• Proceedings of the Korea Multimedia Society Conference
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• 2002.05c
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• pp.416-421
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• 2002

본 논문에서는 인터넷 상에서 UDP 소켓 인터페이스를 이용하여 실시간 스트리밍 전송을 시뮬레이션 하였고 또한 수신자로부터 피드백 된 정보를 이용하여 송신자가 전송률을 제어하는 것을 시뮬레이션 하였다. 수신자로부터 제어정보를 피드백 받아 송신자가 전송률을 제어하는 경우와 송신자가 전혀 전송률제어를 하지 않는 경우의 패킷 손실 값을 비교했다. 결과로서, 피드백 되는 정보를 이용하여 제어를 하는 경우가 지속적인 패킷손실을 방지함을 보여 준다.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10e
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• pp.406-408
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• 2002

TFRC 혼잡제어는 멀티미디어, 인터넷 전화등 실시간성이 강조된 서비스에 적합한 프로토콜이다. 그러나 이러한 TCP-friendly 혼잡제어 알고리즘은 네트워크 혼잡이 심해져 손실률이 커짐에 따라 TCP와의 공정성(fairness)이 떨어지는 문제점을 가지고 있다. 이러한 문제를 해결하기 위해서는 전송률을 결정하는 제어식을 높은 손실률일 때 보정을 해주어야 한다. 본 논문에서는 TFRC 혼잡제어 알고리즘의 전송률 결정에 있어서 중요한 변수인 재전송 타임아웃 값(RTO)의 재 정의를 통하여 전송률을 보정함으로서 공정성 하락을 방지함을 보이고, 시뮬레이션을 통하여 이를 입증한다.

• Journal of KIISE:Software and Applications
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• v.29 no.7
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• pp.425-435
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• 2002

This paper introduces a macroblock-based rate control algorithm using the neural classifier based in Self Organization feature Maps (SOFM). In contrast to the conventional rate control methods based on the mathematical rate distortion (RD) model and the feedback regression, proposed method can actively adapt to the rapid-varying image characteristics by establishing the global model for bitrate control and by using the SOFM based neural classifier to manage that model. Proposed rate control algorithm has 0.2 dB ~ 0.6 dB better performances than MPEG-4 macroblock-based rate control algorithm by evaluating with the encoded Peak Signal to Noise Ratios while maintaining similar overall computational complexity.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.2
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• pp.114-124
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• 2009

In this paper, we propose a practical TCP friendly rate control scheme that considers the minimum channel bandwidth of the network when transporting SVC (scalable video coding) video over IP netowrks such as Internet. RTP and RTCP is mainly designed for use with UDP (User Datagram Protocol) for real-time video transport over the Internet. TCP-friendly rate control was proposed to satisfy the demands of multimedia applications while being reasonably fair when competing for bandwidth with conventional TCP applications. However the rate control model of the conventional TCP-friendly rate control scheme does not consider the minimum channel bandwidth of the network. Thus the estimated channel bandwidth by the conventional rate control model might be quite different from the real channel bandwidth when the packet loss ratio of the network is very large. In this paper, we propose a modified TCP-friendly rate control scheme that considers the minimum channel bandwidth of the network. Based on the modified TCP-friendly rate control, we assign the minimum channel bandwidth to the base layer bitstream of SVC video, and remaining available bandwidth is allocated to the enhancement layer of SVC video for the TCP friendly scalable video transmission. It is shown by simulations that the modified TCP-friendly rate control scheme can be effectively used for a wider range of controlled bit rates depending on the packet loss ratio than the conventional TCP-friendly control scheme. Furthermore, the effectiveness of the proposed scheme in terms of objective video quality is proved by comparing PSNR performance with the conventional scheme.

• 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.2A
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• pp.121-127
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• 2010

In this paper, we propose a computationally efficient scheduling algorithm that can arbitrarily control the throughput-fairness tradeoff in a multiuser wireless communication environment. As a new scheduling criterion, we combine linearly two well-known scheduling criteria such as one of achieving the maximum sum throughput and the other of achieving the maximum fairness, so as to control the relative proportion of the throughput and the fairness according to a control factor. For linear combining two different criteria, their optimization directivenesses and the units should be unified first. To meet these requirements, we choose an instantaneous channel capacity as a scheduling criterion for maximizing the sum throughput and the average serving throughput for maximizing the fairness. Through a unified linear combining of two optimization objectives with the control factor, it can provide various throughput-fairness tradeoffs according to the control factors. For further simplification, we exploit a high signal-to-noise ratio (SNR) approximation of the instantaneous channel capacity. Through computer simulations, we evaluate the throughput and fairness performances of the proposed algorithm according to the control factors, assuming an independent Rayleigh fading multiuser channel. We also evaluate the proposed algorithm employing the high SNR approximation. From simulation results, we could see that the proposed algorithm can control arbitrarily the throughput-fairness performance between the performance of the scheduler aiming to the maximum sum throughput and that of the scheduler aiming to the maximum fairness, finally, we see that the high SNR approximation can give a satisfactory performance in this situation.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.181-183
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• 2004

본 논문은 TCP에서 사용되는 혼잡 제어 방식의 문제점인 전송 시간에 대한 전송률 편중 현상을 완화시키기 위한 비례 증가 혼잡 제어 방식을 제안한다. TCP는 네트워크의 혼잡 상황을 제어하기 위하여 ACK 기반의 혼잡 윈도우 조정 방식을 사용한다. 그러나 기존 TCP에서 사용되는 혼잡 제어 방식은 그 자체적으로 네트워크의 혼잡 상황을 유도하며, 전송 시간이 다른 두 개의 TCP 연결이 하나의 병목 지점을 공유할 경우, 전송 시간의 차이에 따라 전송률의 편중 현상이 나타난다. 본 논문에서는 이러한 네트워크 혼잡 상황 유발과 전송 시간의 차이에 따른 전송률 편중 현상을 완화시키기 위한 송신자 기반의 네트워크 대역폭 측정 방법 및 비례 증가 혼잡 제어 알고리즘을 제안하며, 구현 및 실험을 통해 기존 TCP의 문제점을 해결할 수 있음을 보인다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.8
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• pp.1434-1440
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• 2008

Performance of TCP/IP is studied on the wireless network using flow control and congestion control mechanism based on transmission rate. We discuss the elimination or the reduction of various phenomena of burst by flow controlling on transmission rate and verify that there are TCP ACK compression promblems on the queue by burst reaction while executing transmission rate controlled channels. Analyzing periodic burst reaction on the queue of source IP, the maximum value of queue is expected, which represents the applible expectation of throughput reduce and shows the improvement of performance by the reduce of throughput due to hi-directional traffic.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.6B
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• pp.559-568
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• 2002

In this paper, we studied on combining the control of transmission fates and power for the real system where a finite set of transmission rates are used. In [1], the combined control of transmission rates and power was first researched, and suggested the Selective Power Control (SPC) algorithm. However, it can't guarantee the minimum rate to each user and results in frequent changes of rate due to oscillation of the SIR (Signal to Interference Ratio) values. As a main purpose of this paper, we derive a formulation model and propose a distributed iteration algorithm to solve these problems. To evaluate the performance of the proposed algorithm, we carried out numerical analysis and computational experiments. The results indicate that the proposed algorithm achieves better throughput than conventional one by keeping the low average transmission power.

• The KIPS Transactions:PartC
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• v.12C no.3 s.99
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• pp.395-400
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• 2005

The IEEE 802.11b WLAN supports multiple transmission rates and the rate is chosen in an adaptive manner by an auto rate control algorithm. This auto rate control algorithm deeply affects the total system performance of the IEEE 802.11b WLAN. In this paper, we examine the WLAN performance with regard to the auto rate control algorithm especially the ARF scheme. The experimental results indicate that the ARF scheme works well in the face of signal noise due to node location. However, the ARF scheme severely degrades system performance when multiple nodes contend to obtain the wireless channel and the packet is lost due to signal collision. In addition, TCP prevent the performance degradation due to ARF scheme by retaining number of active nodes. However, some applications, such as transporting multimedia data, adopt the UDP. Therefore, the TCP cannot be an optimal solution for all WLAN applications.