Performance Issues of HLA Run Time Infrastructure based on CORBA

The High Level Architecture (HLA) is a new standard technical architecture for distributed simulation to facilitate interoperability and reuse of simulation systems. The HLA provides a common simulation framework in which a set of basic simulation services is available to developers using an object-oriented approach. The underlying Run Time Infrastructure (RTI) provides a communications framework for the HLA through which federates can distribute the intersimulation information to the appropriate parties. The design of the RTI is intended to provide the required simulation services and data exchange mechanisms in a common, modular and scalable manner. This concept can be designed in a distributed fashion using the Common Object Request Broker Architecture (CORBA) as middleware infrastructure in which different RTI modules are running on a number of networked machines. CORBA is a natural implementation framework for the object-based HLA providing low level message handling, data marshalling, exceptions and process control among participating machines. This object-oriented design is able to integrate simulation software in different languages. Nevertheless, the performance of current CORBA implementations is not yet suited for real-time simulations. Additional processing and communications overhead is required to hide such implementation details from the users. In this paper, we describe the implementation of HLA RTI using CORBA, which is expected to meet the real-time performance requirement of distributed simulations. We discuss performance issues of the RTI implementation based on CORBA that should be addressed to support simulation activities.