Achieving simulation interoperability between autonomous federations is always a challenging problem. Despite the fact that different federations might accomplish seemingly similar tasks, they frequently implement solutions using drastically different approaches. A recent federation bridge development project implemented a unique approach to federation interoperability between differing Run-Time Infrastructure (RTI) solutions, Federation Object Models (FOMs), and federation level protocols. The ability to provide interoperability between two High Level Architecture (HLA) federations in a single software process using different versions of the RTI allows for an interoperability solution that requires no implementation changes to either federation while demonstrating the collective benefits combining the two federations.

Providing interoperability between two HLA federations in a single software process using different versions of the RTI poses a unique challenge, as one normally cannot compile and link an application in this way. This challenge can be overcome using a specialized proxy that enables different versions of the RTI to simultaneously coexist in a single software process. This paper details the technological approach of using such a proxy for a federation bridge, including its applicability, architecture, and performance characteristics. The approach is proven via the successful implementation of a federation bridge that enables interoperability between two federations using the DMSO 1.3 NG v4 and Raytheon VTC NG Pro v2.0.4 RTIs. Examples of using the techniques presented in this paper in other situations are also given, as well as alternative approaches.