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Traffic Flow (traffic + flow)
Terms modified by Traffic Flow Selected AbstractsWavelet Packet-Autocorrelation Function Method for Traffic Flow Pattern AnalysisCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 5 2004Xiaomo Jiang A detailed understanding of the properties of traffic flow is essential for building a reliable forecasting model. The discrete wavelet packet transform (DWPT) provides more coefficients than the conventional discrete wavelet transform (DWT), representing additional subtle details of a signal. In wavelet multiresolution analysis, an important decision is the selection of the decomposition level. In this research, the statistical autocorrelation function (ACF) is proposed for the selection of the decomposition level in wavelet multiresolution analysis of traffic flow time series. A hybrid wavelet packet-ACF method is proposed for analysis of traffic flow time series and determining its self-similar, singular, and fractal properties. A DWPT-based approach combined with a wavelet coefficients penalization scheme and soft thresholding is presented for denoising the traffic flow. The proposed methodology provides a powerful tool in removing the noise and identifying singularities in the traffic flow. The methods created in this research are of value in developing accurate traffic-forecasting models. [source] Minimisation of end-to-end delay in reconfigurable WDM networks using genetic algorithmsEUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 8 2009Ramón J. Durán Barroso A new genetic algorithm (GA) is proposed to design logical topologies for wavelength-routed optical networks (WRONs) with the objective of minimising the end-to-end delay. Two versions of the algorithm, called D-GALD (Delay-optimised Genetic Algorithm for Logical topology Design), have been developed. The first one minimises the average end-to-end delay of the packets transported by the network, while the second one minimises the average delay of the most delayed traffic flow. By means of a simulation study, we show that the logical topologies designed by D-GALD support more than 50 per cent higher traffic load,without causing network instability,than those ones designed by other heuristics. Moreover, the utilisation of D-GALD leads to reductions of up to 15 per cent in the average end-to-end delay and around 30 per cent in the average end-to-end delay of the most delayed traffic flow. Copyright © 2008 John Wiley & Sons, Ltd. [source] Data assimilation and inverse problem for fluid traffic flow models and algorithmsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 6 2008P. Jaisson Abstract This article deals with traffic data assimilation and algorithms that are able to predict the traffic flow on a road section. The traffic flow is modellized by the Aw,Rascle hyperbolic system. We have to minimize a functional whose optimization variables are initial condition. We use the Roe method to compute the solution to the traffic flow modelling system. Then we compute the gradient of the functional by an adjoint method. This gradient will be used to optimize the functional. Copyright © 2008 John Wiley & Sons, Ltd. [source] QoS-aware fair packet scheduling in IEEE 802.16 wireless mesh networksINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 6-7 2010Yajun Li Abstract In this paper, we address the problem of heterogeneous quality-of-service (QoS) provisioning in IEEE 802.16-based wireless mesh networks. Our objective is to provide a novel service differentiation scheme based on distributed scheduling in the IEEE 802.16-based mesh mode, thereby offering QoS guarantees. We first devise a novel scheme for the traffic class differentiation, which can be implemented at the medium access control layer. We then present a QoS-aware fair packet scheduling (QFPS) algorithm to fulfill the QoS provisioning. With QFPS, a traffic flow with urgent QoS demand is guaranteed to be given priority in wireless resource allocation over those ones with mild QoS requirements. A shorter end-to-end delay is therefore expected to be offered for the traffic flows with time-urgent requirements. Moreover, we propose a new fairness model among different traffic flows traversing the same node. All traffic flows passing through a node are served by the Deficit Round-Robin scheduling algorithm to achieve fairness within the same priority group. The experimental results of the QFPS demonstrate that various traffic flows are provided with a differentiated service that offers QoS guarantees. Copyright © 2009 John Wiley & Sons, Ltd. [source] Neural bandwidth allocation function (NBAF) control scheme at WiMAX MAC layer interfaceINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 9 2007Mario Marchese Abstract The paper proposes a bandwidth allocation scheme to be applied at the interface between upper layers (IP, in this paper) and Medium Access Control (MAC) layer over IEEE 802.16 protocol stack. The aim is to optimally tune the resource allocation to match objective QoS (Quality of Service) requirements. Traffic flows characterized by different performance requirements at the IP layer are conveyed to the IEEE 802.16 MAC layer. This process leads to the need for providing the necessary bandwidth at the MAC layer so that the traffic flow can receive the requested QoS. The proposed control algorithm is based on real measures processed by a neural network and it is studied within the framework of optimal bandwidth allocation and Call Admission Control in the presence of statistically heterogeneous flows. Specific implementation details are provided to match the application of the control algorithm by using the existing features of 802.16 request,grant protocol acting at MAC layer. The performance evaluation reported in the paper shows the quick reaction of the bandwidth allocation scheme to traffic variations and the advantage provided in the number of accepted calls. Copyright © 2006 John Wiley & Sons, Ltd. [source] A tutorial on using genetic algorithms for the design of network topologyINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 4 2006Bassam Al-Bassam The design of network topology is an important part of network design, since network topology is directly associated with network operational behavior, capacity, reliability, and cost. This paper is a tutorial paper concerned with illustrating how the optimization capabilities of genetic algorithms can be used to design suitable network topologies considering basic topology problems. Simple genetic algorithms have been developed for the topology problem of mesh networks, considering single node and single link failure tolerance. The algorithms are based on criteria of two important measures: minimizing the length of communication links; and minimizing traffic flow through these links for given traffic loads. The first measure contributes to minimizing the cost of cabling, while the second measure contributes to minimizing the cost of link capacity. The work provides a useful approach and tools to network students and professionals concerned with the topology design of backbone networks. The developed software is made available on the Internet.,Copyright © 2006 John Wiley & Sons, Ltd. [source] Performance evaluation of adaptive routing algorithms in packet-switched intersatellite link networksINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 2 2002Mihael Mohor Abstract This paper addresses the performance evaluation of adaptive routing algorithms in non-geostationary packet-switched satellite communication systems. The dynamic topology of satellite networks and variable traffic load in satellite coverage areas, due to the motion of satellites in their orbit planes, pose stringent requirements to routing algorithms. We have limited the scope of our interest to routing in the intersatellite link (ISL) segment. In order to analyse the applicability of different routing algorithms used in terrestrial networks, and to evaluate the performance of new algorithms designed for satellite networks, we have built a simulation model of a satellite communication system with intersatellite links. In the paper, we present simulation results considering a network-uniform source/destination distribution model and a uniform source,destination traffic flow, thus showing the inherent routing characteristics of a selected Celestri-like LEO satellite constellation. The updates of the routing tables are centrally calculated according to the Dijkstra shortest path algorithm. Copyright © 2002 John Wiley & Sons, Ltd. [source] Modeling and simulation of vehicle projection arrival,discharge process in adaptive traffic signal controlsJOURNAL OF ADVANCED TRANSPORTATION, Issue 3 2010Fang Clara Fang Abstract Real-time signal control operates as a function of the vehicular arrival and discharge process to satisfy a pre-specified operational performance. This process is often predicted based on loop detectors placed upstream of the signal. In our newly developed signal control for diamond interchanges, a microscopic model is proposed to estimate traffic flows at the stop-line. The model considers the traffic dynamics of vehicular detection, arrivals, and departures, by taking into account varying speeds, length of queues, and signal control. As the signal control is optimized over a rolling horizon that is divided into intervals, the vehicular detection for and projection into the corresponding horizon intervals are also modeled. The signal control algorithm is based on dynamic programming and the optimization of signal policy is performed using a certain performance measure involving delays, queue lengths, and queue storage ratios. The arrival,discharge model is embedded in the optimization algorithm and both are programmed into AIMSUN, a microscopic stochastic simulation program. AIMSUN is then used to simulate the traffic flow and implement the optimal signal control by accessing internal data including detected traffic demand and vehicle speeds. Sensitivity analysis is conducted to study the effect of selecting different optimization criteria on the signal control performance. It is concluded that the queue length and queue storage ratio are the most appropriate performance measures in real-time signal control of interchanges. Copyright © 2010 John Wiley & Sons, Ltd. [source] Characterization and comparison of traffic flow on reversible roadwaysJOURNAL OF ADVANCED TRANSPORTATION, Issue 2 2010Laurence Lambert Abstract Reversible traffic operations have become an increasingly popular strategy for mitigating traffic congestion associated with the directionally unbalanced traffic flows that are a routine part of peak commute periods, planned special events, and emergency evacuations. It is interesting that despite its widespread and long-term use, relatively little is known about the operational characteristics of this form of operation. For example, the capacity of a reversed lane has been estimated by some to be equal to that of a normal lane while others have theorized it to be half of this value. Without accurate estimates of reversible lane performance it is not possible to confidently gauge the benefits of reversible roadways or model them using traffic simulation. This paper presents the results of a study to measure and evaluate the speed and flow characteristics of reverse-flow traffic streams by comparing them under various operating conditions and locations. It was found that, contrary to some opinions, the flow characteristics of reverse-flowing lanes were generally similar to normally flowing lanes under a variety of traffic volume, time-of-day, location, and type-of-use conditions. The study also revealed that drivers will readily use reversible lanes without diminished operating speeds, particularly as volumes increase. Copyright © 2010 John Wiley & Sons, Ltd. [source] Greenhouse gas reduction potential of advanced traffic controlJOURNAL OF ADVANCED TRANSPORTATION, Issue 3 2000Abdulkader Alkadry Reducing greenhouse gas (GHG) emissions from transportation in the context of the climate change issue and the associated Kyoto Agreement of 1997 is a challenge. Since urban transportation is a major contributor to greenhouse gases, measures are required to reduce these emissions. Given that during peak periods, road vehicles propelled by petroleum fuel-based internal combustion engines produce a high level of GHG emissions due to stop and go operations, measures to improve traffic flow can play an effective mitigation role. This paper describes a simulation-based methodology and a case study for the quantification of GHG emission reduction owing to advanced traffic control systems. [source] Short-term prediction of motorway travel time using ANPR and loop dataJOURNAL OF FORECASTING, Issue 6 2008Yanying LiArticle first published online: 28 MAY 200 Abstract Travel time is a good operational measure of the effectiveness of transportation systems. The ability to accurately predict motorway and arterial travel times is a critical component for many intelligent transportation systems (ITS) applications. Advanced traffic data collection systems using inductive loop detectors and video cameras have been installed, particularly for motorway networks. An inductive loop can provide traffic flow at its location. Video cameras with image-processing software, e.g. Automatic Number Plate Recognition (ANPR) software, are able to provide travel time of a road section. This research developed a dynamic linear model (DLM) model to forecast short-term travel time using both loop and ANPR data. The DLM approach was tested on three motorway sections in southern England. Overall, the model produced good prediction results, albeit large prediction errors occurred at congested traffic conditions due to the dynamic nature of traffic. This result indicated advantages of use of the both data sources. Copyright © 2008 John Wiley & Sons, Ltd. [source] Instantaneous control for traffic flowMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 2 2007M. Herty Abstract The solution methods for optimal control problems with coupled partial differential equations as constraints are computationally costly and memory intensive; in particular for problems stated on networks, this prevents the methods from being relevant. We present instantaneous control problems for the optimization of traffic flow problems on road networks. We derive the optimality conditions, investigate the relation to the full optimal control problem and prove that certain properties of the optimal control problem carry over to the instantaneous one. We propose a solution algorithm and compare quality of the computed controls and run-times. Copyright © 2006 John Wiley & Sons, Ltd. [source] Slipperiness on roads ,an expert system classificationMETEOROLOGICAL APPLICATIONS, Issue 1 2000Jonas Norrman A method for classifying different types of slipperiness on roads in Sweden is described. Using this method it is possible to survey road conditions in different areas and between different years to optimise winter road maintenance. Winter road maintenance in Sweden is generally undertaken by the national road administration to improve winter-time road conditions, thereby keeping up the traffic flow and decreasing the accident rate. As a number of different types of slipperiness may develop on roads in winter, each due to a specific set of meteorological variables, maintenance work can be a complicated task. With the proposed classification method it becomes easier for the winter maintenance personnel to analyse information on road conditions and survey the distribution of road slipperiness in a region. The classification is performed with an expert system using meteorological data from the Swedish Road Weather Information System. The road condition is classified as good or as one out of ten different types of slipperiness on roads. Road conditions during three different winter periods are analysed. The results show that variations in climate produce substantial differences in annual road condition characteristics. The output from the expert system classifying road slipperiness is compared with recorded winter road maintenance reports. Maintenance action took place on 49% of all occasions when road conditions were classified as slippery. Copyright © 2000 Royal Meteorological Society [source] Application of LQ modelling and optimization in urban traffic controlOPTIMAL CONTROL APPLICATIONS AND METHODS, Issue 6 2003Majura F. Selekwa Abstract The increasing congestion on urban streets demands traffic control signal timing to be well co-ordinated and optimized even during the transition between timing patterns used in different periods of time-of-day (TOD). The TOD timing plans, defined by fixed-time co-ordination parameters, need to change from one TOD period to another. The current methods used in transitioning are aimed at achieving quick transition rather than optimizing traffic flow during the transition period. As a result, they generally cause increased vehicle delays during the transition period particularly for vehicles on the minor street, which face lengthened red times. This paper proposes a quadratic optimization method that can be used to reduce disutility measures to motorists during the transition period. The transition is modeled as a linear dynamic process, and the disutility measures are modeled as the sum of squares of the deviations of the co-ordination parameters,that is, cycle length, phase split, and offset,from the optimal values during the transition. A linear quadratic (LQ) optimization technique of optimal control is used to determine the step size and the number of steps necessary to complete the transition with minimum disutility. The proposed transition period optimization method has the advantage that the user need not specify minimum and maximum cycle length to achieve optimization, as is the case with current methods. Simulation results for three co-ordinated intersections showed that the proposed method reduces total vehicle delay when compared to the ,immediate' transition method embedded in CORSIM traffic simulation software. This is due to the fact that vehicles on the minor street approaches get proportional green time without significantly affecting green times on the major street approach green phase. However, the method showed a slight increase in total delay for vehicles on the major street. Copyright © 2003 John Wiley & Sons, Ltd. [source] Distribution sensitivity in a highway flow modelAPPLIED STOCHASTIC MODELS IN BUSINESS AND INDUSTRY, Issue 6 2009Andrew M. Ross, Article first published online: 13 FEB 200 Abstract We examine a model of traffic flow on a highway segment, where traffic can be impaired by random incidents (usually, collisions). Using analytical and numerical methods, we show the degree of sensitivity that the model exhibits to the distributions of service times (in the queueing model) and incident clearance times. Its sensitivity to the distribution of time until an incident is much less pronounced. Our analytical methods include an M/Gt/, analysis (Gt denotes a service process whose distribution changes with time) and a fluid approximation for an M/M/c queue with general distributions for the incident clearance times. Our numerical methods include M/PH2/c/K models with many servers and with phase-type distributions for the time until an incident occurs or is cleared. We also investigate different time scalings for the rate of incident occurrence and clearance. Copyright © 2009 John Wiley & Sons, Ltd. [source] BML revisited: Statistical physics, computer simulation, and probability,COMPLEXITY, Issue 2 2006Raissa M. D'Souza Abstract Statistical physics, computer simulation, and discrete mathematics are intimately related through the study of shared lattice models. These models lie at the foundation of all three fields, are studied extensively, and can be highly influential. Yet new computational and mathematical tools may challenge even well-established beliefs. Consider the BML model, which is a paradigm for modeling self-organized patterns of traffic flow and first-order jamming transitions. Recent findings, on the existence of intermediate states, bring into question the standard understanding of the jamming transition. We review the results and show that the onset of full-jamming can be considerably delayed based on the geometry of the system. We also introduce an asynchronous version of BML, which lacks the self-organizing properties of BML, has none of the puzzling intermediate states, but has a sharp, discontinuous, transition to full jamming. We believe this asynchronous version will be more amenable to rigorous mathematical analysis than standard BML. We discuss additional models, such as bootstrap percolation, the honey-comb dimer model and the rotor-router, all of which exemplify the interplay between the three fields, while also providing cautionary tales. Finally, we synthesize implications for how results from one field may relate to the other, and also implications specific to computer implementations. © 2006 Wiley Periodicals, Inc. Complexity, 12, 30,39, 2006 [source] QoS-aware fair packet scheduling in IEEE 802.16 wireless mesh networksINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 6-7 2010Yajun Li Abstract In this paper, we address the problem of heterogeneous quality-of-service (QoS) provisioning in IEEE 802.16-based wireless mesh networks. Our objective is to provide a novel service differentiation scheme based on distributed scheduling in the IEEE 802.16-based mesh mode, thereby offering QoS guarantees. We first devise a novel scheme for the traffic class differentiation, which can be implemented at the medium access control layer. We then present a QoS-aware fair packet scheduling (QFPS) algorithm to fulfill the QoS provisioning. With QFPS, a traffic flow with urgent QoS demand is guaranteed to be given priority in wireless resource allocation over those ones with mild QoS requirements. A shorter end-to-end delay is therefore expected to be offered for the traffic flows with time-urgent requirements. Moreover, we propose a new fairness model among different traffic flows traversing the same node. All traffic flows passing through a node are served by the Deficit Round-Robin scheduling algorithm to achieve fairness within the same priority group. The experimental results of the QFPS demonstrate that various traffic flows are provided with a differentiated service that offers QoS guarantees. Copyright © 2009 John Wiley & Sons, Ltd. [source] Architecture for dynamic and fair distribution of bandwidthINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 5 2006Vasil Hnatyshin The problem of fair distribution of available bandwidth among traffic flows or aggregates remains an essential issue in computer networks. This paper introduces a novel approach, called the Exact Bandwidth Distribution Scheme (X-BDS), for dynamic and fair distribution of available bandwidth among individual flows. In this approach, the edge routers keep per-flow information, while the core routers maintain the aggregate flow requirements. The X-BDS approach employs a distributed message exchange protocol for providing network feedback and for distributing aggregate flow requirements among the nodes in the network. Based on the obtained feedback, the edge routers employ the X-BDS resource management unit to dynamically distribute available bandwidth among individual flows. The X-BDS admission control and resource management units are responsible for fair resource allocation that supports minimum bandwidth guarantees of individual flows. This paper evaluates the Bandwidth Distribution Scheme through simulation and shows that the X-BDS is capable of supporting per-flow bandwidth guarantees in a dynamically changing network environment. Copyright © 2006 John Wiley & Sons, Ltd. [source] Semantic networking: Flow-based, traffic-aware, and self-managed networkingBELL LABS TECHNICAL JOURNAL, Issue 2 2009Ludovic Noirie In order to overcome current Internet limitations on overall network scalability and complexity, we introduce a new paradigm of semantic networking for the networks of the future, which brings together flow-based networking, traffic awareness, and self-management concepts to deliver plug-and-play networks. The natural traffic granularity is the flow between packet and circuit and between connection-less and connection-oriented modes. Using flow aggregation capabilities, we simplify traffic processing in the nodes through elastic fluid switching, and simplify traffic control through flow admission control, policing, and implicit quality of service (QoS) routing. By leveraging deep packet inspection and behavioral traffic analysis, network elements can autonomously and efficiently process the traffic flows they transport through real-time awareness gained via semantic analysis. The global consistency of node decisions within the whole network is ensured by self-management, applying the concepts of "knowledge plane" and "network mining." © 2009 Alcatel-Lucent. [source] | ||||||||||||||||