• Proceedings of the Korea Information Processing Society Conference
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• 2011.04a
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• pp.631-634
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• 2011

IETF(Internet Engineering Task Force)는 신속하고 안전한 이동성 서비스를 위하여 네트워크 자원의 사용을 안전하게 하고 법적으로 보장하는 핵심기술 같은 많은 의미있는 작업들을 해오고 있으며 기존의 MIPv6(Mobile IPv6)에서 핸드오버 지연과 시그널링 오버헤드 같은 문제를 보완하기 위하여 HMIPv6(Hierarchical Mobile IPv6)를 제안하였다. 현재 HMIPv6에 관한 연구의 대부분은 HMIPv6와 AAA(Authentication, Authorization, Accounting) 프로토콜 사이의 상호작용 절차를 최적화하기 위한 방법에 초점을 맞추고 있다. 해당 논문에서는 AAA 절차에서 인증대기를 최소화하는데 중점을 둔 비용효율적인 계층 인증 기법을 제안한다. 이 기법에서는 MAP(Mobility Anchor Point)에 배포되어진 AAA 서버들, 그리고 홈 도메인 안에 있는 AAA 서버를 대신하는 브로커들의 계층적 AAA 아키텍처를 제안한다. 이 시뮬레이션 결과는 제안된 기법이 이전의 전통적인 인증 조합 모델링과 비교하여 핸드오프 지연과 인증대기 시간이 상당히 줄어들었음을 보여준다.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10d
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• pp.445-450
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• 2006

IPv6를 사용하는 계층적 모바일 인터넷(HMIPv6)에서는 단말의 이동을 관리하기 위해 MAP (Mobility Anchor Point)를 사용한다. 현재는 매크로 핸드오프 발생 시 단말로부터 가장 멀리 떨어져있는 MAP을 선택하는 기법을 사용하고 있다. 그러나 이 경우 하나의 큰 MAP으로 전체 부하가 몰리는 문제와 이동 단말과 MAP 간의 긴 거리로 인해 통신 비용이 증가하는 문제가 있다. 따라서 이 연구에서는 단말의 이동속도와 패킷 전송률을 종합적으로 고려하여 새 MAP 영역에서 소요될 이동지역비용을 계산하고 이를 최소화하는 MAP 도메인 크기를 구하여 실제 서비스 받을 MAP들 중 이와 가장 유사한 크기의 MAP을 선택하는 기법을 제안한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.04b
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• pp.639-642
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• 2001

차세대 이동통신망은 "ALL-IP Network" 이라고 불리는 차세대 이동 통신망을 위한 새로운 전송기술과 새로운 망으로 기존 망이 진화하게 될 것이다. 네트웍 계층에서 볼 때 기본적으로 이동단말기에서 IP 패킷을 생성하고 무선/유선 통신망을 통과할 때 이 IP 패킷이 그대로 유지되어 End-to-end 로 전달되는 것을 그 목표로 하고 있다. 본 논문에서는 두 상이한 이동 패킷 통신 시스템간의 Seamless한 통신을 위한 핸드오프를 Mobile IPv6 [4]관점에서 접근할 것이다. (Voice에 대한 고려는 생략하였다.)

• The KIPS Transactions:PartC
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• v.14C no.3 s.113
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• pp.305-312
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• 2007

In this paper, we present a received signal strength (RSS) prediction model to timely Initiate link layer triggers for fast handoff in a wireless LAN system. Noting that the distance between a mobile terminal and an access point is not changed abruptly in a short time interval, an adaptive RSS predictor based on a stationary time series model is proposed. RSS data obtained from ns-2 simulations are used to identity the time series model and verify the predictability of the RSS data. The results suggest that an autoregressive process of order 1 (AR(1)) can be used to represent the measured RSSs in a short time interval and predict at least 1-step ahead RSS with a high confidence level.

• Journal of KIISE:Information Networking
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• v.29 no.1
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• pp.1-14
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• 2002

The most important issue in providing multimedia traffic on a mobile computing environments is to guarantee the mobile host(client) with consistent QoS(Quality of Service). However, the QoS negotiated between the client and network in one cell may not be honored due to client mobility, causing hand-offs between cells. In this paper, a call admission control mechanism is proposed to provide consistent QoS guarantees for multimedia traffics in a mobile computing environment. Each cell can reserve fractional bandwidths for hand-off calls to its adjacent cells. It is important to determine the right amount of reserved bandwidth for hand-off calls because the blocking probability of new calls may increase if the amount of reserved bandwidth is more than necessary. An adaptive bandwidth reservation based on an MPP(Mobility Pattern Profile) and a 2-tier cell structure has been proposed to determine the amount of bandwidth to be reserved in the cell and to control dynamically its amount based on its network condition. We also propose a call admission control based on this bandwidth reservation and "next-cell prediction" scheme using an MPP. In order to evaluate the performance of our call admission control mechanism, we measure the metrics such as the blocking probability of our call admission control mechanism, we measure the metrics such as the blocking probability of new calls, dropping probability of hand-off calls, and bandwidth utilization. The simulation results show that the performance of our mechanism is superior to that of the existing mechanisms such as NR-CAT1, FR-CAT1, and AR-CAT1.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.12A
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• pp.1309-1318
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• 2004

The rapid growth of the mobile Internet has enabled its application area to expand, and its users want services that require more bandwidth for multimedia services. There are limits to support the various multimedia service to mobile station provided by existing mobile communications. The wireless MAN called the IEEE 802.16 Broadband Wireless Access systems which the IEEE 802.11 wireless LAN is similar to wireline Internet service being able to supper a various contents is used and is designed to consider a handoff is studying. Especially, TG(Task Group)e of IEEE 802.16 is in progress discussion to support a handoff to higher layer using BS(Base Station) or unit of sector, to UC. Yet a scheme is not detail. This thesis proposes the network model for IEEE 802.16e to support a soft handoff between BSs to use a mobile communication network called cdma2000 Ix EV-DO network. The proposed network model supports soft handoff to add a management skill in MA of each BS for MC(Mobility Controller). The proposed network model has merits that is able to apply existing systems as it is and that is able to use a various multimedia service, when using a wireless Internet.

• Journal of KIISE:Information Networking
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• v.33 no.1
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• pp.38-48
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• 2006

For extending of hot-spot of WLAN, (2) proposes internetworking scheme between wireless LAN (WLAN) and mobile ad-hoc network (MANET), which employ the same layer-2 protocol with different mode. Compared to internetworking schemes between UMTS (Universal Mobile Telecommunications Systems) and WLAN (3-4), the scheme from (2) has relatively low overhead and latencies because WLAN and MANET are physically and logically similar to each other. However, the mode switching algorithm proposed in r2] for internetworking between WLAN and MANET only considers signal strength and determines handoff, and mobile nodes following a zigzag course in pollution area may perform handoff at short intervals. Furthermore, (2) employs mobile IPv6 (MIPv6) at base, which brings still high delay on handoff and overhead due to signal message exchange. In this paper, we present optimized internetworking scheme between WLAN and MANET, modified from (2). To settle ping-pong handoff from (2), we propose adaptive mode switching algorithm. HMIPv6 is employed for IP connectivity and mobility service in WLAN, which solves some shortcomings, such as high handoff overhead and vulnerable security. For routing in MANET, OLSR is employed, which is a proactive Protocol and has optimally reduced signal broadcasting overhead. OLSR operates with current P protocol compatibly with no change or modification. The proposed internetworking scheme based on adaptive mode switching algorithm shows better performance than scheme from (2).

• Journal of Korea Multimedia Society
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• v.4 no.2
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• pp.161-170
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• 2001

Mobility management technology is one among the most important issues in future mobile communication systems. The mobility management technology includes location management and handoff technologies. In this paper, we present a hierarchical distributed dynamic location management scheme that is compatible with the IMT-2000 environment. The proposed scheme composes a cluster with location registers, then makes up a hierarchical structures consisting of clusters. Each layer in the hierarchical structure uses different location management strategies cooperating another layers with each other. Also, the proposed scheme uses location update algorithm considering the frequency of location queries from nodes outside the local cells. We evaluate the performance of the proposed scheme through an analytical model.

• Journal of Internet Computing and Services
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• v.12 no.4
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• pp.15-26
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• 2011

As quick and secure mobility service is becoming a critical issue in the ubiquitous environment. Internet Engineering Task Force (IETF) has done a lot of meaningful work in order to cope with the critical issues, which is a key technology of guaranteeing the legally and safely using of network resources, they has proposed Hierarchical Mobile IPv6 (HMIPv6) to complement for such problems as handover latency and signaling overhead in existing MIPv6. Most of the current research about HMIPv6 focuses on how to optimize the interactive processes between the HMIPv6 and AAA (Authentication, Authorization, Accounting) protocol. This paper describes a cost-effective hierarchical authentication scheme, which makes its focus on minimizing the authentication latency in AAA processing. In this scheme, a hierarchical AAA architecture is proposed, in which the AAA servers are deployed on the Mobility Anchor Point (MAP), the Root AAA server manages several Leaf AAA servers and the Brokers on behalf of the AAA server in home domain. The simulation results shows that the proposed scheme reduces the handoff and authentication latency evidently compared to the previous traditional authentication combination modeling.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04a
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• pp.139-141
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• 2002

차세대 인터넷은 유.무선이 혼합된 초고속의 네트워크 구조에서 사용자가 시간과 장소에 관계없이 실시간 멀티미디어 서비스를 제공받을 수 있는 환경으로 변화될 것이다. 이 변화에 잘 대응하기 위해서는 이동하는 사용자에게 효율적으로 멀티캐스팅을 지원할 필요가 있다. Mobile IP 기반의 이동 네트워크 환경에서 멀티캐스팅을 지원하기 위만 연구는 크게 HA(Home Agent)기반 방식과 FA(Foreign Agent)기반 방식으로 연구되어 왔다. HA기반 방식은 데이터 전송 경로의 비최적화, 비효율적인 데이터 중복 전송의 문제를 가지고, FA기반 방식은 빈번한 멀티캐스트 전송 트리의 재구성으로 인한 오버헤드의 문제를 내포하고 있다. 따라서, 본 논문에서는 MH(Mobile Host)의 잦은 핸드오프(handoff) 문제를 해결하고, 멀티캐스트 전송 트리의 재구성으로 인한 오버헤드를 줄이는 방법을 제안한다. 이 방법은 계층적 트리 구조의 도메인을 구성하고 MFA(Multicast Forwarding Agent)와 홉 카운터로 정의된 MFA의 서비스 범위를 사용한다. 또한, MFA를 Root FA들 중에서 선택함으로써 멀티캐스트 전송 트리 재구성의 회수를 줄여 Mobile IP를 이용하는 MH에게 효과적인 멀티캐스팅을 제공한다.