AT&T picks Etherstack for IWF tech, makes VoLTE call over satellite

After a successful beta of Etherstack’s land mobile radio interworking function (LMR IWF) over the past 12 months, AT&T has selected the Australian-headquartered company as its 3GPP-compliant IWF supplier for a new FirstNet, Built with AT&T mission-critical solution. The IWF solution is being deployed into secure, highly available data centres across the US to provide crucial bridging technology between LMR networks and FirstNet — America’s public safety network.

IWF is a standard created by the 3rd Generation Partnership Project (3GPP) to enable interoperable communications between commercial wireless systems and private LMR networks. As a fault-tolerant network application that securely bridges traditional digital radio communications, LMR IWF can be used daily by first responders.

Etherstack’s LMR IWF solution was connected to digital LMR networks in multiple states during the beta, including those deployed by the largest LMR equipment manufacturers, and trialled by first responders to assess audio quality, security and essential service types like emergency calls and those made under duress. The first production-interoperable call between LMR and the FirstNet mission-critical solution utilising IWF was made in Fairfax County, Virginia.

Matt Walsh, AVP Product, FirstNet and Next Generation 9-1-1, AT&T, said, “As public safety’s partner, we are always looking for the best collaborators to innovate for first responders. We strive to create better platforms and evolve with the needs of public safety. Etherstack’s proven record will help us give America’s public safety community the flexibility to adapt to whatever emergency they might face.”

Etherstack CEO David Deacon added, “FirstNet, Built with AT&T is an innovator of mission-critical communications that is dedicated to public safety. The expansive network build, integration with other vendors and ease of end-agency provisioning is industry-leading. We are so pleased to work alongside AT&T on what is truly an industry-changing journey.”

The news was announced not long after AT&T separately revealed it had successfully completed the first ever native voice-over-LTE (VoLTE) call made through AST SpaceMobile’s Block 1 satellites with a standard mobile phone using AT&T spectrum and passing through the AT&T core network. According to the telco, this milestone paves the way for expanding mobile coverage to unmodified cellular devices in remote and underserved areas using satellite-direct-to-device technology. The service is planned for consumers, enterprise business, small and medium-sized business, IoT, and FirstNet.

“The goal here is to provide a basic level of connectivity — messaging, voice, low-bandwidth data, location services … while also offering mission-critical push-to-talk,” said AT&T’s Mohammad Baig, Lead Product Management & Development, at the recent APCO 2025 conference. “There are text-based services out there today. Our goal is to make it so that you have a bare minimum level of connectivity available to public safety in those areas where we have not been able to deploy terrestrial service.”

Image credit: iStock.com/PeopleImages