A Universal Interworking Function (UIWF) for LMR and LTE Networks

Interoperability has been a communications objective for for first responders in the United Stats for many years. The need for digital interoperability brought about the establishment of the Telecommunications Industry Association (TIA) Association of Public Safety Communications Officials (APCO) Project 25 standard in 1989.Today, P25 standards are very mature, and include an Inter-RF Subsystem Interface (ISSI) which allows interconnection of P25 standard systems.As LTE is commercially available, a number of proprietary broadband Push-To-Talk (PTT) solutions have seen substantial operational uptake and have arguably made the problem of interoperability worse.These Pre-MCPTT services are often communications islands with few if any provisions for interoperability.With the allocation of700MHz spectrum to a nationwide, interoperable LTE network and creation of Firstnet a new generation of interoperability is now needed.A final challenge to MC LTE-LMR interoperability is the fact that 3GPP defines the Mission Critical Interworking Function (IWF) as out of scope of the standards. This leaves a blank space between LMR and MC LTE.The purpose of this project is to develop the requirements, feature sets, architecture, and design analysis to establish the feasibility of a Universal Interworking Function (UIWF) that closes the gap between standards-based MC LTE and P25 ISSI as well as establishing solutions for MC LTE to Pre-MCPTT and other LMR system types.