제시된 유도트리와 프로세스 대수를 사용한 프로토콜 동작의 분석을 통해, 구현된 LDP의 상호 연동성과 완전성, 생존성, 도달성, 안전성을 검증한다. 또한 이를 사용하여 구현된 LDP가 기존 상용 제품들과의 연동성과 그 동작의 신뢰성을 확보할 것을 기대한다. 결과적으로 구현된 LDP의 프로토콜 동작들의 검증을 제공한다.

• Genomics & Informatics
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• 제6권3호
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• pp.157-159
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• 2008

Multiple sequence alignment (MSA) is the most important step for many of biological sequence analyses, homology search, and protein structural assignments. However, large amount of data make biologists difficult to perform MSA analyses and it requires much computational time to align many sequences. Here, we have developed a simple and fast web alignment tool for aligning, editing, and visualizing large amount of sequence data. We used a cluster server installed ClustalW-MPI using web services and message passing interface (MPI). It also enables users to edit multiple sequence alignments for manual editing and to download the input data and results such as alignments and phylogenetic tree.

• Journal of Convergence Society for SMB
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• 제4권4호
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• pp.19-23
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• 2014

Group communication is becoming increasingly popular in Internet applications such as videoconferences, online chatting programs, games, and gambling. For secure communications, the integrity of messages, member authentication, and confidentiality must be provided among group members. To maintain message integrity, all group members use the Group Key (GK) for encrypting and decrypting messages while providing enough security to protect against passive attacks. Tree-based Group Diffie-Hellman (TGDH) is an efficient group key agreement protocol to generate the GK. TGDH assumes all members have an equal computing power. One of the characteristics of distributed computing and grid environments is heterogeneity; the member can be at a workstation, a laptop or even a mobile computer. Member reordering in the TDGH protocol could potentially lead to an improved protocol; such reordering should capture the heterogeneity of the network as well as latency. This research investigates dynamic reordering mechanisms to consider not only the overhead involved but also the scalability of the proposed protocol.