• Proceedings of the Korea Multimedia Society Conference
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• 2003.11b
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• pp.782-785
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• 2003

최근 이동환경에서 고속 데이터 서비스를 제공하기 위해 WLAN망과 3G망의 각각의 장점을 취하기 위한 상호 보완관계로의 로밍에 관한 연구들이 많이 진행되고 있다. 따라서 본 논문에서는 IPv6의 장점을 그대로 수용하면서 단말의 이동성을 제공해 주는 MIPv6를 이용하여 전세계 70% 이상의 사용자를 보유한 3GPP(WCDMA)망과 WLAN망간의 로밍을 설계하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2016.10a
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• pp.100-101
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• 2016

비면허대역을 이용한 LTE(즉, LTE-U)에 대한 관심이 증가하고 있다. LTE와 WLAN은 같은 대역에서 동작할 때 필요한 공존 방법을 가지고 있지 않기 때문에 성능열화가 발생할 수 있다. 본 논문에서는 기존 연구들이 LTE와 WLAN의 공존을 어떻게 모색하고 있는지에 대해 정리한다.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2003.12a
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• pp.351-355
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• 2003

본 논문에서는 3GPP-WLAN 연동 보안에 필수인 EAP-AKA를 기반으로 한 인증/재인증의 개요와 인증 진행 부분에서 협상되는 마스터 세션 키 생성과 EAP AKA 패킷을 보호하기 위해 사용되는 키 생성에 관하여 설명하고, EAP-AKA 과정에서 생성되는 키의 안전성을 분석하고, EAP-AKA를 사용하는 3GPP-WLAN 연동의 효율성 및 고려사항에 대하여 고찰하였다.

• Proceedings of the Korea Multimedia Society Conference
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• 2004.05a
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• pp.475-478
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• 2004

최근 이동환경에서 고속 데이터 서비스를 제공하기 위해 WLAN망과 3G망의 각각의 장점을 취하기 위한 상호 보완관계로의 로밍에 관한 연구들이 많이 진행되고 있다. 따라서 본 고에서는 IPv6의 장점을 그대로 수용하면서 단말의 이동성을 제공해 주는 MIPv6를 이용하여 전세계 70% 이상의 사용자를 보유한 3GPP(WCDMA)망과 WLAN망간의 로밍을 구현하고 테스트하였다.

• 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.

• Journal of Advanced Navigation Technology
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• v.19 no.6
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• pp.623-629
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• 2015

In the present study, a coplanar waveguide (CPW)-fed printed monopole antenna with an inverted n-shaped slot is newly proposed for dual band operations which cover bandwidths of CDMA (1.85~2.025 GHz) and WLAN (2.4~2.484 GHz) as well as implementation of omnidirectional radiation pattern. For enhancement of impedance bandwidth ($S11{\leq}10dB$) in 2.4 GHz WLAN frequency band, an inverted n-shaped slot instead of the previous n-shaped slot is etched on the printed radiating monopole. The proposed antenna is designed and fabricated on one side of FR4 substrate with dielectric constant of 4.4, thickness of 1.6 mm, and size of $50{\times}25mm^2$. It has been observed that the measured impedance bandwidths are 280 MHz (1.84~2.12 GHz) in frequency band of CDMA and 420 MHz (2.38~2.8 GHz) in WLAN frequency band respectively. It is noticeable that impedance bandwidth in 2.4 GHz frequency band of WLAN is enlarged to three times due to use of inverted L-shaped slot in comparison with impedance bandwidth 140 MHz (2.39~2.53 GHz) obtained by use of the previous n-shaped slot. In addition, good omnidirectional radiation patterns have been observed over the entire frequency band of interest.

• TTA Journal
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• s.103
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• pp.123-127
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• 2006

• Journal of KIISE:Information Networking
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• v.32 no.4
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• pp.508-514
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• 2005

The research in internetworking between UMTS and WLAN, which is completed with merits and demerits, Is actively progressed to establish global roaming environments. This internetworking is classified into two groups: loosely-coupled and tightly-coupled. h tightly-coupled mechanism demands lots of investment and considerable amountof time to construct, which is directly connoted between UNTS and WLAN via IWU. On the other hand, a tersely-coupled mechanism is more scalable and easier to implement than a tightly-coupled one while it has critical drawbacks of packet loss and blocking of services due to handover delay. To alleviate these drawbacks. this work proposes a handover scheme between UMTS and WLAN, which is based on HMIPv6. The performance of the proposed scheme is evaluated by the simaulation. The proposed internetworking scheme based on HMIPv6 shows hotter performance than those based on MIPv6.

• Journal of Digital Contents Society
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• v.9 no.1
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• pp.61-67
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• 2008

In this paper, MAC algorithm for the IEEE 802.11 DCF improving the performance is proposed and analyzed by simulation. The MAC of IEEE 802.11 WLAN to control data transmission uses two control methods called DCF(Distributed Coordination Function) and PCF(Point Coordination Function). The DCF controls the transmission based on CSMA/CA(Carrier Sense Multiple Access with Collision Avoidance), that decides a random backoff time with the range of CW(Contention Window) for each station. Normally, each station increase the CW to double after collision, and reduces the CW to the minimum after successful transmission. The DCF shows excellent performance relatively in situation that competition station is less but has a problem that performance is fallen from throughput and delay viewpoint in situation that competition station is increased. This paper proposes an enhanced DCF algorithm that increases the CW to maximal CW after collision and decreases the CW smoothly after successful transmission in order to reduce the collision probability by utilizing the current status information of WLAN. To prove efficiency of proposed algorithm, a lots of simulations are conducted and analyzed.

• The KIPS Transactions:PartC
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• v.13C no.5 s.108
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• pp.607-612
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• 2006

Universal Mobile Telecommunications System (UMTS) and Wireless Local Area Network (WLAN) have been developed independently. Then, many researchers have studied UMTS-WLAN interworking architecture for the efficiency. However, the transmission capacity difference of two networks causes the transmission quality degradation. Therefore, this paper proposes a UMTS-WLAN interworking architecture for Quality of Service (QoS). The proposed architecture is based on tight coupling and dynamically guarantees QoS by the mobility prediction method. The proposed architecture is simulated by ns-2. Performance experimental results show that the proposed architecture reduces the handover dropping probability comparing with the existing method and enhances the amount of receiving packets comparing with the method without guaranteeing QoS.