Traffic Descriptors Research Articles

A CONTENT DISCLOSURE AND TEXT IDENTIFICATION BASED ON ROAD-LEVEL SYMBOLISM USING TCH ALGORITHM

Image enhancement is a process of improving the quality of image by improving its feature. Image contrast enrichment techniques have been largely studied in the past decades. Traffic sign disclosure and realization has been fully prepared for a great past. Traffic board detection and text recognition still leaving a protest in computer view due to its various group and the vast changeability of the data illustrated in them. The essential function can be to make an automated index of the traffic panels placed in a road to holding its care and to aid drivers. Then the figure are defined as a “bag of visual words” and restricted to applying support vector machines. Completely our own text detection and recognition method is tested on those images where a traffic board has been disclosure in system to naturally read and save the data details in the panels. Leading driver aid scheme could also use from text recognition for automated traffic signs and panels description. This visual appearance categorization method is a new approach for traffic panel detection in the state of the art. We propose a language model partly based on a dynamic dictionary for a limited geographical area using a reverse geocoding service. Experimental results on real images from Google Street View prove the efficiency of the proposed method and give way to using street-level images for different applications on ITS.

Primary User Traffic Classification in Dynamic Spectrum Access Networks

This paper focuses on analytical studies of the primary user (PU) traffic classification problem. Observing that the gamma distribution can represent positively skewed data and exponential distribution (popular in communication networks performance analysis literature) it is considered here as the PU traffic descriptor. We investigate two PU traffic classifiers utilizing perfectly measured PU activity (busy) and inactivity (idle) periods: (i) maximum likelihood classifier (MLC) and (ii) multi-hypothesis sequential probability ratio test classifier (MSPRTC). Then, relaxing the assumption on perfect period measurement, we consider a PU traffic observation through channel sampling. For a special case of negligible probability of PU state change in between two samplings, we propose a minimum variance PU busy/idle period length estimator. Later, relaxing the assumption of the complete knowledge of the parameters of the PU period length distribution, we propose two PU traffic classification schemes: (i) estimate-then-classify (ETC), and (ii) average likelihood function (ALF) classifiers considering time domain fluctuation of the PU traffic parameters. Numerical results show that both MLC and MSPRTC are sensitive to the periods measurement errors when the distance among distribution hypotheses is small, and to the distribution parameter estimation errors when the distance among hypotheses is large. For PU traffic parameters with a partial prior knowledge of the distribution, the ETC outperforms ALF when the distance among hypotheses is small, while the opposite holds when the distance is large.

Connecting Networkwide Travel Time Reliability and the Network Fundamental Diagram of Traffic Flow

The existence of the network fundamental diagram (NFD) has been established at the urban network scale. It relates three traffic descriptors: speed, density, and flow. However, its deterministic nature does not convey the underlying variability within the network. In contrast, travel time reliability as a network performance descriptor is of growing concern to both the traveling public and traffic managers and policy makers. The objectives of this paper were to extend travel time reliability modeling from the link–path level to the network level and to connect overall network variability to NFD. Robust relationships between travel time variability and network density and flow rate were analytically derived, investigated, and validated with both simulated and real-world trajectory data. The distance-weighted standard deviation of travel time rate, as a measure of travel time variability, was found to increase monotonically with network density. A maximum network flow rate existed beyond which network travel time reliability deteriorated at a much faster pace. The results also suggest that these relationships are inherent network properties (signature) that are independent of demand level. The effects of en route information on the proposed relationships were also studied. The results showed that en route information reduced network travel time variability. The findings provide a strong connection between NFD and travel time variability, and this connection can be used further for modeling of network travel time reliability and assessment of measures intended to improve reliability of travel in a network.

Earthquake Damage Evaluation of Tunnels

The state of art of tunnel earthquake damages and tunnel earthquake damage mechanism are briefly introduced in this paper. According to tunnel’s traffic function and damage descriptions based on the investigation, tunnel damages are divided into five grades: no damage, minor damage, moderate damage, major damage and collapse, and their corresponding damage index range and characteristic values are defined. The influence of tunnel materials in Kobe earthquake and Chi-Chi earthquake are collected in this paper, and the damage grades are determined based on the performance in the earthquake. After comparative analysis, the seismic intensity, overburden depth, rock classification, distance to faults and the tunnel length are chosen as the seismic damage influence factors. A formula for tunnel seismic damage evaluation is deducted using these factors and the least square method and with the modification of construction time, seismic fortification intensity and portal stability. The damage of four tunnels is evaluated using the derived formula, and the results are the same with that of static and dynamic methods. It shows that the method provided in this paper is effective, reliable.

A joint moments based analysis of networks of MAP/MAP/1 queues

The decomposition based approximate numerical analysis of queueing networks of MAP/MAP/1 queues with FIFO scheduling is considered in this paper. One of the most crucial decisions of decomposition based queueing network analysis is the description of inter-node traffic. Utilizing recent results on Markov arrival processes (MAPs), we apply a given number of joint moments of the consecutive inter-event times to describe the inter-node traffic. This traffic description is compact (uses far less parameters than the alternative methods) and flexible (allows an easy reduction of the complexity of the model). Numerical examples demonstrate the accuracy and the computational complexity of the proposed approximate analysis method.

Packet Classification with Hierarchical Cross-Producting

Packet classification has become one of the most important application techniques in network security since the last decade. The technique involves a traffic descriptor or user-defined criteria to categorize packets to a specific forwarding class which will be accessible for future security handling. To achieve fast packet classification, we propose a new scheme, Hierarchical Cross-Producting. This approach simplifies the classification procedure and decreases the distinct combinations of fields by hierarchically decomposing the multi-dimensional space based on the concept of telescopic search. Analogous to the use of telescopes with different powers**, a multiple-step process is used to search for targets. In our scheme, the multi-dimensional space is endowed with a hierarchical property which self-divides into several smaller subspaces, whereas the procedure of packet classification is translated into recursive searching for matching subspaces. The required storage of our scheme could be significantly reduced since the distinct field specifications of subspaces is manageable. The performance are evaluated based on both real and synthetic filter databases. The experimental results demonstrate the effectiveness and scalability of the proposed scheme.

A traffic based decomposition of two-class queueing networks with priority service

This paper presents a Markov arrival process (MAP) based methodology for the analysis of two-class queueing networks with priority service nodes. We apply the multi-class extension of MAP, referred to as Marked MAP (MMAP), for the description of the input and internal traffic in the queueing network. The MMAP traffic description allows to capture not only the dependency structure of the traffic classes themselves, but also the inter-class dependency of the high and low priority traffic. To carry out MMAP based queueing network analysis the paper presents several contributions: the departure process analysis of the MMAP/MAP/1 priority queue, an MMAP construction method based on the joint moments of two consecutive inter-departure times and some new results towards the efficient performance analysis of the MMAP/MAP/1 priority queue. Numerical examples illustrate the accuracy of the proposed traffic based decomposition method.

An adaptive fuzzy-based CAC scheme for uplink and downlink congestion control in converged IP and DVB-S2 networks

This paper introduces a robust buffer occupancy-based connection admission control (CAC) mechanism to alleviate both uplink and downlink congestions in converged IP and broadcasting networks. The scheme also ensures a fair share of downlink bandwidth among competing satellite terminals (subnetworks) in the event of congestion. The proposed scheme is dubbed Weighted Fair CAC (W-FCAC). It accepts or rejects connections based on an adaptive fuzzy-based approach. The use of the fuzzy-based mechanism is for the purpose of overcoming issues related to instantaneous link capacity assessment, flow characterization and the associated high computational complexity, and use of traffic descriptors for new flows. Additionally, the adaptive fuzzy logic makes the proposed CAC approach robust to traffic dynamics. These features make the scheme highly suitable for DVB-S2 environments where the link capacity frequently fluctuates due to the adaptive coding/modulation of the physical layer during noisy periods. Simulation results elucidate that the proposed W-FCAC scheme prevents downlink congestion and fairly allocates network resources among satellite terminals. It also minimizes the frequency of congestion events while maintaining efficient utilization of network resources.

Scalable packet classification with controlled cross-producting

Packet classification is central among traffic classification techniques that categorize packets with a traffic descriptor or with user-defined criteria. This categorization may make information accessible for quality of service or security handling on the network. To make packet classification both fast and scalable, we propose a new algorithm that combines cross-producting with linear search. The new algorithm, Controlled Cross-producting, could improve the scalability of cross-producting significantly with respect to storage, while maintaining the search latency. In addition, we introduce several refinements and procedures for incremental update. We evaluate the performance of our scheme with filter databases of varying sizes and characteristics. Specifically, we experimented with 12 different types of filter databases, whose sizes vary from 16K to 128K. The experimental results demonstrate the feasibility and scalability of our scheme. A comparison with the prominent existing schemes further indicates that the proposed scheme takes less time and space.

TCP throughput guarantee in the DiffServ Assured Forwarding service: what about the results?

Since the proposition of quality of service (QoS) architectures by the Internet Engineering Task Force (IETF), the interaction between TCP and the QoS services has been intensively studied. This paper proposes to look forward to the results obtained in terms of TCP throughput guarantee in the DiffServ assured forwarding (DiffServ/AF) service and to present an overview of the different proposals to solve the problem. It has been demonstrated that the standardized IETF DiffServ conditioners such as the token bucket color marker and the time sliding window color maker were not good TCP traffic descriptors. Starting with this point, several propositions have been made, and most of them present new marking schemes in order to replace or improve the traditional token bucket color marker. The main problem is that TCP congestion control is not designed to work with the AF service. Indeed, both mechanisms are antagonists. TCP has the property to share in a fair manner the bottleneck bandwidth between flows while DiffServ network provides a level of service that is controllable and predictable. In this paper, we build a classification of all the propositions made during the past few years and compare them. As a result, we will see that these conditioning schemes can be separated into three sets of action levels and that the conditioning at the network edge level is the most accepted one. We conclude that the problem is still unsolved and that TCP, conditioned or not conditioned, remains inappropriate for the DiffServ/AF service.

Hybrid approaches to the solutions of the “Lighthill–Whitham–Richards” model

This paper presents a hybrid “Lighthill–Whitham–Richards” (LWR) model combining both macroscopic and microscopic traffic descriptions. Simple interfaces are defined to translate the boundary conditions when changing the traffic description. They are located in discrete points in space and are based on a generalisation of demand and supply concepts. Simulation results show that the proposed interfaces ensure an accurate wave propagation along two links differently described. Furthermore, the demand and supply formulation of the hybrid model makes it fully compatible with major LWR extensions developed over the past few years (intersections modeling, multi-lanes representation, etc.). Finally, we prove that Newell’s optimal velocity car-following model can be derived from the Godunov scheme applied to the LWR model in Lagrangian coordinates. This proposes a microscopic resolution of the LWR model that is fully compatible with the usual macroscopic representation. This microscopic resolution is included in the hybrid model.

LIMITS OF PERFORMANCE OF ADAPTIVE VARIABLE-WINDOW CSMA

The paper addresses the limits of performance of adaptive variable-window CSMA random access protocol with collision avoidance. A unified method of traffic description based on scaling coefficients, integrating various addressing and message service types, is proposed. Furthermore, the fundamental tradeoff of the adaptive variable-window CSMA protocol operation is highlighted. In particular, it is shown that the maximization of the channel bandwidth utilization is obtained at the cost of minimization of the fraction of bandwidth devoted to a transmission of messages carrying application data. Copyright © 2007 IFAC

Statistical Traffic Regulation at the Network Edge

In order to increase bandwidth utilization, next generation communication networks could offer a Quality of Service (QoS) to active connections in a statistical sense rather than deterministic sense. For this to be practical the presence of new regulation algorithms at the network edge would be required. These new algorithms would be designed to bound incoming traffic flows with predetermined statistical descriptors. Here, we propose a novel yet simple regulation algorithm which bounds an arrival process with the statistical traffic descriptor known as exponentially bounded burstiness (EBB). We show that by setting the parameters of the algorithm appropriately, the arrival process can be regulated so as to bound the flow with another statistical descriptor---the effective bandwidth. Both of these statistical descriptors have a well-developed network calculus related to bandwidth utilization for a requested statistical QoS metric. Our algorithm allows us to apply with confidence the EBB and effective bandwidth network calculus to traffic flows within the network core.

An Empirical Study on Renegotiated CBR for VBR Video Services Based on Network Testbed

For multimedia network services, bandwidth reservation levels for video transmissions are conventionally defined using traffic descriptors that remain static over the entire playback duration of the video transmissions. Aimed at addressing the bandwidth wastefulness of using the static reservation, renegotiated Constant-Bit-Rate (RCBR) mechanism has been proposed to perform dynamic bandwidth allocation with periodical bandwidth renegotiation during any multimedia transmission sessions. However, this mechanism has been only examined via simulations and theoretical analysis previously. In this study, we have conducted rigorous empirical studies on RCBR scheme using a real network testbed to study its performance. Our study reveals interesting results and provides new insight to any practical deployment of RCBR mechanism and service over broadband packet networks. Moreover, a smoothing technique at application layer is proposed and evaluated in RCBR context to maximize the efficiency of RCBR scheme. We present empirical results and analysis, and highlight our observations.

Cluster-based resource provisioning for optical backbone networks

Feature Issue on High Availability in Optical NetworksA resource provisioning method for optical backbone networks running IP or multiprotocol label switching (MPLS) is presented. Trunk and hose models are well-known bandwidth provisioning models, but both have significant disadvantages if applied to large-scale networks. The management complexity of the trunk model highly increases with the size of the network, and the bandwidth efficiency of the hose model is often excessively low. We propose an intermediate solution between the hose and trunk models. By dividing the network into clusters and using a cluster-based traffic description, an appropriate equilibrium can be found between management complexity and overprovisioning.

The Impact of Network Applications (Web, FTP and E-mail) and Network Profiles on the Self-Similar Parameter

Self-similarity is an important characteristic of modern network traffic, and an accurate traffic description must take this characteristic into account. This work analyzes traffic's self-similar behavior for the three most expressive application protocols used in IP networks (HTTP, FTP and SMTP) by varying the user profiles (in terms of the transferred file size and file inter-arrival times) and the network characteristics (with respect to the transfer delay and packages loss rate). The simulation results show that the intrinsic characteristics of application protocols, of the TCP transport protocol, and of user and network profiles affect the traffic self-similar characteristics in distinct ways. Experimental results also reveal that different quantities of contribution from different application protocols in the traffic load can also change traffic's self-similar characteristics.

An energy-efficient slack distribution technique for multimode distributed real-time embedded systems

In multimode distributed systems, active task sets are assigned to their distributed components for realizing one or more functions. Many of these systems encounter runtime task variations at the input and across the system while processing their tasks in real time. Very few efforts have been made to address energy efficient scheduling in these types of distributed systems. In this paper, we propose an analytical model for energy efficient scheduling in distributed real-time embedded systems to handle time-varying task inputs. A new slack distribution scheme is introduced and adopted during the schedule of the task sets in the system. The slack distribution is made according to the service demand at the nodes which affects the energy consumption in the system. The active component at a node periodically determines the service rate and applies voltage scaling according to the dynamic traffic condition observed at various network nodes. The proposed approach uses a comprehensive traffic description function at nodes and provides adequate information about the worst-case traffic behavior anywhere in the distributed network, thereby enhancing the system power management capabilities. We evaluate the proposed technique using several benchmarks employing an event driven simulator and demonstrate its performance for multimode applications. Experimental results indicate significant energy savings in various examples and case studies.

Network internal traffic characterization and end-to-end delay bound calculus for generalized processor sharing scheduling discipline

This paper addresses the end-to-end performance bound provisioning problem for one of the most significant traffic scheduling algorithms, generalized processor sharing (GPS). In particular, solutions are given to the network internal traffic characterization and end-to-end delay bound calculation problems in arbitrary topology GPS networks, where sessions are allowed to be arbitrary weighted. In the first part of the paper methods are given for determining internal (at inputs of network nodes) traffic descriptors of sessions, which are originally leaky bucket constrained at the network edge. The output burstiness behaviour of the arbitrary weighted GPS server is analyzed, and based on these results two algorithms are proposed that not only calculate internal traffic descriptors, but can also be used to manage network stability questions in non-feedforward networks. In the second part the end-to-end service curve is introduced to capture end-to-end worst-case traffic conditions of sessions, which forms the basis of the proposed method for end-to-end delay bound calculation. Extensive numerical analysis is shown to illustrate the tightness of this delay bound and various examples for internal traffic characterization are also conducted.

Dynamic Service Management in Heterogeneous Networks

Novel network architectures allow users to get specific performance guarantees via the definition of a document where QoS (Quality of Service) requirements are linked to the user traffic description. Such a document is defined SLA (Service Level Agreement), and it is a formal high level definition (user view) of characteristics for a communication service, whereas low level specification (network view) is obtained translating the SLA in a different document named SLS (Service Level Specification). Although in the case of static services the network configuration process is a well defined activity, when dynamic services come into play a more complicated scenario where SLA translation into the appropriate SLS is not a one-step and static process, but it needs an active and consistent evaluation with respect to the current situation. We claim that to make this process happen automatically, we need to have intelligent devices able to translate request specified inside SLAs in the most appropriate network configuration (by means of dynamic SLS) depending on client's current “service conditions.” In this paper we introduce a framework for distributed network management through an entity, namely AcMe (Active Mediator), which performs dynamic creation of network services in a transparent to the user fashion. A new protocol, HNMP (Heterogeneous Network Management Protocol), orchestrates all AcMe functionality. Finally, an experimental analysis is presented.

Rate control for UWB mobile radios

This paper shows a technique for regulating the rate emitted by UWB mobile terminals. This technique is designed to adapt the emission rate to the effects of channel capacity variations. We assume that individual flows are shaped at edge routers by means of dual leaky buckets. The proposal is based on the evaluation of certain parameters, which reflect the channel status, sent to the application layer. This information is generated by the scheduler designed to guarantee appropriate channel sharing for the various traffic components. We describe some results which highlight how performance depends on the specific operating conditions, as well as on the traffic descriptors of the flows, their reciprocal difference, and performance requirements.