• Proceedings of the Korean Information Science Society Conference
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• 2003.10c
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• pp.61-63
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• 2003

본 논문에서는 PDA에서 IP Multicast방법을 이용한 멀티미디어 통신 시스템을 설계하고 구현한다. IP Multicast는 하나이상의 송신지에서 다수의 수신지로 패킷을 보내게 되는 통신방식으로 특정 그룹내에서의 통신을 가능하게 한다. 본 논문에서 구현한 PDA용 멀티미디어 통신 시스템은 음성, 문자, 필기체등으로 구성된 멀티미디어 요소를 IP Multicast를 응용한 통신 시스템이다. 구현된 PDA용 멀티미디어 통신 시스템은 네트워킹의 이동성(mobility)과 단말의 휴대성(portability)이 요구되는 유통업계의 POS시스템이나, 서비스업계의 사고보고, 주차통제, 응급서비스 및 수리, 유지보수등의 분야에서 폭넓게 사용될 수 있다.

• Journal of the Korea Society for Simulation
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• v.15 no.3
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• pp.87-91
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• 2006

With the growth of the internet, the number of wireless internet users has increased continuously up to date. However, mobile communications could not support high speed transmission rate with cheap communication fee and wireless LAN has problems in providing terminal mobility and wide area connectivity, respectively. So the WMAN standard has been newly designed to make up for these limits. The initial 802.16 specification effectively offers a solution for providing fixed users with high speed wireless communication but it does not offer terminal mobility. So the 802.16d and 802.16e have been developed as the next generation solution that can support various PHY layer (SC, SCa, OFDM, OFDMA) and offer the terminal mobility. In this paper, we propose an effective uplink scheduling algorithm for VoIP with using UGS, and we show that our proposed algorithm is superior in view of average delay and management of uplink bandwidth to conventional rtPS algorithm and the scheme in reference, with using NS-2 network simulator.

• The KIPS Transactions:PartC
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• v.13C no.2 s.105
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• pp.211-218
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• 2006

The Mobile IPv6 provides the enhanced internet services to user by supporting a node's mobility. In Mobile IPv6(MIPv6), the mobile node sends the binding message which binds home address(HoA) with care-of address(CoA) to the home agent whenever it changes its point of attachment to the internet. To reduce the mobility management signal message the Paging Hierarchical Mobile IPv6(PHMIPv6) is proposed. The mobile node does not send the binding message within the domain if the mobile node's state is idle. Therefore the mobility signal message cost can be reduced. However, when the mobile node's session arrival rate is high the many mobility management signal cost are needed because the paging cost is very high. In this paper, we analysis the drawback of PHMIPv6 and propose the scheme which can reduce the mobility management signal cost. The proposed scheme works independent of the number of subnet in the domain. Therefore the proposed scheme can improve the mobile node's mobility management scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.6B
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• pp.387-395
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• 2005

In this paper, we propose an end-to-end mobility management and TCP flow control scheme which considers different link characteristics for vertical handover environments. The end-to-end mobility management is performed by using SIP protocol. When a mobile node moves to a new network, it informs its movement of the correspondent node by sending SIP INFO message containing a new IP address which will be used in the new network. And then the corresponding node encapsulates all packets with the new IP address and sends them to the mobile node. in general, RTT of WLAN is shorter than RTT of cdma2000. when the MN moves from WLAN network to cdma2000 network, TCP retransmission timeout will be occurred in spite of non congestion situations. Thus, TCP congestion window size will be decreased and TCP throughput will be also decreased. To prevent this phenomenon, we propose a method using probe packets after handover to estimate a link delay of the new network. We also propose a method using bandwidth ratio of each network to update RTT. It is shown through NS-2 simulations that the proposed schemes can have better performance than the previous works.

• Journal of Internet Computing and Services
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• v.13 no.3
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• pp.1-16
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• 2012

Cost-effective mobility management for the roaming mobile users is very important in the seamless services on next-generation wireless network (NGWN). MIPv6 (Mobile IPv6) is one of the mobility management schemes proposed by the IETF (The Internet Engineering Task Force) and various IPv6-based mobility management schemes have been developed. They are directly involved with data transfer from MN (Mobile Node). In this paper, two kinds of schemes in analyzing of mobility management schemes are proposed. The signaling transfer and packet delivery procedures for each mobility management schemes are analyzed, respectively. The signaling cost for mobility management schemes are calculated, and the cost of each protocol are analyzed numerically. In other word, applying the sum of signaling cost and packet delivery cost to each mobility management scheme, their costs are analyzed. Finally, our performance evaluation results that the network-based mobility management scheme shows better performance in terms of overall cost.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.12 s.354
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• pp.42-52
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• 2006

The interest for IPv6, Which is next generation IP, increases, while th difficulty for adopting it into IT indestries also increase too. We also expect that Internet technologies develop 0 basis of All-IP networks, which include various heterogeneous networks. Therefore, it is necessary for network to support mobility and multicast capavility to create application with wide-variety- In this paper, we propose a scheme that be able to provide mobility and multicast efficient in IPv6 networks. The proposed scheme has been implemented and experimented on NS-2 and validated with respect to multicast packet delay time and count of Joining and pruning)

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.12B
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• pp.1135-1144
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• 2003

In this paper, we proposed a semi-soft handoff mechanism to provide link mobility in IEEE 802.11 wireless LAN environment. Buffers and routing tables in APs and portals are provided in order to reroute frames, which have not been received during handoff time and have been buffered in an old AP, to a new AP after handoff is performed. For the re -routing operation, the MAC routing table should be updated by exchanging information of a mobile terminal between neighbor APs. With our proposed scheme. a wireless LAN node can perform semi soft handoff while changing its attached AP and provide mobile IP and/or real time service like voice over IP. Also, we have done simulation for evaluation of the performance of the proposed scheme. We show that our semi soft handoff mechanism can be applied for real-time service with no frame loss in mobile environment.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10a
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• pp.208-210
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• 1998

본 논문에서는 무선 ATM에서 이동 IP 서비스를 제공하기위해 "Mobile NHRP"라는 새로운 방안을 제안한다. IP망과 WATM망을 연동하고자할 때 사용하는NHRP기법과 Mobile PNNI기법을 혼용할 때 발생하는 비효율성을 지적하고 그 대안을 제시한다. 제안된 Mobile NHRP에서 이동 NHC와 연결설정을 이루기 위해 홈LIS를 거치지 않고 직접적으로 NHC와 연결하도록 하는 ATM망에서 효율적으로 빠르게 이동 단말로의 IP연결성이 이루어지도록한다. 이루어지도록한다.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10c
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• pp.241-243
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• 2001

Cellular IP는 micro-mobility와 seamless handoff를 지원하기 위해 제안된 프로토콜이다. Cellular IP는 핸드오프 동안 지연과 패킷 손실을 줄이기 위해 semi-soft handoff 메커니즘을 사용한다. 반면. 이 메커니즘은 네트워크 자원의 낭비를 초래한다는 단점을 가지고 있다. 본 논문에서는 이러한 낭비를 줄이면서. 핸드오프 동안의 패킷 손실을 방지하는 방안을 제시하고, ns2를 이용한 시뮬레이션을 통해 제안된 메커니즘의 성능을 측정하도록 한다.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10c
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• pp.223-225
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• 2001

본 논문에서는 미시적 이동성 지원을 위해서 Mobile IP를 수정하는 방안을 제안하였다. 기존의 방안들은 미시적 이동성 지원만을 위한 새로운 프로토콜을 제안하였기 때문에 도메인 내에 하나의 루트 라우터를 두어야만 하는 한계가 있었다. 본 논문에서는 이를 해결하기 위해서 Mobile IP 자체에 몇 가지 새로운 메시지와 자료 구조를 추가하여 임의의 개수의 경계 라우터를 가질 수 있는 방안을 제안하였다.