• Journal of Information Processing Systems
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• v.6 no.4
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• pp.575-596
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• 2010

Video-on-Demand services are increasing rapidly nowadays. The load on servers can be very high, even exceeding their capacity. For popular contents, we can use a Periodic Broadcast (PB) strategy using multicast to serve all clients. Recent development of PB uses multiple channels broadcasting for segments of movies in certain patterns, so that users only need to wait for a small segment to start the service. However, users need higher download capacity to download multiple segments at a time. In order to compensate for this, a proxy server can help to reduce download bandwidth requirements by holding some segments for a certain time. This research will focus on more recent PB schemes that couldn't be covered by previous Proxy-Assisted Periodic Broadcast strategies.

• 한국IT서비스학회:학술대회논문집
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• 2006.11a
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• pp.360-365
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• 2006

VoD (Video-on-Demand) 서비스는 가입자가 원하는 컨텐츠를 실시간으로 전송하는 서비스의 형태이다. 오늘날은 방대한 양의 멀티미디어 데이터를 효율적으로 압축하고 보다 빠르게 전송할 수 있는 시스템의 발달이 가속화되고 있고 이는 VoD 서비스의 증가로도 이어지고 있다. 그러므로 가입자가 원하는 컨텐츠를 보다 효과적으로 제공할 수 있는 VoD 서비스의 방법을 찾는 것은 중요한 일이다. 본 논문에서는 기존의 NVoD (Near-VoD) 서비스 또는 TVoD (True-VoD) 서비스 만을 제공함으로서 생길 수 있는 단점을 없애고 장점만 살릴 수 있는 방법을 제안하였다. 이는 기존의 가입자단에 Buffer를 제공하여 NVoD를 TVoD화 함으로서 가능하게 하였다. 또한, 본 논문에서 제안한 방법이 필요한 버퍼의 크기를 제시하고 전체적인 알고리즘을 제시하여 이를 구체화 하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.724-726
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• 2004

IPv6 기술은 IPv4의 문제점인 주소고갈, 보안문제 등을 해결하기 위해 제시된 차세대 인터넷 기술이다. IPv6 기술은 현재 프로토콜의 정의가 완료된 상황이지만 사업자들의 이해관계로 인해 아직까지 널리 보급되지 못하고 6Bone 과 같은 시험 망에서만 사용되고 있는 실정이다. 그러나 IPv6는 가까운 미래에 Ipv4를 대체할 것으로 보이며 기존에 있던 IPv4를 기반으로 하는 응용 프로그램들도 IPv6 용으로 새로이 바뀌게 될 것이다. 이러한 배경 하에 본 연구팀은 IPv6 multicast를 기반으로 하는 화상회의 응용프로그램을 개발하였으며 본 논문은 그 개발에 대한 내용을 담고 있다. 본 논문에서는 화상회의 응용프로그램의 전체적인 구조와 구현 시 사용된 기술과 화상회의 플랫폼기술에 대해서 살펴보고 응용프로그램을 바탕으로 측정한 사용 bandwidth 와 delay를 분석해 보도록 하겠다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.1
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• pp.183-195
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• 2014

Multicasting is an efficient way of group communications because one sender can transmit data to multiple receivers with only one transmission. Furthermore, multicasting is considered an appropriate transmission method for multimedia services. Multimedia applications are expected to become more prevalent over mobile ad-hoc networks in the near future. Therefore, achieving reliability in multimedia communications is an important task. In this paper, we propose a leader-based reliable multicast medium access control layer protocol for multimedia applications to enhance video quality. We present a Markov chain model and numerical formulation of our proposed system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.8
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• pp.1498-1507
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• 2017

According to recent report, global mobile data traffic is expected to increase by 11 times from 2016 to 2020. Moreover, this growth is expected to be driven mainly by mobile video traffic which is expected to account for about 70% of the total mobile data traffic. To cope with enormous mobile traffic, we need to understand video traffic's characteristic. Recently, the repetitive requests of some popular content such as popular YouTube videos cause a enormous network traffic overheads. If we constitute a network with the nodes capable of content caching based on the content popularity, we can reduce the network overheads by using the cached content for every request. Through device-to-device, multicast, and helpers, the video throughput can improve about 1.5~2 times and prefix caching reduces the playback delay by about 0.2~0.5 times than the conventional method. In this paper, we introduce some recent work on content popularity-based caching techniques in wireless networks.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.7
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• pp.879-884
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• 2020

In the conventional video file system, videos are stored in a high performance server which has mass storage hard disks or disk arrays. For 3D internet broadcasting, real time operations are required to transmit video files to many clients. This paper describes the design of the 3D internet broadcasting system which can provide realtime streaming service to many users in the 5G environment. In reality, unicast is used to transmit multimedia contents over the internet rather than IP multicast since IP multicast has its own drawbacks in deployment, security, maintenance and so on. In addition, multimedia broadcasting service system like VoD has difficulties in applying to 3D internet broadcasting system since it requires a large amount of system and network resources. In this work, we develop a 3D internet broadcasting system which can construct effective data delivery by minimizing performance-degrading factors.

• The Transactions of the Korea Information Processing Society
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• v.4 no.1
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• pp.288-297
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• 1997

Real-time video multicast using a single computer system is a difficult task because capturing, compressing and delivering video causes a long delay in internetworking environments. This paper describes an implementation of the real time video multicasting server which processes video capture, compression and multicasting in parallel. This paper also presents a flow control mechanism to solve a problem caused by difference between the three tasks.

• The KIPS Transactions:PartC
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• v.15C no.6
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• pp.573-586
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• 2008

The improved performance and miniaturization of computer and the improvement of wireless communication technology have enabled the emergence of many high quality services. Among them multicast services are receiving much attention and their usage is increasing due to the increase of Internet multimedia services such as video conference, multimedia stream, internet TV, etc. Security plays an important role in mobile multicast services. In this paper, we proposed a secure multicast protocol for a hierarchical micro-mobility environment. The proposed secure multicast protocol provides security services such as authentication, access control, confidentiality and integrity using mechanisms including symmetric/asymmetric key crypto-algorithms and capabilities. To provide forward/backward secrecy and scalability, we used sub-group keys based on the hierarchical micro-mobility environment. With this security services, it is possible to guard against all kinds of security attacks performed by illegal mobile nodes. Attacks executed by internal nodes can be thwarted except those attacks which delete packet or cause network resources to be wasted. We used simulator to measure the performance of proposed protocol. As a result, the simulation showed that effect of these security mechanisms on the multicast protocol was not too high.

• Journal of Korea Multimedia Society
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• v.8 no.4
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• pp.502-508
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• 2005

This paper proposes a dynamic hybrid patching technique that can improve the performance of VOD systems by adopting the advantages of both greedy patching and grace patching to use a VOD server's limited network-I/O bandwidth. The proposed technique uses grace patching to the requests for the videos, arrival intervals of which are smaller than the size of patching window, and uses greedy patching to the rest requests. In addition, proposed patching technique expands the latest particular patching multicast into a regular multicast for a new request. In result, the patching multicast data for the new request can be the data from the beginning to the skew point of the video and the holding time of a dispatched channel can exceedingly decrease. Simulation results confirm that the proposed technique is better than grace patching in terms of defection rate and average service latency.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.7
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• pp.837-844
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• 2019

As the demand for video streaming has been rapidly increasing recently, video streaming schemes for increasing the efficiency of radio resource has attracted a lot of attention. In this paper, we propose an adaptive video streaming scheme to enhance the efficiency of video streaming by using receivers' caching capability. The proposed streaming scheme can transmit video data on a broadcast basis even when two clients request different video data, only if specific conditions satisfied, while existing schemes can only transmit video data on a broadcast basis only when two clients request the same video data. In this paper, we mathematically derive the average transmission time of the proposed scheme and the approximation of the average transmission time. The accuracy of the mathematical analysis is verified by simulations. Mathematical analysis and simulation results show that the proposed scheme can significantly reduce the average transmission time, compared to the existing scheme.