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