• The KIPS Transactions:PartB
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• v.15B no.3
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• pp.219-228
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• 2008

For real-time social networking service, mobile interaction in a usable-unified-ubiquitous (U3) web service was studied. Both as a convenient mobile HCI for real-time social networks and as indexing keys to metadata information in ubiquitous web service, the multi-lingual single-character domain names (e.g. 김.net, 이.net, 가.net, ㄱ.net, ㄴ.net, ㅎ.net, ㅏ.net, ㅔ.net, ㄱ.com, ㅎ.com) are convenient mobile interfaces when searching for social information and registering information. We introduce the sketched design goals and experience of mobile interaction in Korea, Japan and China, with the implementation of real-time social networking service as an example of U3 Web service. We also introduce the possibility of extending the application to the metadata directory service in IP-USN (IP-based Ubiquitous Sensor Network) for a unified information management in the service of social networking and sensor networking.

• The KIPS Transactions:PartC
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• v.15C no.1
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• pp.51-60
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• 2008

Micro-mobility protocols have been developed to reduce the control message overhead due to movements of mobile nodes. With the spread of mobile devices, services using mobile nodes are increasing and multicast services are becoming more important in providing multimedia services. In this paper we propose a new multicast protocol suitable for micro-mobility environments. The proposed protocol is designed to maintain optimal multicast routing paths and continue to provide multicast services without disruption in spite of frequent handoffs due to movements of mobile nodes. We used simulation to evaluate the proposed protocol, compared its performance with existing multicast protocols for mobile environments including bi-directional tunneling, remote subscription, and MMA, and observed that the proposed protocol exhibited better performance in terms of transmission success ratio and overhead on the network.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.05a
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• pp.955-957
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• 2007

본 연구에서는 모바일 기기의 중요한 성능 요소 중 하나인 스토리지에 초점을 맞추고 멀티미디어 콘텐츠 재생 성능 향상을 위한 시스템을 제안한다. 이를 위해 모바일 기기에서 사용 가능한 여러 스토리지 기술 중 최신 기술인 객체기반 IP 스토리지 시스템을 기반으로 모바일 단말 측에 캐시 및 선반입(prefech) 기능을 적용하여 네트워크를 사용하는 입출력으로 인한 재생 시스템의 성능저하를 보완한다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.685-687
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• 2004

본 논문에서는 이동 인터넷 환경에서 핸드오프 시, 링크 계층 (L2) 정보를 이용하며 새로 발견한 모바일 에이전트와의 등록 절차를 L2 핸드오프 완료 후 곧바로 수행하는 로우-레이턴시 (Low-Latency) 핸드오프 방안을 제안하고 이를 구현한다. 제안한 방법은 기존 연구들에 비해 추가적인 L2 핸드오프 지연 및 별도 네트워크 구성요소를 필요로 하지 않으며 보다 일반적이고 현실적인 네트워크 환경에서 적용될 수 있는 방안이다. 실험 결과는 제안된 방법이 인프라스트럭처 (infrastructure) 모드로 설정된 무선 랜에서 모바일 IP의 핸드오프 지연을 크게 개선하여 이동 인터넷 환경의 실시간 멀티미디어 서비스에 적합함을 보여준다.

• Proceedings of the Korea Information Processing Society Conference
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• 2018.10a
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• pp.8-10
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• 2018

우리는 5G 시대를 눈앞에 두고 있다. 5G는 더 빠른 것뿐만이 아니라, 더 저렴한 데이터 서비스를 제공하게 된다. 하지만 4G는 이동 통신망이 모바일 단말 간의 통신에 최적화된 망 구조였다면, 5G는 서로 다른 속성을 갖는 다양한 대상에게 서비스를 제공해주어야 한다. 이 환경에서 스마트폰을 기반으로 한 모바일 통신은 5G 통신망의 비주류 통신영역이 되며, 전체적인 할당량 또한 줄어들 것이다. 이때 통신망의 제약으로 인해 통화장애가 발생한다면 이를 효과적으로 관리하여 통화자체가 끊어지지 않도록 유지할 수 있어야 한다. 본 논문에서는 VoIP를 기반으로 한 통화 트래픽 제어 전략을 제시한다. 5G의 빠른 속도와 VoIP의 음성코덱 제어를 통해 순간 통화 연결시도가 늘어 트래픽의 한계상황에서도 서비스가 끊어지지 않고 유지될 것이다.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.8
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• pp.582-585
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• 2009

VoIP technology for transmitting voice over IP network such as packet-based network has a lot of benefits by integrating services and reducing costs. The network is different from PSTN-based communications in some aspect such as transmitting not only voice but also text, image, multimedia data. In addition, portable terminals like a mobile phone, and ubiquitous communicator can easily access the internet for VoIP. Therefore, To prevent illegal users, offering certificate services is necessary, This study proposes a solution of user certification for a VoIP environment.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.1
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• pp.55-60
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• 2011

The mobile internet telephony service rapidly grows according to the extending deployment of smartphones. Unlike telephony service over a conventional public switched telephone network (PSTN) or mobile network, internet telephony service cannot guarantee its service quality, which can be severer in a wireless environment. Therefore, a more strict and systematic quality management is required for successful settlement and popularization of mobile internet telephony service. Existing quality management scheme using a specific measurement equipment cannot measure all the time so that it performs late management. In order to overcome the problem, this paper develops a software that can be equipped on a user terminal and measures the service quality all the time. By using the developed software, all-time and user-activating service quality monitoring can be supported.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.6
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• pp.1487-1492
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• 2012

Providing node mobility on IP-based wireless networks is required by the increasing Internet access of the mobile nodes and Mobile-IPv6 was suggested for IPv6. But Mobile-IPv6 degrades the overall performance of wireless networks by the packet loss while performing its handover function. Therefore, lots of efforts and researches to resolve this problem have been doing from now on. FMIPv6 is one of the improved methods that was designed to provide seemless handover. But it still has a problem that the handover is strictly depended on the triggered information of the unreliable link layer. In this paper, a scheme called mptFMIPv6 that minimizes delay of critical section of CoA registration process by reducing the link layer dependency was proposed.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2006.07a
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• pp.517-517
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• 2006

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.12
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• pp.20-29
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• 2014

Recently, LTE is preparing to make a new leap forward LTE-A all over the world. As LTE privides high speed service, the role of mobile phones seems to change from voice to data service. According to Cisco, global mobile data traffic will increase nearly 11-fold between 2013 and 2018. Mobile video traffic will reach 75% by 2018 from 66% in 2013 in Korea. However, voice service is still the most important role of mobile phones. Thus, controllability of throughput and low BLER is indispensable for high-quality VoIP service among various type of traffic. Although the maximum AMR-WB, 23.85 Kbps is sufficient to a VoIP call, it is difficult for the LTE which can provide tens to hundreds of MB/s may not keep the certain level VoIP QoS especially in the cell-edge area. This paper proposes a new scheduling algorithm in order to improve VoIP performance after analyzing various scheduling algorithms. The proposal is the technology which applies more priority processing for VoIP than other applications in cell-edge area based on two-tier scheduling algorithm. The simulation result shows the improvement of VoIP performance in the view point of throughput and BLER.