This dissertation investigates the High Level Architecture (HLA) as a possible distributed simulation framework for transportation systems. The HLA is an object-oriented approach to distributed simulations developed by the Department of Defense (DoD) to handle the issues of reuse and interoperability of simulations. The research objectives are as follows: (1) determine the feasibility of making existing traffic management simulation environments HLA compliant; (2) evaluate the usability of existing HLA support software in the transportation arena; (3) determine the usability of methods developed by the military to test for HLA compliance on traffic simulation models; and (4) examine the possibility of using the HLA to create Internet-based virtual environments for transportation research. These objectives were achieved in part via the development of a distributed simulation environment using the HLA. Two independent traffic simulation models (federates) comprised the environment (federation). A CORSIM federate models a freeway feeder road with an on-ramp while an Arena federate models a tollbooth exchange.

This dissertation investigates the High Level Architecture (HLA) as a possible distributed simulation framework for transportation systems. The HLA is an object-oriented approach to distributed simulations developed by the Department of Defense (DoD) to handle the issues of reuse and interoperability of simulations. The research objectives are as follows: (1) determine the feasibility of making existing traffic management simulation environments HLA compliant; (2) evaluate the usability of existing HLA support software in the transportation arena; (3) determine the usability of methods developed by the military to test for HLA compliance on traffic simulation models; and (4) examine the possibility of using the HLA to create Internet-based virtual environments for transportation research. These objectives were achieved in part via the development of a distributed simulation environment using the HLA. Two independent traffic simulation models (federates) comprised the environment (federation). A CORSIM federate models a freeway feeder road with an on-ramp while an Arena federate models a tollbooth exchange.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

The High Level Architecture (HLA) provides a universal solution for interconnecting various simulation environments and applications thus creating a more complex simulation entity. The idea is built upon controlled and directed data exchanges of objects and events (via the RunTime Interface - RTI) shared by participants (i.e. simulations) thus creating a distributed data environment. The aim of this thesis is to investigate usability of HLA for agent based development platforms (e.g. Pogamut) as well as providing transparent and simple to use access to HLA for HLA unaware applications. The thesis describes architecture and provides a prototype proof-of-concept implementation, which integrates HLA with two different (closed source) game engines providing them the ability to communicate to a simple client application according to a reasonable subset of the HLA standard. The thesis also provides performance measurements of prototype implementation.

The enforcement of reusability and shareability of products or components based on new technology standards for simulation and modeling is of paramount importance. In this thesis we first utilize DMSO HLA as the basic fundamental to design a customization environment for Web-based modeling and simulation. The environment is able to offer the interoperability framework between a broad spectrum of simulation paradigms, including both real-time and logical time models and to support a huge number of participants. To fulfill the goal we proposed three main tasks to be done. First, we proposed the mechanism to reduce the communication overhead and to balance the information consistency among large participants by incorporating a three-level control mechanism and Dynamic Filtering Strategy (DFS) within HLA RTI. In the second task, we proposed a load balancing algorithm to efficiently utilize the resource over the network environment. At the last task we use Java 3D to build a virtual reality application on the environment.

Multiagent simulation is gaining popularity due to its intuitiveness and ability in coping with domain complexity. HLA, being a distributed simulation architecture standard, is a good candidate for implementing a multiagent simulation infrastructure on, provided that agent communication can be implemented. HLA, being a standard designed towards a wide coverage of simulation system architectures and styles, is not an easy system to master. In this thesis, an abstraction layer called the Federate Abstraction Layer (FAL) is described for better engineering of software systems participating in an HLA simulation, providing lower project risks for the project manager and ease of use for the C++ programmers. The FAL is in use in project SAVMOS in Modelling and Simulation Laboratory. Discussion of FAL is followed by discussion of the study for realizing KQML for use in multiagent architectures to be built on top of HLA as the data transfer medium. The results are demonstrated with 10 federates implemented using the FAL.

Modelica is a domain independent modeling language allowing for componentbased modeling of complex systems. Functional Mock-up Interface (FMI) defines a standardized interface for complex computer simulations. High Level Architecture (HLA) is an interoperability standard of a general purpose architecture for distributed simulation. This thesis aims to show the possibilities of having Modelica models in a distributed environment by usage of FMI and HLA. An additional objective is to provide a base for a possible generic solution.

Load management is an essential and important factor for distributed simulations running on shared resources due to load imbalances that can caused considerable performance loss. High Level Architecture (HLA) -based simulation is a framework that works to facilitate the design and management of distributed simulations. HLA coordinates the interaction between simulation entities (federates). However, HLA-based simulation standards do not present the ability to manage resources or help detect load imbalances that could directly cause decrease of performance. Focusing on this constraint, a migration-aware dynamic balancing system has been designed for HLA simulations to offer an efficient load-balancing scheme that works in large-scale environments. This system presents some limitations on estimating costs and benefits, so we propose an enhancement to this existing load balancing system, which improves the accuracy of estimating the number of migrations for the next load redistribution. The proposed scheme detects the load imbalances by evaluating the recourses overhead. The scheme classifies the recourses based on the overhead as overloaded and underloaded, followed by matching the highest overloaded recourses with the lowest underloaded recourses. Furthermore, the proposed scheme aims to precisely estimate the number of migrations by evaluating and analyzing the recourses to obtain the best number of migrations. Therefore, certain migrations that do not contribute to an improvement in the simulation performance are avoided. This avoidance is based on comparing time delay and time gain. Moreover, to be considered for migration, the overall sum of the time gains should be larger than the overall sum of the time delays. The proposed scheme has shown an improvement on decreasing the execution time.

As the size, complexity, and functionality of systems we need to model and simulate con-tinue to increase, benefits such as interoperability and reusability enabled by distributed discrete-event simulation are becoming extremely important in many disciplines, not only military but also many engineering disciplines such as distributed manufacturing, supply chain management, and enterprise engineering, etc. In this dissertation we propose a distributed simulation framework for the development of modeling and the simulation of complex systems. The framework is based on the interoperability of a simulation system enabled by distributed simulation and the gateways which enable Com-mercial Off-the-Shelf (COTS) simulation packages to interconnect to the distributed simulation engine. In the case study of modeling Virtual Test Bed (VTB), the framework has been designed as a distributed simulation to facilitate the integrated execution of different simulations, (shuttle process model, Monte Carlo model, Delay and Scrub Model) each of which is addressing differ-ent mission components as well as other non-simulation applications (Weather Expert System and Virtual Range). Although these models were developed independently and at various times, the original purposes have been seamlessly integrated, and interact with each other through Run-time Infrastructure (RTI) to simulate shuttle launch related processes. This study found that with the framework the defining properties of complex systems - interaction and emergence – are realized and that the software life cycle models (including the spiral model and prototyping) can be used as metaphors to manage the complexity of modeling and simulation of the system. The system of systems (a complex system is intrinsically a "system of systems") continuously evolves to accomplish its goals, during the evolution subsystems co-ordinate with one another and adapt with environmental factors such as policies, requirements, and objectives. In the case study we first demonstrate how the legacy models developed in COTS simulation languages/packages and non-simulation tools can be integrated to address a compli-cated system of systems. We then describe the techniques that can be used to display the state of remote federates in a local federate in the High Level Architecture (HLA) based distributed simulation using COTS simulation packages.

The establishment of a network of persistent shared simulations depends on the presence of a robust standard for communicating state information between those simulations. The High Level Architecture (HLA) can serve as the basis for such a standard. While the HLA is architecture, not software, use of Run Time Infrastructure (RTI) software is required to support operations of a federation execution. The integration of RTI with existing simulation models is complex and requires a lot of expertise. This thesis implements a less complex and effective interaction between a legacy simulation model and RTI using a middleware tool known as Distributed Manufacturing Simulation (DMS) adapter. Shuttle Model, an Arena based discrete-event simulation model for shuttle operations, is connected to the RTI using the DMS adapter. The adapter provides a set of functions that are to be incorporated within the Shuttle Model, in a procedural manner, in order to connect to RTI. This thesis presents the procedure when the Shuttle Model connects to the RTI, to communicate with the Scrub Model for approval of its shuttle's launch.