• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.1
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• pp.107-109
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• 2016

In this paper, we address the TCP-over-WLAN performance problem that occurs during periodic active background scanning with which mobile devices discover available APs in the vicinity. We measure the impact of the scanning period on the TCP throughput and observe a significant performance degradation when the scan operation period is shortened. Our experimental analysis has identified the main cause of the problem, that is, the associated AP continues to send packets to the mobile device even when the device is not able to receive due to the scanning operation.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.1352-1355
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• 2009

TCP에서 사용되는 혼잡제어(Congestion control)는 많은 이점이 있지만 그에 상응하는 단점이 존재한다. 가장 널리 사용되고 있는 TCP-Reno는 혼잡이 발생되면 혼잡 윈도우(Congestion Window)크기를 절반으로 줄이고 빠른 회복(fast recovery), 빠른 재전송(fast transmit)을 수행한다. 하지만 네트워크가 고속 네트워크로 접어들면서 효율적인 측면에서 이러한 기법들을 적용하기에는 문제가 따른다. 현재 사용되고 있는 TCP는 혼잡이 발생하면 선형적으로 점진적으로 증가 하기 때문에 많은 대역폭을 지원하는 고속 네트워크에서는 이러한 TCP의 혼잡 제어가 오히려 비 효율적이다. 본 논문에서는 이러한 문제점을 해결하기 위해 혼잡 윈도우 증가율을 추가한 혼잡제어 기법인 TCP-FBA(Fast Bandwidth Acquisition)를 제안한다.

• 대한공업교육학회지
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• v.33 no.2
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• pp.248-258
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• 2008

Current Internet uses HTTP (Hyper Text Transfer Protocol) as an application layer protocol and TCP (Transmission Control Protocol) as a transport layer protocol to provide web service. SCTP (Stream Control Transmission Protocol) is a recently proposed transport protocol with very similar congestion control mechanisms as TCP, except the initial congestion window during the slow start phase. In this paper, we present a mathematical model of object transfer latency during the slow start phase for HTTP over SCTP and compare with the latency of HTTP over TCP. Validation of the model using experimental result shows that the mean object transfer latency for HTTP over SCTP during the slow start phase is less than that for HTTP over TCP by 11%.

• Journal of Digital Contents Society
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• v.10 no.2
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• pp.279-289
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• 2009

As the TCP is the protocol designed for the wired network that packet loss probability is very low, because TCP transmitter takes it for granted that the packet loss by the wireless network characteristics is occurred by the network congestion and lowers the transmitter's transmission rate, the performance is degraded. In this article, we suggest the newly improved algorithm using two parameters, the local retransmission time value and the local retransmission critical value to the BS based on the Snoop. This technique adjusts the base stations local retransmission timer effectively according to the wireless link status to recover the wireless packet loss rapidly. We checked that as a result of the suggested algorithm through various simulations, A-Snoop protocol improve more the wireless TCP transmission rate by recovering the packet loss effectively in the wireless link that the continuous packet loss occur than the Snoop protocol.

• BMB Reports
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• v.53 no.8
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• pp.431-436
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• 2020

Alpha-fetoprotein (AFP) is one of the most commonly used and reliable biomarkers for Hepatocellular carcinoma（HCC). However, the underlying mechanism of AFP expression in HCC is poorly understood. In this study, we found that TCP10L, a gene specifically expressed in the liver, is down-regulated in HCC and that its expression inversely correlates with AFP expression. Moreover, overexpression of TCP10L suppresses AFP expression whereas knockdown of TCP10L increases AFP expression, suggesting that TCP10L might be a negative regulator of AFP. We found that TCP10L is associated with the AFP promoter and inhibits AFP promoter-driven transcriptional activity. Taken together, these results indicate that TCP10L negatively regulates AFP expression in HCC and that it could be a potential prognostic marker and therapeutic target for HCC.

• Journal of KIISE:Information Networking
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• v.32 no.1
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• pp.12-19
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• 2005

Reliable transport protocols such as TCP are tuned to Perform well in traditional networks where packet losses occur mainly because of congestion. In a wireless network, however, packet losses will occur more often due to reasons such as the high bit error rate and the handoff rather than due to congestion. When using TCP over wireless network, TCP responds to losses due to the high bit error rate and the handoff by invoking congestion control and avoidance algorithms, resulting in the degraded end-to-end performance in the wireless network. There have been several schemes for improving TCP performance over wireless links. Among them, SNOOP Is a very promising scheme because of the localized retransmission. In this thesis, an efficient scheme is proposed by modifying SNOOP scheme. The invocation of congestion control mechanism is now minimized by knowing the cause of packet loss.

• Journal of KIISE
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• v.43 no.8
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• pp.919-926
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• 2016

In a wireless network, TCP causes the performance degradation because of mistaking packet loss, which is caused by characteristics of wireless link and throughput oscillation due to change of devices connected on a limited bandwidth. Delay based TCP is not affected by packet loss because it controls window size by using the RTT. Therefore, it can solve the problem of unnecessary degradation of the rate caused by misunderstanding reason of packet loss. In this paper, we propose an algorithm for improving the remaining problems by using delay based TCP. The proposed scheme can change throughput adaptively by adding the RTT, which rapidly reflects the network conditions to BaseRTT. It changes the weight of RTT and the increases and decreases window size based on the remaining amount of the buffer. The simulation indicated that proposed scheme can alleviate the throughput oscillation problem, as compared to the legacy TCP Vegas.

• Journal of Communications and Networks
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• v.7 no.1
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• pp.45-53
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• 2005

In this paper, we present a cross-layer analysis of wireless TCP systems over correlated channels. The effects of error correlation on the behavior of link retransmission strategy and the end-to-end throughput of TCP layer are investigated. Based on the cross-layer analysis, an efficient refinement of link layer protocol is proposed by consciously utilizing the information of channel correlations, which leads to the performance improvement of wireless TCP systems.

• Journal of Korea Society of Digital Industry and Information Management
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• v.5 no.2
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• pp.141-156
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• 2009

As the TCP is the protocol designed for the wired network that packet loss probability is very low, because TCP transmitter takes it for granted that the packet loss by the wireless network characteristics is occurred by the network congestion and lowers the transmitter's transmission rate, the performance is degraded. The Snoop Protocol was designed for the wired network by putting the Snoop agent module on the BS(Base Station) that connect the wire network to the wireless network to complement the TCP problem. The Snoop agent cash the packets being transferred to the wireless terminal and recover the loss by resending locally for the error occurred in the wireless link. The Snoop agent blocks the unnecessary congestion control by preventing the dupack (duplicate acknowledgement)for the retransmitted packet from sending to the sender and hiding the loss in the wireless link from the sender. We evaluated the performance in the wired/wireless network and in various TCP versions using the TCP designed for the wired network and the Snoop designed for the wireless network and evaluated the performance of the wired/wireless hybrid network in the wireless link environment that the continuous packet loss occur.

• The Journal of the Korea Contents Association
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• v.10 no.3
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• pp.44-52
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• 2010

The most popular world wide web traffic in the Internet uses TCP as the transport layer protocol. Since TCP utilizes the single path, it can not communicate with the correspondent host during the link-down. On the other hand, SCTP can still communicate with the other SCTP entity by using alternate path even while the primary path is down. Most of previous studies have conducted the performance comparison research between TCP and SCTP by using typical file transfer. Since web traffic with self-similarity is characterized by the packet inter-arrival times and shape parameter affecting the size of web file in the Pareto distribution, it is necessary to perform the experiments considering these parameters. This paper aims to compare the throughput between TCP and SCTP while varying parameters reflecting the web traffic characteristics in link-down environment. Experimental results for web traffic using NS-2 simulator show that the throughput of SCTP using multi-homing is better than that of TCP. Simulation also shows that TCP is more affected than SCTP by mean inter-arrival and shape parameters with regard to the web traffic. These results can be applied to estimate the performance variation of web traffic due to the duration of link-down.