• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6B
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• pp.867-874
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• 2010

Since high packet losses occur in multi-hop transmission of wireless sensor networks, reliable data transmission is required. Especially, in case of event-driven data, a loss recovery mechanism should be provided for lost packets. Because retransmission for lost packets is requested to a node that caches the packets, the caching node should maintains all of data for transmission in its buffer. However, nodes of wireless sensor networks have limited resources. Thus, both a loss recovery mechanism and a buffer management technique are provided for reliable data transmission in wireless sensor networks. In this paper, we propose a buffer management technique at a caching position determined by a loss recovery mechanism. The caching position of data is determined according to desirable reliability for the data. In addition, we validate the performance of the proposed method through computer simulations.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.4
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• pp.741-746
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• 2012

Transmission control protocol(TCP) widely used as a transport protocol in the Internet includes a loss recovery function that detects and recovers packet losses by retransmissions. The loss recovery function consists of the two algorithms; fast retransmit and fast recovery. There have been researches to avoid nonnecessary retransmission timeouts (RTOs), which leads to selective acknowledgement (SACK) option and limited transmit scheme that are standardized by IETF (Internet Engineering Task Force). Recently, a method that covers the case in which a retransmitted packet is lost again has been propsed. The method, however, is not proved in terms of the additive increase multiplicative decrease (AIMD) principle of TCP congestion control. In this paper, therefore, we analyzed the method in terms of the principle by ns-simulations.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.2
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• pp.392-401
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• 2007

Wireless network has high BER characteristic because of path loss, fading, noise and interference. Many packet losses occur without any congestion in wireless network. Therefore, many wireless TCP algorithms have been proposed. SNOOP, one of wireless TCP algorithms, hides packet losses for Fixed Host and retransmits lost packets in wireless network. However, SNOOP has a weakness for bust errors in wireless network. This paper proposes the SACK-SNOOP to improve TCP performance based on SNOOP and Freeze-TCP that use ZWA messages in wireless network. This message makes FH stop sending packets to MH. BS could retransmit error packets to MH for this time. SACK-SNOOP use improved Selective ACK, thereby reducing the number of packet sequences according to error environment. This method reduces the processing time for generation, transmission, analysis of ACK. This time gain is enough to retransmit local burst errors in wireless link. Furthermore, SACK-SNOOP can manage the retransmitted error by extending delay time to FH. The simulation shows that our proposed protocol is more effective for packet losses in wireless networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.11B
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• pp.673-684
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• 2007

In this paper, we introduce an FARNS (Flooding algorithm with Adaptive Retransmission Nodes Selection). It is an efficient cross layer-based flooding technique to solve broadcast storm problem that is produced by simple flooding of nodes in wireless sensor network. FARNS can decrease waste of unnecessary energy by preventing retransmission action of whole network node by deciding retransmission candidate nodes that are selected by identification in MAC and distance with neighborhood node through received signal strength information in PHY. In simulation part, we show the results that FARNS has excellent performance than the other flooding schemes in terms of broadcast forwarding ratio, broadcast delivery ratio, number of redundancy packets and overhead. And FARNS can adjust of node ratio for retransmission operation, it can solve broadcast storm problem as well as meet the requirements of various network environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4B
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• pp.288-297
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• 2003

The fast retransmit and fast recovery algorithm of TCP Reno, when multiple packets in the same window are lost, cannot recover them without RTO (Retransmission Timeout). TCP New-Reno can recover multiple lost packets by extending fast recovery using partial acknowledgement. If the retransmitted packet is lost again during fast recovery, however, RTO cannot be avoided. In this paper, we propose an algorithm called "Duplicate Acknowledgement Counting(DAC)" to alleviate this problem. DAC can detect the retransmitted packet loss by counting duplicate ACKs. Conditions that a lost packet can be recovered by loss recovery of TCP Reno, TCP New-Reno and TCP New-Reno using DAC are derived by modeling loss recovery behavior of each TCP. We calculate the loss recovery probability for random packet loss probability numerically, and show that DAC can improve loss recovery behavior of TCP New-Reno.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.313-315
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• 2004

본 논문은 IEEE 802.l1b 유무선 환경 에 서 TCP를 이용한 데이터 전송 시 에이젼트를 이용하여 패킷 손실의 원인을 분석, 무선 링크에서 발생한 패킷 손실에 대해서는 혼잡 윈도우 크기를 유지하고, 유선 링크에서 발생한 패킷 손실에 대해서는 지역 재전송을 수행하는 저전력 전송 기법을 제안하고 실제 구현한다. 제안하는 저전력 전송기법 은 전송 후 WNIC를 저 전력 모드로 전환 시킴으로써 WNIC 전력 소비를 최소화 한다. 실험 결과 높은 무선 링크 에러율(1~2%)에서 기존 TCP-Reno 보다 약 18% 에너지 감소 효과를 나타냈다.

• The Journal of the Acoustical Society of Korea
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• v.16 no.6
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• pp.48-53
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• 1997

The multicasting of MCS(Multicast Server) requires a effective traffic control scheme to prevent buffer overflow on ATM subnetworks. This paper considers MCS multicasting to TCP packets, and propose EPD + SPD scheme(Early Packet Discard-same Source Packet Discard) using common buffer. When the threshold of output buffer is reached, MCS drops an entire packet prior to buffer overflow, so that corrupted packets will not be transmitted by the server. And SPD scheme show that the EPD + SPD results in higher TCP throughput than that of tail drop and EPD + DFF.

• The KIPS Transactions:PartC
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• v.8C no.1
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• pp.97-104
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• 2001

In this paper, we present a new hierarchical model for performance analysis of channel allocation and packet service protocol in wireless n network. The proposed hierarchical model consists of two parts : upper and lower layer models. The upper layer model is the structure state model representing the state of the channel allocation and call service. The lower layer model, which captures the performance of the system within a given structure state, is the wireless packet retransmission protocol model. These models are developed using SRN which is an modeling tool. SRN, an extension of stochastic Petri net, provides compact modeling facilities for system analysis. To get the performance index, appropriate reward rates are assigned to its SRN. Fixed point iteration is used to determine the model parameters that are not available directly as input. That is, the call service time of the upper model can be obtained by packet delay in the lower model, and the packet generation rates of the lower model come from call generation rates of the upper model.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.3
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• pp.637-644
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• 2004

This paper proposed and implemented the adaptive transmission middleware for video streaming, which is able to support the adaptive transmission of video data to the fluctuating changes of network environment in the packet-based network and the properties of transmitted video data. The adaptive transmission middleware is made up SR-RTP-based transfer module and TFRC(TCP Friendly Rate Control)-based transfer-rate control module. The SR-RTP-based transfer module supports RTP-based real-time transfer of video data and packet retransmission scheme retransmitting the high-priority packets selectively in the damaged video data to reduce the error induced by the packet loss. Sharing the transmission bandwidth of network with the TCP-based data transfer, the TFRC-based transfer-rate control module controls the transfer rate of video data according to the most allowable transmission bandwidth in the network, so that the transfer rate is controlled adaptively to the fluctuating changes of transmission bandwidth. This paper, for the experiment, applied the adaptive transmission middleware to video streaming in the external Internet environment, and analyzed the effective frame transfer rate and the degree of the streaming jitter to evaluate the performance of packet-loss recovery and adaptive transfer rate control. In the external Internet environment where the packet-loss rate is high a bit, the relatively high streaming performance was showed compared with the case that didn't apply the adaptive transmission middleware.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.319-321
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• 2015

인지무선네트워크 (Cognitive Radio Networks) 환경에서 스펙트럼의 원소유주인 1차사용자가 전송을 개시하는 경우, 같은 채널을 사용하는 2차사용자의 TCP (Transmission Control Protocol) 는 전송 불능 상태가 되어 심각한 성능저하가 발생한다. 이러한 성능저하는 1차사용자의 등장으로 인해 채널이 사용 불가능 해지는 상태를 패킷 손실로 판단하여 재전송 타임아웃이 발생하기 때문에 발생된다. 우리는 이 문제를 링크 또는 물리 계층 (하위계층) 과 TCP간의 크로스레이어링을 통하여 해결하고자 한다. 하위 계층은 1차사용자의 전송이 감지되면, 이를 TCP에게 시그널링하고, TCP는 이를 통해 재전송 타이머와 혼잡 윈도우를 고정시키고, 패킷 전송을 중단하도록 한다. 또, 하위계층이 가용 채널을 감지하게 되면, 재차 TCP에게 시그널링을 함으로써, 전송이 신속하게 재개되도록 한다. 제안하는 방법은 실제 USRP(Universal Software Radio Peripheral)에 구현하여 성능의 향상을 검증한다.