Traffic Configuration Research Articles

Real-Time Fault-Tolerant Ethernet Technology - TTEthernet and its Feature

Imported clock synchronization and time-triggered strategy in standard Ethernet, Time-Triggered Ethernet has its unique features. This paper introduces its traffic features, clock synchronization, standard configuration and scheduling strategy. Due to its new features Time-triggered Ethernet will have completely new application areas.

Flow Control Research between ForCES Channels

In order to enhance the performance of ForCES network fully, and ensure the security and accuracy of communication between Control Elements (CEs) and Forwarding Elements (FEs), we designed Prediction-based Traffic Control and Configuration (PTCC) to reduce the likelihood, severity and duration of congestion. Through predicting the average reaching rate of the news package in the following time to control well the flow of every ForCES channel, and distribute available bandwidth for every ForCES channel according to news throughput reasonably and instantaneously. The experimental results validated the validity of this flow control mechanism.

Volume-to-Capacity Estimation of Signalized Road Networks for Metropolitan Transportation Planning

Transportation planning plays a critical role in shaping economic health and quality of life. Transportation planning not only provides insight into the mobility of people and goods but also influences patterns of growth and economic activity. Metropolitan transportation planning is a challenging topic because of the lack of future traffic information, such as evaluations of capacity sufficiency on large metropolitan road networks with signalized intersections. The Highway Capacity Manual provides methods for the analysis of signalized intersections and urban streets for planning; however, these methods need detailed traffic volume inputs and lane configurations at signalized intersections, which are not normally available in metropolitan transportation planning. The conventional four-step planning process is widely used to forecast directional traffic volumes on road segments, but the projected volumes are not enough for the analysis of the capacity sufficiency of future road networks through existing methods. This paper discusses a proposed method developed through the integration of available transportation planning data and the characteristics of signalized intersections. The paper links traffic assignment results from conventional transportation planning procedures to the estimation of capacity sufficiency. With the proposed method, transportation planners can estimate the capacity sufficiency of future metropolitan road networks through the use of data that are readily available in transportation planning. This method will dramatically decrease the effort required for the capacity evaluation of large signalized metropolitan road networks.

Modeling and Optimization of the IEEE 802.15.4 Protocol for Reliable and Timely Communications

Distributed processing through ad hoc and sensor networks is having a major impact on scale and applications of computing. The creation of new cyber-physical services based on wireless sensor devices relies heavily on how well communication protocols can be adapted and optimized to meet quality constraints under limited energy resources. The IEEE 802.15.4 medium access control protocol for wireless sensor networks can support energy efficient, reliable, and timely packet transmission by a parallel and distributed tuning of the medium access control parameters. Such a tuning is difficult, because simple and accurate models of the influence of these parameters on the probability of successful packet transmission, packet delay, and energy consumption are not available. Moreover, it is not clear how to adapt the parameters to the changes of the network and traffic regimes by algorithms that can run on resource-constrained devices. In this paper, a Markov chain is proposed to model these relations by simple expressions without giving up the accuracy. In contrast to previous work, the presence of limited number of retransmissions, acknowledgments, unsaturated traffic, packet size, and packet copying delay due to hardware limitations is accounted for. The model is then used to derive a distributed adaptive algorithm for minimizing the power consumption while guaranteeing a given successful packet reception probability and delay constraints in the packet transmission. The algorithm does not require any modification of the IEEE 802.15.4 medium access control and can be easily implemented on network devices. The algorithm has been experimentally implemented and evaluated on a testbed with off-the-shelf wireless sensor devices. Experimental results show that the analysis is accurate, that the proposed algorithm satisfies reliability and delay constraints, and that the approach reduces the energy consumption of the network under both stationary and transient conditions. Specifically, even if the number of devices and traffic configuration change sharply, the proposed parallel and distributed algorithm allows the system to operate close to its optimal state by estimating the busy channel and channel access probabilities. Furthermore, results indicate that the protocol reacts promptly to errors in the estimation of the number of devices and in the traffic load that can appear due to device mobility. It is also shown that the effect of imperfect channel and carrier sensing on system performance heavily depends on the traffic load and limited range of the protocol parameters.

Molecular phylogeny of recurrent road killed butterflies in Nilgiri biosphere reserve, India, using CO1 gene marker

We examined the spatial patterns and factors influencing butterflies aggregations of road-kill at Mudumalai Tiger Reserve, Mukuruthi National Park and Avalanche Forest region in NBR (Nilgiri Biosphere Reserve) Southern India. We surveyed roads varying in high traffic volume, configuration and adjacent landscape attributes for analyzing road-kills between January 2010 and December 2010. The aim of the present study was to assess the level of mortality and their causes for the road kills of the study area. Our findings conclude that five species were frequently affected namely;Danaus chrysippus (Linnaeus), Danaus plexippus (Cramer), Tirumala limniace(Cramer), Pachliopta hector (Fabricius), Pachliopta aristolochiae (Linnaeus), and we analyzed phylogenetic relationship between these five species. Key words: Nilgiri biosphere reserve, molecular phylogeny, CO1 gene marker, Southern India.

Tools for Assessing the Safety Impact of Interventions on Road Safety

This paper is the result of a PhD in Transport Infrastructure, realized at CTL, aimed to investigate issues related to the evaluation of interventions producing changes in traffic configuration and to develop an information system (Road safety Impact Assessment - RIA Module) to be integrated in an existing Decision Support System on road safety.The research created a library of SPF and developed an information system, called “RIA Module”, updating the existing “DSS - ISIDE”, developed by CTL.

Optimisation of control parameters for genetic algorithms to test computer networks under realistic traffic loads

Although many studies have focused on testing computer networks under realistic traffic loads by means of genetic algorithms (GAs), little attention has been paid to optimising the parameters of the GAs in this problem. The objective of this work is to design and validate a system that, given some constraints on traffic bandwidth, generates the worst-case traffic for a given computer network and finds the traffic configuration (critical background traffic) that minimises throughput in that computer network. The proposed system is based on a meta-GA, which is combined with an adaptation strategy that finds the optimum values for the GA control parameters and adjusts them to improve the GA's performance. To validate the approach, different comparisons are performed with the goal of assessing the acceptable optimisation power of the proposed system. Moreover, a statistical analysis was conducted to ascertain whether differences between the proposed system and other algorithms are significant. The results demonstrate the effectiveness of the system and prove that, when the background traffic is driven by a GA that uses the parameters obtained from the system, the computer network's performance is much lower than when the traffic is generated by Poisson statistical processes or by other algorithms. This system has identified the worst traffic pattern for the protocol under analysis.

Defining Design Space for Parameters of Traffic Signal Timing: Empirical Approach

This paper proposes an agile, scalable approach for an agency to use for defining a design space for parameters of traffic signal controllers that reflect the agency's procedures. This design space is more commonly known as a checklist of parameters that must be configured in a controller database. The procedure for establishing this design space used simple network-monitoring protocol messages from programmed traffic signal controllers to traverse the controller database tree systematically with the get-next command that was available on controllers that supported the National Transportation Communications for Intelligent Transportation System Protocol (NTCIP). In the case study, a corridor of 22 intersections (five isolated and 17 coordinated) was analyzed to establish the design space empirically. The controllers that were studied had approximately 74,000 configurable parameters, although many of these are seldom configured by most agencies. Longitudinally along a five-intersection corridor, approximately 430 parameters (0.6%) on isolated intersections were changed. Longitudinally along a 17-intersection coordinated system, approximately 1,700 parameters (2.2%) were changed. Approximately 93% of the parameters that were changed on the isolated intersections were defined by NTCIP 1202. Only 28% of the parameters that were changed on the coordinated intersections were defined by NTCIP 1202; the remaining 72% were vendor specific. The paper concludes with a series of tables that summarize the broad spectrum of parameters to be configured for a modern traffic signal controller to operate properly. Agencies can use these tables as a checklist for defining expectations precisely when individuals develop new traffic signal controller configurations or update existing ones. Similarly, consultants can use these tables and procedures to define a clear scope of work on signal-timing projects.

Effects of Open Road Tolling on Safety Performance of Freeway Mainline Toll Plazas

Advances in intelligent transportation systems technologies promoted the implementation of open road tolling (ORT) on tolled freeways worldwide. This new tolling solution converts existing barrier toll booths to express lanes that are capable of collecting tolls at high speed. ORT has demonstrated numerous benefits in reducing traffic congestion and air pollution. However, the effects of ORT on safety are still not clear because most ORT systems have been operated for a relatively short period. Therefore, this study aimed to evaluate the safety impacts of ORT by examining recent practices in New Jersey. Multiple-year crash data at toll plazas before and after the implementation of the ORT systems were analyzed. The full Bayes methodology was employed to develop crash frequency models as a function of traffic and toll plaza configurations. These models were used to estimate the crash frequency on the assumption that the ORT systems were not installed. The estimations were then compared with the observed crash counts that occurred after the deployment of the ORT systems. Comparisons showed that crash reductions were obtained at most of the toll plazas. The overall comparison showed that crash frequency decreased by about 24% after the deployment of the ORT systems and suggested that the use of ORT is a beneficial solution to improve the safety of the toll plazas. From an implementation point of view, the analysis results also indicated that special attention should be paid to operational elements such as signage, diversion, and merge designs of the ORT systems.

A Simplified Internet Routing Architecture

This paper studies the effect of disaggregation on the size of the routing table in the Internet's Default Free Zone (DFZ). Current practises for traffic balancing and protection against prefix hijacking in the Internet are based in disaggregating prefixes that cause an increase in size of the Internet's core routing table. I propose an algorithm to assess their effect on the table size of these techniques. This algorithm is applied on routing tables collected by the RIPE's Routing Repository between January 2001 and February 2011. The results show that before 2010, the IPv4 addressing space was gradually getting more fragmented. This trend is slowing down since the beginning of 2010, possibly as the result of the economic downturn. In the second part of this paper, I propose an alternative architecture that allows local Traffic Engineering configurations but keeps their effects from spreading over the Internet and outline an implementation for this architecture on a Linux platform.

A Layered Architecture for Fair Resource Allocation in Multicellular Multicarrier Systems

We consider a multicell multicarrier system with frequency reuse distance that is equal to one. Allowing all cells to transmit on the whole bandwidth unveils large potential gains in terms of spectral efficiency, in comparison with conventional cellular systems. Such a scenario, however, is often deemed unfeasible because of the strong multiple access interference (MAI) that negatively affects system performance. This paper presents a layered architecture that integrates a packet scheduler with an adaptive resource allocator that was explicitly designed to take care of the MAI. Each cell performs its resource management in a distributed way with no central controller. Iterative resource allocation assigns radio channels to the users to minimize interference. Packet scheduling guarantees that all users get a fair share of resources, regardless of their position in the cell. This scheduler-allocator architecture integrates both goals and is able to self-adapt to any traffic and user configuration. An adaptive distributed load control strategy can reduce the cell load so that the iterative procedure always converges to a stable allocation, regardless of the interference. Numerical results show that the proposed architecture guarantees both high spectral efficiency and throughput fairness among flows.

Optimisation of control parameters for genetic algorithms to test computer networks under realistic traffic loads

Although many studies have focused on testing computer networks under realistic traffic loads by means of genetic algorithms (GAs), little attention has been paid to optimising the parameters of the GAs in this problem. The objective of this work is to design and validate a system that, given some constraints on traffic bandwidth, generates the worst-case traffic for a given computer network and finds the traffic configuration (critical background traffic) that minimises throughput in that computer network. The proposed system is based on a meta-GA, which is combined with an adaptation strategy that finds the optimum values for the GA control parameters and adjusts them to improve the GA's performance. To validate the approach, different comparisons are performed with the goal of assessing the acceptable optimisation power of the proposed system. Moreover, a statistical analysis was conducted to ascertain whether differences between the proposed system and other algorithms are significant. The results demonstrate the effectiveness of the system and prove that, when the background traffic is driven by a GA that uses the parameters obtained from the system, the computer network's performance is much lower than when the traffic is generated by Poisson statistical processes or by other algorithms. This system has identified the worst traffic pattern for the protocol under analysis.

Feasibility of Converting Two-Way Left-Turn Lane into Bus Rapid Transit Lane

Although past research and experience have demonstrated the benefits of bus rapid transit (BRT) to the transportation system, implementation of BRT on congested local arterials having minimal or no rights-of-way remains a challenge. A feasible solution is to use the two-way left-turn lane (TWLTL) in the center of local streets for the purpose of BRT during peak hours. However, a TWLTL can be used in two ways for this purpose: directly as a median BRT lane and as a reversible general traffic lane (so that the curb lane is reserved for BRT). Without a clear understanding of the impacts of traffic characteristics, intersection layouts, and traffic signal control types on each of the alternatives, transit agencies usually have difficulty in determining the option that best serves transit vehicles and simultaneously minimizes impacts to the general traffic. This study evaluates the performance of a median BRT lane and a curb BRT lane and considers varying traffic conditions and physical configurations of the street and the intersections. The pros and cons of each alternative are also specified, in accordance with the simulation analysis.

A New Approach for Allocating Highway Costs

The allocation of highway costs is constantly debated among legislatures, highway agencies, and highway users as it directly relates to concerns about equity in terms of cost responsibility and actual user charges. One of the major challenges in highway cost allocation stems from the need to estimate pavement damage by different vehicle classes. Normally, the calculation of damage caused by heavy vehicles to the highway infrastructure utilizes the concept of Equivalent Single Axle Load (ESAL). This concept was empirically established after the American Association of State Highway Officials America (AASHO) Road Test almost half a century ago. Although the ESAL concept is widely used in pavement design, it has a number of shortcomings when applied for the estimation of pavement damage by different vehicle classes. Some of these limitations include: failure to account for specific infrastructure and environmental conditions, disregard of the differences in traffic configurations and composition, and the inability to capture different distress types. This leads to a fairly inaccurate and generic estimation of pavement damage by vehicle class. This paper proposes an innovative and more rational highway cost allocation approach based on the recently completed guide for the "Mechanistic-Empirical Design Guide of New and Rehabilitated Pavement Structures" developed under the National Cooperative Highway Research Program (NCHRP) Project 1-37A. The Guide accounts for all factors that contribute to pavement deterioration, thereby addressing the shortcomings of an ESAL-based analysis listed earlier. Estimates for pavement damage attributable to each vehicle class can thus be accurately simulated. For the purposes of this study, traffic data collected at a weigh-in-motion station in Texas were used to estimate the highway cost shares of different vehicle classes, given different pavement structural capacities.

SINR Feedback Based Rate Control for Dual-Antenna-Array Multi-Cellular Networks with Cochannel Interference

We propose in this paper a dual-antenna-array (with transmitter antenna array and receiver antenna array) architecture, where the antenna elements are divided into several antenna element sets and each traffic channel is transmitted over an antenna element set, to realize the multiple traffic channels set up by a user. A SINR feedback based algorithm, which can regulate the transmission rate by iteratively adjusting the power on each traffic channel, is proposed to execute the rate control for the proposed dual-antenna-array architecture under cochannel interference. It is shown that the proposed algorithm can make the throughput meet the throughput requirement or achieve the weighted bandwidth sharing for certain fairness. In addition, we further propose a traffic channel configuration algorithm to help the SINR feedback based algorithm find the optimal traffic channel configuration that can meet the throughput requirement for each traffic channel or results in the maximal total throughput for each user.

Flow-Admission Control Based on Equality of Heterogeneous Traffic (Two-Type Flow Model)

Multimedia applications such as video and audio have recently come into much wider use. Because this heterogeneous traffic consumes most of the network's resources, call admission control (CAC) is required to maintain high-quality services. User satisfaction depends on CAC's success in accommodating application flows. Conventional CACs do not take into consideration user satisfaction because their main purpose is to improve the utilization of resources. Moreover, if we assume a service where an ISP provides a “flat-based charging,” each user may receive same user satisfaction as a result of users being accommodated in a network, even if each has a different bandwidth. Therefore, we propose a novel CAC to maximize total user satisfaction based on a new philosophy where heterog eneous traffic is treated equally in networks. Theoretical analysis is used to derive optimal thresholds for various traffic configurations with a full search system. We also carried out theoretical numerical analysis to demonstrate the effectiveness of our new CAC. Moreover, we propose a sub-optimal threshold configuration obtained by using an approximation formula to develop practical CAC from these observations. We tested and confirmed that performance could be improved by using sub-optimal parameters.

Self-Management Principles in Autonomic Service Architecture Supported by Load Balancing Algorithm

This paper is about the role of a heuristic algorithm for load balancing that can be incorporated in Multi-Protocol Label Switching/ Differentiated Services (MPLS/DS) networks based on self-management principles for automated traffic configuration. Delivery of Quality of Services (QoS) differentiation according to specific service level agreements, Service Level Agreement (SLA), has to be in relation to resource management and bandwidth allocation, to ensure better end-to-end QoS provisioning and to avoid traffic congestion. To ensure simultaneous traffic flows with different priorities we need some load-balancing procedure. It could start much earlier than usual, possibly during SLA negotiation. If SLA creation is supported by load control mechanism it can ensure better performances of the network in the moment of service invocation. LSP (Label Switching Path) creation could be influenced by former contracted SLAs and such approach could be more effective than pure routing technique based on the shortest path algorithm (LSP creation in the moment of service invocation). So we propose application of heuristic algorithm tested on numerical examples with maximum M routers on the path and with differentiation of N service classes. Further, we introduced some capacity state restrictions in the process of network optimization, considering different algorithm options. We compared their performances, especially the algorithm complexity that is very important for efficient load control in huge networks.

A medium access protocol exploiting multiuser-detection in CDMA ad-hoc networks

A new medium access protocol which exploits the physical layer capability of multiuser detection is proposed to help in improving the throughput/delay performance of ad-hoc networks. When more than one node has packets buffered for a common node in the neighborhood, all such nodes can simultaneously transmit their packets to the common receiver after reserving their surrounding channel. This is achieved in our protocol by extending the (sender-initiated) CSMA/CA collision avoidance framework by the receiver-initiated medium access technique and incorporating the transmission power control. We analyze the improvement in the throughput that can be achieved over the basic sender-initiated collision avoidance protocol in the network. Since the throughput improvement via multi-packet reception is influenced by the network layer activity as well, the performance of our protocol rolls back to that of the basic sender-initiated protocol in case of no coordination from the network layer. For the evaluation of performance of our protocol we simulate ad-hoc networks for different network topologies and traffic configurations. We observe the scheme to be capable in significantly improving the throughput/delay performance of the network.

P‐183L: Late‐News Poster: Motion Parallax Enhances Depth in a Perspective Air‐Traffic Display

AbstractIn this paper we investigate the utility of motion parallax induced by head movement in the context of a perspective rendering of three‐dimensional air traffic configurations. Discrimination of altitude differences is improved by the addition of motion parallax (compared to a static display), but does not afford the large changes of viewpoint possible with manually‐controlled rotations.

Graceful Degradation of Air Traffic Operations: Airspace Sensitivity to Degraded Surveillance Systems

The introduction of new technologies and concepts of operation in the air transportation system is not possible unless they can be proven not to adversely affect the system operation under not only nominal but also degraded conditions. In extreme scenarios, degraded operations due to partial or complete technological failures should never endanger system safety. Many past system evolutions, whether ground-based or airborne, have been based on trial and error, and system safety was addressed only after a specific event yielded dramatic or near-dramatic consequences. Future system evolutions, however, must leverage available computation, prior knowledge, and abstract reasoning to anticipate all possible system degradations and prove that such degradations are graceful and safe. This paper is concerned with the graceful degradation of high-density structured arrival traffic against partial or complete surveillance failures. It is shown that for equal performance requirements, some traffic configurations might be easier to handle than others, thereby offering a quantitative perspective on these traffic configurations' ability to ldquogracefully degrade.rdquo To support our work, we also introduce a new conflict resolution algorithm aimed at solving conflicts involving many aircraft when aircraft position information is in the process of degrading.