• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.637-640
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• 2011

Recently, rapid spreading of smart-phone make an expectation for increase of practical application for MANET(Mobile Ad-Hoc Network) which is not used infrastructure like as base-station. One of important application for MANET will be VoIP(Voice over Internet Protocol) known as Internet telephony. On the other hand, information intrusions causing serious problems is not allowed exception of MANET. Especially, there are some dangerous problems of intrusions to MANET, differently to other networks, because of it's usage of military purpose or emergency application of rescue. In this paper, to analyze this intrusion problem on MANET with blackhohe attacks, effect of intrusion to transmission performance is studied. VoIP traffic is assumed as an application service on MANET, computer simulation with NS-2 is used for this analysis.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10c
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• pp.445-447
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• 2003

최근 무선네트워크의 급속한 확대로 무선인터넷 접속 또한 크게 증가하고 있다. 무선인터넷을 이용하는 Voice over IP 서비스는 IP 기반의 인터넷과 셀룰러 네트워크를 합쳐 놓은 것과 유사하며 모바일 노드의 이동성 확보가 핵심 기술이다. 특히 VoIP 서비스 이용자는 지연이나 끊어짐에 대하여 매우 민감하므로 가급적 지연시간이 적은 핸드오프 기법이 필요하다. 본 연구에서는 무선네트워크를 이용하는 VoIP 서비스 프로토콜 중 하나인 SIP를 기반으로 이동성 관리를 위한 신호의 흐름을 도시하여 발생 가능한 지연의 구성요소를 분석하였으며 핸드오프 지연을 줄이기 위한 Prediction Shadow Registration을 제안하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.11
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• pp.2405-2410
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• 2012

The 4th generation mobile communication system, LTE, does not support an additional core network to provide voice service, and it is merged into a packet network based on all IP. Although Voice service over LTE can be supported by VoIP, it will be provided by the existing 3G networks because of the discontinuity of LTE coverage. However, it is inevitable to adopt VoIP over LTE to provide high quality voice service. In this paper, we investigate the capacity of VoIP over LTE. Our results indicate that spectral efficiency can be significantly improved as channel bandwidth increases in terms of VoLTE capacity. In addition, we can achieve higher VoLTE capacity without decreasing control channel capacity.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.1
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• pp.49-54
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• 2011

In this paper, End-to-End VoIP(Voice over Internet Protocol) performance over large scale MANET(Mobile Ad-hoc Networks) is evaluated. VoIP implementation model, which can be used for large scale MANET, is suggested through this evaluation. VoIP simulator based on NS-2 network simulator is used for performance measurement. Call connection ratio as a connection performance, MOS and network delay as a transmission performance, packet loss rate as other performance is measured with this simulation. Finally, maximum $10{\sim}15km^2$ as a single MANET, 500 nodes and 100 call connections is suggested for VoIP implementation and operation conditions over large scale MANETs.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.11-14
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• 2005

In this paper, we propose a method for transmitting SMS(Short Message Service) for VoIP(Voice over IP) service supporting multi-protocol. The multi-protocol VoIP under consideration are generally composed of H.323, SIP and MGCP and Most ITSPs(Internet Telephony Service Provider) provide VoIP service with H.323 and SIP now. SMS is killer application in mobile telecom service and many people of various field use that service. For example, user can send many SMS messages and substitute e-mail. Also SMS can be provided with various internet application. Ahn, legacy phone of KT, can use SMS. Therefore VoIP phone also can be required with the same requirement. With the multi-protocol VoIP we will propose several methods sending efficiently SMS. To show the validity of the proposed method some examples are given in which the results can be expected by intuitive observation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.8
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• pp.1640-1646
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• 2004

In this study, we propose the multiple VoIP service networks for P2P network environments based on portable internet. We found that voiceservice using portable internet is possible for real time services. After we designe the multiple VoIP service networks for P2P network environments based on portable internet, evaluate the performances. from the performance evaluations, we found satisfactory results and so we can expect the possibility of the portable internet services.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.513-516
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• 2003

데이터 패킷 전송을 지원하는 인터넷망에서는 여러 부가 서비스를 제공할 수 있다. 그중 VoIP 는 킬러 에플리케이션이라고 주목받고 있다. 그러나 기존 회선교환망에서 제공하던 음성전송을 패킷망에서 제공할 경우 여러 문제점이 나타난다. 가장 큰 문제점은 서비스 품질면 즉 많은 유저들이 접속함으로써 일어나는 지연이다. 특히 핸드오프가 빈번한 도메인 환경에서는 접속자수가 증가함에 따라 품질저하는 더 크게 일어난다. Mobile IP 는 도메인내의 빈번한 핸드오프상에서는 많은 단점이 있다. HA(Home Agent)로 빈번하게 시그널을 보내기 때문에 많은 제어 메시지 오버헤드가 있으며, 핸드오프중의 많은 패킷 손실이 있다. Micro-mobility 프로토콜은 기존 mobile IP 의 단점을 보완하기 위해 나온 프로토콜이다. 무선 네트웍상의 도메인내에서의 이동성을 지원하며, 손실과 메시지 오버헤드를 줄여 핸드오프시 높은 성능향상을 주고, 효율적인 위치관리를 제공한다. 본 논문은 NS-2(Network Simulator-2)를 이용하여 여러 마이크로 모빌리티 프로토콜하에서 VoIP 를 운용하였을 때, 어느 프로토콜의 확장성이 우수한지를 비교하고, 빈번한 핸드오프시에 어느 프로토콜이 가장 효율적인지를 제시한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.719-721
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• 2010

VoIP over MANET is an important IP phone technique used in mobile ad-hoc networks. VoIP system over wired networks is based on SIP, SIP UA and SIP server which process the users invite, register and so on. Since no base stations in MANETs to perform as SIP servers, VoIP service on MANETs is being done with tiny SIP server which is done on each node. In this paper, VoIP system is implemented with pseudo SIP server which can process 1 call based on modification of standard SIP server which is used on communication environment such as wired networks. The propesed system is performed well and compatible with SIP and SIP UA.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.431-433
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• 2010

VoIP is a communication technique can be used anywhere you can find wifi signal and it costs much lower than conventional mobile service. However, security of VoIP is not as robust as former, the converse could be easily intercepted and attacked especially in MANETs which the attackers access easier than in wired networks. Sercurity of VoIP system in MANETs is an important issue nowadays. In this paper, a typical attack method of VoIP systems in MANETs is described and we implement how to prevent it.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.4
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• pp.747-752
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• 2012

In this paper we evaluated by simulation the effect of VoIP roaming and data traffic roaming on other VoIP calls. Regardless of MIPv4 or MIPv6, the quality of voice of all VoIP calls falls down quickly to the bottom level after the start of roaming by one voice terminal. That was caused by the excessive retransmission on downlink. Thus it seems that we need a kind of call admission control when we adopt the roaming service on VoIP calls. Data traffic degrades also the voice quality especially at the foreign agent side.