• Journal of KIISE:Information Networking
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• v.36 no.2
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• pp.143-152
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• 2009

IEEE 802.11 WLANs provide multiple transmission rates to improve the system throughput by adapting the transmission rate to the current wireless channel conditions. Many rate adaptation schemes have been proposed because IEEE 802.11 standard does not contain any specifications for the rate adaptation scheme. In this paper, in order to overcome limitations of the previous research, we propose a new rate adaptation scheme called SARA(Sender-oriented Automatic Rate Adaptation). The SARA scheme, a proposed rate adaptation scheme, appropriately adjusts the data transmission rate based on the estimated wireless channel conditions, specifically the measured RSSI at the sender-side. Moreover it continuously updates the thresholds for selecting the transmission rate and selectively enforces the RTS/CTS exchanges to adapt the changes in the wireless channel conditions. Through the performance evaluations, we prove that the SARA scheme overcomes the limitations of the previous research and improves the wireless link utilization.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06d
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• pp.172-174
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• 2012

본 논문에서는 광대역 무선 네트워크 환경에서 제공되는 스트리밍 서비스의 품질 보장을 위한 적응적 전송률 제어 기법을 제안한다. 기존 기법들은 다수의 사용자들이 존재하는 광대역 무선 네트워크 환경에서 적응적으로 전송률을 조절하지 못하여 네트워크 자원 활용도가 낮고 패킷 손실률이 큰 문제점이 있다. 이를 해결하기 위해 제안하는 기법은 기지국에 접속한 단말의 수와 네트워크 상태를 고려하여 전송률을 조절한다. 실험 결과를 통해 낮은 패킷 손실률과 전송률 향상을 확인하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.7B
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• pp.1034-1042
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• 2010

As many researchers have been interested in Green IT, Energy Efficient Ethernet(EEE) with rate adaptation has recently begun to receive many attention. However, the rate adaptation scheme can have different energy efficiency and delay according to the characteristics of various traffic patterns. Therefore, in this paper, we analyze the impact of different traffic patterns on the energy efficiency and delay in Ethernet with rate adaptation. To do this, firstly we design a rate adaptation simulator which consists of Poisson based traffic generator, Pareto distribution based ON-OFF generator and Ethernet node with rate adaptation by using OPNET Modeler. Using this simulator, we perform the simulation in view of the total number of switching, transmission rate reduction, energy saving ratio and average queueing delay. Simulation results show that IP traffic patterns with high self-similarity affect the number of switching, rate reduction and energy saving ratio. Additionally, the transition overhead is caused due to the high self-similar traffic.

• Journal of Broadcast Engineering
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• v.14 no.1
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• pp.44-58
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• 2009

To provide efficient video streaming service over a wireless networks, the rate adaptation scheme should be applied at the low layer and the quality adaptation scheme should be considered at the high layer. In this paper, we propose a new cross-layer design which includes rate adaptation scheme at the MAC/PHY layers and quality control at the application layer. Proposed rate adaptation scheme improves the wireless channel utilization by transmitting the consecutive frames and selects optimal transmission mode by calculating the goodputs for each transmission mode. Based on selected transmission mode, the rate adaptation scheme calculates the rate limits and informs that to the application layer. Then the video streaming application utilizes this rate limits to adjust the quality of the video stream. Through performance evaluations, we prove that our cross-layer design improves the quality of the wireless video streaming service by means of the proposed rate adaptation scheme.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06d
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• pp.234-237
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• 2011

최근 인터넷을 통한 멀티미디어 스트리밍 서비스 이용이 증가함에 따라 스트리밍 서비스 품질을 향상 시키기 위한 연구들이 진행되고 있다. 하지만 기존 연구들은 네트워크 상태에 적응적으로 전송률을 조절함으로써 네트워크의 효율성 및 안전성을 개선하는데 초점을 맞추고 있어서 사용자 측면의 체감품질에 대한 고려가 부족하다. 본 논문에서는 멀티미디어 스트리밍 서비스의 사용자 체감품질 (QoE)을 향상시키기 위한 적응적인 전송률 및 비디오 품질 조절 기법을 제안한다. 제안하는 기법은 네트워크의 가용대역폭과 클라이언트의 버퍼 상태를 기반으로 전송률 및 비디오 품질을 조절함으로써 멀티미디어 재생의 불연속성과 잦은 비디오 품질 변화에 의한 사용자 체감품질을 개선하였다. 시험 결과를 통해서 제안하는 기법이 부드럽게 (Smoothly) 비디오 품질을 조절하는 것을 보였다.

• Journal of KIISE:Information Networking
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• v.34 no.3
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• pp.143-155
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• 2007

In video streaming applications over the Internet, TCP-friendly rate control schemes are useful for improving network stability and inter-protocol fairness. However it does not always guarantee a smooth quality for video streaming. To simultaneously satisfy both the network and application requirements, video streaming applications should be quality-adaptive. In this paper, we propose a new quality adaptation mechanism to adjust the quality of congestion controlled video stream by controlling the frame rate. Based on the current network condition, it controls the frame rate and sending rate of video stream. Through the simulation, we prove that our adaptation mechanism appropriately adjusts the quality of video stream while improving network stability.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.10
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• pp.1934-1936
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• 2015

This paper proposes an optimal relay selection and adaptive throughput enhancement scheme utilizing superposition modulation in cooperative communication. The optimal relay is selected and the channel state is estimated by utilizing superposition modulation. The source determines the number of superimposed signal in accordance with the estated channel state. As a result, throughput is increased in accordance with the channel state.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.8
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• pp.1673-1678
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• 2009

Multicast can transmit data packet to multiple terminals by using only one transmission and enhances the system performance. However, the multicast transmission rate is fixed and the system performance is not optimized. In this paper, we propose an adaptive multicast rate control method. In the proposed method, orthogonal subcarrier is assigned to each terminal. Each terminal informs the channel status using the allocated subcarrier. Transmitter selects the optimal rate using the feedback information. With the proposed adaptive rate control method, the system performance is enhanced compared with the legacy multicast method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3B
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• pp.85-94
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• 2005

In this paper, we propose a reliable high-speed UDP-based media transport with an adaptive error control. The proposed adaptive transport scheme controls the amount of redundancy by monitoring the network in order to adapt to network fluctuations efficiently. The feedback of receiver enables the sender to be aware of current reception status (i.e., rate and type of packet loss) and to estimate the expected network status. Based on this, the proposed transport attempts to enable reliable transport by adaptively controlling the amount of both whole sending rate and the ratio for adaptive FEC code. Experiment with high-speed network has been conducted to verify the performance of the proposed system that demonstrates the enhanced reliability of the proposed transport at the speed of up to several hundred Mbps.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06d
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• pp.196-198
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• 2012

본 논문에서는 무선 네트워크 환경에서 미디어 스트리밍의 품질을 향상시키기 위해 패킷 손실과 수신측의 버퍼 상태를 고려하여 적응적으로 전송률을 조절하는 기법을 제안하였다. 제안하는 기법은 멀티미디어 프레임을 구성하는 패킷의 일부가 손실되어도 멀티미디어의 품질에 미치는 영향이 적은 특성을 이용하여 TCP(Transmission Control Protocol)의 단일 패킷 손실이 아닌 다중 패킷 손실을 기반으로 전송률을 조절하고, 수신측의 버퍼 상태에 따라 TCP의 감소율을 조절한다. 이를 통해 안정된 멀티미디어 스트리밍을 제공하여 사용자의 품질을 향상시킨다. 실험 결과를 통해 제안한 기법이 기존 기법에 비해 부드러운 스트리밍 서비스를 제공하는 것을 확인하였다.