• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.1B
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• pp.26-38
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• 2006

To construct seamless collaborative environments, what all participants intent should be delivered, and visual elements such gesture, facial expression, and ambiance should be shared with all participants. In this paper, we propose high-quality video service to support DV(digital video) and HDV(high-definition DV) based on Access Grid(AG) which is a prevalent collaborative system. The proposed service is designed for employing versatile media tools and codecs with SDP(session description protocol) and SAP(session announcement protocol). We also design network-adaptive video transmission module to mitigate the impact of network fluctuation. This periodically monitors multicast performance and controls frame rate on sender side considering network condition. The experimental results over the test bed show that proposed service enhances quality of AG video service and provides seamless high-quality video transport by mitigating the impact of network fluctuation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12B
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• pp.1017-1027
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• 2006

Recently, Internet service providers are offering triple play service which combines voice and video services with the existing high speed Internet service under the common network infrastructure of IP protocol, so that they can create more benefit from operating a single network architecture. In line with this movement in the convergence of network and services, in this work we propose a bandwidth dimensioning method for the subscriber network of the IP network at flow level. To that purpose, let us propose a series of bandwidth dimensioning methods: bandwidth for best effort service only, bandwidth dimensioning for premium services, and bandwidth dimensioning schemes for the premium Internet services as well as the best effort service which comprise the TPS. Our link dimensioning method is based on the flow level that incorporates the flow blocking probability as a measure of grade of services(GoS), and investigates the characteristics of the proposed methods via extensive numerical experiments. After that, let us carry out a simulation experiment concerning the delay and loss performance of the packet scheduling for the premium services (QoS) using the bandwidth designed by our proposed method, via which the packet level quality of service (QoS) for the proposed link dimensioning method can be observed.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2008.11a
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• pp.235-238
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• 2008

KT는 디지털 홈네트워크 사업의 일환으로 2004년 셋탑 기반의 홈엔VOD서비스를 제공한 바 있으며, IP망을 통한 방송서비스의 기반을 마련하기 위해 가입자단까지 IP-멀티캐스팅이 가능한 장비로 교체하여 BcN시범사업의 일환으로 KT CAST 서비스를 제공한 바 있다. 그리고 2006년에는 IPTV사업자로 선정되어 2007년 7월 VOD및 양방향 데이타 서비스만을 포함한 iCOD 서비스를 서울 지역을 시작으로 전국으로 확대 제공하였으며 실시간 방송에 대한 KT의 다각적인 노력의 결실로 지상파 방송서비스에 대한 정부 규제가 풀려 2008년 11월부터 지상파 실시간 방송을 포함하여 다양한 채널 방송이 가능해졌다. 본 논문에서는 일련의 KT가 준비하고 제공하였던 여러 형태의 디지털 영상서비스의 발전 단계를 소개하고 앞으로 메가TV가 나아가야 할 방향에 대하여 기술하고자 한다.

• The KIPS Transactions:PartD
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• v.9D no.3
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• pp.501-510
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• 2002

A various multimedia application services should be developed with techniques of high speed networks and computer. Among these, video-conference system over Internet is useful and important, and the standardization for it should be showed in ITU-T H.323. H.323 standardization consists of four components such as Terminal, MCU(Multipoint Control Unit), Gatekeeper, and Gateway. Among these, the functions of Gatekeeper are as follows, firstly the address translation service to translate the alias address into the IP address, secondary conference admission control service to control of conference start and termination, thirdly bandwidth management service for H.323 terminals. In this paper, we implemented the Gatekeeper for an efficient management of video-conference components in Internet environment, and will introduce our system. As the experimental results with CUSeeMe and Netmeeting which are well-known H.323 terminal, it is known that our gatekeeper should be satisfied with H.323 standardization.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.9
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• pp.2118-2135
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• 2012

With the rapid development of heterogeneous emerging wireless technologies and numerous types of mobile devices, the need to support robust mobile video streaming based on the seamless handover in Future Internet is growing. To support the seamless handover, several IP-based mobility management protocols such as Mobile IPv6 (MIPv6), fast handover for the MIPv6 (FMIPv6), Hierarchical MIPv6 (HMIPv6) and Proxy Mobile IPv6 (PMIPv6) were developed. However, MIPv6 depreciates the Quality-of-Service (QoS) and FMIPv6 is not robust for the video services in heterogeneous emerging wireless networks when the Mobile Node (MN) may move to another visited network in contrast with its anticipation. In Future Internet, the possibility of mobile video service failure is more increased because mobile users consisting of multiple wireless network interfaces (WNICs) can frequently change the access networks according to their mobility in heterogeneous wireless access networks such as 3Generation (3G), Wireless Fidelity (Wi-Fi), Worldwide Interoperability for Microwave Access (WiMax) and Bluetooth co-existed. And in this environment, seamless mobility is coupled according to user preferences, enabling mobile users to be "Always Best Connected" (ABC) so that Quality of Experience is optimised and maintained. Even though HMIPv6 and PMIPv6 are proposed for the location management, handover latency enhancement, they still have limit of local mobility region. In this paper, we propose a robust mobile video streaming in Heterogeneous Emerging Wireless Systems. In the proposed scheme, the MN selects the best-according to an appropriate metric-wireless technology for a robust video streaming service among all wireless technologies by reducing the handover latency and initiation time when handover may fail. Through performance evaluation, we show that our scheme provides more robust mechanism than other schemes.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.9
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• pp.2078-2083
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• 2012

Tactical communication environment evolving for the purpose of providing services such as voice, video and text based on ALL-IP. Therefore, To be able to guarantee QoS level which meets the required level of subscriber for these services in the constrained tactical communication infrastructure, it is required to take the characteristics such as wireless transmission link, mobility of troops or personal into service quality scheme. In this paper, to support differentiated QoS for each individual or mission in the tactical communication environment, we presents a technique that can provide same QoS level which was served originally regardless of the situation to user's move through dynamically determining the QoS level to be provided at the time of the service request on VoIP-Switch.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.5B
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• pp.430-441
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• 2006

As the various A/V devices and home networks are delivered to users, home networks are changing to an entertainment network. It is expected that the required network bandwidth and the amount of usage of media content in home entertainment networks will be increased. Although the access networks and home networks becoming a high speed network, there remains the problems for QoS-guaranteed media content transfer in home networks. Also, in the home network, there can be network traffic caused by applications like video conferencing, video telephone, and VoIP(voice over IP) as well as inner network traffic of home network. Since media content transfer requires the real-time delivery, it is very important and basic requirement that is to transfer media content to A/V device user wants while keeping the media quality. Even though there are many middleware protocol for home networking, they provide basic device discovery and control or simple functions for QoS-guaranteed media content transfer that are not enough to provide QoS-guaranteed media transfer service that user wants. Thus, in this paper, we propose the technique based on UPnP(universal plug and play) protocol for QoS-guaranteed media content transfer in the home network. The proposed technique is compatible with UPnP and can be used with UPnP as additional functions. In this paper, we utilize VideoLAN application to verify the proposed technique. We add the additional modules that support the proposed technique's function to VideoLAN and we verify the its functions through various test scenarios.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.10
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• pp.1190-1196
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• 2016

In this paper, a cross-layer interworking scheme for different protocols is proposed to provide an efficient internet services in very small aperture terminal (VSAT) based satellite communication systems. In addition, we implement the proposed interworking model and prove the feasibility of the proposed system. VSAT based satellite communication systems commonly use digital video broadcasting (DVB)-S2 standard. Unfortunately, DVB-S2 has inefficient parts to support IP based internet services because it has originally been designed to support broadcasting services. Generic stream encapsulation (GSE) protocol, which is a layer 2 protocol, has been proposed to mitigate this inefficiency. We propose a cross-layer interworking scheme to cooperate efficiently between IP and GSE protocols and between GSE protocol and DVB-S2, respectively. In addtion, we implement the proposed interworking schemes via computer softwares and prove the feasibility using NI-USRP and commercial DVB receiver.

• Journal of the Institute of Convergence Signal Processing
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• v.12 no.2
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• pp.102-106
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• 2011

The transfer capability of HFC (Hybrid Fiber Coax) network is superior to xDSL. HFC network, however, is not suitable for transferring high quality video due to cable model interfaces. For the services of high quality IPIV or VOD, the extra exclusive downstream transfer system is required without upgrading pre-equipped cable modem and service capability. This paper is aimed to develop the extra exclusive downstream transfer system not changing existing cable modem system but providing same quality of services. This system is composed of the extra exclusive downstream IP-cable sender and modem. This sender and modem have 30 Mbps transfer capability and HDTV stream can be served in the Cable TV network using 21 Mbps HDTV transport stream.

• The KIPS Transactions:PartC
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• v.13C no.4 s.107
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• pp.471-480
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• 2006

Recently, multimedia communication services, such as video conferencing and voice over IP, have been rapidly spread. H.323 is an international standard that specifies the components, protocols and procedures that provide multimedia communication services of real-time audio, video, and data communications over packet networks, including IP based networks. H.323 is applied to many commercial services because it supports various network environments and has a good performance. But communication services based on H.323 may have some problem because of current network trouble or mis-implementation of H.323. The understanding of this problem is a critical issue because it improves the quality of service and is easy to service maintenance. In this paper, we implement the analysis system for H.323 protocol wihch includes H.245, H.225.0, RTP, RTCP, and so on. Tills system is able to capture, parse, and present the H.323 protocol in real-time. Through the operation test and performance evaluation, we prove that our system is a useful to analyze and understand the problems for communication services based on H.323.