• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.387-390
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• 2009

Wireless Sensor Network (WSN) can easily compromised from attackers because it has the limited resource and deployed in exposed environments. When the sensitive packets are occurred such as enemy's movement or fire alarm, attackers can selectively drop them using a compromised node. It brings the isolation between the basestation and the sensor fields. To detect selective forwarding attack, Xiao, Yu and Gao proposed checkpoint-based multi-hop acknowledgement scheme (CHEMAS). The check-point nodes are used to detect the area which generating selective forwarding attacks. However, CHEMAS has static probability of selecting check-point nodes. It cannot achieve the flexibility to coordinate between the detection ability and the energy consumption. In this paper, we propose the control method for the number fo check-point nodes. Through the control method, we can achieve the flexibility which can provide the sufficient detection ability while conserving the energy consumption.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.3-6
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• 2009

IEEE 802.15.4 기반의 무선 PAN(WPAN: Wireless Personal Area Network)환경에서 기존에 제안된 전송 전력 제어(TPC: Transmission Power Control) 알고리즘은 수신 신호의 세기를 기반으로 반복 전송을 통하여 적합한 최소 전송 전력을 결정하는 방법으로 진행되어 왔다. 이러한 방법은 통신 채널의 변화가 잦은 지역에서는 재전송률이 높아지고 전송 품질이 떨어지는 단점을 가지고 있다. 따라서 본 논문에서는 IEEE 80215.4에서 제공하는 링크 품질 지표(LQI: Link quality indicator)값을 바탕으로 최소 전송 전력을 결정하여 재전송률을 줄이고, 통신 채널 변화에 보다 능동적으로 대응할 수 있는 새로운 전송 진력 제어 방법을 제안하고자 한다.

• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.370-373
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• 2005

건물의 무선 센서 네트워크의 개념 도입은 앞으로 도래할 유비쿼터스 환경에서 매우 비중 있는 어플리케이션으로 지능형 및 자동화 모니터링 시스템을 통해 건물의 실시간 모니터링을 함으로써 건물의 안전방지 및 온도, 습도 유지 등 여러 중요한 일을 수행할 수 있다. 본 논문에서는 빌딩에 설치된 각 센서 노드들로부터 조도의 데이터를 수집하고 비쥬얼 스튜디오 환경을 사용하여 호스트에서 모니터링을 하는 어플리케이션을 구현하여 보았다.

• Annual Conference of KIPS
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• 2015.10a
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• pp.335-336
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• 2015

Seamless mobility is one of the most crucial feature of telecommunication industry. Researches are going on in full swing to deal with this feature in most efficient manner. Software Defined Networking (SDN) is seen as the next generation paradigm which can facilitate seamless mobility across heterogeneous networks by segregating the control plane and data plane functionalities, and logically centralizing the control plane. In this paper, we propose a simplified Layer 2 handover mechanism for enterprise wireless networks, based on SDN framework. We present a network assisted L2 handover method using the IEEE 802.21 Media Independent Handover (MIH) protocol and SDN concepts, to achieve seamless mobility across heterogeneous networks.

• Annual Conference of KIPS
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• 2003.05b
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• pp.1209-1212
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• 2003

오늘날 인터넷 환경에서의 망은 유무선의 환경이 통합된 하나의 망으로 달수 있다. 일반적인 TCP에서는 무선망에서의 핸드오프나 비트오류 등으로 인한 패킷 손실이 발생하는 경우에도 흔잡제어 알고리즘으로 손실된 패킷을 복구하게 되며 이러한 복구는 혼잡윈도우를 줄이게 됨으로 인해 현저히 TCP의 처리량을 감소시키게 된다. 본 논문에서는 유무선이 통합된 망에서 데이터 전송 효율을 높일 수 있는 알고리즘을 제시하고자 한다. 이 알고리즘에서는 홈서버를 사용하여 무선망에서 발생한 패킷 손실이 종단간의 재전송이 아닌 홈서버에서 지역 재전송을 함으로써 유무선망의 부하를 줄이고 흔잡제어 알고리즘이 실행되는 것을 방지하여 TCP의 성능향상을 가져올 수 있으며 캐쉬메모리에 재전송 패킷을 보관하여 재전송함으로써 보다 빠른 재전송효과를 얻을 수 있다.

• Annual Conference of KIPS
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• 2005.05a
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• pp.1319-1322
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• 2005

최근 컴퓨터 기술의 발달로 공공 분야에서 구조물 감시 시스템의 중요성이 대두 되고 있다. 현재 구조물 감시 시스템은 감지 능력, 데이터 처리, 피해의 양, 구조물의 상태 예상을 기본 목적으로 하여 운영된다. 기존 감시 시스템은 센서의 측정으로 얻은 데이터를 유선을 통해 기지노드로 전송한다. 유선으로 연결된 감시 시스템에는 많은 초기 설치비용, 네트워크 전송 케이블의 유실 문제와 같은 문제점이 있다. 본 논문에서는 이러한 문제점을 개선하기 위해 전송 장치, 센싱 보드, 무선 장치로 구성된 무선 네트워크 환경에서 동작하는 무선 감시 시스템을 구성하였다. 구현된 시스템은 하중에 따른 변화를 실시간으로 감시하므로 구조물의 안전성 향상에 기여한다.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.64-68
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• 2007

Commercial WiBro and 3G HSDPA services are launched last year in order to provide high speed wireless Internet access and multimedia service. Currently mobile communication service providers concentrate on the deployment of indoor mobile network since indoor traffic is remarkably increased. For fine indoor wireless communication, an installation of access point system via Public IP network which is called Femtocell is required. The development of indoor Femtocell system must be considered in the viewpoint of low hardware complexity, cost reduction, interlocking with WiBro/HSDPA network without change of network component and easy element management. In this paper, we review the implementation issue and technology of dual mode AP which provides WiBro and HSDPA signal to the user simultaneously. Especially, we describe on the HSDPA Femtocell standardization status and possible 3 types of HSDPA communication module development design. Furthermore we analyze the merits and demerits of each HSDPA Femtocell design type and propose a system which enables handover between indoor HSDPA Femtocell and outdoor commercial HSDPA mobile network.

• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.3
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• pp.196-201
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• 2013

In this paper, we propose an asynchronous and adaptive message passing scheme based on S-MAC for handling with the problem on energy efficiency in wireless sensor networks. The proposed scheme consists of a policy that differentiate transmission errors caused by packet collision or radio interference from congestion errors caused by buffer overflow and a method that adaptively controls the size of a fragment according to the variance of traffic loads. Especially, it presents a method that highly reduce the energy consumption by keeping the size of fragment not being excessively smaller than the one that may result in rapid increment of the total transfer time. Finally, with the simulation results we show that network throughput and delay are improved by using the proposed message passing scheme.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.2
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• pp.106-113
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• 2009

Recently, due to many industrial accidents at construction sites, a variety of researches for structural health monitoring (SHM) of buildings are progressing. For real site application of SHM, one of the advanced technologies has blown as wireless sensor networks (WSN). In this paper, we proposed WIVA(WSN Monitoring framework based on 3D Visualization and Augmented Reality in Mobile Devices) system that applies 3D visualization and AR technology to mobile devices with camera based on WSN in order to expand the extent of information can observe. Moreover, we performed experiments to validate effectiveness in 3D and AR mode that utilize WSN data based on IEEE 802.15.4. In real implementation scenario, we demonstrated a fire occurrence test in 3-story building miniature.

• Proceedings of the IEEK Conference
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• 2004.08c
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• pp.552-557
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• 2004

Mobile Ad Hoc Network (MANET) is a network architecture, which has no backbone network and is deployed temporarily and rapidly in emergency or war without fixed mobile infrastructures. All communications between network entities are carried in ad-hoc networks over the wireless medium. Due to the radio communications being extremely vulnerable to propagation impairments, connectivity between network nodes is not guaranteed. Therefore, previously developed routing algorithms in wired networks cannot be used. And many new algorithms have been undergone. This study proposes the secondary leader approach to the cluster based routing protocol(CBRP). In case, the primary leader becomes abnormal status so that the primary leader cannot participate the communications between network entities, the secondary leader immediately replaces the primary header without selecting process of the new primary leader. The performances of proposed algorithm ACBRP(Advanced Cluster. Based Routing Protocol;CBRP using secondary leader) are compared with CBRP and results are presented in order to show the effectiveness of the algorithm.