• KIPS Transactions on Computer and Communication Systems
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• v.3 no.1
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• pp.7-14
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• 2014

The rapid increase of mobile devices such as smart phone and smart pad have raised the needs for seamless multimedia services during moving at anytime and anywhere. Current 4G mobile devices are equipped with both 4G (LTE) and WLAN (WiFi) interfaces, and mobile services operators provide wireless Internet services using 4G network with a wider coverage and WiFi zone. Generally users prefer to use the Internet services through WLAN rather than LTE in the coverage of WLAN. However, since WLAN has a long L2 handover latency, it is difficult to support seamless services during a handover. In this paper, we proposed an efficient handover scheme based on flow mobility for WLANs to support a seamless service during handovers by using the overlaid 4G network with a wider coverage. Also, we showed the outperformance of the proposed scheme on a testbed.

• KSCI Review
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• v.14 no.1
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• pp.265-271
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• 2006

In this paper, we propose a new automatic fingerprint identification system that identifies individuals in large databases. The algorithm consists of three steps: preprocessing, classification, and matching, in the classification, we present a new classification technique based on the statistical approach for directional image distribution. In matching, we also describe improved minutiae candidate pair extraction algorithm that is faster and more accurate than existing algorithm. In matching stage, we extract fingerprint minutiaes from its thinned image for accuracy, and introduce matching process using minutiae linking information. Introduction of linking information into the minutiae matching process is a simple but accurate way, which solves the problem of reference minutiae pair selection in comparison stage of two fingerprints quickly. This algorithm is invariant to translation and rotation of fingerprint. The proposed system was tested on 1000 fingerprint images from the semiconductor chip style scanner. Experimental results reveal false acceptance rate is decreased and genuine acceptance rate is increased than existing method.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05b
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• pp.1169-1172
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• 2003

무선 네트워크에서의 데이터 손실과 일관성 없는 지연, 그리고 전송 속도의 저하 등의 많은 문제점들로 인해 무선 네트워크에서의 QoS의 보장은 필수적이다. 본 논문에서는 Mobile IPv6 에서 제시되었던 AAA 와 MAP, QoS Object등의 솔루션들을 이용하여 MR이동 시 Binding Update로 인한 대기시간을 줄여주고, MR내의 각 노드들의 QoS 경로를 보장해주는 무선 네트워크 내의 네트워크 이동성을 고려한 메커니즘을 제시한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.11b
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• pp.1137-1140
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• 2003

인터넷 mobility 기술의 발전으로 인해 Mobile IPv6 를 기반으로 하는 이동 네트워크(Mobile Network, NEMO)기술이 등장하였으며, MR(Mobile Router)와 HA(Home Agent)간의 bi-directional 터널을 통해 네트워크의 이동성을 지원한다. 그러나. 이동네트워크 안에 또 다른 이동네트워크가 존재하는 중첩된 이동네트워크에서는 bi-directional 터널이 중복되는 routing problem이 발생한다. 따라서 본 논문에서는 중첩된 이동네트워크가 계층적 구조를 가지는 것을 이용하여, 최상위 MR 이 지역 HA 역할을 수행하게 항으로써, 중첩된 이동네트워크내의 노드들을 위한 경로최적화와 마이크로 이동성을 동시에 지원할 수 잇도록 한다.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.137-138
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• 2006

NEMO(Network MObility) is a complex model of mobile network which refers to a forming of Nested Mobile Network by a moving transportation like vessel, bus, or a train which then moves a Mobile Node, or by a movement of a PAN(Personal Area Network). In a Nested NEMO, pinball routing is the primary obstacle as exemplified by the IPv6 environment. This paper will focus on improving such models as RRH, RBU+ and MANET Approach, that attempted to solve pinball routing by route optimization.

• IEMEK Journal of Embedded Systems and Applications
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• v.18 no.4
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• pp.151-157
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• 2023

RPL (IPv6 Routing Protocol for Low-power Lossy Network) is a standardized routing protocol for LLNs (Low power and Lossy Networks) by the IETF (Internet Engineering Task Force). RPL creates routes and builds a DODAG (Destination Oriented Directed Acyclic Graph) through OF (Objective Function) defining routing metrics and optimization objectives. RPL supports a leaf mode which does not allow any child nodes. In this paper, we propose INFRA-RPL which provides a dynamic leaf mode functionality to a leaf node with the mobility. The proposed protocol is implemented in the open-source IoT operating system, Contiki-NG and Cooja simulator, and its performance is evaluated. The evaluation results show that INFRA-RPL outperforms the existing protocols in the terms of PDR, latency, and control message overhead.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.05a
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• pp.1080-1083
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• 2008

유비쿼터스 사회에는 도서관, 커피숍과 같은 공공장소와 자동차, 전철, 비행기등과 같은 대중교통에도 인터넷에 접근할 수 있게 될 것이다. 또한 모든 통신은 끊임없는 인터넷이 지원되어야 하고, 세션이 유지되어야 하며, 이동 중에 통신이 끊어지지 않고, 라우팅이 효율적으로 이루어져야 한다. 이러한 요구를 반영할 수 있는 네트워크 이동성 기술은 이동 IPv6이 가지고 있는 근본적이고, 비효율적인 삼각 라우팅 문제와 중첩된 환경에서 삼각라우팅 문제가 반복되는 핀볼 라우팅 문제를 가지고 있다. 본 논문은 중첩환경의 라우팅 문제를 조사하고, 해결하기 위해 이미 제안된 내용들을 분석하고, 효율성과 안전성을 만족할 수 있는 프로토콜을 제안한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.66-69
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• 2008

As a mobility support for IP have studied, Internet Engineering Task Force(ITEF) standardized the mobile IPv6 protocol. When a mobile node moves between networks, MIPv6 maintains connectivity to network and supports seamless communication, and these processes are called a Handover. IEEE 802.21 standardized MIH(Media Independent Handover) for seamless Handover. MIH used three services for Handover between low layer and upper layer. In this paper, we designed two modes on existing MIH for seamless Handover. We implemented a dual-interface mobile host(MH) model in network simulation2 (ns2) to evaluate how it performs in comparison with single-interface MH.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.11
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• pp.44-52
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• 2011

In this article, we present a QoS-guaranteed IP mobility management scheme of Internet service for fast moving vehicles with multiple wireless network interfaces. The idea of the proposed mechanism consists of two things. One is that new wireless connections are established to available wireless channels whenever the measured data rate at the vehicle equipped with mobile gateway drops below to the required data rate of the user requirement. The other is that parallel distribution packet tunnels between an access router and the mobile gateway are dynamically constructed using multiple wireless network interfaces in order to guarantee the required data rate during the mobile gateway's movement. By doing these methods, the required data rate of the mobile gateway can be preserved while eliminating the possible delay and packet loss during handover operation, thus resulting in the guaranteed QoS. The architecture of the IETF standard HMIPv6 has been extended to realize the proposed scheme, and detailed algorithms for the extension of HMIPv6 has been designed. Finally, simulation has been done for performance evaluation, and the simulation results show that the proposed mechanism demonstrates guaranteed QoS during the handover with regard to the handover delay, packet loss and throughput.

• The KIPS Transactions:PartC
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• v.15C no.1
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• pp.37-44
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• 2008

In order to minimize the signaling delay for a resource reservation on the new routing path after the handover of Mobile Node(MN) is completed, it is important to discover the crossover node where the old and new routing paths meet. With the 크로스오버 노드 being found, the signaling messages only need to be transferred on the changed part of the end-to-end path. The crossover node is generally discovered using the end-to-end Session ID(SID) of the established session between MN and Correspondent Node(CN). However, in the Hierarchical Mobile IPv6(HMIPv6) network, if the Mobile Anchor Point (MAP) reserves the resource by aggregate with the Home Agent(HA), the crossover node discovery cannot be performed in the general way since the aggregate SID that has established between the previous MAP and HA is different from the that of the current MAP and HA after MN's handover. In this paper, we propose a mechanism to discover the crossover node within the tunnel between the MAP and the HA in an HMIPv6 network, assuming that the Next Steps in Signaling(NSIS) is deployed for the resource reservation and the aggregate reservation is applied over the MAP and HA tunnel. The local repair required for the change of path is performed upon the crossover node discovery. The simulation results show that the proposed scheme reduces the signaling delay for the reservation and outperforms the existing scheme with respect to throughput during the handover.