• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.9B
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• pp.813-822
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• 2003

Conventional TCPs are designed to work efficiently on wired network where any transmission errors rarely take place. However, the probability of transmission error in a wireless network is much higher than in a wired network, due to pass loss, multipath fading, and many kinds of interference. There were many researches on preventing the degradation of TCP performance in these wireless networks with bad channel condition. One of these researches is the SNOOP protocol which is link-layer solution for achieving high throughput of TCP. However, this SNOOP protocol is apt to retransmit some TCP segments unnecessarily, which could cause some increased traffic loads in a wireless network. In this paper, we propose a new algorithm to prevent the unnecessary retransmission of TCP segments and to achieve increased performance of TCP.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.3
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• pp.24-30
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• 2015

Wi-Fi STAs in power saving mode described in the Wi-Fi specification can deteriorate the system performance such as throughput, time delay when they receive data frames from a Wi-Fi AP. This problem is caused by data frame reception failure due to the channel state, and it increases re-transmissions. In this paper, we propose a modified power saving mode considering fairness of Wi-Fi system in order to solve the problem. By simulation, we showed that data throughput can be increased without time delay degradation if the proposed method restricting the number of packet transmission attempts and HARQ are used.

• The KIPS Transactions:PartC
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• v.13C no.3 s.106
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• pp.345-352
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• 2006

In the integrated wired/wireless network which consists of the Internet and moving networks, multiple wireless links are used to connect a fixed host(FH) in the Internet to a mobile host(MH) in the moving network. For use in such an environment, we propose a scheme to overcome the TCP performance degradation due to the packet losses over the wireless links without losing the end-to-end TCP semantics. The proposed scheme in each mobile router(MR) allows to obtain the information regarding packet losses over the upstream wireless links based on the received packet sequence number and the ACK number. This information is delivered to the upstream router, which enables the upstream access router(AR) or MR to quickly retransmit the lost packets. The proposed scheme has the feature to quickly recover the packet losses incurred over the upstream wireless links and the performance of the proposed scheme is evaluated through simulation. It is shown that the significant performance gain can be obtained using the proposed scheme compared with the snoop mechanism which maintains end-to-end TCP semantics and does not require any additional features at the source and/or destination nodes.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.1
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• pp.20-28
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• 1999

In this paper, we propose a new datagram delivery strategy at the home agent to improve the end-to-end performance by reducing retransmission overheads during handover. Changed routing might be able to cause packet disordering and this in turn could cause unnecessary retransmission at the fixed host and finally results in performance degradation. In our proposal, the home agent begins to buffer received datagrams instead of transmitting them after receiving a registration request message from the foreign agent and then transmits them again after for a certain time. Simulation results show that our proposal may successfully solve this problem at little cost.

• Journal of Korea Society of Industrial Information Systems
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• v.15 no.1
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• pp.1-14
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• 2010

It is recently issued scalability, mobility and external internet connection on Wire-less sensor network. The low power wireless sensor networks based on IPv6 technology 6LoWPAN technology is being standardized in the IETF. This paper for the 6LoWPAN environment based on the routing protocol LOAD, route cost applied the packet re-transmission rate which follows in Link Qualities price which uses at course expense and packet transmission Minimum route Cost routing protocol where does on the course wherethe smallest packet re-transmission becomes accomplished proposed. The technique which proposes compared and LOAD and AODV that about 13%, about 16% energy consumption is few respectively averagely, Energy of the entire network equally, used and energy effectiveness and improvement of network life time experiment led and confirmed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1998.11a
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• pp.549-552
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• 1998

본 논문에서는 wavelet 패킷의 직교성을 이용한 새로운 다중 통신 시스템을 구성하고 그 특성을 분석하였다. 유한에너지 신호공간 L$^2$(R)로부터 부분공간으로 신호를 분해할 수 있는 MRA(Multiresolution Analysis)의 기본개념과 이를 이용한 wavelet와 QMF(Quadrature Mirror Filter)와의 관계를 검토하였다. MRA의 개념을 보다 일반화한 신호의 wavelet 패킷 변환과 역변환을 실현하기 위한 알고리즘을 고찰하고 MRF(Multirate Filter Bank)를 이용하여 다중화 시스템을 설계하였다. 제안된 시스템은 구성이 간단하며 최대 이용자의 수와 정보 데이터의 전송율에 대한 유연성을 기대할 수 있음을 보였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.4B
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• pp.218-225
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• 2005

Although Snoop protocol can enhance TCP throughput efficiently in a wired-cum-wireless environment, it has a problem in performing local packet retransmissions under a burst error-prone wireless link. AT-Snoop protocol is proposed to cope with this Snoop protocol's problem by adopting adaptive timer. In this paper, TCP throughputs of AT-Snoop protocol have been analyzed with varying wireless link conditions and the ways of setting parameters of AT-Snoop protocol for higher TCP throughput are found out through computer simulations. From the simulation results, AT-Snoop protocol's two parameters, local retransmission threshold value and local retransmission timeout value, are closely related with the fading changing rate. To get higher TCP throughput, local retransmission threshold value and local retransmission timeout value should be set to a little bit larger values than average WSRTT(Wireless Smoothed Round Trip Time) and mean bad period of the wireless link, respectively.

• Proceedings of the Korean Information Science Society Conference
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• 2000.04a
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• pp.379-381
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• 2000

인터넷과 같은 WAN환경에서 멀티미디어 전송품질을 향상시키기 위해서 Proxy Cache가 많이 이용되고 있으며, 이에 기반하여 클라이언트에게 실시간으로 연속미디어를 서비스하기 위한 여러 가지 전송기법들이 요구되어지고 있다. 본 논문에서는 Proxy Cache안에 일정양의 메모리를 Relay Buffer로 할당하고 이를 이용한 흐름제어기법을 구현하며, RTSP서버의 전송스케쥴러의 idle time을 이용하는 재전송기법을 제안하고 구현한다. 실험 결과, 제안된 기법은 WAN상에서의 RTSP서버와 Proxy Cache사이 패킷손실량 현저하게 줄일 수 있음을 확인하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.05a
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• pp.971-974
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• 2008

오늘날 네트워크는 장비의 발달로 인해 패킷 재배치(packet reordering)가 빈번히 일어나고 있다. 패킷 재배치는 TCP의 성능을 저하시키는 문제점을 가지는데, 이러한 문제점을 해결하기 위해 TCPDAD 메커니즘이 제안되었다. TCP-DAD는 중복 응답 임계값을 동적으로 조절함으로써, TCP의 패킷 재배치 문제를 완화하는 메커니즘이다. 하지만 TCP-DAD는 중복 응답 임계값을 조절하는 메커니즘에 문제가 있어 패킷 손실이 일어날 경우, 패킷 손실에 대한 복구가 늦어지고 심지어 재전송 타이머가 불필요하게 종료되어 TCP의 성능저하를 야기하기도 한다. 본 논문에서는 이러한 TCP-DAD의 문제점을 해결하기 위해 새로운 중복 응답 임계값 조절 기법으로 Smooth-dupthresh를 제안한다. NS-2를 이용한 시뮬레이션을 통해 Smooth-dupthresh 기법을 적용한 TCP-DAD가 기존의 TCP-DAD 보다 평균적으로 약 8% 향상된 성능을 보임을 증명하였다.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.6
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• pp.1045-1054
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• 2020

In this paper, we designed a TCP/IP based ring buffer system that can stably transfer bulk data streams in the unstable network environments. In the scheme we proposed, The observation data stream generated and output by each radio observatory's backend system as a UDP frame is stored as a UDP packet in a large capacity ring buffer via a socket buffer in the client system. Thereafter, for stable transmission to the remote destination, the packets are processed in TCP and transmitted to the socket buffer of server system in the correlation center, which packets are stored in a large capacity ring buffer if there is no problem with the packets. In case of errors such as loss, duplication, and out of order delivery, the packets are retransmitted through TCP flow control, and we guaranteed that the reliability of data arriving at the correlation center. When congestion avoidance occurs due to network performance instability, we also suggest that performance degradation can be minimized by applying parallel streams.