In this Phase I project, we will determine the feasibility of building an interworking solution to provide interoperability between LTE and LMR systems for mission critical operations, while improving interoperability between current LMR systems.InPhase I we will build upon the requirements work already done by NPSTC to determine the feasibility of meeting requirements for interworking when standard interfaces are used.In Phase II, we will combine innovations created through this study with our interoperability products to deliver a software-based prototype LMR to LTE MCPTT solution and will commercialize this interworking service software product in Phase III.To support the transition to LTE MCPTT, we will create a scalable architecture that leverages Radio over IP technology that we have perfected over the last twenty years.As part of our research and development, we will summarize feasibility results by creating comprehensive solutions matrices of standards interfaces versus interworking requirements.We will focus on Project 25 standard interfaces such as ISSI and also evaluate other standards-based systems and proprietary LMR systems.The Catalyst team brings many years of real-world experience in delivering interoperability solutions, ensuring the successful completion of this SBIR program for DHS.The result for DHS and other critical communicators will be smoother transitions to LTE at a lower cost.We have identified a multimillion dollar market for the resulting product that would allow each Public Safety agency to independently route PTT voice between its existing LMR system, FirstNet's LTE network, and other LMR systems.