• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2008.10a
• /
• pp.66-69
• /
• 2008

As a mobility support for IP have studied, Internet Engineering Task Force(ITEF) standardized the mobile IPv6 protocol. When a mobile node moves between networks, MIPv6 maintains connectivity to network and supports seamless communication, and these processes are called a Handover. IEEE 802.21 standardized MIH(Media Independent Handover) for seamless Handover. MIH used three services for Handover between low layer and upper layer. In this paper, we designed two modes on existing MIH for seamless Handover. We implemented a dual-interface mobile host(MH) model in network simulation2 (ns2) to evaluate how it performs in comparison with single-interface MH.

• Information and Communications Magazine
• /
• v.24 no.4
• /
• pp.116-125
• /
• 2007

무선랜, WCDMA/HSDPA, 휴대인터넷 와이브로 등 각종 초고속 이동통신 기술이 상용화되면서 모바일 서비스가 화두로 부상했다. 즉 이동 단말 사용자들은 이종망을 넘나들면서도 이동성에 제약 받지 않는 끊김 없는 서비스를 요구하게 되었으며, 이를 실현하기 위해서는각종 액세스 망을 통합하여 관리/운용할 수 있는 공통적인 IP 기반의 이동성 기술이 필요하다. 본 고에서는 Mobile IP 및 Mobile IP를 확장한 주요 이동성 지원 기술을 살펴 본 후 이종망간의 정보 교환 및 상호 작용을 통해 이들을 효율적으로 지원하기 위한 MIH (Media Independent Handover) 기술을 소개한다.

• Information and Communications Magazine
• /
• v.21 no.6
• /
• pp.67-88
• /
• 2004

유비쿼터스 네트워킹 환경은 사람 주변의 모든 기기가 하나의 네트워크로 연결되어 끊김없이 정보를 주고받으며 통신을 가능하게 해 주는 전자공간과 실제 공간의 융합이다［1, 2, 3, 4］. 이와 같은 유비쿼터스 환경이 지원되면 우리가 살고 있는 세상은 평온하고 지능화된 느낌에 상황인지 능력을 갖추게 되어 생산적이며 대응 능력을 지원 받을 수 있는 안락한 상황이 된다. 이러한 유비쿼터스 환경의 제공을 위해서는 "AlWays Connected"와 "Broadband" 그리고 ＂Every Device in One Network"의 세 가지의 키워드가 필수적인 요소［2］이다. 이 세 가지의 요소가 충족되려면 많은 기술들이 필요하게 된다. (중략)되려면 많은 기술들이 필요하게 된다. (중략)

• Journal of Digital Contents Society
• /
• v.19 no.8
• /
• pp.1545-1554
• /
• 2018

In order to support the mobility of the wireless devices, at least two APs (Access Points) must be arranged in a single AP area to maintain communication area. In the WLAN (Wireless LAN) environment, seamless handover is one of the most important issues in terms of effective utilization of wireless networks and maximization of services for users. On the other hand, SDN (Software-Defined Networking), which is emerging rapidly in recent years, is revolutionizing network management in terms of flexibility, fine control, and convenience. SDN originally reduces latency time or increases network robustness by real-time flow table control reducing or bypassing paths between switches in LAN-based data centers. In this study, we apply OpenFlow, a SDN platform focused on wired LAN, to a dense WLAN environment using legacy APs to implement and evaluate seamless handover for streaming services of digital contents.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2007.10a
• /
• pp.54-57
• /
• 2007

Much researches have studied for seamless mobility service. Those focused on minimizing the delay time due to the handover. In this paper, we suggest seamless mobility service with the network-based preemptive operations. With these operations, if it's found that the MT(Mobile Terminal)'s handover using L2-trigger event, old access network buffers the delivering data. Therefore this can decrease the data drop rates. And also, this can deal with the ping-pong's phenomenon of MT. At the end of MT's movement, these operations can provide seamless mobility service sending buffered data after checking the MT's movement. This mechanism uses MPLS-LSP(MultiProtocol Label Switching-Label Switched Path) in core network for fast process.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.39B no.6
• /
• pp.341-349
• /
• 2014

Dynamic adaptive streaming over HTTP (DASH) is the most recent and promising technology to support high quality streaming services. In dynamic adaptive streaming over HTTP (DASH), a client consecutively estimates the available network bandwidth and decides the transmission rate for the forthcoming video chunks to be downloaded. In this paper, we propose a novel rate adaptation algorithm called quality of experience QoE-enhanced adaptation algorithm over DASH (QAAD), which preserves the minimum buffer length to avoid interruption and minimizes the video quality changes during the playback. We implemented a DASH test bed and conducted extensive experiments. Experimental results demonstrate that under fluctuating network conditions, QAAD provides seamless streaming with stabilized video quality while the previous buffer-aware algorithm (i.e., QDASH[9]) frequently changes the video quality and undergoes the interruption.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38A no.3
• /
• pp.258-267
• /
• 2013

Recently, Proxy Mobile IPv6(PMIPv6) networks have been drawing attention as the mobility management protocol that uses limited wireless resources effectively. And the multicast, which is a core technology of the Internet broadcast system such as mobile IPTV, has been widely discussed mainly based on PMIPv6 network. However, PMIPv6-based multicast cannot support the global mobility directly between different PMIPv6 domains because PMIPv6 is basically designed for local mobility in single PMIPv6 domain. Moreover, PMIPv6-based multicast causes the disconnection of services because it does not solve the packet loss problem during binding and group joining procedure. In this paper, we propose a global mobility scheme that supports the seamless multicast service in PMIPv6 networks. The proposed scheme supports the global mobility due to the addition of extra signalling messages between LMAs. Also, it achieves low latency because it performs fast binding and group joining procedure. We present the simulation results which show that the proposed scheme achieves the global mobility with low latency through the NS-2 simulation.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.5C
• /
• pp.476-485
• /
• 2003

This paper proposers a preprocessing approach to improving the quality of the music produced by the EVRC(enhanced variable rate codec) which is one of the CDMA(Code Division Multiple Access) voice codecs. Since the EVRC is optimized only for speech signals, it can deteriorate the quality of the music passed through it. One of the problems with the EVRC-coded music is time-clipping, which usually occurs when subsequent frames are encoded at Rate l/8. Since the EVRC determines the bit rate for an input frame based on the long-term prediction gain, we increase the long-term prediction gain in order for the most of the frames to be encoded at Rate 1 or Rate 1/2. Experimental results show that the approach works well on music signals and the number of time-clipped frames is considerably reduced.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2017.04a
• /
• pp.121-122
• /
• 2017

스마트폰이나 노트북 등 무선 단말기는 가까운 AP를 통하여 인터넷에 접속하게 된다. 만약 이 무선 단말기가 이동하여 이전의 AP와 멀어지고 새로운 AP에 다가가면 이 단말기는 AP를 변경하는 절차를 따라야하는데 이를 핸드오버라 한다. 핸드오버가 일어날 때 새로운 AP에서는 이동 단말기가 정당한 것인지를 검증하여 끊김 없는 통신 환경을 제공한다. 이 논문에서는 끊김 없는 핸드오버 환경 구현을 목표로 하는 연구과제에 연구 보조원으로 참여하여 여러 번의 수행착오를 거쳐 터득한 공개 소프트웨어 기반 인증 서버 구축 과정을 발표한다.

• Proceedings of the Korean Information Science Society Conference
• /
• 2011.06d
• /
• pp.256-258
• /
• 2011

유무선 통신기술의 발달로 멀티미디어 스트리밍 서비스의 이용이 증가함에 따라 비디오 스트리밍 기법에 관한 연구가 필요하다. 본 논문에서는 끊김 없는 스트리밍 서비스를 제공하기 위하여 네트워크의 상태와 클라이언트의 버퍼 상태를 고려한 전송률 조절 기법을 제안한다. 제안하는 기법은 네트워크의 상태와 클라이언트의 버퍼 상태를 기반으로 전송 비디오의 프레임 수를 우선순위에 따라 차등적으로 폐기함으로써 전송률을 조절한다. 제안 기법을 적용한 스트리밍 시스템을 구현하고 실험을 통해 끊김 없는 비디오의 전송을 확인할 수 있었다.