• The KIPS Transactions:PartC
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• v.14C no.1 s.111
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• pp.95-104
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• 2007

Mobile multimedia services such as TV-call or video streaming are gradually becoming popular in the 3rd or more generation mobile network (IMT-2000). Multimedia traffic is expected to continue increasing into the coming years, and IP technology is considered to be the efficient way of transporting such huge volumes of multimedia traffic. IP-based IMT network platform represents an evolution from IMT-2000. The structure of IP-based IMT network as ubiquitous platform is three-layered model : Middleware including Network Control PlatForm (NCPF) and Service Support PlatForm (SSPF), IP-BackBone (IP-BB), access network including sensor network. Mobility Management (MM) architecture in NCPF is proposed for IP-based IMT network in order to manage routing information and location information separately. The generous existing method of multicast control in IP-based IMT network is Remote Subscription. But Remote Subscription has problem that should be reconstructed whole multicast tree when sender in multicast tree moves to another area. To solve this problem, we propose the way to put Multicast-manager in NCPF.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.3B
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• pp.339-348
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• 2004

Packet classification is an important factor to support various services such as QoS guarantee and VPN for users in Internet. Packet classification is a searching process for best matching rule on rule tables by employing multi-field such as source address, protocol, and port number as well as destination address in If header. In this paper, we propose hardware based packet classification algorithm by employing tree bitmap of multi-bit trio. We divided prefixes of searching fields and rule into multi-bit stride, and perform a rule searching with multi-bit of fixed size. The proposed scheme can reduce the access times taking for rule search by employing indexing key in a fixed size of upper bits of rule prefixes. We also employ a marker prefixes in order to remove backtracking during searching a rule. In this paper, we generate two dimensional random rule set of source address and destination address using routing tables provided by IPMA Project, and compare its memory usages and performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.11
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• pp.763-770
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• 2014

In traditional routing protocols including LEACH for wireless sensor networks, nodes suffer from unbalanced energy consumption because the nodes require large transmission energy as the distance to the sink node increase. Multi-hop based routing protocols have been studied to address this problem. In existing protocols, each cluster head usually chooses the closest head as a relay node. We propose LEACH-CHT, in which cluster heads choose the path with least energy consumption to send data to the sink node. In our research, each hop, a cluster head selects the least cost path to the sink node. This method solves the looping problem efficiently as well as make it possible that a cluster head excludes other cluster heads placed farther than its location from the path, without additional energy consumption. By balancing the energy consumption among the nodes, our proposed scheme outperforms existing multi-hop schemes by up to 36% in terms of average network lifetime.

• Journal of the Korea Society of Computer and Information
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• v.14 no.10
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• pp.11-22
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• 2009

For a wireless ad-hoc network, event routing algorithm of the publish/subscribe system is especially important for the performance of the system because of the dynamic characteristic and constraint network of its own. In this paper, we propose a new hybrid event routing algorithm. TopSim for efficient publish/subscribe system on the wireless ad-hoc network by extending the ShopParent algorithm by considering not only network overheads to choose a Parent of the publish/subscribe tree, but also topic similarity which is closeness of subscriptions. Our evaluation shows our proposed TopSim performs better for the case where a new joining node subscribed to the multiple topics and there is a node among Parent candidate nodes who subscribe to the ones in the list of multiple topics (related topics).

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.1
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• pp.10-15
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• 2002

This paper proposes the Pipelined Broadcast that broadcasts a message of size m in O(m+n-1) time in an n-dimensional hypercube. It is based on the replication tree, which is derived from the reachable sets. It greatly improves the performance compared to Ho-Kao s algorithm with the time of O(m[n/log(n+1)]). The communication in the broadcast uses all-port wormhole router with message replication capability. This paper includes the algorithm together with performance comparisons to previous schemes in practical implementation.

• Journal of Korea Multimedia Society
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• v.2 no.4
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• pp.451-458
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• 1999

This paper considers the problem of routing connections in multi-optical tree network using WDM (Wavelength Division Multiplexing), where each connection between a pair of nodes in the network is assigned a path through the network and a wavelength on that path, such that connections whose paths share a common link in the network are assigned different wavelengths. The problem of optimal colouring of paths on multi-optical network is NP-hard[1], but if that is the colouring of all paths, then there exists an efficient polynomial time algorithm. In this paper, using divided & conquer method we gave an efficient algorithm to assign wavelengths to the all paths of a tree network based on the theory of (7) and our time complexity $O(n^4log\; n)$.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.04a
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• pp.623-626
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• 2010

최근 무선 네트워크 기술이 점차 각광을 받으면서 다양한 애드 혹 환경에서의 라우팅 프로토콜이 제안되고 있다. 하지만 애드 혹 네트워크라는 환경의 특성 상 보안상 취약한 문제점을 가지고 있으며, 기존의 유선 네트워크 환경에서 제안되었던 보안 라우팅 프로토콜을 적용시키기 힘들다는 문제점이 있다. 이에 따라 보안성을 보완한 새로운 애드 혹 라우팅 프로토콜이 제안되었지만 다양한 무선 네트워크 환경의 변화에 유동적으로 대응하기 힘들고 보안적인 측면에 집중을 한 나머지 에너지소모 측면에서는 단점을 노출하고 있다. 본 논문에서는 다양한 애드 혹 네트워크 환경에 적용 가능하고, 기존의 보안 라우팅 프로토콜에 비해 에너지 효율적인 보안 라우팅 프로토콜을 제안하고자 한다. 보안 정보의 보호를 위해 Tree 구조를 도입하고 보안 단계를 통한 Multi-path를 구성하여 악의적인 노드의 Dropping Attack에 대비하고, 예기치 못한 Data Packet의 손실에 대해서도 효율적으로 대처하게 하였다. 실험 결과 악의적인 노드가 존재하는 네트워크 환경에서 기존의 애드 혹 네트워크 보안 라우팅 프로토콜보다 21%정도의 패킷 전송 성공률을 높일 수 있었으며 또한 각 노드의 에너지를 균등하게 소모함으로써 전체적인 네트워크의 생존시간이 연장되는 것을 확인할 수 있었다.

• The KIPS Transactions:PartC
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• v.15C no.5
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• pp.329-342
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• 2008

The Sensor Networks have limitations in utilizing energies, developing energy-efficient routing protocol and secure routing protocol are important issues in Sensor Network. In the field of data management, Tributaries and Deltas(TD) which incorporates tree topology and multi-path topology effectively have been suggested to provide efficiency and robustness in data aggregation. And our research rendered hierarchical property to TD and proposed Clustering-based Tributaries-Deltas. Through this new structure, we integrated efficiency and robustness of TD structure and advantages of hierarchical Sensor Network. Clustering-based Tributaries-Deltas was proven to perform better than TD in two situations through our research. The first is when a Base Station (BS) notices received information as wrong and requests the network's sensing data retransmission and aggregation. And the second is when the BS is mobile agent with mobility. In addition, we proposed key establishment mechanism proper for the newly proposed structure which resulted in new Sensor Network structure with improved security and energy efficiency as well. We demonstrated that the new mechanism is more energy-efficient than previous one by analyzing consumed amount of energy, and realized the mechanism on TmoteSKY sensor board using TinyOS 2.0. Through this we proved that the new mechanism could be actually utilized in network design.

• Journal of Internet Computing and Services
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• v.10 no.5
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• pp.65-78
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• 2009

The most commonly adopted approach to find valuable information from tree data is to extract frequently occurring subtree patterns from them. Because mining frequent tree patterns has a wide range of applications such as xml mining, web usage mining, bioinformatics, and network multicast routing, many algorithms have been recently proposed to find the patterns. However, existing tree mining algorithms suffer from several serious pitfalls in finding frequent tree patterns from massive tree datasets. Some of the major problems are due to (1) modeling data as hierarchical tree structure, (2) the computationally high cost of the candidate maintenance, (3) the repetitious input dataset scans, and (4) the high memory dependency. These problems stem from that most of these algorithms are based on the well-known apriori algorithm and have used anti-monotone property for candidate generation and frequency counting in their algorithms. To solve the problems, we base a pattern-growth approach rather than the apriori approach, and choose to extract maximal frequent subtree patterns instead of frequent subtree patterns. The proposed method not only gets rid of the process for infrequent subtrees pruning, but also totally eliminates the problem of generating candidate subtrees. Hence, it significantly improves the whole mining process.

• Journal of KIISE:Information Networking
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• v.30 no.4
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• pp.513-519
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• 2003

In order to deliver multicast traffic efficiently, multicast routing and reliable transmission mechanisms are required. The reliable delivery implies that lost packets must be retransmitted, which in turn requires that transmitted packets be stored in a retransmission buffer. Therefore how to manage a retransmission buffer is important and, in this paper, we try to solve the problem of how many packets should be maintained in the buffer. Our proposed scheme, the timer-based buffer management (TBM), maintains only necessary amount of buffer based on the timer value calculated from the NAKs between the replier and receivers on a multicast tree and can adjust to the dynamic network conditions. By performing simulations, we show that TBM manages the buffer efficiently regardless of the error situation, network size, and so on.