• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.8
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• pp.1653-1660
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• 2003

In this paper, we proposed an enhanced TCP congestion control algorithm using RTT with congestion window parameter cwnd to minimize the effect of TCP congestion. The proposed scheme could avoid the occurrence of frequent congestion and decrease the delay caused by the recovery time and the using amount of switch buffer. Through the simulation, we showed that the proposed scheme cm acquire higher performance than the existing scheme. There are 22.56％ improvement at the average using buffer efficiency, and packet drop rate is 0.1％ which is less than existing scheme.

• Proceedings of the Korea Contents Association Conference
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• 2007.11a
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• pp.126-129
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• 2007

Recently the use of wireless network increases according to it solves the hand-off and with path loss, pading, noise etc of wireless network the research for transmission error improvement is developed. TCP and SCTP of standard where it guarantees the reliability of wire network apply in wireless network the congestion control, flow control mechanism used it decreases the efficiency of data transfer throughputs. In this paper, It mixes SCTP and SNOOP for SCTP apply on wireless network, to improve BS(Basic Station) operation processes when the transmission error occurs in wireless network. BS send ZWP(Zero Window Probe) to MN(Mobile Node) when the transmission error occurs so, check path and status and update RWND and error status checked. It selects the new path, send ZWA(Zero Window Advertisement) to FH(Fixed Host) and the prevents call to congestion control or flow control and it does to make wait status standing. Continuously of data transfer after the connection of wireless network is stabilized, it make increase about 10% the transmission throughput of data.

• 전자공학회논문지 IE
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• v.43 no.3
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• pp.41-48
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• 2006

In this paper, we propose a new active queue management (AQM) scheme by utilizing the predictability of the Internet traffic. The proposed scheme predicts future traffic input rate by using the auto-regressive (AR) time series model and determines the future congestion level by comparing the predicted input rate with the service rate. If the congestion is expected, the packet drop probability is dynamically adjusted to avoid the anticipated congestion level. Unlike the previous AQM schemes which use the queue length variation as the congestion measure, the proposed scheme uses the variation of the traffic input rate as the congestion measure. By predicting the network congestion level, the proposed scheme can adapt more rapidly to the changing network condition and stabilize the average queue length and its variation even if the traffic input level varies widely. Through ns-2 simulation study in varying network environments, we compare the performance among RED, Adaptive RED (ARED), REM, Predicted AQM (PAQM) and the proposed scheme in terms of average queue length and packet drop rate, and show that the proposed scheme is more adaptive to the varying network conditions and has shorter response time.

• Journal of KIISE:Information Networking
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• v.33 no.5
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• pp.369-379
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• 2006

In recent years, there have been many researches about Ad-hoc Networks which is available to communicate freely between mobile devices by using multi-hop without any support of relay base or access point. TCP that used the most widely transport protocol in the Internet repeats packet loss and retransmission because it increases congestion window size by using reactive congestion control until packet loss occurs. As a result of this, energy of mobile device is wasted unnecessarily. In this paper, we propose TCP-New Veno in order to improve the energy efficiency of mobile device. According to the state of network, the scheme adjusts appropriate size of congestion window. Therefore, the energy efficiency of mobile device and utilization of bandwidth are improved by the scheme. From the simulation by using ns-2, we could see more improved energy efficiency with TCP-New Veno than those with TCP in Ad-hoc Networks.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.11a
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• pp.1494-1497
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• 2011

본 논문에서는 유 무선 이종망의 네트워크에서 혼잡손실과 무선손실의 구별을 하지 못하고 전송률을 감소하는 TFRC의 성능을 개선하기 위한 최소 전송률을 보장하는 TFRC 제어방법을 제안한다. 제안하는 TFRC기법은 기존의 TFRC기법의 패킷손실률에 따른 loss event rate를 제한하고 피드백 타임아웃에 따른 전송률 감소를 제한하여 비디오의 최소전송률을 보장하는 방법이다. TCP와 제안하는 TFRC를 같은 네트워크망에서 경쟁하는 환경으로 실험 했을 때 기존의 TFRC와 비교해서 제안한 TFRC의 전송률이 보장되어 더 좋은 성능을 보였다. 무선구간에서의 손실까지도 혼잡손실로 판단하고 전송률을 감소시켜 다중 네트워크에서 대역폭을 보장받지 못하는 TFRC기법을 최소전송률 보장을 통해 비디오 스트리밍 서비스를 제공함으로써 서비스의 품질을 보장한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.5B
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• pp.413-420
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• 2006

HMIPv6 is designed to reduce the signaling load to external network and improve handover speed of MN by including Mobility Anchor Point(MAP) in local handover. However in this case of macro handover, it's just used pervious MIPv6 handover algorithm. So, it occurs packet loss and transmission delay problem. In this paper, we propose the mechanism applying the HMIPv6 for Fast Handover to choose suitable to the condition buffering handover. The condition for the selection is result distance measurement between MN and CN, between MN and NAR. Furthermore, using F-SNOOP protocol, it is possible to improve wireless network performance. Wireless network has high Bit Error Rate(BER) characteristic because of path loss, fading, noise and interference. TCP regards such errors as congestion and starts congestion control. This congestion control makes packet transmission rate low. However, F-SNOOP improves TCP performance based on SNOOP and Freeze TCP that use Zero Window Advertisement(ZWA) message when handoff occurs in wireless network.

• KIPS Transactions on Computer and Communication Systems
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• v.2 no.3
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• pp.117-124
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• 2013

In this paper we propose a TFRC(TCP Friendly Rate Control) which guarantees a minimum rate in order to improve the efficiency of the previous TFRC which cannot distinguish congestion losses and wireless losses and decreases throughput both in wired and wireless networks. This TFRC technique is able to guarantee a minimum rate for video by restricting a loss event rate with packet loss probability about existing TFRC and constraining a rate reduction from the feedback timeout. When we experimented both the existing TFRC and the new one with TCP in the same network, we found that the latter is better than the former. Consequently, it shows that the proposed TFRC can improve video streaming quality using a guaranteed minimum transmission rate.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10e
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• pp.181-183
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• 2002

현재의 인터넷 라우터는 Drop tail 방식으로 큐 안의 패킷을 관리한다. 따라서 네트워크 트래픽의 지수적인 증가로 인해 발생하는 혼잡 상황을 명시적으로 해결 한 수 없다. 이 문제를 해결하기 위해 IETF (Internet Engineering Task Force)에서는 RED(Random Early Detection)알고리즘과 같은 능동적인 큐 관리 알고리즘(AQM: Active Queue Algorithm)을 제시하였다. 하지만 RED 알고리즘은 네트워크 환경에 따른 매개 변수의 설정의 어려움을 가지고 있어 잘못된 매개변수 설정으로 인하여 네트워크 성능을 저하시키는 문제를 발생시키며 전체 망에 불안정한 혼잡제어를 야기 시킨다. 본 논문에서는 기존의 AQM를 개선한 SOQuM(Stabilized Operation of Queue Management) 알고리즘을 제안하였다. 제안한 알고리즘의 성능을 검증하기 위해 기존의 방법과 시뮬레이션을 이용하여 비교하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.04a
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• pp.721-724
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• 2011

UDT(UDP-based Data Transfer protocol)는 연구망과 같은 대용량 고속 네트워크에서 신속하고 안정적인 데이터 전송에 효율적인 전송 프로토콜이다. 하지만 네트워크가 혼잡한 상황이거나 데이터 패킷 손실이 발생할 경우 매우 공격적인 전송 메커니즘으로 인해 오히려 성능이 감소하는 경우가 발생한다. 본 논문에서는 네트워크 지연 예측을 통해 혼잡을 제어하는 TCP-Vegas 기법을 UDT에 적용하여 네트워크 상황에 보다 적응적인 UDT 혼잡제어 기법을 제안한다. 즉, 네트워크 라우터 큐에 빌드된 Diff 값을 미리 예측하고 Diff 값에 따라 UDT rate control을 조절하여 기존 방법보다 향상된 성능을 얻는다. 네트워크 시뮬레이터인 NS2를 통해 실험한 결과 패킷 손실이 없는 상황에서 최대 11%, 손실률 0.01%인 상황에서는 최대 31%의 성능 향상을 확인하였다.

• Electronics and Telecommunications Trends
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• v.7 no.1
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• pp.114-120
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• 1992

이동 가입자에게 통신 서비스를 제공하기 위한 공중 육상이동 통신망은 SS No.7 공통선 신호망을 이용하여 이동 통신망 구성요소 (HLR, VLR, MSC 등) 들을 연결시킨다. HLR, VLR 등은 SS No.7 에서 신호점의 형태로 구현되며 이러한 신호점들은 신호 메시지 중계기능을 갖는 신호 전달점과 신호 메시지 전송기능을 갖는 신호링크를 통하여 메시지를 서로 교환한다. 신호 메시지 전송시 신호링크의 혼잡상태로 인한 트래픽 상의 문제가 발생할 수 있으며 이의 해결을 위한 트래픽 제어방법이 필요하게 된다. SS No.7은 고유의 레벨-3 트래픽 제어 방법(Congestion Control Scheme)을 이용하여 신호 링크 혼잡시 신호 메시지 발신 신호점을 제어한다.