Real-time Scheduling of HLA Simulator Components

For several years TNO has done research on the use of component based HLA federates. An individual simulator, participating in an HLA federation, can itself be composed of various components interacting through the same HLA interface as the overall federation. Simulator components communicate via a middleware layer called the Run-time Communication Infrastructure (RCI). The RCI is based on the HLA Run-Time Interface (RTI), but allows the use of other standards as well. Currently, HLA developers that are interested in real-time performance disregard most of the RTI functionality with respect to time management in an attempt to minimize the overhead of the RTI. The limited
performance of the RTIs holds back potential HLA developers from building HLA compliant federates and it certainly raises doubts over the feasibility of HLA federations with real-time requirements, including component based federates. In the recent past, TNO has performed tests regarding performance of component based architectures that use the RCI in combination with the DMSO RTI. These results indicated the areas on which further research should focus, that is real-time HLA simulations and high-performance RTIs. In addition to the time management services of the RTI, the RCI middleware has been extended with a time triggered scheduling mechanism based on a globally synchronized wallclock
time. This easy to use real-time scheduler can be of great support in the development of man-in-the-loop simulators. TNO has also developed a high performance RTI, which can easily use different communication media due to its layered design. The RCI middleware, RTI, and network has to provide a guaranteed ‘Quality of Service’ (QoS) to meet the real-time requirements of HLA federations. Therefore, TNO is in the process of extending the RCI with QoS policies. This paper discusses the results of our research into real-time scheduling and presents test results on a realtime Linux variant called RedHawk that prove the feasibility of a real-time simulator built as a Component Based Federate.