First responders in the United Kingdom (UK) are slated to complete the communications transition from the Airwave TETRA system to the LTE-based Emergency Services Network (ESN) in 2020, although LMR technology likely will continue to be used when off-network voice communications are needed, according to a UK official.

Gordon Shipley, program director for the Emergency Services Mobile Communications Programme at the Home Office, said public-safety users are expected to begin migrating to the ESN LTE network during the middle of next year, with the transition slated for completion during the latter half of 2020.

When completed, the ESN will provide the 97% geographic coverage and 99.86% availability metrics that the Airwave system provides today, with the benefits of broadband data and lower operational costs, Shipley said. Unlike FirstNet in the United States, the ESN does not have dedicated public-safety spectrum to leverage, so the system will utilize the commercial wireless network of BT-owned EE—operating on spectrum at 800 MHz, 1.8 GHz and 2.6 GHz—and services from Motorola Solutions.

Since early 2016, Motorola Solutions also owns the Airwave network, which is scheduled to be shut down at the end of 2019—although the TETRA system is expected to be needed into the third quarter of 2020 in a handful of regions, Shipley said.

Completing the transition to the ESN public-safety LTE network is important to the UK government, which pays Motorola Solutions about 400 million pounds annually for use of the Airwave system, Shipley said. The annual cost of the 3,800-site Airwave system is about double the projected cost of the 19,000-site ESN, he said.

“If EE and Motorola can’t deliver the ESN on time, then—of course—we run on Airwave, and we run on Airwave at a very expensive price,” Shipley said during a breakout session at the recent PSCR Broadband Stakeholder Meeting in San Antonio. “So, we’ve had to incentivize Motorola to not only deliver the ESN on time but also incentivize them to shut down Airwave at a time that we require—2020.”

Shipley said initial performance on the ESN test system has been positive.

“We’ve done priority and preemption,” he said. “We’ve proven it works on the reference system, which is built out … We’ve proved the push-to-talk [over LTE] works.”

While push-to-talk services on the network work well, Shipley said he is not as confident about off-network voice communications, also known as direct-mode voice. Although the 3GPP standards body approved the mission-critical push-to-talk (MCPTT) standard leveraging proximity services (pro se) in March 2016, testing of standardized solutions are just beginning. Samsung has a pre-standard version of MCPTT, but the signal range is about half the range of direct-mode voice using a TETRA handheld, he said.

Indeed, engineers worldwide have noted the physics challenges associated with direct-mode LTE, which typically operates at much lower power levels and at higher frequencies—and lesser propagation—than LMR solutions.

There are other challenges, as well, Shipley said.

“There’s a lot of question as to how direct mode of operations—or device-to-device [communications]—is going to work, particularly when it comes to users who go out of coverage, but they don’t realize they’ve gone out of coverage and the rest of the team don’t realize they’ve gone out of coverage,” he said.

“So, how do you go from where you think you’re connected to the macro network [and] re-engineer everything to move to a local, device-to-device arrangement for your team. There are a lot of issues that still need to be worked through for this to be fully successful.”