• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7A
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• pp.659-665
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• 2006

When using the Mobile IP which is the representative technology to secure the mobility in general IP networks, the packet loss during the handover is inescapable. To remedy the packet loss problem, the smooth handover was introduced. However, the smooth handover causes the packets sequence disruption during the packet forwarding procedure and it may result in the degradation of the network performance. The same problem also occurs in the WiBro (High-speed Portable Internet) system that is the next generation portable IP service system. The WiBro system, which provides the high speed data service just like xDSL and leased line in wired internet, aims to guarantee the portability, mobility, and the differentiated service based on IEEE 802.16. So, the handover mechanisms that solve the problems of packet loss and packet sequence distribution are required in the WiBro system. In this paper, we propose the handover mechanism and the packet sequence control algorithm that provide the reliability and the differentiated service for the unicast service in the WiBro system.

• Journal of Internet Computing and Services
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• v.7 no.5
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• pp.43-57
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• 2006

Next-generation mobile communication systems evolve in the form of high speed data transmission along with integration of wired-wireless network. Therefore, it needs researches on integrating service to heterogeneous networks to offer high speed data transmission and various services while supporting user mobility. In existing studies, heterogeneous networks are linked to single core network separatively, Since vertical handoff between heterogeneous networks leads to some delay, packets may be lost during vertical handoff. To solve this problem, this paper proposes an hierarchically integrated network architecture considering the characteristics of CDMA2000, WiBro, and WLAN. The hierarchically integrated networks are overlaid according to coverage of each network. Therefore, the proposed architecture can minimize handoff delay and packet loss. In addition, this paper proposes an integrated framework for next generation mobile communication networks.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.6
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• pp.1256-1264
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• 2011

MBS (Multicast Broadcast Service) is defined in WiBro networks for implementing multicast-based services. However, most of the WiBro networks currently used in Korea do not have the MBS functionality and it causes some difficulty in implementing multicast-based services. This paper evaluates the performance of VoIP-based group communication services when implementing using the following two cases: unicast-based and multicast-based group communication systems. The performance evaluation is done using QualNet for each case in terms of the amount of network resource for the service, the delay and delay jitter of packets, and the difference of the delay of members in a group. The simulation result shows that the number of groups and members in a group in a WiBro network is limited because the amount of network resource for the service is increased according to the number of members in a group, and so, the MBS service is required in a WiBro network for a fully-fledged service of VoIP-based group communications. The simulation result also shows that, when a packet bundling is used, the number of groups and members in a group that can be supported in a WiBro network can be increased due to the decrease of the amount of network resource for the service.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.414-416
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• 2010

WiBro network technologies developed mainly by Korea are one of very promising 4G technologies. WiBro has been standardized as international standard called Mobile WiMAX, and has been deployed in many countries. Emergency Services are infrastructural servicesa and very essential to induce subscribers from other types of networks. This paper propose a network architecture for supporting emergency services for mobile VoIP services in WiBro networks. The proposed architecture is based on WMF's architecture for internationa compatibilities, and reflects national considerations on interfacing PSAP for domestic compatibilities.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2006.07a
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• pp.199-199
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• 2006

• The KIPS Transactions:PartD
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• v.15D no.1
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• pp.131-138
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• 2008

This paper describes the implementations of the first application service based on embedded Linux; Mobile Teller which uses WiBro network for data communications and CDMA network for voice communications. Currently, with the appearance of WiBro service, dual-mode terminals which support two heterogeneous networks are available. But, the development of applications which effectively use these networks for providing better service to user is rarely prepared. At Mobile Teller, when a sender on a dual-mode terminal types texts, the texts are transmitted to a TTS server located in the Internet through WiBro network. Subsequently, the TTS server converts the texts into voices and transmits the voice data to the dual-mode terminal. At last the dual-mode terminal sends the voice to the receiver through the CDMA network. In case of noisy environment or when a user has difficulty in speaking, Mobile Teller makes voice communication possible

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.1B
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• pp.39-45
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• 2006

In this paper, existing technology that uses broadcasting and multicasting IP addrsses at the wireless access network, based on Internet as a core network, is upgraded. By employing broadcasting service request by receivers, convergence of multicasting and broadcasting, and lower level filtering of broadcast data, the load and traffic of network, server, base station, and receiver is substantially reduced. The technology proposed in this paper could be useful for general broadcasting services, and especially optimum for LBS and Telematics services.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.20 no.2
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• pp.23-32
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• 2010

WiBro(Wireless Broadband), the service based on IEEE 802.16e(mobile WiMAX) standard, is a wireless broadband Internet technology being developed by the domestic telecommunication industry. In this paper, we analyze security vulnerabilities of WiBro focusing on initial authentication phase and propose a specification-based intrusion detection system that can detect those vulnerabilities. We first derive a specification from the normally operational process of the initial authentication based on PKMv2 EAP-AKA and formalize the derived specification as a state transition diagram. Proposed system executes the intrusion detection based on those specification and state transition diagram. In this paper, to verify the detection capability of proposed system, we construct a test bed network and execute scenario-based test.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.643-644
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• 2006

In this paper, WiBro system which is one of the mobile wireless metropolitan area network systems is presented. WiBro is an OFDMA system which has a sub-channelization process unlike conventional OFDM systems. The sub-channelization is the time consuming processing, so a time-efficient hardware architecture is needed. WiBro RAS(Radio Access Station) demodulator is designed with Verilog HDL, and the gate count is 81k using the $0.18{\mu}m$ processing.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.11a
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• pp.1320-1323
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• 2008

통신망의 통합은 현존하는 네트워크의 중요한 발전과정으로 인식되면서 가속화되고 있으며 대표적으로 WLAN와 WiBro 네트워크와의 연동에 관심이 집중되고 있다. 뿐만 아니라 이기종 망에 대한 연동방법 연구도 광범위하게 연구되고 있다. 이러한 궁극적인 망 통합을 이루어 낼 수 있는 단말 재구성을 지원하는 SDR기반 연동기법을 통해 실질적인 기지국 공용화를 완성할 수 있을 것이다. 본 논문에서는 SDR 공용기지국 환경에서 밀결합 방식 연동망을 구성하여 단말의 속도를 고려한 WiBro와 WLAN 간의 효율적인 핸드오프 알고리즘을 제안하였다.