• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.1509-1512
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• 2004

본 논문은 무선통신망 환경에서 이동체(Mobile Node)에 멀티미디어 서비스를 제공하기 위한 효율적인 핸드오프 알고리즘에 관한 연구로서 QoS에 미치는 영향이 큰 요소들에 대해 분석하고 이를 기반으로 효율적인 핸드오프 방안을 제시한다. 이를 위해 QoS와 밀접한 관련이 있는 이동체의 속도에 따른 핸드오프 호의 실패율(Blocking Rate)을 분석하였다. 또한 현재 각 이동통신 서비스 업체들이 제공중인 인구밀집지역에서의 무선 멀티미디어 서비스를 가정하여 피코셀(Pico Cell) 환경에서 멀티캐스트 그룹설정에 따른 핸드오프 호의 실패율을 분석하였으며, 이를 기반으로 무선통신망에서 향상된 QoS를 제공할 수 있는 핸드오프 방안을 제시하였다.

• 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 KIPS Transactions:PartC
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• v.15C no.1
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• pp.51-60
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• 2008

Micro-mobility protocols have been developed to reduce the control message overhead due to movements of mobile nodes. With the spread of mobile devices, services using mobile nodes are increasing and multicast services are becoming more important in providing multimedia services. In this paper we propose a new multicast protocol suitable for micro-mobility environments. The proposed protocol is designed to maintain optimal multicast routing paths and continue to provide multicast services without disruption in spite of frequent handoffs due to movements of mobile nodes. We used simulation to evaluate the proposed protocol, compared its performance with existing multicast protocols for mobile environments including bi-directional tunneling, remote subscription, and MMA, and observed that the proposed protocol exhibited better performance in terms of transmission success ratio and overhead on the network.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5B
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• pp.253-263
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• 2005

This paper proposed a mobile multicast technique to satisfy end-to-end QoS for various user requirements in mobile network environment. In order to provide seamless mobility, fast handoff technique was applied. By using L2 mobile trigger, it was possible to minimize remarkable amount of packet loss by delay occurred during handoff. To provide efficient multicast, concept of hierarchy was introduced to Xcast++, which results in a creation of HXcast++. HXcast++ optimized transfer path of multicast and reduced expensive multicast maintenance costs caused by frequent handoff. Suggestion of GMA (Group Management Agent) mechanism allows joining to group immediately without waiting IGMP Membership query during handoff. GMA mechanism will minimize the delay for group registration process and the resource usage due to delay of withdrawal process. And also use of buffering & forwarding technique minimized packet loss during generation of multicast tree. IntServ/RSVP was used to provide End-to-End QoS in local domain and DiffServ was used in global domain. To minimize reestablishment of RSVP session delay, extended HXcast++ control messages ware designed to require PATH message. HXcast++ proposed in this thesis is defined as multicast technique to provide end-to-end QoS and also to satisfy various user requirements in mobile network environment.

• The Transactions of the Korea Information Processing Society
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• v.5 no.12
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• pp.3206-3213
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• 1998

피코셀룰라망은 셀 반경이 수십 미터 내외인 피코셀로 구성된다. 작은 셀은 이동 호스트의 작은 핸드오프를 초대한다. 이동 사용자에게 중단없는 연결 서비스를 제공하기 위해서는 새로운 핸드오프 방법이 필요하다. 본 논문에서는 멀티캐스트 연결에 기초한 핸드오프 방법을 제안한다. 제안한 방법(SGMH: SubGroup Multicast-based Handoff)은 핸드오프 처리 지연뿐만 아니라 버퍼 오버헤드를 최소화한다. 분석과 시뮬레이션을 통해 블록킹 확률에 대해 성능 평가를 했다.

• Journal of Internet Computing and Services
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• v.6 no.4
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• pp.115-124
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• 2005

The packet loss problem that occurs in the mobile multicast (MoM) protocol due to designated multicast service provider(DMSP) handoff is investigated through simulation experiments for several DMSP selection policies. Then, two enhanced DMSP schemes are proposed to minimize the packet loss of the MoM protocol with single DMSP. The first scheme uses a backup DMSP and greatly reduces the packet loss rate at the expense of the increased network traffic. The second scheme utilizes the extended DMSP operation and shows many desirable features such as the almost zero packet loss rate and relatively low network traffic.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.16 no.1
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• pp.97-104
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• 2006

For successfully deploying many multicast service in the mobile environment, security infrastructures must be developed that manage the keys needed to provide access control to content. In this paper, we propose two methods for designing the key management scheme for the mobile multicast environment. The proposed schemes match the key management tree to the mobile multicast environment for localizing the delivery of he rekeying messages, reducing the communication costs, and solving the handoff problem in wireless region.

• The KIPS Transactions:PartC
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• v.9C no.1
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• pp.97-106
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• 2002

In 3GPP2 standard, MIP is used and a PDSN performs the function of FA to support macro mobility. When a MS is roaming from a PDSN area to another, the mobility supported is called macro mobility, while it is called micro mobility when a MS is roaming from a RN area to another in a PDSN area. Since a PDSN performs the function of FA in 3GPP2 standard, it is possible to support mobility but its mechanism is actually for supporting macro mobility, not for micro mobility, thus it is weak in processing fast and seamless handoff to support micro mobility. In this paper, we suggest the seamless handoff algorithm barred on multicast group mechanism to support micro mobility. Depending on the moving direction and velocity of a MS, the suggested algorithm constructs a multicast group of RNs on the forecasted MS's moving path, and maximally delays RNs'joining to a multicast group to increase the network efficiency. Moreover, to resolve the buffer overhead problem of the existent multicast scheme, the algorithm suggests that each RN buffers data only after the forecasted handoff time. To prove deadlock freeness and liveness of the algorithm. we use state transition diagrams, a Petri-net modeling and its reachability tree. Then, we evaluate the performance by simulation.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.1585-1588
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• 2004

이동 단말의 수요가 급증하고 무선 인터넷 환경이 널리 보급되면서 무선 멀티캐스트 환경의 필요성이 커지고 있다. 이를 위해 유니캐스트와 마찬가지로 핸드오프를 위한 프로토콜로 양방향 터널링과 원격 가입이 제시되고 있다. 하지만, 이들 프로토콜은 각각 데이터 전달 경로의 최적성과 실시간성에 있어서 문제점을 가지고 있다. 따라서 원격 가입 지연 시간을 최소화 시키기 위해 핸드오프 발생시 빠르게 그룹 참가 메시지를 보내도록 IGMP 를 수정하고 이를 직접 리눅스 커널에 구현 및 실험해 보았다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.757-759
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• 2004

무선 통신 기술이 급속히 발전하면서 이동 중 데이터 통신이 가능하도록 하기 위한 연구가 활발하게 이루어지고 있다. 본 논문에서는 효율적인 이동성 제공 방안으로 멀티캐스트 기반 이동성 제공 방안을 제안하고 모의실험을 통하여 TCP 트래픽에 대한 성능을 분석하였다. 본 논문에서 제안한 방안은 이동 단말이 외부 도메인 내에서 핸드오프 시 자신의 위치 갱신을 멀티캐스트 그룹에 조인하는 방법으로 바인딩 갱신에 따른 추가적인 신호를 지역 내에서 처리함으로써 Mobile IPv6와 Hierarchical Mobile IPv6 보다 TCP 처리율을 높임을 알 수 있었다.