• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.19 no.1
• /
• pp.81-92
• /
• 2009

Recently, there is a drastic increase in users interested in real-time multimedia services in the WLAN environment, as the demand of IEEE 802.11 WLAN-based services increases. However, the handoff delay based on 802.11i security policy is not acceptable for the seamless real-time multimedia services provided to MS frequently moving in the WLAN environment, and there is a possibility of DoS attacks against session key derivation process and handoff mechanism. In this paper, a secure and efficient handoff mechanism in the centralized WLAN environment is introduced to solve the security problems. The 4-way Handshake for both mutual authentication and session key derivation is replaced by the 2-way Reassociation process.

• Proceedings of the KIEE Conference
• /
• 2006.10b
• /
• pp.199-203
• /
• 2006

무선통신 환경에서 단말의 이동에 의해 발생되는 끊김 현상을 제거하고, 지속적인 서비스를 제공하기 위해서는 빠른 핸드오프(Handoff) 방식이 필요하다. 본 논문에서는 모든 채널을 탐색한 후, 가장 상태가 좋은 채널을 선택하는 기존 방식을 개선한다. 각 AP(Access Point)가 현재 사용하고 있는 채널정보와 ACR(Access Control Router)가 제공하는 인접 AP들 정 보의 주기적인 NEB-ADV에 포함하여 이동단말에 제공 한다. 본 논문에서는 정보를 습득한 단말이 인접한 AP들의 사용 채널만 탐색하는 새로운 Fast Channel Detection(FCD)방식을 제안한다. 제안하는 방식은 기존 방식과 비교하여 채널탐색 시간이 감소되므로 총 지연시간을 감소시킨다. 제안된 방식에 대한 시뮬레이션 모델을 통해서 링크 효율성과 블록킹 확률의 비교 분석을 통하여 제안방식의 우수성을 입증한다.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2004.05a
• /
• pp.1549-1552
• /
• 2004

초고속 인터넷 서비스가 일반화되고, PDA 및 노트북 등의 휴대 이동 컴퓨팅 기기의 사용이 증가하면서 인터넷 환경이 유선망에서 무선망으로 점차 변화하고 있다. 무선 인터넷 제공을 위한 주요 인프라는 이동 통신망이나 무선 랜 망이며, 서비스 가입자들은 무선망에서도 유선망과 같은 높은 품질과 안전한 서비스를 요구하고 있다. 그러나 무선망은 유선망에 비해 외부로부터의 공격에 매우 취약하므로 사용자의 QoS 요구사항 뿐만이 아니라 안전한 통신을 보장해야 한다. 현재 표준화 기관인 IETF의 Mobile IPv6 워킹그룹에서도 보안문제를 가장 중요하게 다루고 있으며, 기존의 보안 기법들의 취약성을 극복하기 위한 방안으로 표준작업 그룹에서는 인프라 차원의 AAA인증 절차를 이용한 이동노드의 인증 방안이 연구되고 있다. 본 눈문에서는 무선인터넷 가입자의 안전성과 서비스 품질을 보장하기 위해 차별화 서비스를 적용한 Mobile IPv6와 AAA연동 방안을 제안 하였으며, AAA 인증 절차에 따르는 핸드오프 지연을 줄이기 위해 Fast Handoff를 적용한 방안을 제안한다.

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

• Journal of KIISE:Computing Practices and Letters
• /
• v.8 no.3
• /
• pp.336-343
• /
• 2002

Nowadays, after appearance of wireless network the existent internet environment is changing into the united wire/wireless network. But the present TCP regards all of the packet losses on transmission as the packet tosses due to the congestion. When it is applied on the wireless path, it deteriorates the end-to-end TCP throughput because it regards the packet loss by handoff or bit error as the packet loss by the congestion and it reduces the congestion window. In this paper, for solving these problems we propose the method that controls the performance of TCP on the wireless link by extending ECN which is used as a congestion control mechanism on the existent wire link. This is the method that distinguished the packet loss due to the congestion from due to bit error or handoff on the wireless network, so it calls the congestion control mechanism only when there occurs the congestion in the united wire/wireless network.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.14 no.1
• /
• pp.79-89
• /
• 2004

Mobile IP Low Latency Handoffs allow greater support for real-time services on a Mobile W network by minimizing the period of time when a mobile node is unable to send or receive IP packets due to the delay in the Mobile IP Registration process. However, on Mobile IP network with AAA servers that are capable of performing Authentication, Authorization, and Accounting(AAA) services, every Registration has to be traversed to the home network to achieve new session keys, that are distributed by home AAA server, for a new Mobile IP session. This communication delay is the time taken to re-authenticate the mobile node and to traverse between foreign and home network even if the mobile node has been previously authorized to old foreign agent. In order to reduce these extra time overheads, we present a method that performs Low Latency Handoffs without requiring funker involvement by home AAA server. The method re-uses the previously assigned session keys. To provide confidentiality and integrity of session keys in the phase of key exchange between agents, it uses a key sharing method by gateway foreign agent that Performs a ousted thirty party. The Proposed method allows the mobile node to perform Low Latency Handoffs with fast as well as secure operation

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 1998.10a
• /
• pp.182-185
• /
• 1998

In the two-tier CDMA cellular system with microcells and overlaying macrocells, slow-moving mobile user are assigned to microcells and those who move fast are assigned to overlaying macrocells in order to minimize the total number of handoffs. With this consideration the problem is how to find the thresholds by which the system distinguishes fast-moving user from those who move slowly based on the estimated speed of users. In this paper, two methods for the mobile speed estimation are proposed and two operations schemes for micro-macro cellular CDMA system are suggested. Based on these, Optimization models to find the optimal thresholds for micro-macrocell selection, which are subject to the constrains of QoS, are developed in view of minimizing the weighted total number of handoffs. And then algorithms to find optimal solutions of the models are devised.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.8B
• /
• pp.1115-1121
• /
• 2010

The DNAv6 was designed to support fast attachment for a host, which is corresponding to the movement detection part in the mobility management. Since, however, the DNAv6 has supported only DNAv6-capable ARs and DNAv6-capable hosts, an non-DNAv6 host could not support fast handoff function in a DNAv6 network. In this paper, we consider a new method of the fast attachment of non-DNAv6 hosts. To support the non-DNAv6 host in DNAv6 networks, we suggest a novel algorithm, RCA algorithm, where an AR can decide whether a host has the DNAv6 function and whether it has moved to a new link or not, and then the AR can inform the host of new link information. For the RCA algorithm, we proposed to modify the RS message and the Reconf_Link message with addition of some fields. To validate our RCA algorithm and its performance, we have accomplished simulation tests for the ND process, the DNAv6 process and the modified DNAv6 process with our RCA algorithm. In the viewpoints of the attachment delay and complexity, the proposed algorithm gives the better delay performance than the ND process while it presents the less complexity than the DNAv6 process.

• Journal of KIISE:Information Networking
• /
• v.31 no.6
• /
• pp.566-572
• /
• 2004

In this paper, we define the secure authentication model to provide a mobile node with global roaming service and integrate the Fast Handoff scheme with our approach to minimize the service latency. By starting the AAA(Authentication, Authorization and Account) procedure with Fast Handoff simultaneously when a roaming occurs, authentication latency is reduced significantly and provision of fast and seamless service is possible. The previous works such as IPsec(Internet Protocol Security), RR (Return Routability) and AAA define the procedures performed after the completion of Layer2 Handoff which leads us to study a way of providing the real time and QoS guaranteed service during this period. The proposed scheme is for this goal and when appling it to roaming environment it shows the cost reduction up to 55% and 17% for the case of the MN receiving the FBACK and not respectively before L2 Handoff occurs.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.5B
• /
• pp.413-420
• /
• 2006

HMIPv6 is designed to reduce the signaling load to external network and improve handover speed of MN by including Mobility Anchor Point(MAP) in local handover. However in this case of macro handover, it's just used pervious MIPv6 handover algorithm. So, it occurs packet loss and transmission delay problem. In this paper, we propose the mechanism applying the HMIPv6 for Fast Handover to choose suitable to the condition buffering handover. The condition for the selection is result distance measurement between MN and CN, between MN and NAR. Furthermore, using F-SNOOP protocol, it is possible to improve wireless network performance. Wireless network has high Bit Error Rate(BER) characteristic because of path loss, fading, noise and interference. TCP regards such errors as congestion and starts congestion control. This congestion control makes packet transmission rate low. However, F-SNOOP improves TCP performance based on SNOOP and Freeze TCP that use Zero Window Advertisement(ZWA) message when handoff occurs in wireless network.