Equipment supporting standardized mission-critical voice over LTE (VoLTE)—including off-network push-to-talk functionality—should be commercially available in 2018, while mission-critical voice solutions outside the standard could be offered in the marketplace years before that, an Alcatel-Lucent official said last week during an IWCE session.

While some commercial carriers in the U.S. have deployed LTE nationwide for data offerings, telephony voice services typically have remained on the carriers’ 2G and 3G systems, according to Kenneth Budka, Alcatel-Lucent’s chief technology officer (CTO) for strategic industries. But carriers want to migrate voice services to LTE, so they do not have to pay for the operation and maintenance of multiple network platforms, he said.

Public-safety agencies will face a similar scenario in the future, as they try to decide how long to maintain simultaneous operations of land-mobile-radio (LMR) networks for mission-critical voice services and pay subscriber fees to a carrier or FirstNet to access an LTE network for data, Budka said.

“Running two networks is darned expensive,” Budka said during an IWCE lunch-and-learn session examining VoLTE. “It would be much cheaper if you could do it on one network, provided that you can provide mission-critical services.

“If we did, in the future, have a FirstNet [LTE system] that was capable of providing voice services, the money that we currently spend on land mobile radio could be plunged into LTE. That means better coverage. That means a broader ecosystem. That means lower costs overall for taxpayers and better coverage for first responders and citizens.”

In addition, mission-critical voice over LTE promises to provide much better voice quality than is possible with an LMR network, largely because of rapid advancements in codec software, Budka said.

“You are able to do a lot more, first, because you have more bandwidth [in a broadband LTE system],” he said. “But, even with the same amount of bandwidth, the codec technology has gotten incredibly good over the last three or four years.

“If you look at the codecs that are out there for LTE today, the performance is superior to P25 codecs. There’s also the ability to support hi-definition codecs. A lot of the VoLTE services that carriers are introducing are almost-wireline-quality voice. That’s one of the drivers to release LTE in the commercial world is to cater to those users that want a very high-definition voice user experience, and [carriers] can provide that using VoLTE.”