Dallas/Fort Worth International Airport personnel will be able to utilize the ESChat push-to-talk-over-cellular (PoC) solution to communicate with other PoC users and subscribers on the EF Johnson-built P25 network, according to ESChat President Josh Lober.

Lober said the arrangement leverages the P25 Inter RF Subsystem Interface (ISSI) standard-based technology to let smartphone users with ESChat engage in fully encrypted push-to-talk conversations with users of the airport’s P25 users.

“It gives them the ability to perform secure push-to-talk calls from Android- and iOS-based smartphones to P25 radios, whether the smartphone users are on LTE, Wi-Fi or even 3G—regardless whether they are in the P25 coverage area,” Lober said during an interview with IWCE’s Urgent Communications. “So, supervisors at home can monitor and communicate securely with radio users on the [airport] site.

“Because we are using standards-based interoperability—ISSI—to the core, we have full capability to interface with the Zetron console that’s on site. From the perspective of the person sitting at a console position, it’s transparent to them, whether they’re talking to a radio user or an LTE user. All of the features are the same—P25 user ID persists through the LTE side to the P25 side.”

Enterprises seeking such an integrated LTE-LMR solution are becoming increasingly commonplace in the market—and ISSI is a logical gateway to enable interoperability, Lober said.

“We’re seeing more and more RFPs and RFIs that are requesting information and proposals to interface with P25 via ISSI,” he said. “We want to emphasize the importance of the promotion and utilization of standards-based protocols to facilitate interoperability. And this is not just from the LMR-to-LTE side; this is between all systems.

“There is no defined specification, but the obvious one is ISSI. This is why companies like us have invested in it, because it allows us to provide full capability when interfacing between—in this case—our PTT network and a P25 network. By the same token, we can connect—via ISSI—to another LTE PTT vendor, if they have ISSI, and get that same benefit. That’s what we would like to see.”

Many industry analysts project even more integration between P25 and PoC solutions as FirstNet’s nationwide public-safety broadband network (NPSBN) is deployed in earnest during the next several years. Contractor AT&T’s commitment to provide priority and preemption to public-safety FirstNet subscribers could be a boon to over-the-top applications like ESChat, which previously found it challenging to provide performance assurances during times of heavy traffic at a network cell site, Lober said.

“With FirstNet initially going out with indiscriminate priority or preemption, any over-the-top vendor can take advantage of that capability, including ESChat,” Lober said.

“If vendors can take advantage of QPP [quality of service, priority and preemption] and create offerings that are more in line with the desires of public safety—whether they’re for mission support or mission critical is up to the agency—the important thing is that we need standards-based interoperability.”

Last year, ESChat announced that it would develop a version of the PoC application that would include both its current protocol and the mission-critical-push-to-talk (MCPTT) protocol. Although ESChat has “started down that path with the full intention of completing it,” Lober said there are significant business-model issues that over-the-top PoC vendors need to be answered by FirstNet and AT&T.

Lober said he would like to see more information about the business case associated with applications being part of the FirstNet/AT&T application store. But the bigger question revolves around the access to the application server in the FirstNet system, he said.

“Will they expose the interface for others to use?” Lober said. “And, if they do, will there be a charge?

“From a business perspective, there’s no information coming from FirstNet with regard to access to the application server—whether it’s going to be included with the network fees, if our customers are going to have to pay a premium, or if we’re going to have to split some fees. We just don’t know the business case.”