Showing papers on "Network traffic simulation published in 1990"

Multimedia traffic management principles for guaranteed ATM network performance

Abstract: A framework is presented for the specification of performance requirements, and several high-level design principles for performance-driven ATM traffic controls based on resource reservation are developed. Simulation results illustrate that to guarantee performance levels, bursty traffic should be statistically multiplexed only if connection peak rates are low relative to the network link speed or burst durations are short. A pragmatic traffic management approach that favors simplicity and robustness in the traffic control design rather than optimizing bandwidth efficiency is stressed. >

ATM communications network control by neural networks

Abstract: A learning method that uses neural networks for service quality control in the asynchronous transfer mode (ATM) communications network is described. Because the precise characteristics of the source traffic are not known and the service quality requirements change over time, building an efficient network controller which can control the network traffic is a difficult task. The proposed ATM network controller uses backpropagation neural networks for learning the relations between the offered traffic and service quality. The neural network is adaptive and easy to implement. A training data selection method called the leaky pattern table method is proposed to learn precise relations. The performance of the proposed controller is evaluated by simulation of basic call admission models. >

TEVACS: Decision Support System for Evacuation Planning in Taiwan

Abstract: A microcomputer‐based decision support system is developed for transportation network evacuation applications in Taiwan, the Republic of China. Input to the system mainly includes the trip‐generation‐related attributes, the street network topology and traffic data, the control variables regarding the routing of public transportation vehicles, and the use of traffic control measures. A dynamic network simulation model based on traffic flow theory is used to simulate the vehicles' movement on the street network during the evacuation process. For a given evacuation plan, the network simulation module calculates the estimated network clearance time. The intermediate results of each simulation interval are saved in graphic data files. The planner can use the graphic display module of the system to visually observe the dynamic change of traffic congestion on each link of the network throughout the simulated evacuation process. The system thus provides a convenient tool not only for evaluating different evacuati...

Urban Network Traffic Simulation:TRAF-NETSIM Program

Abstract: The network simulation program NETSIM is now a component model of the integrated traffic simulation system TRAF. The current version of the model is therefore referred to as the TRAF-NETSIM program. As part of an effort aimed at developing, maintaining, and supporting the TRAF simulation system, TRAF-NETSIM has been extensively modified over the past five years. Four new features have been added to the TRAF-NETSIM simulation program: actuated controller logic, identical traffic streams, conditional turning movements, and signal transition. Several major modifications have also been made to the simulation logic to resolve the problems encountered during the testing of the simulation program; to enhance the logic to represent complex decision processes; and to enhance and extend the input-output capabilities, user-interaction, and the computational efficiency of the program. These new features and the modifications incorporated in the TRAF-NETSIM simulation model are described in this paper.

Method of managing traffic flows in a wideband integrated services digital network, and a network for implementing the method

Abstract: Method and apparatus for controlling traffic flow in a wideband integrated services digital network including an asynchronous time division multiplexed switch network and a plurality of terminals operating at various data rates and providing different types of service. Control of traffic flow in the network is achieved by delaying data cells or allowing them to be lost, within limits that are predetermined as a function of the type of service provided by the terminals.

Distributed discrete event simulation for communication networks

Abstract: A survey of the techniques used in distributed discrete event simulation is presented. Some of the algorithms that have been developed to overcome some of the inherent problems of simulating on distribution systems are then described. The application of distributed discrete event simulation to the performance evaluation of communication networks is addressed. The design and implementation of the DISDESNET (distributed discrete event simulation of networks) simulation package for the simulation of general communication networks is described. Results of tests performed on different configurations are examined and found to demonstrate the flexibility of the package. >

Integrating microscopic simulation and optimization: application to freeway work zone traffic control

Abstract: This paper presents a methodology for optimizing performance of a traffic system on the basis of simulated observations of its microscopic behavior. The method integrates simulation and optimization submodels for describing traffic flow on urban freeway lane closures. The stochastic nature of traffic is accounted for in determining the true system response to traffic control variables. The simulation submodel has been validated at a series of work sites in the Chicago area expressway system. The optimization submodel optimizes a single objective function subject to a set of linear constraints. Preliminary model applications included the determination of an optimum merging strategy to be adopted by traffic entering the work zone in lanes to be closed for traffic. The model recommendation yielded the lowest average travel time in the work zone and, interestingly, did not incorporate many early merges; the latter is often viewed as a desired merging strategy. In addition, the optimum merging strategy varied with the traffic flow level entering the work zone and with the character of the objective function to be optimized.

Monitoring integrated networks for performance management

Abstract: An object-oriented model for network independent monitoring and performance evaluation in real-time is presented. the model describes the behavior of network objects by a set of state variables and a set of invariants. The model is used to evaluate quality-of-service characteristics of different classes of traffic in an integrated network testbed. An objective-driven measurement strategy to establish the dynamic database of the network is discussed. A statistical database derived from the dynamic database is also obtained. >

A simulation tool for traffic signal control planning

Abstract: The testing and evaluation of alternative signal control strategies is time consuming and the classic methods in delay and queue length estimation do not always give sufficient and valid information in changing traffic conditions. New ways are therefore needed. One possible method is advanced computer simulation. To be useful in signal control planning and research a simulator must be able to simulate the functions of the signal controller; and the behaviour and reactions of traffic flow to the signals. The paper summarizes the principles and experiences gained so far in the building and testing of this new kind of a simulator at The Helsinki University of Technology.< >

Dynamic simulation-assignment methodology to evaluate in-vehicle information strategies in urban traffic networks

Abstract: A model combining traffic simulation and path assignment capabilities is presented to analyze the effect of in-vehicle real-time information on the performance of a congested traffic network. The research integrates the main components of a traffic network under real-time information, namely, the traffic flow, the driver behavior, and the network information dissemination, into a single modeling framework which is then used to study the underlying dynamics and evaluate alternative designs of such traffic systems. Drivers' route decisions in response to the information are modeled individually at each node. Results of a series of simulation experiments are discussed. Special coding considerations for efficient vector processing on supercomputers are also examined. >

Identical traffic streams in the traf-netsim simulation program

Abstract: This paper describes an enhancement to the TRAF-NETSIM simulation model which provides users with the ability to simulate, with traffic streams exhibiting identical routeing patterns, driver-vehicle characteristics and other operational characteristics through a series of runs. The paper describes the generation of stochastic (random) behaviour in the TRAF-NETSIM simulation model and discusses the need for generation of identical traffic streams

Introduction—discrete event simulation

Abstract: This special section deals with the simulation of complex systems, such as computer, communications, and manufacturing systems—specifically focusing on stochastic discrete event simulation. Such systems are typically (but not always) modeled by a network of queues, in which jobs compete for the system's resources. For example, in an on-line computer database system, the jobs would represent transactions, and the system's resources would include processors, disks, main memory, data locks, etc. Since job arrival patterns and resource requirements are unpredictable, such systems are inherently stochastic (random). As these systems increase in complexity, it becomes increasingly difficult to build analytically tractable performance models; thus simulation, because of its versatility, often becomes the only viable analysis technique.This issue contains articles which span a broad range of current topics in simulation, includingEfficient execution of simulation models using parallel processors;Integration of real-time systems, artificial intelligence, and simulation for automated factory control,Rapid prototyping and simulation of distributed systems,Sensitivity analysis of simulation output,Random number generation, andEffective use of simulation in analyzing and improving the performance of actual systems.Richard Fujimoto's article is a state-of-the-art survey on the execution of simulation models on parallel processors. Fujimoto describes why discrete event simulations have proven to be a difficult class of applications to parallelize. He then describes two basic parallelization approaches (conservative and optimistic), and recent experience with these approaches, including his own results in which significant speedups have been obtained on nontrivial problems using the optimistic “Time Warp” approach. He also provides a critique and assessment of the basic approaches to parallel simulation.The article by Sanjay Jain, Karon Barber and David Osterfeld describes a system for factory scheduling. The scheduling system obtains the status of the plant floor using the factory's real-time monitoring and control computer system. This information is fed into the scheduler which generates a new schedule, and sends it back to the factory control computer. The scheduler integrates a simulation model (which simulates backwards in time), and an expert system whose rules encode scheduling heuristics. The system is currently in use at a highly automated General Motors component production facility.Alexander Dupuy, Jed Schwartz, Yechiam Yemini and David Bacon's article describes NEST, a UNIX-based environment for prototyping, modeling, and simulating distributed systems. NEST has a graphical interface for building simulation models. In addition, users can program (or prototype) “node functions” that implement the system's control algorithms (e.g., routing protocols in a communications network). The node functions are linked into the simulation, allowing simulation (and debugging) of a system using its actual control logic. With only minor modification, the node functions can be decoupled from the simulation and used to build the actual system. The authors illustrate this combined use of prototyping and simulation using the RIP protocol, a simple routing protocol for IP (Internet Protocol) networks. The authors also describe other features of NEST, including its ability to dynamically reconfigure the simulation model during execution, which permits the study of how the system reacts to changing conditions, such as link failures.The article by Peter Glynn is concerned with sensitivity analysis of simulation output. He discusses a general-purpose method for using simulation to estimate the derivative of a performance measure, and provides explicit formulae for estimating derivatives for several broad classes of stochastic processes that typically arise in discrete event simulations.Pierre L'Ecuyer's article is a timely survey on pseudorandom number generation. As L'Ecuyer explains, this topic has recently received renewed attention for a variety of reasons, including the proliferation of generators on microcomputers, the need for portable generators, the requirement for generators with very long periods (as machines get faster), and the application of pseudorandom number generators to cryptology. L'Ecuyer examines several classes of generators, outlines their theoretical and empirical properties, and discusses implementation issues as well.The article by David Miller presents a case study illustrating the use of simulation modeling to analyze the performance of an IBM semiconductor manufacturing facility in Essex Junction, Vermont. Miller describes the relevant background and goals of the modeling study, the modeling approach, and model validation. He then describes the results of the simulation experiments, which included investigating a variety of line-loading and scheduling policies. Miller found that a lot-release policy that keeps a fixed amount of work-in-progress in the line could significantly reduce the lot turnaround time without reducing throughput, when compared to the policy that was in use in the facility. Miller then describes the specific changes, suggested by the modeling study, that were implemented in Essex Junction, and the corresponding improvement in the facility's efficiency.

Simulation of event-based control of continuous systems

Abstract: An example of an event-based motor speed control system is presented and modeling and simulation strategies for combined discrete-continuous simulation are discussed. The approach is based on system-theoretic formalisms and relies on the abstract simulator concept for discrete event simulation developed by B.P. Zeigler (1985). The main characteristics of the approach are presented. >

Innovations in telecommunications network management under demand uncertainty

Abstract: Two kinds of innovations are important for telecommunications network management under demand uncertainty. The first is a flexible mechanism for assigning network resources in the most timely manner based on network performance evaluation, called “performance-oriented management”. The second is the so-called state-dependent dynamic routing. In this paper, the concept and methodologies for performance-oriented management are described. It is shown that, by using call-by-call simulation, performance-oriented management combined with any state-dependent dynamic routing noticeably saves investment in the network life cycle under demand uncertainty.

Network management algebra

Abstract: A vector algebra environment for highly-survivable network planning and control is described. This environment incorporates deterministic and stochastic parameters and can be readily automated. The algebra is useful in determining best network routes for transmitting information under normal and disturbed conditions. Algorithms that can handle node loss and path disruption due to physical faults, environmental variability, and enemy interception or jamming are discussed. >

A train traffic simulation system permitting application of knowledge engineering

Abstract: A train traffic simulation system to which users themselves can add their own knowledge is introduced. The simulation system accepts sentences describing knowledge about train traffic rearrangement, transforms them into programs of rule-based language, then adds them to itself. Knowledge addition can be done in natural language. Thus, users can easily upgrade the simulation system into an intelligent one by adding their own knowldege which is specific to their own circumstances. An algorithm to determine priorities among mutually contradictory pieces of knowledge is also proposed.

Neural network-based routing in an intelligent computer communication network

Abstract: A neural network-based traffic routing algorithm, to be implemented in an intelligent computer communication network, is presented. It simultaneously takes into account the shortest path and channel capacity and determines the necessary connections and weights of the neural network, thus providing an optimum transmission path from source node to destination node. The algorithm is based on the Hopfield type of neural network approach, and can be considered as a massively parallel distributed processing system with the ability to improve performance through dynamic learning. The power of neural network algorithms to solve routing problems and provide dynamic response to traffic conditions measured throughout the network system is investigated. No congestion occurs in this network because of the changes in the statistics of the input traffic load. A computer simulation result for a 10-node network shows the efficiency of using the neural network-based algorithm. >

End-to-end planning model for optimal evolution of telecommunications network

Abstract: An analytical model of the telecommunications network is formulated, representing the entire network as a single entity. The resulting model contains a realistic (i.e. not overly simplified) view of the network, and hence can be used to develop the optimal evolution strategy for the Bell Operating Companies (BOC's) network. The process of developing the optimal evolution strategy is referred to as the strategic planning process. Background associated with the strategic planning process of a telecommunications network is given. Attempts are made to illustrate some basic underlying assumptions in the telephony. The problem to be solved and nomenclature are defined. Models for the fundamental elements of the network, i.e. links and nodes, are defined. The optimization problem that includes all aspects of the network, i.e. end-to-end connectivity, is formulated. >

Modelling and simulation of intelligent multimedia communication networks

Abstract: Techniques and features that have been found useful for modeling and simulating intelligent multimedia communications networks are described. Key ingredients are a robust, commercially available and supported simulation language and a modeling and simulation architecture that consists of custom-designed modules of the features that clearly occur in communication network simulation. The simulation architecture used is described at length. >

Definition of timing models for compiler-driven logic simulation

Abstract: The Munich Simulation Engine accelerates compiler-driven simulation and is able to exploit a design's parallelism without restrictions. Advocates of table-driven simulation-engines, however, claim that concerning timing simulation the advantage of compiler-driven simulation engines only exists for zero-delay and, maybe, unit-delay simulation. Based on experience with an operational model of the Munich Simulation Computer, it is shown how to define all types of timing models for compilers-driven simulation and to discuss how far the performance potential of the Munich Simulation Computer is affected when timing models are coded and executed by means of event-flow graphs. >

Servicing of bursty systems

Abstract: This paper treats the practical problem of engineering an existing system having “bursty” traffic for incremental growth. A typical method of treating such problems is to assume a characterization for the input traffic and then use a network of queues type model to analyze delays and performance. While this approach is appropriate when designing a network, it does not make use of measurements of existing performance. In this paper we will explore a different approach. Using readily available data, we will infer the traffic characteristics at specific points in the network. We will then assume that these characteristics hold when the traffic is increased. We apply this method to a sample packet switch network. The results suggest that the accuracy of this method is surprisingly good. This suggests that the philosophy of inferring traffic characteristics from observed network performance may be extendable to more complex situations that occur in ISDN/BISDN and other applications. Since our work is not fully developed, we detail a number of issues that need to be resolved.

Simulation of automatic ship navigation and vessel traffics. 3rd report: hierarchical structure of simulation system and marine traffic simulation

Abstract: A new simulation system is proposed for future investigation of vessel traffic systems and ship navigation. It has a hierarchical structure and consists of a macro network model for marine traffic and a micro ship operation model. This enables marine traffic simulation for a large sea area to take account of precise ship behaviour as well as traffic control. A simulation for Tokyo Bay has been carried out using the prototype system.

Analysis of a Data Communication Network's Performance under Varying Retransmission Disciplines

Abstract: : A stochastic simulation model is developed, using the SLAM II simulation language, to study the dynamics and performance of a small data communication network. The simulation program models pertinent aspects of Defense Data Network (DDN) protocols. The effect of changes in node-to-node and host-to-host retransmission timeout intervals upon expected response time is studied using the model.