07 August 2025 - With the increasing development of critical broadband networks, the key issue for network operators is how to ensure mission critical services delivered over broadband interwork with the existing narrowband land mobile radio (LMR) networks such as TETRA.

A new white paper from TCCA titled ‘Interworking Function (IWF) Interworking of LMR networks with 3GPP Mission Critical Services’ explores the opportunities and challenges of interworking LMR networks with 4G/5G-based 3GPP Mission Critical Services (MCX) solutions by leveraging the standard-defined Interworking Function (IWF). The aim of this integration is to strengthen communication capabilities, achieve seamless interoperability, and enable a gradual and successful adoption of broadband technologies.

The white paper, authored by TCCA’s IWF Working Group, outlines the current status of the IWF standard, emerging feature capabilities, and the level of industry adoption, including support from organisations such as ETSI and 3GPP. Key opportunities discussed include seamless voice interoperability between LMR and MCX, data service integration, hybrid network support, multimedia feature enhancements for LMR users, standards-based interoperability, and unified control room integration.

Due to their proven reliability and critical role in public safety, LMR networks cannot be replaced immediately – transitioning from LMR to broadband MCX must follow a phased, carefully managed approach.  Past implementations have shown that public safety organisations benefit most from progressive adoption of broadband communications. A hybrid LMR–MCX configuration, particularly for voice communications, represents an effective starting point. The IWF plays a central role in enabling this step-by-step migration strategy.

While the core market for MCX lies in public safety however, its applications span a broad range of sectors including defence, critical infrastructure, utilities, and commercial operations such as mining, oil and gas, and major event management. All these sectors share a common requirement: highly dependable and efficient communication tools for use in critical and high-stakes environments.

The integration of LMR networks with broadband MCX services via the IWF standard marks a major advancement in mission-critical communications. This convergence harnesses the reliability of LMR with the expanded capabilities of 4G and 5G—enabling seamless voice, real-time data transfer, high-resolution video, and enhanced coverage.

The white paper provides a detailed assessment of interworking functionalities and technical requirements, exploring both standardised and proprietary architectural models to connect LMR networks with MCX services. TETRA is presented as a representative case, though the same principles apply to other narrowband technologies such as APCO P25.

The paper concludes that the LMR–MCX hybrid model offers a practical, scalable, and future-proof strategy for enhancing mission-critical communications—ensuring operational resilience, user adoption, and ongoing capability enrichment throughout the migration journey.

“Congratulations all the members and industry experts from TCCA who contributed to the preparation of this important white paper,” said TCCA CEO Kevin Graham. “End users need hybrid co-existence or graceful transition of critical networks to ensure functional and operational interoperability. Standards based IWF will be essential to delivering this enhanced capability. TCCA supports harmonising  a multivendor approach.”

Read/download the white paper ‘Interworking Function (IWF) Interworking of LMR networks with 3GPP Mission Critical Services’ here

Image courtesy of Capgemini