• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.1
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• pp.187-195
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• 2013

In this paper, we propose a transmission power control scheme for performance improvement of VANET using STPC algorithm considering traffic-flow model. In traffic congestion, a transmission power between car and car increases the collision probability of control messages, which causes the problems to decrease the performance of VANET. The proposed scheme is evaluated by OPNet modeler 16.0 for analyzing its performance and effectiveness in terms of end-to-end delays in hops, packet success probability, and throughput. The simulation result show that the proposed scheme reduces a delay in hops and increases high packet transmission success ratio. Furthermore, a throughput under high density traffic is improved effectively.

• The Transactions of the Korea Information Processing Society
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• v.4 no.1
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• pp.224-236
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• 1997

In order to control the flow of traffic in ATM networks and optimize the usage of network resources, an appropriate control mechanism is necessary to cope with congestion or prevent degradation of network performance caused by congestion. While the conventional UPC algorithm provides only unstable preventive function unrelated with the state of networks and is unable to recover congestion, the proposed adaptive UPC algorithm supervises the situation of ATM networks using the information from OAM cell. Then the monitor of the proposed adaptive UPC algorithm controls leaky rate and buffer threshold value according to QOS. Therefore, the proposed algorithm can cope with congestion as well as prevent and react sensitively to buffer delay. In proportion to the diversity of traffic and the increase of transmission rate in networks, the adaptive UPC-BT algorithm proposed in this paper can be effectively used in ATM networks with wide applications. This paper shows that the proposed algorithm efficiently uses in ATM networks with application. This paper shows that the proposed algorithm efficiently use network resources and provides QOS to users for various kinds of traffics by comparing with conventional UPC algorithms.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.11
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• pp.1-8
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• 2001

Adaptive and Strict Packet Dropping mechanism we proposed in this paper drops adaptively packets for the congestion control, as predicting traffic pattern between each cycle. Therefore the proposed mechanism makes up for the drawback of RIO mechanism and minimizes the wastes of the bandwidth being capable of predicting in Dynamic and Strict Packet Dropping (DSPD) mechanism. And we executed a simulation and analyzed the throughput and packet drop rate based on the Sending Drop Precedence changing dynamically depending on the network traffic and compared RIO and the DSPD. The results show that the proposed mechanism provides better performance on drop precedence levels and stricter drop precedence policy for AF class than RIO and the DSPD mechanism.

• Journal of KIISE:Information Networking
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• v.29 no.3
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• pp.233-241
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• 2002

In this paper, we proposed a new mechanism that solves the fairness problem between unicast traffic using the TCP and multicast traffic using the UDP, and satisfies the requirement of various receivers fairly in the Internet. The proposed mechanism decentralizes the load of blanket transmission rate control from sender to designated server, and uses the method that talc designated server intercepts the sender's data and controls the transmission rate suitable for it's local network. Therefore, the proposed mechanism not only provides multicast service by accurate estimation of the network status of each receiver, but also realizes both the inter-session fairness and the intra-session fairness problem.

• The KIPS Transactions:PartC
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• v.15C no.4
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• pp.321-328
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• 2008

In this paper, we analyze web response time depending on queue managements and transmission latencies in highly congested network situation. Under FIFO scheme, the response times are for three different sizes of queue are almost the same, but the response time increases as traffic intensity increases. The performance between different queue sizes shows more different in 90% and 98% traffic intensity than in 80% traffic intensity. Especially the difference becomes bigger in short latency case than long latency case. Under RED scheme, three differently tunned RED schemes do not impact on the response time when the size of queue is relatively large. When the queue size becomes smaller, the response time of the differently tunned RED schemes becomes different for short latency case while the response times are almost same for long latency case. When comparing FIFO and RED schemes under same size of queue, RED scheme shows less response time than that of FIFO for the long latency case in high traffic intensity.

• 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.26 no.8B
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• pp.1057-1069
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• 2001

오디오 부호화 시스템에 널리 쓰이는 시간 영역 엘리어싱 제거(TDAC) 필터 뱅크의 성능 개선을 위하여, 다중 중첩-합 구조를 바탕으로 한 개선된 TDAC 필터 뱅크를 제안하였다. 제안된 구조는 필터 뱅크의 분해 부분과 합성 부분 사이에서 발생하는 양자화 잡음의 효과를 줄이도록 제안되었다. 모의 실험을 통해 같은 양자화 비트 수를 사용하는 경우에 제안한 시스템이 SNR 측면에서 보다 나은 성능을 나타냄을 보였으며, 망 전송 데이터 양을 같게 한 경우에도 제안한 시스템이 더 적은 데이터 양의 블록 단위를 가질 수 있으므로 데이터 망의 혼잡 제어에 있어 보다 유리할 수 있음을 보였다.

• Proceedings of the KOR-KST Conference
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• 1998.10a
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• pp.41-41
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• 1998

ITS틀 내의 한 분야인 도로교통정보체계 (ATIS: Advanced Traveler Information system)는 실시간 교통정보를 운전자에게 직접 제공하는 것으로서, 이를 위해 매 순간마다 가로망에 배정되는 교통량 및 통행시간을 예측할 수 있는 범용의 동적 통행배정모형(dynamic route choice model)의 개발이 필히 수반되어야 한다. 본 연구에서는 ITS사업에서 필수적으로 수반되어야 할 최적 제어이론에 의한 동적 통행 배정모형을 ATIS의 핵심 소프트웨어로 응용하기 위해 기존 연구성과를 발판으로, 순간 동적 통행 배정모형(Ran, Boyce &LeBlanc, 1993)의 통행제약조건인 링크통행함수, 특히, 과부하 시 엘켈릭의 일반식의 파라메터를 조정, 적용하여, 서울시 강남지역의 실제 가로망의 사례연구를 통해 지체식의 각각의 파라메터에 따른 결과를 O/D에 따른 통행시간, 링크통행시간, 혼잡도를 중심으로 비교 평가하여, ATIS의 핵심 소프트웨어로서 순간 동적 통행배정을 통해 보다 현실여건을 잘 반영할 수 있는 링크 통행 성능 함수를 도출하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.11b
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• pp.1257-1260
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• 2002

유선에서와는 달리 무선망에서는 채널의 대역폭이 이동 단말기의 위치와 시간에 따라 변하는 특성을 가지고 있다. 유선 망의 대역폭과 TCP의 RTT와의 관계에 대한 논문은 이미 많이 발표 되어 있다[1]. 하지만 고정된 대역폭에서 최적화 되어있는 TCP 의 혼잡 제어 알고리즘이 다양한 변화를 가지는 무선 환경에서도 좋은 성능을 내는 지에 대해 발표된 연구 결과는 많지 않다. 이 논문에서는 RTT 에 영향을 받는 TCP 의 throughput 이 무선 채널의 변화와는 어떤 관계가 있는 지를 살펴보고자 한다[2]. 오랫동안 지속되는 TCP 연결에 의해 생성되는 CDMA 1X EV-DO 시스템에서 사용되는 비례 공정 스케줄링과 기존의 스케줄링을 이용하여 packet 을 전송하였을 경우 무선 채널의 변화와 RTT의 관계에 의해 나타나는 결과를 살펴보겠다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.295-303
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• 2004

In this Paper, we discuss an active TCP link of unsynchronized transmission mode network in two-way traffic and the Improvement of its traffic patron thorough the network pathway of protocol is shown. This is because the traffic pattern is performed on the basis of existing windows which are distributing information in several periods of time in the way of interfacing LTS control module, which is controlling by an information of exceeding the time limit of feedback loop determined by RTP, with TCP. The simulation to utilize this efficiently is performed with the circumstance of bench mark based on physical modeling of the self-similarity traffic in the performance of TCP. In this paper, we use a methodology to understand and evaluate the effect of change of transmitting protocol in sticks under the condition of the self-similar traffic in two-way network and it is shown that an improvement of congestion control by self-similarity under a heavy condition.