In the near term, the ability to link MCPTT services with legacy LMR system will play a crucial role in allowing agencies to pursue a smooth migration path for mission-critical voice, Patel said.

“Interoperability—that is the key thing,” Patel said. “If you want any user to start using broadband service, you’ve got to have interoperability. Without interoperability, nothing will work.”

In June, Texas A&M University will host the second ETSI plugfest that is designed to provide an environment for MCPTT vendors to work with each other to address any interoperability issues.

Interoperability between existing LMR systems and PoC is a major driver for the surge of PoC used by public safety today, because it lets users access the LMR system from a much greater coverage footprint than with traditional LMR. However, expense is proving to be a significant barrier, particularly when agencies want to use an ISSI gateway to provide a link between a P25 system and a broadband LTE network.

“ISSI pricing runs from $30,000 to $500,000, depending on who the vendor is—that’s a huge gap,” longtime wireless analyst Andrew Seybold said during an IWCE 2018 panel. “And, at $500,000, nobody can afford it.”

Will public-safety agencies migrate to MCPTT as a primary mission-critical voice solution and abandon their LMR systems?  A growing number of industry experts believe that such a migration will happen, although there is still considerable debate about when the transition will occur.

However, public-safety agencies should beware of any vendor that promises a quick transition to MCPTT, according to Anna Ossa, associate director of product management for Verizon Wireless.

“We will start seeing features later this year that get us closer to that mission-critical-push-to-talk standard,” Ossa said during an IWCE 2018 session, reiterating Verizon’s plans to offer MCPTT services. “But if anybody’s telling you that mission-critical push-to-talk is going to be available anytime in the next 12 months, you should ask again.”

No industry experts believe such a transition will happen in the near term, but an increasing number believe the migration is almost inevitable. Given the long-term financial and resource commitments associated with LMR networks, the development of FirstNet and MCPTT promise to impact government’s budgetary decisions soon.

“I personally believe that the number of LMR RFPs going forward will start to dramatically reduce,” Sonim Technologies CEO Bob Plaschke said. “Why would you possibly go to your constituents and raise tens of millions of dollars to build out a hardened network when, indeed, the federal government has authorized and empowered a company like AT&T to do exactly the same over the next 10 years?”

Motorola Solutions’ Patel said that a key component of an LMR-LTE transition will be that first responders have to be confident that MCPTT will work well for them.

“First, the network needs to be hardened, and the application needs to be compliant to the standards and performance,” Patel said. “On top of that, the user needs to feel comfortable with those services. So, I believe there initially will be a lot of years of augmentation and that there will be a lot more new subscribers who are not using those services to get on board to increase the overall subscriber base.

“Over time, I think it’s going to be slow. It could take more than 10 years, but nobody knows.”