The Experts below are selected from a list of 32259 Experts worldwide ranked by ideXlab platform
Fangchun Yang - One of the best experts on this subject based on the ideXlab platform.
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A traffic Congestion detection and Information dissemination scheme for urban expressways using vehicular networks
Transportation Research Part C: Emerging Technologies, 2014Co-Authors: Quan Yuan, Zhihan Liu, Jinglin Li, Junming Zhang, Fangchun YangAbstract:The cooperative vehicle-infrastructure technologies have enabled vehicles to collect and exchange traffic Information in real time. Therefore, it is possible to use Vehicular Ad-hoc NETworks (VANETs) for detecting traffic Congestion on urban expressways. However, because of the special topology of urban expressways (consisting of both major and auxiliary roadways), the existing traffic Congestion detection methods using VANETs do not work very well. In addition, the existing dissemination methods of Congestion Information lack the necessary control mechanism, so the Information may be disseminated to irrelevant geographical areas. This paper proposes a Congestion detection and notification scheme using VANETs for urban expressways. The scheme adopts a simplified Doppler frequency shift method to estimate and differentiate traffic conditions for major and auxiliary roadways. Vehicular cooperation and human cognition are introduced to improve the estimation accuracy and to describe the overall traffic conditions. Additionally, the scheme develops a spatial-temporal effectiveness model based on the potential energy theory to control the dissemination area and survival time of the Congestion Information. Meanwhile, the proposed scheme uses several broadcast control mechanisms to alleviate vehicular network Congestion. Simulations through TransModeler indicate that our scheme ensures the accuracy of the estimation of Congestion degree. Consequently, the scheme can provide effective references for driving decision-making and path-planning.
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Traffic Congestion Detection and Notification in the Urban Expressway System Using VANETs
ICTIS 2013, 2013Co-Authors: Quan Yuan, Zhihan Liu, Fangchun YangAbstract:Cooperative vehicle-infrastructure technologies have made it possible for vehicles to collect and exchange real-time traffic Information for the purpose of traffic guidance. However, traffic Congestion detection using Vehicular Ad-hoc NETworks (VANETs) is inaccurate on urban expressways due to the complex road and traffic conditions. What’s more, the necessary control mechanism is lacking for the dissemination of Congestion Information. This study proposes an urban expressway Congestion detection and notification method using VANETs. The method adopts the simplified Doppler frequency shift method to estimate and distinguish the degree of Congestion along major and auxiliary roads. Human cognitive abilities are used to cooperatively amend the estimation and describe the overall situation of the Congestion. The method also develops a spatial-temporal effectiveness model based on the field and potential energy theory to control the dissemination range and survival time of the Congestion Information, thus alleviating the vehicular network Congestion. The proposed method ensures the accuracy and effectiveness of the Congestion Information and provides a reference for driver decision making and path planning.
Quan Yuan - One of the best experts on this subject based on the ideXlab platform.
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A traffic Congestion detection and Information dissemination scheme for urban expressways using vehicular networks
Transportation Research Part C: Emerging Technologies, 2014Co-Authors: Quan Yuan, Zhihan Liu, Jinglin Li, Junming Zhang, Fangchun YangAbstract:The cooperative vehicle-infrastructure technologies have enabled vehicles to collect and exchange traffic Information in real time. Therefore, it is possible to use Vehicular Ad-hoc NETworks (VANETs) for detecting traffic Congestion on urban expressways. However, because of the special topology of urban expressways (consisting of both major and auxiliary roadways), the existing traffic Congestion detection methods using VANETs do not work very well. In addition, the existing dissemination methods of Congestion Information lack the necessary control mechanism, so the Information may be disseminated to irrelevant geographical areas. This paper proposes a Congestion detection and notification scheme using VANETs for urban expressways. The scheme adopts a simplified Doppler frequency shift method to estimate and differentiate traffic conditions for major and auxiliary roadways. Vehicular cooperation and human cognition are introduced to improve the estimation accuracy and to describe the overall traffic conditions. Additionally, the scheme develops a spatial-temporal effectiveness model based on the potential energy theory to control the dissemination area and survival time of the Congestion Information. Meanwhile, the proposed scheme uses several broadcast control mechanisms to alleviate vehicular network Congestion. Simulations through TransModeler indicate that our scheme ensures the accuracy of the estimation of Congestion degree. Consequently, the scheme can provide effective references for driving decision-making and path-planning.
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Traffic Congestion Detection and Notification in the Urban Expressway System Using VANETs
ICTIS 2013, 2013Co-Authors: Quan Yuan, Zhihan Liu, Fangchun YangAbstract:Cooperative vehicle-infrastructure technologies have made it possible for vehicles to collect and exchange real-time traffic Information for the purpose of traffic guidance. However, traffic Congestion detection using Vehicular Ad-hoc NETworks (VANETs) is inaccurate on urban expressways due to the complex road and traffic conditions. What’s more, the necessary control mechanism is lacking for the dissemination of Congestion Information. This study proposes an urban expressway Congestion detection and notification method using VANETs. The method adopts the simplified Doppler frequency shift method to estimate and distinguish the degree of Congestion along major and auxiliary roads. Human cognitive abilities are used to cooperatively amend the estimation and describe the overall situation of the Congestion. The method also develops a spatial-temporal effectiveness model based on the field and potential energy theory to control the dissemination range and survival time of the Congestion Information, thus alleviating the vehicular network Congestion. The proposed method ensures the accuracy and effectiveness of the Congestion Information and provides a reference for driver decision making and path planning.
David B Johnson - One of the best experts on this subject based on the ideXlab platform.
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exploiting Congestion Information in network and higher layer protocols in multihop wireless ad hoc networks
International Conference on Distributed Computing Systems, 2004Co-Authors: David B JohnsonAbstract:With most routing protocols for ad hoc networks, shorter paths are generally considered more desirable, making some areas of network more prone to Congestion and decreasing overall network throughput. We examine the use of Congestion Information to avoid these network hotspots. By locally monitoring the network interface transmission queue length and MAC layer behavior at each node, a node can establish an approximation of the degree to which the wireless medium around it is busy; this measurement reflects not only the behavior of the node itself, but also the behavior of other nearby nodes sharing the wireless medium. We suggest a number of uses of such Congestion Information in an ad hoc network, in the network, transport, and higher layers, and we evaluate a set of such uses through simulation. Our results based on modifications to the dynamic source routing protocol (DSR) and TCP demonstrate substantial performance improvement in terms of scalability, packet delivery, overhead, and fairness resulting from this use of Congestion Information.
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ICDCS - Exploiting Congestion Information in network and higher layer protocols in multihop wireless ad hoc networks
24th International Conference on Distributed Computing Systems 2004. Proceedings., 2004Co-Authors: David B JohnsonAbstract:With most routing protocols for ad hoc networks, shorter paths are generally considered more desirable, making some areas of network more prone to Congestion and decreasing overall network throughput. We examine the use of Congestion Information to avoid these network hotspots. By locally monitoring the network interface transmission queue length and MAC layer behavior at each node, a node can establish an approximation of the degree to which the wireless medium around it is busy; this measurement reflects not only the behavior of the node itself, but also the behavior of other nearby nodes sharing the wireless medium. We suggest a number of uses of such Congestion Information in an ad hoc network, in the network, transport, and higher layers, and we evaluate a set of such uses through simulation. Our results based on modifications to the dynamic source routing protocol (DSR) and TCP demonstrate substantial performance improvement in terms of scalability, packet delivery, overhead, and fairness resulting from this use of Congestion Information.
Sheue-ling Hwang - One of the best experts on this subject based on the ideXlab platform.
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EFFECTS ON DRIVING BEHAVIOR OF Congestion Information AND OF SCALE OF IN-VEHICLE NAVIGATION SYSTEMS
Transportation Research Part C: Emerging Technologies, 2003Co-Authors: Shiaw-tsyr Uang, Sheue-ling HwangAbstract:The purpose of this research was to compare the usage of a traditional paper map and electronic route maps during driving, and to consider the effects of Congestion Information and map scale sizes on driving performance, workload and subjective feelings. Experiments were conducted in desktop virtual driving environments with a 17-in. color monitor simulating driving environments and a 14-in. color monitor showing different kinds of navigation systems. A total of 20 undergraduate students of National Tsing Hua University were paid to participate in the Experiment I. The criteria for driving performance were trip duration, driving speed and number of navigation errors. Heart rate was measured as an index for workload. The 5-point Likert-type questionnaire was used to reflect the perceived nervousness, fatigue and task difficulty. Results indicated that the performance difference between a paper map and electronic route maps depended on the design characteristics of electronic route maps. Comparisons among four electronic maps revealed two significant main effects of Congestion Information and scale sizes on trip duration. Besides, it seemed that the availability of Congestion Information was useful for reducing navigation errors. Neither statistically significant main effects nor interaction was found on subjective feelings and driving speed. Another 18 subjects were used in the Experiment II to determine the optimum map scale size. Finally, the implications of the findings may provide suggestions on designing safer and more efficient in-vehicle navigation systems.
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A STUDY OF THE PRESENTATION OF TRAFFIC Congestion Information IN IN-VEHICLE NAVIGATION MAPS
Journal of the Chinese Institute of Industrial Engineers, 2002Co-Authors: Shiaw-tsyr Uang, Sheue-ling HwangAbstract:ABSTRACT The purpose of the present study was to compare the effect of presentation of traffic Congestion Information and map-scale on driving behavior so that design principles for in-vehicle navigation systems can be generated. A total of 18 undergraduate students (9 males and 9 females) of National Tsing Hua University were randomly assigned to only one condition of presentation of traffic Congestion Information (red dots, speech, or both) and experienced three map-scale conditions (large, median, and small) in virtual driving environments. Two-way analyses of variance with two block effects were conducted on the performance measures. Major findings were obtained and discussed on driving speed, trip duration, missing response, subjective ratings, and driving experience.
Bechir Hamdaoui - One of the best experts on this subject based on the ideXlab platform.
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IWCMC - CAFT: Congestion-Aware Fault-Tolerant Load Balancing for Three-Tier Clos Data Centers
2020 International Wireless Communications and Mobile Computing (IWCMC), 2020Co-Authors: Alanazi, Bechir HamdaouiAbstract:Production data centers operate under various workload sizes ranging from latency-sensitive mice flows to long-lived elephant flows. However, the predominant load balancing scheme in data center networks, equal-cost multi-path (ECMP), is agnostic to path conditions and performs poorly in asymmetric topologies, resulting in low throughput and high latencies. In this paper, we propose CAFT, a distributed Congestion-aware fault-tolerant load balancing protocol for 3-tier data center networks. It first collects, in real time, the complete Congestion Information of two subsets from the set of all possible paths between any two hosts. Then, the best path Congestion Information from each subset is carried across the switches, during the Transport Control Protocol (TCP) connection process, to make path selection decision. Having two candidate paths improve the robustness of CAFT to asymmetries caused by link failures. Large-scale ns-3 simulations show that CAFT outperforms Expeditus in mean flow completion time (FCT) and network throughput for both symmetric and asymmetric scenarios.