• Title/Summary/Keyword: Congestion

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Improved Global Placement Technique to Relieve Routing Congestion (배선 밀집도를 완화하기 위한 개선된 광역배치 기법)

  • Oh, Eun-Kyung;Hur, Sung-Woo
    • Journal of KIISE:Computing Practices and Letters
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    • v.14 no.4
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    • pp.431-435
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    • 2008
  • Since previous work CDP(Congestion Driven Placement) [1] considers all possible directions to move every cell in nets which contribute highly to routing congestion, it consumes CPU time a lot. In this paper, we propose a faster global placement technique, so called ICDGP(Improved Congestion Driven Global Placement) to relieve the routing congestion. ICDGP uses the force-directed method to determine the target locations of the cells in the nets in the congested spots, and considers only to move the target location for each cell. If moving multiple cells simultaneously is considered better than moving each cell one by one it moves multiple cells simultaneously. By experimental results, ICDGP produces less congested placement than CDP does. Particularly, the CPU time is reduced by 36% on average.

A congestion control scheme estimating global channel busy ratio in VANETs

  • Kim, Tae-won;Jung, Jae-il;Lee, Joo-young
    • Journal of IKEEE
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    • v.21 no.2
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    • pp.115-122
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    • 2017
  • In vehicular safety service, every vehicle broadcasts Basic Safety Message (BSM) periodically to inform neighbor vehicles of host vehicle information. However, this can cause network congestion in a region that is crowded with vehicles resulting in a reduction in the message delivery ratio and an increase in the end-to-end delay. Therefore, it could destabilize the vehicular safety service system. In this paper, in order to improve the congestion control and to consider the hidden node problem, we propose a congestion control scheme using entire network congestion level estimation combined with transmission power control, data rate control and time slot based transmission control algorithm. The performance of this scheme is evaluated using a Qualnet network simulator. The simulation result shows that our scheme mitigates network congestion in heavy traffic cases and enhances network capacity in light traffic cases, so that packet error rate is perfectly within 10% and entire network load level is maintained within 60~70%. Thus, it can be concluded that the proposed congestion control scheme has quite good performance.

TCP Performance Optimization Using Congestion Window Limit in Ad Hoc Networks with MAC Frame Aggregation (MAC Frame Aggregation이 가능한 에드혹 네트워크에서의 Congestion Window Limit을 통한 TCP 성능의 최적화)

  • Kang, Min-Woo;Park, Hee-Min;Park, Joon-Sang
    • The Journal of The Korea Institute of Intelligent Transport Systems
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    • v.9 no.4
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    • pp.52-59
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    • 2010
  • MAC frame aggregation is a method that combines multiple MPDUs (MAC protocol data units) into one PPDU (PHY protocol data units) to enhance network performance at the MAC layer. In ad hoc networks, TCP underperforms due to the congestion window overshooting problem and thus by setting CWL (congestion window limit) TCP performance can be improved. In this paper, we investigate the problem of setting CWL for TCP performance optimization in ad hoc networks with MAC frame aggregation.

Congestion Detection and Avoidance for Reliable Data Transmission in Wireless Sensor Networks (무선 센서 네트워크에서 신뢰성 있는 데이터 전송을 위한 혼잡 탐지와 회피)

  • Park, Hong-Jin;Jang, Jae-Bok
    • Journal of Advanced Navigation Technology
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    • v.14 no.3
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    • pp.343-350
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    • 2010
  • Wireless Sensor Network is an event-driven system that a large number of micro sensor nodes are collected, giving and Wing information. Congestion can take place easily since a great number of sensor nodes are sensing data and transferring them to sink nodes when an event occurs, comparing to the existing wired network. Current internet transport protocol is TCP/UDP, however, this is not proper for wireless sensor network event-driven ESRT, STCP and CODA are being studied for reliable data transport in the wireless sensor network. Congestion are being detected local buffer and channel loading with these techniques. Broadcasting is mainly used and can avoid congestion when one happens. The way that combining local buffer and channel loading information and detecting congestion is being studied in this paper. When congestion occurs, buffering state is divided into three in order to lessen the broadcasting sending the message on congestion control to the node having frequent channel loading. Thus they have advantage of decreasing network's loading.

Development of an Algorithm for Estimating Subway Platform Congestion Using Public Transportation Card Data (대중교통카드 자료를 활용한 도시철도 승강장 혼잡도 추정 알고리즘 개발)

  • Lee, Ho;Choi, Jin-Kyung
    • Journal of the Korean Society for Railway
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    • v.18 no.3
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    • pp.270-277
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    • 2015
  • In some sections of the Seoul Metropolitan Subway, severe congestion can be observed during rush hours and on specific days. The subway operators have been conducting regular surveys to measure the level of congestion on trains: the results are then used to make plans for congestion reduction. However, the survey has so far focused just on train' congestion and has been unable to determine non-recurring congestion due to special events. This study develops an algorithm to estimate the platform congestion rate by time using individual public transportation card data. The algorithm is evaluated by comparison of the estimated congestion rate and the ground truth data that are actually observed at non-transfer subway stations on Seoul subway line 2. The error rates are within ${pm}2%$ and the performance of the algorithm is fairly good. However, varying walking times from gates to platforms, which are applied to both non-peak periods and peak time periods, are needed to improve the algorithm.

A Congestion Control Scheme Using Duty-Cycle Adjustment in Wireless Sensor Networks (무선 센서 네트워크에서 듀티사이클 조절을 통한 혼잡 제어 기법)

  • Lee, Dong-Ho;Chung, Kwang-Sue
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.1B
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    • pp.154-161
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    • 2010
  • In wireless sensor networks, due to the many-to-one convergence of upstream traffic, congestion more probably appears. The existing congestion control protocols avoid congestion by controlling incoming traffic, but the duty-cycle operation of MAC(Medium Access Control) layer has not considered. In this paper, we propose DCA(Duty-cycle Based Congestion Avoidance), an energy efficient congestion control scheme using duty-cycle adjustment for wireless sensor networks. The DCA scheme uses both a resource control approach by increasing the packet reception rate of the receiving node and a traffic control approach by decreasing the packet transmission rate of the sending node for the congestion avoidance. Our results show that the DCA operates energy efficiently and achieves reliability by its congestion control scheme in duty-cycled wireless sensor networks.

Adaptive Congestion Control for Effective Data Transmission in Wireless Sensor Networks (센서네트워크에서의 효율적인 데이터 전송을 위한 적응적 혼잡 제어)

  • Lee, Joa-Hyoung;Gim, Dong-Gug;Jung, In-Bum
    • The KIPS Transactions:PartC
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    • v.16C no.2
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    • pp.237-244
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    • 2009
  • The congestion in wireless sensor network increases the ratio of data loss and causes the delay of data. The existing congestion protocols for wireless sensor network reduces the amount of transmission by control the sampling frequency of the sensor nodes related to the congestion when the congestion has occurred and was detected. However, the control method of sampling frequency is not applicable on the situation which is sensitive to the temporal data loss. In the paper, we propose a new congestion control, ACT - Adaptive Congestion conTrol. The ACT monitors the network traffic with the queue usage and detects the congestion based on the multi level threshold of queue usage. Given network congestion, the ACT increases the efficiency of network by adaptive flow control method which adjusts the frequency of packet transmission and guarantees the fairness of packet transmission between nodes. Furthermore, ACT increases the quality of data by using the variable compression method. Through experiment, we show that ACT increases the network efficiency and guarantees the fairness to sensor nodes compared with existing method.

A TCP-Friendly Congestion Control Scheme using Hybrid Approach for Reduction of Transmission Delay for Real-Time Video Stream (실시간 비디오 스트림의 전송지연 축소를 위한 TCP 친화적 하이브리드 혼잡제어 기법)

  • 김형진;조정현;나인호
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.8 no.2
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    • pp.304-309
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    • 2004
  • Recently, the needs for multimedia stream such as digital audio and video in the Internet has increased tremendously. Unlike TCP, the UDP protocol, which has been used to transmit streaming traffic thorough the Internet, does not apply any congestion control mechanism to regulate the data flow thorough the shared network And it leads to congestion collapse of the Internet and results in long-term transmission delay. To avoid any adverse effect on the current Internet functionality, a now protocol of modification or addition of some functionality to perform congestion control and to reduce huge transmission delay in transmitting of multimedia stream are in study. TCP-friendly congestion control mechanism is classified into two : one is window-based congestion control scheme using general window management functionalities, the other is rate-based congestion control scheme using TCP modeling equation. In this paper, we propose an algorithm for improving the transmitting rate on a hybrid TCP-friendly congestion control scheme combined with widow-based and late-based congestion control for multimedia stream. And we also simulate the performance of improved TEAR implementation using NS. With He simulation results, we show that the improved TEAR can provide better fairness and lower rate fluctuations than TCP.

A Design of Hop-by-Hop based Reliable Congestion Control Protocol for WSNs (무선 센서 네트워크를 위한 Hop-by-Hop 기반의 신뢰성 있는 혼잡제어 기법 설계)

  • Heo Kwan;Kim Hyun-Tae;Ra In-Ho
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.10 no.6
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    • pp.1055-1059
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    • 2006
  • In Wireless Sensor Networks(WSNs), a sensor node broadcasts the acquisited sensing data to neighboring other nodes and it makes serious data duplication problem that increases network traffic loads and data loss. This problem is concerned with the conflict condition for supporting both the reliability of data transfer and avoidance of network congestion. To solve the problem, a reliable congestion control protocol is necessary that considers critical factors affecting on data transfer reliability such as reliable data transmission, wireless loss, and congestion loss for supporting effective congestion control in WSNs. In his paper, we proposes a reliable congestion protocol, called HRCCP, based on hop-hop sequence number, and DSbACK by minimizing useless data transfers as an energy-saved congestion control method.

A Design of Hop-by-Hop based Reliable Congestion Control Protocol for WSNs (무선 센서 네트워크를 위한 Hop-by-Hop 기반의 신뢰성 있는 혼잡제어 기법 설계)

  • Heo Kwan;Kim Hyun-Tae;Yang Hae-Kwon;Ra In-Ho
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2006.05a
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    • pp.442-445
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    • 2006
  • In Wireless Sensor Networks(WSNs), a sensor node broadcasts an acquisited data to neighboring other nodes and it makes serious data duplication problem that increases network traffic loads and data loss. This problem is concerned with the conflict condition for supporting both the reliability of data transfer and avoidance of network congestion. To solve the problem, a reliable congestion control protocol is necessary that considers critical factors affecting on data transfer reliability such as reliable data transmission, wireless loss, and congestion loss for supporting effective congestion control in WSNs. In this paper, we proposes a reliable congestion protocol, ratted HRCCP, based on hop-hop sequence number, and DSbACK by minimizing useless data transfers as an energy-saved congestion control method.

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