• Proceedings of the Korean Information Science Society Conference
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• 2001.10c
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• pp.832-834
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• 2001

이동 컴퓨팅 환경이란 사용자가 어떤 장소로 이동하더라도 동일한 환경에서 네트워크 서비스를 끊임없이 제공받을 수 있는 환경을 말하며, Mobile-IP는 이러한 환경이 가지는 특성들을 고려한 네트워크 프로토콜이다. 그러나 이 프로토콜도 이동 노드의 빈번한 핸드오프시 위치 등록과정에서 반드시 홈 에이전트를 거쳐야 하므로, 네트워크 자원과 서비스 지연을 초래하는 단점을 가진다. 본 논문의 제안 기법은 Mobile-IP 환경에 이동 예측기법을 이용하여, 이동 노드의 움직임을 추적하여 이동 방향을 예측하고 이동노드가 핸드오프를 수행하기 전에 사전 등록(pre-registration) 과정을 두어 문제점이었던 등록과정의 지연과 패킷의 손실의 지연을 줄이고자 한다.

• Journal of the Korean Society for Railway
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• v.10 no.6
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• pp.758-765
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• 2007

In this paper, we propose an efficient seamless handoff scheme to minimize packet loss and unnecessary packets on the Internet using the peculiar mobility characteristics of public vehicles such as trains. MR (Mobile Router) in a train visits each AR (Access Router) in the fixed order. As the MR detects reachability to the NAR (Next Access Router) on the new link, the PAR (Previous Access Router) can directly deliver packets from MR's HA (Home Agent) to the NAR according to the HML (Handoff Mobile router List). Then. the NAR buffers them until the MR finishes L3 (Layer 3) handoff procedure with the NAR. Therefore, our scheme can support a seamless handoff without the packet loss and unnecessary packets on the Internet. The result of our performance evaluation has shown that the proposed scheme could provide excellent performance, compared with the NEMO basic support protocol and the Bi-casting protocol.

• Journal of Internet Computing and Services
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• v.6 no.3
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• pp.55-70
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• 2005

In order to provide mobile hosts with multicast service in mobile communication environment, we proposed a multicast mechanism named HXcast++ which is an extended version of the existing Xcast++ with hierarchical architecture, We assured that mobile hosts could get multicast service through an optimal path regardless of their location by making DR(Designated Router) join a group on behalf of the mobile hosts, In this present research we introduced hierarchical architecture in order to reduce the maintenance cost resulting from frequent handoff. We also proposed a GMA (Group Management Agent) based group management mechanism which enables the mobile hosts to join the group without waiting for a new IGMP Membership Query. A fast handoff method with L2 Mobile Trigger was, in this work, employed in order to reduce the amount of the packet loss which occurs as a result of the handoff, We also managed to curtail the packet loss caused by the latency of the group join by using a buffering and forward mechanism.

• Journal of Advanced Navigation Technology
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• v.13 no.3
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• pp.372-377
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• 2009

This paper evaluates the performance of three methods for predicting resources requested by mobile's calls and a call admission algorithm based on these predicting methods respectively in wireless networks. The first method is based on Wiener prediction model and the second method is based on the MMOSPRED algorithm and the third method is based on the neural network. The proposed call admission algorithm is based on prioritized handoff call in resource allocation. The resources for future handoff calls are therefore predicted and reserved in advance, and then new calls are admitted as long as the remaining resources are sufficient. We compare their performances in terms of prediction error, new call blocking and handoff dropping probabilities by simulation. Results show that the CAC based on Wiener prediction model performs favorably due to exact resources prediction.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.2
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• pp.75-82
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• 2008

Mobile IP was proposed to overcome identity problem of original IP address system caused by mobility of wireless mobile host. To complete its network handoff procedure, it must receive a mobile advertisement broadcasted by mobile agent. Generally, in a mobile IP system, mean time delay, 500ms, in a network handoff procedure is a critical problem of wireless service such as Voip, multimedia streaming. A caching agent caches a latest mobile advertisement, and replays it by receiving solicitation message from a mobile node finishing link layer detection. But, during the procedure of mobile registration, many packets from service provider to the mobile host would be lost and handoff time delay would be increased. In this thesis, we propose an unproved caching agent technique which can forward data packets while handoff procedure, and CoA pool for fast mobile IP registration.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.11a
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• pp.950-953
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• 2007

무선 인프라와 이동성 지원 기술의 발달로 한 장소에서 머물던 무선 인터넷 서비스를 이동 중에도 받을 수 있게 되었다. 이러한 환경의 변화로 인해 모바일 기기의 이동성에 대한 관심은 더욱 더 커지고 있으며, 이동성뿐만 아니라 유선과 마찬가지로 끊김 없는 서비스를 받고자 하는 요구도 높아지고 있다. 모바일 노드의 이동성을 지원하기 위해서 기존 네트워크 계층의 Mobile IP 와는 달리 전송 계층에서 동작하는 mSCTP (mobile Stream Control Transmission Protocol)가 등장하였다. mSCTP 는 기존 SCTP 의 멀티호밍과 동적으로 IP 주소를 변경할 수 있는 DAR (Dynamic Address Resolution) 시그널을 이용하여 모바일 노드의 핸드오프를 지원하고 있다. 하지만, IP 주소의 추가, 변경 및 삭제에 대한 각 시그널의 전송 시기에 대한 정의가 없어 전송 시기를 결정하는 메커니즘이 필요하다. 따라서 본 논문에서는 퍼지 IF-THEN 룰을 적용한 퍼지 모델을 이용하여 이러한 문제점을 해결하고자 한다. 모바일 노드가 이동하게 될 새로운 네트워크의 신호 세기와 현재 네트워크 신호와의 신호비를 퍼지 모델에 입력하고 그 결과 값을 통해 시그널 전송 시기를 판단한다. 모바일 노드는 핸드오프 시기를 적절히 판단 할 수 있기 때문에 잘못된 핸드오프로 인한 세션의 단절을 줄일 수 있고, 기존에 발생하던 핸드오프 지연 시간을 줄일 수 있어 이동 중에도 손실 없는 서비스를 제공 받을 수 있게 된다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.4C
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• pp.353-364
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• 2002

To prevent the performance degradation of TCP due to packet loss in the smooth handoff by the route optimization extension of Mobile If protocol, a buffering of packets at a base station is needed. A buffering of packets at a base station recovers the packets dropped during the handoff by forwarding the buffered packets at the old base station to the mobile user. But, when the mobile user moves to a new foreign network which is connected to a congested router, the buffered packets forwarded by the old base station are dropped and the link utilization performance degraded due to increased congestion by the forwarded packets. In this paper, when the mobile user moves to a new foreign network which is connected to a congested router, Ive propose a packet forwarding control scheme required far the old base station to improve TCP performance in mobile networks. The old base station forwards or discards the buffered packets during handoff by proposed packet forwarding control scheme based on congestion states of RED(Random Early Detection) at the congested router. Simulation results slow that link utilization performance can be improved by applying proposed packet forwarding control scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.9B
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• pp.774-782
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• 2003

Generally, in the Mobile IP technologies, the use of RSVP(Resource ReSerVation Protocol) is recommended in order to provide a mobile node real-time service. However, the handoff of a mobile node increases the registration delay, RSVP reservation delay and signalling overhead in the Mobile IP and RSVP interworking. Specially, the resource reservation on the path between a mobile node and a correspondent node is the duplicated reservation and then causes unnecessary creation of the signalling overhead and waste of the resource, since the majority of the path before handoff and after handoff is same. If the radius of a cell providing a wireless interface to a mobile node is small, the number of handoff will increase and also signalling overhead and duplicated resource reservation will increase. In this paper, we proposed the integration model of Cellular IP and RSVP with RSVP proxy scheme. Here, Cellular IP protocol minimizes registration delay, transfer delay, and loss by handoff in micro cell network, the RS VP proxy that minimizes the duplication of resource reservation prevents the path for RSVP session from change using the address for reservation of a mobile node. Proposed scheme was evaluated in comparison with the existing Mobile IP and RSVP interworking scheme using the probability of resource reservation fail to the radius of a cell and the handoff rate.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05b
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• pp.1301-1304
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• 2003

Mobile IP는 현재의 인터넷에서 노드가 링크를 변화시킬 때 통신이 지속 될 수 있도록 Mobility를 제공하기 위한 방안이다. Mobile IP는 MN(Mobile Node)가 HA(Home Agent) 와 FA(Foreign Agent) 사이에서 링크가 변화할 매 CN(Correspondent Node)와 지속적인 통신을 할 수 있도록 한다. 그러나 FA에서 FA로 MN이 노드의 위치를 바꿀 때에는 핸드 오프가 발생하여 패킷이 손실 될 수도 있다. 본 논문은 MN이 여러 FA를 이동할 때 발생하는 패킷 손실에 대한 경우를 살펴 이를 해결하기 위한 Seamless 핸드오프(Handoff) 알고리즘을 기술한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05b
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• pp.1377-1380
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• 2003

계층적 모바일 IPv6는 이동 노드의 지역적인 이동시 보다 빠르고 효과적으로 서비스를 제공하기 위하여 네트워치를 계층적으로 구성한 프로토콜로써, 모바일 IPv6의 단점인 핸드오프시의 긴 지연시간을 단축시켜 손실되는 패킷을 줄이며, 외부로 전송되는 트래픽의 양을 감소시키는 장점이 있다. 따라서 많은 양의 데이타 처리가 필요한 멀티미디어 통신이나, 신속한 서비스를 필요로 하는 실시간 통신에 적용이 가능하다. 본 논문에서는 기존의 모바일 IPv6와 계층적 모바일 IPv6를 구현하여 핸드오프 지연시간과 패킷 손실량을 측정하고 성능 비교를 통하여 계층적 모바일 IPv6의 성능 향상을 확인하였다.