• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6A
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• pp.832-844
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• 1999

In this paper, we analyzed mobile-IP protocol of IETF, and propose new method to improve performance in handover environments. In proposed method, cache agent manages mobility binding information for mobile host. Thus, effective support of mobility is possible. Also, when handover occurs, mobile host recognizes change of foreign agent, and transmits registration message to new foreign agent. However, during registration time, data packet loss is occurs in old foreign agent. Thus, we prevent data loss by using data packet buffering and forwarding in old foreign agent.According to simulation results for data packet transmission performance in the case of handover occurring, proposed method has better performance than previous method in the view of transmission delay and throughput. Especially, if handover occurs very often, data buffering and forwarding method in foreign agent could guarantee better performance.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.4
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• pp.9-16
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• 2015

Quick and safe message transmission is an important research topic of vehicular ad hoc networks (VANET). Most studies assume that the periodic broadcast of beacon-frames between vehicles increases the safety of the driver. In this paper, we propose a medium access control (MAC) protocol and location-based clustering for the VANET to support reliable data transfer. In our proposal, the cluster heade (CH) manage the access and allocate the resources of the node. Our proposal uses simulation to confirm the reduction of the transmission delay and the collision rate of the signal.

• Proceedings of the Korea Contents Association Conference
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• 2004.05a
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• pp.342-347
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• 2004

The VoIP(Voice over Internet Protocol) technology which is able to use a voice service through internet is more cheaper then existing telephone charges, and is easily accept the various of multimedia services from internet. Previous connection method of VoIP used H.323 protocol, but it is very complex to connection establishment. so, the SIP(Session Initiation Protocol) protocol that propose in SIP-Working Group Is in use recently. Therefore, we need new interworking methodology between H.323 and SW products. In this thesis, the progress interworking method between H.323 and SIP are propose, then interpret unnecessary packet delay for call setup and improved feature of message exchange.

• Journal of Korea Multimedia Society
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• v.3 no.6
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• pp.625-632
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• 2000

This paper proposes an adaptive multislot allocation algorithm in order to achieve large system capacity and higher throughput data transmissions. The proposed system is the combination of the slow adaptive modulation system, in which the base station dynamically a signs optimum modulation parameters measuring the CNR(carrier to noise power ratio) of each transmission terminal, and the multislot allocation scheme, in which the base station flexibly allocates an appropriate number of TDMA data slots according to the instantaneous load conditions. Computer simulations confirm that the proposed system can tremendously improve average message delay characteristics in comparison with the conventional fixed slot allocation method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.6
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• pp.1241-1246
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• 2005

This paper proposes an adaptive multislot allocation algorithm in order to achieve larger system capacity and higher throughput data transmissions. The proposed system is the combination of the slow adaptive modulation system, in which the base station dynamically assigns optimum modulation parameters measuring the SNR of each transmission terminal, and the multislot allocation scheme, in which the base station flexibly allocates an appropriate number of TDMA data slots according to the instantaneous load conditions. Computer simulations confirm that the proposed system can tremendously improve average message delay characteristics in comparison with the conventional fixed slot allocation method.

• Journal of Digital Convergence
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• v.11 no.3
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• pp.279-284
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• 2013

Wireless access network section needs strong security which supports high data rate and mobility not to invade patient's privacy by exposing patient's sensitive biometric from automatic implantable device that is adapted to u-healthcare service. This paper builds test bed and performs assessment and measurement of security ability of WiMAX network to transmit and receive mobile patient's biometric by building WiMAX network in wireless access network not to expose paitne's biometirc at wireless access network section to the third person. Specially, this paper compares and assesses data security, MAC control message security, handover conection delay, and frame loss and bandwidth of ECDH at the layer of WiMAX security compliance, WiMAX MAC IPSec, and MAC.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.105-106
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• 2015

본 논문에서는 DTN(Delay Tolerant Network) 환경에서 효율적인 메시지 전달을 위해 확률적으로 중계 노드를 선택하는 기법을 제안한다. DTN은 종단 간 연결이 불확실한 네트워크에서의 통신을 Store-Carry-Forward 방식을 사용하여 메시지를 목적 노드에 전달한다. 또한 종단 간 연결이 불확실한 상황에서도 중계 노드를 통해 메시지를 목적 노드에 전달하여 높은 전송률을 보장한다. 하지만 에피데믹(Epidemic) 라우팅이나 Spray and Wait 라우팅과 같은 기존 다중 복사 라우팅 알고리즘은 접촉한 모든 노드에게 메시지를 복사하여 메시지 복사로 인한 오버헤드가 높아진다. 반면에 PROPHET 라우팅과 같은 단일 복사 알고리즘은 적은 오버헤드를 발생시키지만 중계 노드 수 감소로 인한 메시지 전송률 감소 현상이 나타난다. 본 논문에서 제안하는 알고리즘은 기존 DTN 라우팅의 문제점을 보완하기 위해 확률적으로 노드 분포를 분석하여 현재 네트워크에 효율적인 메시지 복사 방식을 선택하여 작동한다. 본 논문에서는 제안하는 알고리즘이 기존 DTN 라우팅 알고리즘과 오버헤드와 전송률을 비교하여 더 효율적임을 증명한다.

• Journal of Electrical Engineering and Technology
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• v.7 no.3
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• pp.443-450
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• 2012

As power grids are integrated into one big umbrella (i.e., Smart Grid), communication network plays a key role in reliable and stable operation of power grids. For successful operation of smart grid, interoperability and security issues must be resolved. Security means providing network system integrity, authentication, and confidentiality service. For a cyber-attack to a power grid system, which may jeopardize the national security, vulnerability of communication infrastructure has a serious impact on the power grid network. While security aspects of power grid network have been studied much, security mechanisms are rarely adopted in power gird communication network. For security issues, strict timing requirements are defined in IEC 61850 for mission critical messages (i.e., GOOSE). In this paper, we apply security algorithms (i.e., MD-5, SHA-1, and RSA) and measure their processing time and transmission delay of secured mission critical messages. The results show the algorithms satisfying the timing requirements defined in IEC 61850 and we observer the algorithm that is optimal for secure communication of mission critical messages. Numerical analysis shows that SHA-1 is preferable for secure GOOSE message sending.

• ETRI Journal
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• v.37 no.4
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• pp.696-706
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• 2015

This paper presents an achievable secure videoconferencing system based on quantum key encryption in which key management can be directly applied and embedded in a server/client videoconferencing model using, for example, OpenMeeting. A secure key management methodology is proposed to ensure both a trusted quantum network and a secure videoconferencing system. The proposed methodology presents architecture on how to share secret keys between key management servers and distant parties in a secure domain without transmitting any secrets over insecure channels. The advantages of the proposed secure key management methodology overcome the limitations of quantum point-to-point key sharing by simultaneously distributing keys to multiple users; thus, it makes quantum cryptography a more practical and secure solution. The time required for the encryption and decryption may cause a few seconds delay in video transmission, but this proposed method protects against adversary attacks.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.4
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• pp.239-243
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• 2011

In wireless ad-hoc network, the detection of link breakage and re-establishing the route path causes lots of network overhead and results in communication delay. In the LBN method, the node causing a link breakage actively sends a message to neighbors so that they can instantly start re-establishing process of new path. In this paper we describe the result of network simulation we performed using NS2 to show the effectiveness of LBN method.