High Level Architecture Phuoc Nguyen HLA Benefits n

High Level Architecture Phuoc Nguyen

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

Overview n HLA Component Breakdown n HLA Specification n HLA As an architecture n Time Synchronization

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

Federates and RTI

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

FOM Object

FOM Interaction

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 n Individual Federate shall be responsible for its own local time n n

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

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

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

Synchronize Mechanism n Prevent deadlock n The slowest federate could hold the entire Federation

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

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

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

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

Resources n “Creating computer simulation systems” n Dr. Federick Kuhl n Dr. Richard Weatherly n Dr. Judith Dahmann n http: //en. wikipedia. org/wiki/High_Level_Archit ecture