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High Level Architecture

High Level Architecture. Phuoc Nguyen. HLA Benefits. Provide a common communication protocol between applications A standardized architecture for all simulations Manage and distribute data across simulation Promote reusability. Overview. HLA Component Breakdown HLA Specification

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High Level Architecture

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  1. High Level Architecture Phuoc Nguyen

  2. HLA Benefits • Provide a common communication protocol between applications • A standardized architecture for all simulations • Manage and distribute data across simulation • Promote reusability

  3. Overview • HLA Component Breakdown • HLA Specification • HLA As an architecture • Time Synchronization

  4. Components • HLA is broken down into RTI and Federates • RTI and Federation communicates through objects and interaction • A collection of Federates makes up a Federation • Federations are connected through Gateway

  5. Federates and RTI

  6. RTI • Data routing to only subscribed Federates • Keep track of objects • Not a repository of data • Handle Federate join • Handle late joiner

  7. FOM Object

  8. FOM Interaction

  9. HLA Specification • A Federation must have a FOM specification • All Object instances reside in federate not RTI • All exchange of objects shall occur via RTI • Object instance may be updated by at most one owner • Individual Federate shall be responsible for its own local time

  10. Time Synchronization • Ensure events are delivered in order • Each Federate has a logical clock • Multiple level of Time Synchronization implemented among federates

  11. Level of Time Management Time-Regulating True False Strictly Time-Synchronized: Conservative and Optimistic Viewer or Federation Management Tool. Stays synchronized to Federation, but generates No events True Time-Constrained Unconstrained operating With conservation Federates, or Pacing federate Externally synchronized Simulation: No time management from RTI’s standpoint False

  12. Events Ordering • Time Stamp Order (TSO) • Only time-regulating federates can send TSO • Only time-constraint federates can receive TSO • RTI will guarantee distribution of TSO in order • No events shall be deliver to federate in its past

  13. Synchronize Mechanism • Prevent deadlock • The slowest federate could hold the entire Federation

  14. Look-ahead • Federates send events at time greater then look-ahead value • Federates are free to advance local clock within the look-ahead value • Larger look-ahead value allows high level of parallelism • Larger look-ahead also mean slow response time.

  15. RTI Regulate Time Advancement • All federates will request for time advancement • RTI responsible to synchronize time advancement Time Advancing Time Granted

  16. Time Advancement Look ahead value Logical Time Logical Time [TAR] [Grant] [TAR] [Grant] [TAR] [Grant] Wall Clock Time

  17. HLA as a Solution • Common architecture • Interchanging components/federation • Drawback is the added overhead • Not suited for real-time simulation due to delay in time synchronization

  18. Resources • “Creating computer simulation systems” • Dr. Federick Kuhl • Dr. Richard Weatherly • Dr. Judith Dahmann • http://en.wikipedia.org/wiki/High_Level_Architecture

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