• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.5
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• pp.691-708
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• 2010

An important issue of supporting multi-users with diverse quality-of-service (QoS) requirements over wireless networks is how to optimize the systematic scheduling by intelligently utilizing the available network resource while, at the same time, to meet each communication service QoS requirement. In this work, we study the problem of a variety of communication services over multi-media heterogeneous cognitive OFDM system. We first divide the communication services into two parts. Multimedia applications such as broadband voice transmission and real-time video streaming are very delay-sensitive (DS) and need guaranteed throughput. On the other side, services like file transmission and email service are relatively delay tolerant (DT) so varying-rate transmission is acceptable. Then, we formulate the scheduling as a convex optimization problem, and propose low complexity distributed solutions by jointly considering channel assignment, bit allocation, and power allocation. Unlike prior works that do not care computational complexity. Furthermore, we propose the FAASA (Fairness Assured Adaptive Sub-carrier Allocation) algorithm for both DS and DT users, which is a dynamic sub-carrier allocation algorithm in order to maximize throughput while taking into account fairness. We provide extensive simulation results which demonstrate the effectiveness of our proposed schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.3B
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• pp.380-389
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• 2010

Since the internet is intend to be the best effort service, the system that stream a large amount of high quality medias need a techniques to overcome the network status for implementation. In this paper, we design and implement a method that estimate quickly whether network permits the needed bandwidth of media and a method that control QoS through that. Presented system uses Relative One-Way Delay(ROWD) trend in the case of the former, and leverages temporal encoding among Scalable Video Coding(SVC) that is apt to apply real time comparatively in the case of the latter. The streaming server classifies the medias by real time to several rates and begins transmission from top-level and is reported ROWD trend periodically from the client. In case of the server reported only 'Increase Trend', the sever decides that the current media exceeds the available bandwidth and downgrades the next media level. The system uses probe packet of difference quantity of the target level and the present level for upgrading the media level. In case of the server reported only 'No Increase Trend' by the ROWD trend response of the probe packet from client, the media level is upgraded. The experiment result in a fiber to the home(FTTH) environment shows progress that proposed system adapts faster in change of available bandwidth and shows that quality of service also improves.

• Journal of Broadcast Engineering
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• v.24 no.2
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• pp.329-340
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• 2019

Recently, broadcasting technologies have evolved as high-quality AV services such as domestic terrestrial UHD(Ultra-High Definition) broadcasting have been increasing, and broadcasting standards have been newly defined. Also, as network technology develops, contents are consumed not only in the country but also the world. Accordingly, content insertion technology, which is a method of providing suitable contents in accordance with the national and local environments, will be needed. This paper proposes a content insertion service system model and synchronization scheme using ATSC(Advanced Television Systems Committee) 3.0 Event Signaling standard under heterogeneous network environment of broadcasting network and internet network based on transmission standard DASH(Dynamic Adaptive Streaming over HTTP)/ROUTE(Real time Object delivery Over Unidirectional Transport) and MMT(MPEG Media Transport) of terrestrial UHD broadcasting. It also verifies that the service operates in an environment that meets the broadcast standard.

• Journal of Broadcast Engineering
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• v.16 no.6
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• pp.1073-1076
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• 2011

In this paper, we propose a scalable random access scheme in SVC based DASH service that enables random access support not only for base layer of SVC but also for enhancement layers. The proposed method includes extension of segment index box ('sidx') from DASH standard, as well as new RAP Synchronization Box ('raps'). Since the proposed scheme provides random access service for movie fragments with SVC encoded video layers, adaptive scalable random access service is possible.

• Journal of KIISE
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• v.43 no.3
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• pp.327-335
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• 2016

In this paper, we propose a buffer management scheme suitable for interactive multimedia services. We consider a typical delay optimization environment so that receiver buffer lengths vary according to the round trip time estimation. In this environment, we propose an optimization technique for minimizing the loss of information that may occur when a reduced buffer length forces I/P/B frames in the buffer to drop. We modeled our problem as a Knapsack Problem for which we used dynamic programing in order to find an approximate solution. The proposed technique is compared with the existing buffer management techniques. Through simulation studies, we found that our approach could increase PSNR, which is important to video quality.

• Journal of Multimedia Information System
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• v.4 no.4
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• pp.179-188
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• 2017

The Internet Video Coding (IVC) standard is due to be published by Moving Picture Experts Group (MPEG) for various Internet applications such as internet broadcast streaming. IVC aims at three things fundamentally: 1) forming IVC patents under a free of charge license, 2) reaching comparable compression performance to AVC/H.264 constrained Baseline Profile (cBP), and 3) maintaining computational complexity for feasible implementation of real-time encoding and decoding. MPEG experts have worked diligently on the intellectual property rights issues for IVC, and they reported that IVC already achieved the second goal (compression performance) and even showed comparable performance to even AVC/H.264 High Profile (HP). For the complexity issue, however, there has not been thorough analysis on IVC decoder. In this paper, we analyze the IVC decoder in view of the time complexity by evaluating running time. Through the experimental results, IVC is 3.6 times and 3.1 times more complex than AVC/H.264 cBP under constrained set (CS) 1 and CS2, respectively. Compared to AVC/H.264 HP, IVC is 2.8 times and 2.9 times slower in decoding time under CS1 and CS2, respectively. The most critical tool to be improved for lightweight IVC decoder is motion compensation process containing a resolution-adaptive interpolation filtering process.

• Journal of KIISE:Software and Applications
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• v.33 no.10
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• pp.823-835
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• 2006

Multimedia is a very popular service in the Internet. But, we cannot provide multimedia service at a uniform content, because networks and devices are various. Thus, an adaptive service is needed for multimedia transmission. Video Transcoding is the good solution that can service multimedia adaptively. This paper proposes the streaming system that is composed of encoder, transcoder, decoder The encoder enhanced time complexity and PSNR in case of transcoding using PP(Prediction Period). The decoder is almost same as the traditional media player. Transcoder reduced time complexity through combination of prediction period in encoder and skipping period to control frame rate in transcoder. In simulation results, the performances of proposed scheme outperform the system with traditional transcoder in time complexity and PSNR.

• ETRI Journal
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• v.36 no.5
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• pp.819-828
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• 2014

To solve the increasing popularity of video streaming services over the Internet, recent research activities have addressed the locality of content delivery from a network edge by introducing a storage module into a router. To employ in-network caching and persistent request routing, this paper introduces a hybrid content delivery network (CDN) system combining novel content routers in an underlay together with a traditional CDN server in an overlay. This system first selects the most suitable delivery scheme (that is, multicast or broadcast) for the content in question and then allocates an appropriate number of channels based on a consideration of the content's popularity. The proposed scheme aims to minimize traffic volume and achieve optimal delivery cost, since the most popular content is delivered through broadcast channels and the least popular through multicast channels. The performance of the adaptive scheme is clearly evaluated and compared against both the multicast and broadcast schemes in terms of the optimal in-network caching size and number of unicast channels in a content router to observe the significant impact of our proposed scheme.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2019.11a
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• pp.230-232
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• 2019

최근 360 미디어 콘텐츠의 수요가 높아지면서 360 영상을 효율적으로 전송하기 위한 다양한 압축 및 전송 기법들이 연구되고 있다. 360 영상의 스트리밍 기법 중 하나인 타일 기반 적응적 스트리밍 기법은 360 비디오를 타일 그리드로 나누어 부호화 하고, 뷰포트(Viewport)에 해당하는 타일만 스트리밍 할 수 있도록 한다. 기존의 타일 기반 스트리밍 기법은 뷰포트가 전환될 때 서버에 새로운 인트라 프레임을 요구하고, 지연 시간을 줄이기 위해 빈번한 RAP(Random Access Point)가 요구된다는 단점이 있다. 본 논문은 기존의 타일 기반 스트리밍 방법에서 인트라 프레임의 공유를 통해 비트율의 효율을 높이는 IFS(Intra Frame Sharing) 알고리즘을 제안한다. 제안된 IFS 방법은 낮은 화질의 인트라 프레임을 높은 화질의 인트라 프레임 부호화 시 공유하여, 뷰포트 스위칭 시점에서 다른 화질 간의 뷰포트 전환 작업이 필요 없어 비트율의 증가를 최소화한다. 실험에서, IFS 방법은 기존의 MCTS 기반의 적응적 스트리밍 방식과 비교했을 때 BD-rate(%)가 약 13% 절감되었다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.99-101
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• 2011

본 논문에서는 WiMAX 의 신호세기(CINR: Carrier to Interference + Noise Ratio)의 변화와 예측 방법에 대해 연구한다. WiMAX 와 같은 무선 네트워크에서는 신호세기가 불규칙하게 변화하기 때문에 비디오 스트리밍시 에러나 지연이 발생할 수 있다. CINR 은 클라이언트 측의 가용 대역폭을 결정하는 중요한 요소이다. 하지만 기존의 RTCP(Real-time Transport Control Protocol)를 이용한 비트율 제어는 RTT(Round Trip time), PLR(Packet Loss Rate) 등의 정보를 사용하기 때문에 부정확하거나 지연이 발생될 수 있다. 이를 보완하기 위한 CINR 을 직접 비트율 제어에 사용하는 방법에 대해 연구하기에 앞서, 본 논문에서는 CINR 을 분석하고 미래의 값을 예측하는 방법에 대해 연구한다. 본 논문의 분석을 통해 CINR 의 예측을 비교적 정확하게 수행할 수 있다면 앞으로의 가용 대역폭을 비교적 정확하게 예측할 수 있고 효율적인 비디오 스트리밍 시스템을 제안할 수 있다.