• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.9B
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• pp.857-866
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• 2009

Recently, IP mobility study of infra's common elements is undergoing processes to achieve FMC based on All-IP. Existing typical mobility technology based on IP is IETF's Mobile IP. However, it faced to limitations due to packet loss, delays when MN is moving on Mobile IP, also existing network infra - routers (FA)-needed to add/change the functions to support Mobile IP. In this paper, existing mobility problems based on IP and the suggested improvements for platforms which support mobility, quality, security are proposed. It discusses the performance on the current existing IP infrastructure derived from simulation analysis on mobility packet loss and delay. From the resulting data, improvements will also be outlined for optimal performance.

• The Transactions of the Korea Information Processing Society
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• v.3 no.2
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• pp.283-294
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• 1996

To operate the automatic devices of manufacturing process more effectively and to solve the needs of the resource sharing, network technology is applied to the unit control devices located in common manufacturing zone and operated by connecting them. This paper introduces deign and test operation of cell system for the management of multivendor PLC by applying to wall paper process based on the manufacturing standardization of CIM. The analysis of designed multivendor PLC group is performed by selecting the parameters such as variation of data packet size and node number of PLC ladder logic program and variation by analyzing the corresponding variation values of token rotation time and waiting time for the system operation. For the method of the analysis,the equation is considering the overhead such as indicated packet service time and transmission safety margin for PLC network connection in M/G/1 queue model,and it is applied to the cell system and PLC group manage-ment for operation .Through the experiment,it is found that the realtime processing is possible with expanded and better result than the resuit obtained by Jayasumana.Browaka with PLC scan time considered,response lower limit of 10-20 msec. data packet size not more than 50 bytes.and the number of nodes less than 40.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.8
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• pp.778-782
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• 2008

The performance in combination of wired and wireless mesh network which will be a main access network in future internet is directly linked with service quality to users. In this paper, we evaluate variant TCP performance and analyze traffic characteristics on Wireless (Seoul National University Mesh testbed) - Wired (KOREN/Abilene) - Wireless (HP Mesh testbed in the USA) Network. We found that RTT is proper in this network to serve a VoIP service. Also we propose an enhanced TCP protocol which can perform well in both wireless network which has many packet losses and wired network which has high bandwidth and long delay.

• Journal of Korea Multimedia Society
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• v.7 no.1
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• pp.54-63
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• 2004

This paper describes a hybrid QoS guarantee scheme for high quality audio streaming services on the Internet. The continuous playback of the audio data requires the isochronous transmission of the audio data packet through the Internet. In order to retain the QoS at the ultimate destination (client) as the same as servers provide, the transmission protocols should consider the error conditions such as packet loss, and out of order delivery. Generally, the protocols supporting the transmission of continuous media data do not try to recover the errors. The protocols are working somehow for the toll quality multimedia streaming services, but rot for the high quality streaming services, such as the DVD sound/music payback. The hybrid QoS guarantee scheme includes the three mechanisms to overcome the problem. The selective retransmission for the lost packet, the adaptive buffering at client-side, and the adaptive transmission rate at server-side are totally adopted to recover the packet loss with the minimal overhead, to prevent from the buffer starvation during the retransmission, and to maintain the isochronous transmission even after the retransmission. The experiments have shown good results for the high Quality audio streaming services on the Internet.

• Journal of the Korea Society for Simulation
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• v.20 no.1
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• pp.19-28
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• 2011

The safety applications based on the IEEE 802.11p, periodically transmit the safety-related information to all surrounding vehicles with high reliability and a strict timeline. However, due to the high vehicle mobility, dynamic network topology and limited network resource, the fixed beacon scheduling scheme excess delay and packet loss due to the channel contention and network congestion. With this motivation, we propose a novel beacon scheduling algorithm referred to as spatial-aware(SA) beacon scheduling based on the spatial context information, dynamically rescheduling the beaconing rate like a TDMA channel access scheme. The proposed SA beacon scheduling algorithm was evaluated using different highway traffic scenarios with both a realistic channel model and 802.11p model in our simulation. The simulation results showed that the performance of our proposed algorithm was better than the fixed scheduling in terms of throughput, channel access delay, and channel load. Also, our proposed algorithm is satisfy the requirements of vehicular safety application.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.6A
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• pp.558-564
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• 2007

3G Long Term Evolution, which aims for various mobile multimedia service provision by enhanced wireless interface, proposes VoIP-based voice service through a Packet Switching (PS) domain. As delay and loss-sensitive VoIP traffic flows through the PS domain, more challenging technical difficulties are expected than in Circuit Switching (CS) domain based VoIP services. Moreover, since 3G LTE, which adopts the OFDM as its physical layer, introduces Physical Resource Block (PRB) as a unit for transmission resources, new types of resource management schemes are needed. This paper proposes a PRB scheduling algorithm of MAC layer for VoIP service in 3G LTE and shows the simulation results. The proposed algorithm has two key parts; dynamic activation of VoIP priority mode to satisfy VoIP QoS requirements and adaptive adjustment of the priority mode duration in order to minimize the degradation of resource utilization.

• Proceedings of the Korean Society of Computer Information Conference
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• 2009.01a
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• pp.293-296
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• 2009

최근에 다양한 네트워크의 기술들이 존재하고 개발되어지고 있다. 이러한 네트워크 기술들을 효과적으로 사용하기위해서 버티컬 핸드오버가 다양한 측면에서 연구되어지고 있다. 버티컬 핸드오버는 단말기가 이종망에서 더 나은 성능을 가진 네트워크로 끊김없는 서비스를 제공하는 핸드오버 기술이다. 버티컬 핸드오버를 수행하는 동안에 라우터간 시그널링의 지연과 더불어 인증과 등록절차에 대한 시간지연으로 인하여 혼잡한 상황이 아님에도 불구하고 TCP에서는 혼잡한 상황으로 인식하여 성능이 낮아지는 문제가 발생한다. 또한, 버티컬 핸드오버를 수행하는 중에 링크의 특성이 다르고 대역폭이 달라서 패킷의 순서번호가 일치하지 않아서 잘못된 빠른 재전송(false fast retransmission:FFR) 발생하고 이러한 현상들은 TCP 처리량의 저하를 가져온다. 논문에서는 이러한 문제를 해결하기 위한 방법들에 대한 동향을 조사 해보았다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.52-54
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• 2004

B3G(Beyond 3 Generation) 망의 구조는 글로벌 로ald환경 구축을 위해서 3세대망인 UMTS와 WLAN의 각각의 장단점을 보완하여 통합한 것이다. 현재 B3G 망의 구조는 크게 loosely-coupled와 장기적 접근을 요구하는 tightly -coupled 방식으로 나눌 수 있다. Loosely-coupled 방식은 tightly-coupled 방식에 비해 독립적 확장이 가능하고 비교적 구현이 쉬우나 핸드오버의 지연으로 인한 패킷 손실과 서비스 끊김 등의 단점이 있다. 본 논문에서는 이를 개선하기 위하여 HMIPv6의 MAP를 사용하여 UMTS와 WLAN의 인터네트워킹에 대한 수직적 핸드오버 프로시저를 제안한다. 각 단계별 총 지연시간을 통하여 블로킹 확률을 측정해 본 결과 제안된 HMIPv6를 사용한 방식이 기존의 MIPv6를 사용한 방식보다 성능이 우수함을 확인하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.04a
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• pp.449-452
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• 2001

이동 컴퓨팅 환경에서의 통신은 유선 네트워크 상에서 이루어지는 통신에 비해 대역폭이 적고 패킷 에러율이 크다는 제약 사항들을 갖는다. 이러한 환경에서 분산 파일 시스템 서비스는 데이터 송수신이 시간과 위치에 따라 일정하지 않고 데이터가 손실되었을 때 복구 가능성이 낮은 문제점이 있다. 본 논문에서는 기존의 파일 시스템에 사용되는 저널링 기법과 기존의 이동 컴퓨팅 환경을 위한 파일 시스템(mobile filesystem)에서 사용되는 연산 적재(operation shipping)기법을 혼합한 방식으로 이동 컴퓨팅 환경을 위한 파일 시스템을 고안하였다. 이 기법은 기존의 이동 컴퓨팅 환경을 위한 파일 시스템보다는 데이터 복구가능성을 높이고 데이터 재통합(reintegration) 기능을 효율적으로 수행할 수 있다.

• Journal of Korea Multimedia Society
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• v.7 no.1
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• pp.106-112
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• 2004

Mobile IP is a solution for mobility on the global Internet. However, it causes service delay incase of frequent movement of mobile node and mobile users. Mobile IP regional registration is Proposed to reduce the service delay. In this paper, we introduce an optimal regional location management mechanism for Mobile IP that reduces the registration delay. The movement of mobile node is described by a discrete analytical model. The proposed model explains analytically average packet rate and registration cost as the size of regional networks with mobility of mobile node.