• The Journal of the Korea Contents Association
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• v.10 no.9
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• pp.36-44
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• 2010

In this paper, we propose video quality control system(VQCS) which can control video service quality through the monitoring of end-to-end available bandwidth for video streaming service like IPTV in NGN convergence network. Various multimedia services such as video, voice and gaming service can be provided by IPTV, and these services require large amounts of bandwidth. At this time, video quality degradation like video jerkiness, block distortion and blurring is caused when network available bandwidth is insufficient. Available bandwidth monitoring method is need to stably control video streaming quality. So, we periodically calculate the amount of the packets in link and measure available bandwidth by using total length field in IP header at terminal. Scalability extractor in network selects suitable video streaming data rate based on available bandwidth and transports video streaming with adaptive data rate to prevent video quality deterioration.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.9A
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• pp.663-668
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• 2003

With the advent of high speed networking technology, computers connected to the high-speed networks tend to consume more of their CPU cycles to process data. So one of the solutions to improve the performance of the computers is to reduce the CPU cycles for processing the data. As the consumption of the CPU cycles is increased in proportion to the number of the packets per second to be processed, reducing the number of the packets per second by increasing the length of the packet is one of the solutions. In order to meet this requirement, two types of jumbo packets such as jumbograms and jumbo frames have already been standardized or being discussed. In case that the jumbograms and general packets are interleaved and scheduled together in a router, the jumbogrms may deteriorate the QoS of the general packets due to the transfer delay. They also frequently exhaust the memory with storing the huge length of the packets. This produces the congestion state easily in the router that results in the loss of the packets. In this paper, we analyze the problems in processing the jumbo packets and suggest a noble solution to overcome the problems.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.1 s.343
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• pp.89-94
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• 2006

We present a generalized version of principal ratio combining (PRC)[1], which is a near-optimum decoding scheme for space-time trellis codes in quasi-static flat fading environments. In [1], the performance penalty increases as the number of receive antennas increases. In the proposed scheme, receive antennas are divided into K groups, and the PRC decoding method is applied to each group. This shows a flexible tradeoff between performance and decoding complexity by choosing the appropriate K. Moreover, we also propose the performance index(PI) to easily predict the decoding performance among the possible different(receive antenna) configurations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.9
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• pp.784-790
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• 2012

In this paper, we propose a upstream transmission method to extend coverage in visible light communication (VLC) systems. We extend transmission distance by using focused infrared(IR) light emitting diodes(LEDs). Since the focused light covers just limited area, it might have a difficulty in transmitting data if the transmitter and receiver are not properly aligned. To solve this problem, we arrange multiple IR-LEDs in different direction and select a single best performing IR-LED among multiple IR-LEDs. Also, the transmission performance is periodically checked and another IR-LED is reselected to support the required quality of service (QoS) and to minimize battery consumption required by a mobile terminal.

• 한국HCI학회:학술대회논문집
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• 2008.02a
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• pp.59-64
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• 2008

In this paper, stability and transparency analysis for client/server haptic-based networked virtual environment (NVE) is introduced. From this analysis the appropriate communication structure for the more stable and transparent haptic interactions can be derived. Also, it is possible to expect and compensate the quality deterioration of haptic interactions according to certain network conditions In order to verify the usefulness of the analysis, simple haptic-based NVE application is implemented. For the stability verification, the vibration or strange movement of haptic interface and virtual object are measured under various network states. In addition, the usefulness of the proposed transparency analysis and network delay compensation scheme is verified by comparing distorted and compensated force feedbacks with real force feedback.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.2
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• pp.280-286
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• 2009

The NGN(Next-Generation Network) structure has been considered from various points of view as all If wireless-wired integration network and its performance is one of the main issue in these days. In this paper, various wired and wireless integrated networks with voice service are designed and simulated to obtain problems and factors affects the network performance using OPnet simulator. The characteristics only showed in the wired and wireless integrated networks are measured and analyzed compared with the single networks such as a wired or wireless networks. Especially, in the wired and wireless integrated networks showed degrading performance even if there are few transmissions in the network and furthermore, the various networks of increasing numbers of the nodes and transmission are simulated and evaluated.

• The Journal of Korean Association of Computer Education
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• v.7 no.1
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• pp.37-44
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• 2004

Differentiated services network (DiffServ) aims to provide the same service to a group of connections that have similar Quality of Service requirements. One of the essential function to realize DiffServ is the traffic conditioning mechanism. The paper proposes the enhanced traffic conditioning mechanism which can assure the reserved rates of TCP and UDP flows and support fair distribution of excess bandwidth. The simulation results show that the new mechanism is rather insensitive of the effect of UDP against TCP throughput, and performs better both in terms of throughput assurance and fair distribution of excess bandwidth in case of well-provisioned and over-provisioned network environment.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11b
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• pp.634-636
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• 2005

본 논문은 UPnP 기반의 홈 네트워크 환경에서 미디어 서비스를 이용하는 사용자가 위치 이동에 따라 AV 서비스 단말의 전환을 요구하는 경우 QoS 저하 없이 유연하게 상호연동 서비스하기 위한 UPnP AV 확장 서비스 모델을 제안한다. 사용자는 AV 서비스를 받기 위하여 기존의 이동단말기기 뿐만 아니라 일반 데스크탑, 그리고 셋탑박스 등의 다양한 형태의 단말환경을 상호연동하여 유기적으로 연결하여 사용할 수 있다. 하나의 단말환경에서 제공되던 미디어 컨텐츠는 미디어 랜더러와 컨트롤 포인트에 의해 다른 단말 환경에서 사용자의 조작 없이 미디어를 연속하여 제공 받을 수 있으며, 사용자는 이러한 UPnP AV 서비스를 별도의 설정 없이 이용할 수 있다. 논문에서 제안된 UPnP AV 확장 서비스는 사용자의 이동에 따라 단말에서 컨텐츠 재생을 위한 미디어 랜더러와 서로 다른 단말의 미디어 랜더러에 서비스하기 위한 컨트롤 포인트 그리고 각기 다른 단말장치로 컨텐츠가 제공되기 위한 미디어 서버로 구성된다. UPnP 포럼에서 정의하는 표준 서비스에 UPnP 프로토콜의 특성을 이용한 SwithingModule을 미디어 랜더러에 구현하여, 사용자의 이동 상황에 따라 AV 서비스를 받기 위한 미디어 전환 서비스를 지원한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2000.10b
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• pp.1609-1612
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• 2000

무선망에서 기존의 회선 서비스뿐만 아니라 패킷 서비스 및 영상 서비스 등을 수용하는 데 있어서 고려되어야 할 것들 중 하나는 무선 자원의 활용이다. 특히 패킷 서비스의 경우 가변적인 패킷의 길이와 양으로 효율적인 무선 자원관리를 어렵게 하는 요소를 지니고 있다. 즉, 무선 자원을 효율적으로 운용하기 위해서는 동적인 무선 자원할당 메커니즘이 중요한 역할을 한다. UMTS 표준 문서에서는 계층 2 전송 프로토콜인 RLC (Radio Link Control) 버퍼의 양만을 측정하여 무선 자원 할당이 제어가 되도록 권고하고 있다. 하지만 트래픽 양의 변화가 큰 VBR 트래픽의 경우, 이와 같은 방법은 갑자기 증가하거나 감소하는 트래픽 양에 적응하기 힘들고 이는 무선 자원의 효율성을 저하시키며, QoS 제공도 어렵다. 본 논문에서는 먼저 트래픽 특성을 알 수 있는 토큰 버켓 모델을 RLC에 적용하고, 동적 무선 자원 할당을 위해 RLC 버퍼의 양뿐만 아니라 예상되는 유입 트래픽 양을 측정 및 보고하는 메커니즘을 제안한다.

• The KIPS Transactions:PartC
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• v.9C no.5
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• pp.679-686
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• 2002

The transmission of prerecorded and compressed video data without degradation of picture quality requires video servers to cope with large fluctuations in bandwidth requirement. Bandwidth smoothing techniques can reduce the burst of a variable-bit rate stream by prefetching data at a series of fixed rates and simplifying the allocation of resources in the video servers and the network. In this paper, the proposed smoothing algorithm results in the optimal transmission plans for (1) the smallest bandwidth requirements, (2) the minimum number of changes in transmission rate, and (3) the minimum amount of the server process overhead. The advantages of the proposed smoothing algorithm have been verified through the comparison with the existing smoothing algorithms in diverse environments.