• Industrial Engineering and Management Systems
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• 제10권3호
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• pp.221-231
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• 2011

One of the critical issues in wireless sensor network is the design of a proper routing protocol. One possible approach is utilizing a virtual infrastructure, which is a subset of sensors to connect all the sensors in the network. Among the many virtual infrastructures, the connected dominating set is widely used. Since a small connected dominating set can help to decrease the protocol overhead and energy consumption, it is preferable to find a small sized connected dominating set. Although many algorithms have been suggested to construct a minimum connected dominating set, there have been few exact approaches. In this paper, we suggest an improved optimal algorithm for the minimum connected dominating set problem, and extensive computational results showed that our algorithm outperformed the previous exact algorithms. Also, we suggest a new heuristic algorithm to find the connected dominating set and computational results show that our algorithm is capable of finding good quality solutions quite fast.

• International Journal of Contents
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• 제4권1호
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• pp.16-19
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• 2008

In this paper, we propose to new dispatcher method, which doesn't depend on an operating system of the server, and the direct routing method, by which a server answers a client's request at first hand. And, propose new web clustering scheme based on the contents on the web where web servers composed of cluster, with each different contents, answer client's request. The other purposes are to reduce overhead of the dispatcher through load balance, and to minimize the time to take in responding to a client's request. The performance of new web cluster scheme was improved by about 39% than that of the existing RR method. It was identified that the performance of the proposed web cluster method was extraordinary improved comparing with that of the existing RR method as a whole.

• Journal of information and communication convergence engineering
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• 제13권4호
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• pp.248-256
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• 2015

With the dramatic increase in mobile traffic in recent years, some of the limitations of mobility management frameworks have magnified. The current centralized mobility management (CMM) strategy has various problems, such as a suboptimal routing path, low scalability, signaling overhead, and a single point of failure. To overcome these weaknesses in the CMM strategy, the Internet Engineering Task Force has been discussing distributed mobility management (DMM) strategies. The fundamental concept of a DMM strategy is to distribute the mobility anchors closer to the users. While the distribution of mobility anchors results in low-cost traffic delivery, it increases the signaling cost. To reduce this higher signaling cost, we propose a new DMM strategy applying the pointer forwarding technique. The proposed strategy keeps the existing tunnels and extends the traffic path as much as possible. In this paper, we analyze the performance of the pointer forwarding-DMM strategy and discuss its pros and cons.

• Journal of information and communication convergence engineering
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• 제18권1호
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• pp.22-27
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• 2020

Content centric networking (CCN) is regarded as promising internet architecture because it can provide network efficiency in terms of bandwidth consumption by separating contents from a specific network location and decrease network congestion events. However, the application of a CCN does not widely consider the side effects of mobile devices, particularly mobile content sources. For content source mobility, a full routing update is required. Therefore, in this study, a route optimization scheme is proposed for mobile content sources in a CCN environment to provide low communication overhead, short download time, and low resource consumption. The proposed scheme establishes a direct path between content requesters and a mobile content source for the exchange of interest and data packets using interest-piggybacked data packets. Based on the inherent CCN naming characteristics, the content source does not know the name prefix of the content consumer, and thus the proposed optimized CCN scheme utilizes the content router in the home domain of the content source.

• 한국통신학회논문지
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• 제32권10A호
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• pp.1004-1014
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• 2007

In sensor networks, it is crucial to reliably and energy-efficiently deliver sensed information from each source to a sink node. Specifically, in mobile sink (user) applications, due to the sink mobility, a stationary dissemination path may no longer be effective. The path will have to be continuously reconfigured according to the current location of the sink. Moreover, the dynamic optimal path from each source to the sink is required in order to reduce end-to-end delay and additional energy wastage. In this paper, an Adaptive Reversal Optimal path Tree (AROT) protocol is proposed. Information delivery from each source to a mobile sink can be easily achieved along the AROT without additional control overhead, because the AROT proactively performs adaptive sink mobility management. In addition, the dynamic path is optimal in terms of hop counts and the AROT can maintain a robust tree structure by quickly recovering the partitioned tree with minimum packet transmission. Finally, the simulation results demonstrate that the AROT is a considerably energy-efficient and robust protocol.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2004년도 가을 학술발표논문집 Vol.31 No.2 (3)
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• pp.274-276
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• 2004

싱크의 이동성은 대규모 센서 네트워킹에 새로운 도전을 야기한다. 이동 싱크의 위치는 센서필드 전역에 걸쳐 전달되어야 하며, 이를 위해 각 센서노드는 새로운 정보를 갱신해야 한다. 그러나 빈번한 위치 갱신은 파워의 제약을 가진 센서에는 초과 에너지 낭비를 일으키고, 무선 통신의 충돌도 증가시킬 것이다. 이에 따라 본 논문은 다중 이동 싱크와 소스가 확장가능하면서 효율적으로 데이터를 전달하는 방법을 제안한다. 각 데이터 소스와 모바일 싱크가 적극적으로 싱크가 이벤트 정보를 획득 가능하도록 그리드 구조를 형성하고, 질의를 보내려는 하는 싱크도 로컬로 질의를 전송함으로써 그리드 형성에 적극 참여하였다. 본 제안 방법은 소스와 싱크가 중간 경유 노드에서 위치 정보를 교환함으로써 낮은 오버헤드로 경로 설정이 가능하게 하였다.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2005년도 한국컴퓨터종합학술대회 논문집 Vol.32 No.1 (A)
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• pp.499-501
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• 2005

Ad-hoc네트워크의 효율적인 라우팅을 위해서는 라우팅 각 과정의 오버헤드를 최소화하여야 한다. 본 논문에서는 기존의 연구물들을 바탕으로 Ad-hoc 네트워크 라우팅에서 흔히 일어 나는 주요 오버헤드 요소들을 살펴보고, 그 오버헤드를 절감시킬 수 있는 간단하고 효율적 인 아이디어를 제시한다. 제안한 방법은 무선 네트워크의 특성을 활용하여 별도의 메시지 교환 없이 엿듣기를 통하여 라우팅 정보를 수집하는 특징을 가지고 있다. 이 엿듣기로 수집된 라우팅 정보를 바탕으로 플러딩 메시지 감소, 멀티 패스, 중앙 병목현상 분산을 구현하고, 이를 통해 라우팅 오버헤드를 크게 경감시킬 수 있을 것으로 기대한다.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2008년도 정보통신설비 학술대회
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• pp.17-20
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• 2008

A clustering scheme for ad hoc networks is aimed at managing a number of mobile devices by utilizing hierarchical structure of the networks. In order to construct and maintain an effective hierarchical structure in ad hoc networks where mobile devices may move at high mobility, the following requirements must be satisfied. The role of each mobile device for the hierarchical structure is adaptive to dynamic change of the topology of the ad hoc networks. The role of each mobile device should thus change autonomously based on the local information. The overhead for management of the hierarchical structure is small. The number of mobile devices in each cluster should thus be almost equivalent. This paper proposes an adaptive multihop clustering scheme for highly mobile ad hoc networks. The results obtained by extensive simulation experiments show that the proposed scheme does not depend on mobility and node degree of mobile devices in the ad hoc network, which satisfy the above requirements.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2002년도 가을 학술발표논문집 Vol.29 No.2 (1)
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• pp.319-321
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• 2002

본 논문에서는 서버의 운영체제에 의존적이지 않은 디스패처(Dispatcher)방식과 클라이언트의 요청에 대한 서버의 응답을 클라이언트와 직접 통신하는 직접 라우팅(Direct Routing) 방식을 혼합하고, 클러스터로 구성된 웹 서버들은 각각 서로 다른 컨텐츠를 가지고 클라이언트 요청에 해당 서버에서 응답하는 컨텐츠를 기반으로 한 웹 서버 클러스터 기법을 제안한다. 기존의 디스패처는 해당 디스패처에 관련된 서버들 간의 부하 분산을 효과적으로 처리하는데 목적을 두지만, 제안한 컨텐츠를 기반으로 한 웹 서버 클러스터 기법은 부하 분산보다는 디스패처에 대한 오버헤드(Overhead)를 감소시키고 클라이언트의 서비스에 대한 응답시간(Response-time)을 최소화하는데 그 목적을 둔다. 또한 본 논문에서는 서로 다른 컨텐츠로 구성되어 있는 서버들 중에 특정한 한 서버가 페일(Fail)이 발생했을 때 전체 컨텐츠로 구성되어 있는 또 하나의 서버를 가지고 페일 문제를 해결한다. 본 논문에서 제안한 컨텐츠를 기반으로 한 웹 서버 클러스터 기법을 월드 와이드 웹(World Wide Web)에 적용시 폭발적으로 증가하는 서비스 요청과 이로 인만 디스패처의 오버헤드를 효과적으로 처리하여 보다 빠르고 신뢰적인 서비스가 가능할 것으로 기대된다.

• 대한임베디드공학회논문지
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• 제14권4호
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• pp.219-226
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• 2019

One of the most widely studied protocols for tactical ad-hoc networks is Optimized Link State Routing Protocol (OLSR). As for OLSR research, most research work focus on reducing control traffic overhead and choosing relay point. In addition, because OLSR is mostly dependent on link detection and propagation, dynamic Hello timer become research challenges. However, different timer interval causes imbalance of link validity time by affecting link lifetime. To solve this problem, we propose a weighted topology graph model for constructing a robust network topology based on the link validity time. In order to calculate the link validity time, we use control message timer, which is set for each node. The simulation results show that the proposed mechanism is able to achieve high end-to-end reliability and low end-to-end delay in small networks.