• Proceedings of the Korean Information Science Society Conference
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• 1999.10c
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• pp.652-654
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• 1999

유무선 고속 네트워크 기술을 통합한 새로운 컴퓨팅 환경을 이동 컴퓨팅이라 한다. 가까운 미래에, 이동 사용자는 고속 네트워크 상에서 다양한 종류의 서비스를 액세스 할 수 있을 것이다. 고속 네트워크에서 그러한 서비스들의 품질은 다수의 QoS 매개변수로 상세될 수 있다. 이동 환경에서 가장 중요한 QoS 매개변수는 이동 사용자에게 단절 자유 서비스를 제공하는 무단절 통신의 보장이다. 서비스 단절은 활동적인 핸드오프에 의해 발생된다. 본 논문에서는 단절 자유 서비스에 대한 확률적 QoS 보장을 제공하는 확장된 지연 멀티캐스트 방법을 제안한다. 이 방법에서는 이동 호스트의 이동 속도와 이동 방향을 예측하고, 그러한 정보를 통하여 모든 이웃 셀이 아닌 제한된 이웃셀에게 지연 멀티캐스트가 가능하다. 제안하는 확장된 지연 멀티캐스트를 통해 확률적 QoS 보장이 가능할 뿐만 아니라 정적 네트워크 대역폭을 많이 절약할 수 있음을 보인다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.4
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• pp.91-96
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• 2018

Recently, as artificial intelligence technology becomes popular, demand for wireless traffic is rapidly increasing. In order to provide services in response to the increase in demand for wireless traffic, telecommunication companies are generalizing the installation of public APs. In order to provide convenience of using wireless APs between communication companies, it is necessary to share the use of APs in public places to efficiently use wireless resources in a public place, to pre-authenticate between wireless APs in a mobile communication service, So as to increase the convenience of the user. In this paper, we propose to share APs in public places through handoff between APs and pre-authentication between carriers in mobile communication services. The simulation results show that the handoff latency is improved by 35.1% and the bandwidth used by the AP selected by the pre-authentication method can utilize more bandwidth than the method of automatically selecting the AP.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.11
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• pp.57-66
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• 2004

It is widely accepted that the coverage with high user densities in mobile multimedia environments can only be achieved with small cell such as micro- and pico-cell. The smaller cell size causes frequent handovers between cells and a decrease in the permissible handover processing delay. This may result in the handover failure, in addition to the loss of some packets during the handover. In these cases, re-transmission is needed in order to compensate errors, which triggers a rapid degradation of throughput. In this paper, we propose a new handover scheme in the next generation mobile communication systems, in which the handover setup process is done in advance before a handover request by predicting the handover cell based on mobile terminal's current position and moving direction. Simulation is focused on the handover failure rate and packet loss rate. The simulation results show that our proposed method provides a better performance than the conventional method.

• Journal of KIISE:Information Networking
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• v.32 no.1
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• pp.34-50
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• 2005

Recently, various proposals for supporting network mobility, which provides efficient Internet access when a network formed within a vehicle moves around as a unit, have emerged. The schemes in those proposals, though, manifest some major drawbacks with respect to scalability: If the number of mobile nodes within a mobile network is large, the handoff latency would increase greatly, causing communication disruption; Data delivery to a node within a nested mobile network nay suffer extremely inefficient pinball routing. We propose a scalable network mobility supporting mechanism named SNEMOS (Scalable NEtwork Mobility Support), which resolves the above two major problems of the existing schemes. The performance of SNEMOS is compared with the existing schemes through extensive simulations. The numerical results show that SNEMOS outperforms the existing schemes with respect to handoff latency hop counts of routing paths, packet delivery time, header overhead in data packets, and signaling overhead.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.11A
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• pp.1085-1091
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• 2006

For an experiment in this paper, designed test bed to secure confidentiality of data and safe transmission that Mobile node exchanges in Mobile network. And, For IPsec use that support basically in MIPv6, modeling and experimented IKEv2 protocol that is used for reliable authentication key management and distribution between End Point. When Mobile node handoff in Mobile network, analyzed effect that authentication key re-exchange and limited bandwidth that happen often get in key exchange. And studied about Performance and latency about authentication setting and exchange process that use multi interface. To conclusion, when Mobile node transmits using IPSec, re-authentication of key confirmed that re-setting by limit of bandwidth that existent Mobile network has can be impossible. According to other result, proposed MN's multi interface is expected to minimise key exchange latency by hand-off when transmit IPSec.

• Journal of KIISE:Information Networking
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• v.30 no.3
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• pp.307-315
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• 2003

This paper proposes a Multicast Tree Extension (MTE) scheme for multicast in IP-based wireless networks. If a group receiver Joins a multicast group in a visited foreign network, multicast service may be disrupted when the foreign network does not have a multicast router. To avoid disruption, our scheme creates a bi-directional tunnel between the previous foreign agent (FA) and new foreign agent, if a mobile node (MN) moves from a foreign network with multicast capability to another foreign network with non-multicast capability. The MN thus continues to receive the multicast packets through the tunnel from the previous FA. Our scheme can avoid a long latency due to a long tunneling for group membership as well as multicast service disruption, even if the MN enters foreign networks with non-multicast capability. Simulation results show that our scheme offers lower costs for multicast delivery, tunneling and handoff latency than the existing scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.2A
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• pp.152-161
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• 2007

IEEE 802.11 Wireless Local Area Network (WLAN) became a prevailing technology for the broadband wireless Internet access, and new applications such as Voice over WLAM (VoWLAN) are fast emerging today. For the battery-powered VoWLAN devices, the standby time extension is a key concern for the market acceptance while today's 802.11 is not optimized for such an operation. In this paper, we propose a novel Idle Mode operation, which comprises paging, idle handoff, and delayed handoff. Under the idle mode operation, a Mobile Host (MH) does not need to perform a handoff within a predefined Paging Area (PA). Only when the MH enters a new PA, an idle handoff is performed with a minimum level of signaling. Due to the absence of such an idle mode operation, both IP paging and Power Saving Mode (PSM) have been considered the alternatives so far even though they are not efficient approaches. We implement our proposed scheme in order to prove the feasibility. The implemented prototype demonstrates that the proposed scheme outperforms the legacy alternatives with respect to energy consumption, thus extending the standby time.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11a
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• pp.169-171
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• 2005

무선으로 인터넷에 접속하는 사용자와 서비스의 급격한 증가로 인하여 차세대 인터넷 주소 체계인 IPv6가 제안되었다. 현재 IPv6의 기능들을 사용하면서 효과적으로 이동성을 제공하기 위한 해결책으로 Mobile IPv6(MIPv6)가 제안되고 있다. 하지만 MIPv6는 핸드오프와 관련된 동작을 하는 동안, 일정 시간 동안 통신이 불가능해짐으로 인해, 끊김 없는 통신 서비스를 제공하지 못하는 단점이 있다. 이 논문에서는 기존의 MIPv6 문제점을 해결하기 위해 context와 쿠키 정보를 이용하여 이동노드의 시그널 재초기화 과정을 없애고 패킷 손실 및 지연을 줄인 효율적이고 안전한 핸드오버 메커니즘을 제안한다.

• The KIPS Transactions:PartC
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• v.9C no.1
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• pp.79-88
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• 2002

Transcoding proxy strategy has been widely used as a means to reduce the delay in retrieving Web pages over wireless mobile data service networks. However, this strategy has the serious drawbacks of being a potential point of failure or a bottleneck of the service. We developed a distributed proxy server system in which multiple proxy servers are installed at geographically dispersed locations and share the workloads among them by serving mobile hosts only within assigned regions. A new handoff message protocol to enable handoffs between proxies as the mobile hosts move between regions is proposed. According to the proxy server handoff protocol, a client agent at the mobile horst requests a proxy server to start handoff processing by which two proxy servers synchronize distilled data belonging to a HTTP session that must be maintained across the handoff. Also, we introduce the architecture of the proxy server and the client agent that handles the proxy server handoff. Finally, we evaluate the proposed system through performance test.

• Proceedings of the IEEK Conference
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• 2009.05a
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• pp.12-15
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• 2009

본 연구는 PDA, 노트북 등에 IP주소의 이동성을 지원해 주는 프로토콜인 mobile IP에서 smooth handoff의 지연 요소를 최대한 줄이기 위해 지역 관리 방식의 FA를 사용하여 성능을 향상시키는 방안에 대해 연구하였다. 본 연구에서는 기존에 알려진 방식들의 성능을 NS-2를 이용하여 전송지연, 처리율 등의 분석을 실시하였으며 모든 FA에 버퍼를 내장한 방식과 지역관리용 FA를 이용한 방식에 대하여도 각종 성능을 측정하여 기존의 방식에 비해 어느 정도 성능 향상이 있는지 확인하였다. 본 연구를 통해 지역관리 기능을 수행하는 GFA를 핸드오프 발생 간격이 25초 이상에서는 바인딩 시간 단축에 의한 효과가 있음을 확인할 수 있었다. 이와 같은 연구 결과를 실제 무선 인터넷망 구축에 활용한다면 무선 인터넷망 구축에 관한 관련 자료가 많지 않은 현 상황에서 FA와 MN의 용량과 성능을 결정하는데 보탬이 될 것으로 확신한다.