• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.6
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• pp.92-100
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• 2008

Ad-hoc network is a collection of wireless mobile hosts forming a temporary network without the aid of any centralized administration or reliable support services such as wired network and base stations. Recently, Ad-hoc networks are evolving to support multimedia contents according to expansion of ad hoc multi-hop communication system. Wireless ad-hoc network is different from the conventional wired network by frequent changes in network topology, number of routers and resources, there are a number of problems in applying conventional routing protocol to ad-hoc network. The AODV routing protocol is proposed for mobile node in ad-hoc networks. AODV protocol that provides to guarantee QoS for data transmission in ad hoc networks that link break frequently occurs. In this paper, AODV routing protocol based NDIS(Network Driver Interface Specification) is implemented. We design high performance image transmission that can operate with software(AODV) for ad-hoc networks without degradation. and verify operation of AODV routing protocol on the test bed.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1112-1115
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• 2006

모바일 GIS를 홍수재해관리 시스템에 도입하기 위한 목적은 홍수에 대비한 신속한 상황대처 통해 인명 및 재산피해를 최소화하는데 있다. 모바일 GIS 시스템 구축의 기본 방향은 하천유역에 대한 행정업무 및 정보화 업무의 효율성을 높여 현장업무에서 실시간으로 제공되는 수문정보 및 지형정보에 대한 다양한 컨텐츠를 주민들이 쉽게 접근하여 서비스를 제공받을 수 있도록 하고 현장 실무자가 하천 수위 및 유량을 관리하는 데 있어 즉각적인 조치를 가능하도록 하기 위한 것이다. 본 연구에서 이동 클라이언트와 홍수재해관리시스템 서버간의 무선통신채널은 AP(Access Point)를 통한 WLAN이나 CDMA망의 모바일 네트워크 또는 차세대 휴대인터넷 망을 대상으로 하였다. 홍수재해관리시스템은 ArcIMS, HTML, Java Script를 이용하여 구축하고 웹 서비스를 위해 마이크로소프트사의 IIS(Internet Information System) 사용하며, ArcIMS의 정상적인 구동을 위해 JRE(Java Runtime Environment)를 설치하도록 하였다. 주요 GIS 기능은 줌인, 줌아웃, 팬, 속성정보 검색, 거리측정, 버퍼링 기능 등이고 Layer는 침수위험건물, 대피건물, 침수지역 건물용도, 건물, 도로, 수계, 침수예상지역(100, 200년 빈도), 위성영상, DEM, 행정경계 등이 포함되도록 하였다. 시스템 구축에 사용될 데이터는 수리수문학적 데이터(유출량, 강우강도, 대상지역의 면적, Manning 계수 등)와 대상지역의 수치지도, DEM, 고해상 위성영상, 문헌조사와 현장조사를 통해 얻은 자료를 바탕으로 구성하도록 하였으며, 수리수문학적 데이터와 DEM 데이터를 바탕으로 침수지역 데이터를 생성하고 문헌조사와 현장조사를 통해 얻은 속성정보와 디지털 지도인 공간정보를 연결하기 위해 디지털 지도에서 건물 Layer, 도로 Layer, 등고선 Layer, 수계 Layer를 추출하여 ArcGIS에서 Coverage로 변환하여 위상관계를 설정한 후 다시 Shape 파일로 변환하여 속성정보와 연결시키도록 데이터베이스 구축방안을 제시하였다. 이와 같이 본 연구에서는 홍수재해 관리시스템에서 모바일 GIS를 적용하기 위하여 Pocket PC를 탑재한 이동 클라이언트인 PDA에 GPS 모듈을 확장하여 GPS 위성으로부터 위치정보를 획득하고 지리정보를 제공하는 모바일 GIS 서버간에 XML 기술을 이용하여 수문정보 및 지형정보 서비스를 제공하는 방안을 제시하였다.

• Convergence Security Journal
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• v.7 no.1
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• pp.77-82
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• 2007

Supporting Quality of Service (QoS) for multimedia services in heterogeneous mobile networks is a part of key issue for Beyond Three Generation (B3G) development. In particular, if QoS degradation are occurred because cell overload and error late patterns of wireless links during the transmission of multimedia data, the efficient QoS management is necessary to maintain the same QoS of transmitted multimedia data because the QoS may be defected by some delay and information loss. This paper deals with QoS Degradation reason Intra-System Handover (D-ISHO) for handling QoS of multimedia services over heterogeneous mobile networks. For this aim, the function modules for supporting QoS of D-ISHO are proposed. The sequence diagram showing interaction between the modules is described and then a scenario for D-ISHO is considered. Simulation is focused on the average delay and packet loss rate. The proposed heterogeneous mobile system using the QoS-Guaranteed Resource Management (QGRM) provides a better performance than each different access system.

• Journal of the Korean Society for Railway
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• v.19 no.4
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• pp.456-467
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• 2016

Wireless Access in Vehicular Environments (WAVE) communication technology, which provides vehicleto-vehicle and vehicle-to-infrastructure communication and offers safe and convenient service, has been developed for application to an Intelligent Transport System (ITS). This paper provides field test results on a study of the feasibility of WAVE technology application to railway communication systems. A test railway communication system based on WAVE technology has been built along the Daebul line and a newly developed EMU. Field tests have been carried out according to the communication function requirements for LTE - R. The test results show that the railway communication system based on WAVE technology meets the functional requirements: maximum transmission length is 730m, maximum transfer delay is 5.69ms, and maximum interruption time is 1.36s; other tests including throughput test, video data transmission test, VoIP data test, and channel switching test also produced results that meets the functional requirements. These results suggest that WAVE technology can be applied to the railway communication system, enabling Vehicle-to-Wayside communication.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.10A
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• pp.1131-1138
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• 2004

In Hierarchical Mobile Ipv6 (HMIPv6) networks, the mobility anchor point (MAP) handles binding update (BU) procedures locally to reduce signaling overhead for mobility. However, as the number of mobile nodes (MNs) handled by the MAP increases, the MAP suffers from the overhead not only to handle signaling traffic but also to Process data tunneling traffic. Therefore, it is important to control the number of MNs serviced by the MAP, in order to mitigate the burden of the MAP. We propose an adaptive load control scheme, which consists of two sub-algorithms: threshold-based admission control algorithm and session-to-mobility ratio (SMR) based replacement algorithm. When the number of MNs at a MAP reaches to the full capacity, the MAP replaces an existing MN at the MAP, whose SMR is high, with an MN that just requests binding update. The replaced MN is redirected to its home agent. We analyze the proposed load control scheme using the .Markov chain model in terms of the new MN and the ongoing MN blocking probabilities. Numerical results indicate that the above probabilities are lowered significantly compared to the threshold-based admission control alone.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.461-465
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• 2007

MANET(Mobile Ad hoc Networks) is free-mobility formation of mobile nodes in the wireless networks. Generally, wireless networks has two main type of structures which Tree and Mesh. These general structure is difficult to do which connectivity, redundancy transmit and network continuant. In this paper, we would suggest a new ODDMRP(Ontology Doppler effect-based Dynamic Multicast Routing Protocol) technology for effective MANET which Ontology Doppler effect-based. ODDMRP consist of the parameters for node entropy when using Doppler effect which moving position of round node, moving time, and distribution chart in velocity also it express distance of destination node and property structure organization. It would be used to provide improvement to keep the optimal communication routing and also could be improve network stabilization, and continuation durability of connectivity.

• The KIPS Transactions:PartC
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• v.13C no.7 s.110
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• pp.873-880
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• 2006

Since various networks are deployed and the most of users request higher mobility, there are many researches about the interworking between widely deployed 3G network and rapidly boarded WLAN. On the other side, WiBro is focused on as a next generation network, because many people expect that WiBro gives satisfaction about the enough mobility and mass data transmission. So the study of the integration between WiBro and cdma2000 will show better effects than the present study of the integration between WLAN and cdma2000. The L2 handoff proposed in this paper takes advantages over the existing L3 handoff scheme because it does not require the L3 procedure for the mobility unlike the L3 handoff. Through extensive computer simulations, the efficiency of the proposed scheme has been validated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7B
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• pp.608-618
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• 2006

The increasing popularity of multimedia streaming services introduces new challenges in content distribution. Especially, it is important to provide the QoS guarantees as they are increasingly expected to support the multimedia applications. The service providers can improve the performance of multimedia streaming by caching the initial segment (prefix) of the popular streams at proxies near the requesting clients. The proxy can initiate transmission to the client while requesting the remainder of the stream from the server. In this paper, in order to apply the prefix caching service based on IETF's RTSP environment to the wireless networks, we propose the effective RTSP handling scheme that can adapt to the radio situation in wireless network and reduce the cutting phenomenon. Also, we propose the traffic based caching algorithm (TSLRU) to improve the performance of caching proxy. TSLRU classifies the traffic into three types, and improve the performance of caching proxy by reflecting the several elements such as traffic types, recency, frequency, object size when performing the replacement decision. In simulation, TSLRU and RTSP handling scheme performs better than the existing schemes in terms of byte hit rate, hit rate, startup latency, and throughput.

• The KIPS Transactions:PartC
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• v.10C no.2
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• pp.241-252
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• 2003

IMT-2000 appeared in order to satisfy the desires of the uses who wish to supply through wireless most of the services being provided through wire, such as Internet services and multimedia high-speed data information. However, during global roaming, the signal data and the user data get transmitted through the networks of other users. Also, it is judged that with the provision of high speed data communication the amount of data communication necessary for confidentiality protection will increase. It is planned that the recent IMT-2000 Project will begin its commercial service in 2002. From this viewpoint, wireless contents, due to their special characteristics, are greatly exposed to illegal actions by third persons. As a result, it can be said that security and certification issues in the mobile telecommunication environment are indispensable matters. For this purpose, it is intended that in this thesis through an analysis of the existent IMT-2000 certification method, a more safe and efficient authentication method is presented and, at the same time, a security protocol necessary in the provision of wireless contents is designed.

• Journal of the Korea Convergence Society
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• v.7 no.4
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• pp.25-32
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• 2016

When using reliable multicast protocol over air links, the multicast packets lost in the air link cause the initiation of retransmission request packets and the implosion of retransmission packets, which deteriorate multicast session performance. This paper proposes on the efficient reliable multicast mechanism in wireless networks utilizing the Agents. In this paper we show the design of a retransmission agent which improves the performance of reliable multicast sessions in wireless network. The main idea is to cache reliable multicast packets at the base station and perform local retransmissions across the wireless link. MATLAB has been used to simulate and to get performance results for signaling overhead and processing delay through the comparison of the proposed agent model to the Multicast File Transfer Protocol. It has been proven from the simulation results that the proxy module make pass trials shorter in Multicast File Transfer Protocol.