DENVEREnabling interoperability between the FirstNet public-safety LTE core being built by AT&T and the LTE cores of Verizon or other carriers is feasible technically, but doing so would be a departure from the FirstNet request for proposals (RFP) and could introduce security issues for public safety, according to an AT&T executive.

“They [FirstNet officials] built the RFP that specified a single nationwide core—you couldn’t have multiple cores,” Chris Sambar, senior vice president of AT&T – FirstNet, said yesterday during an interview with IWCE’s Urgent Communications. “From a technical standpoint on AT&T’s side, you can get any network to talk to any other network. The question is: What seams do you create, and what security risks do you introduce?

“That’s our concern with interoperating with other cores, because there’s been no suggestion that we will introduce any other cores. There will be a single, nationwide interoperable core. That’s the safest, most secure way to do this, and so that’s the way we want to do it. So, I’d be real hesitant to mix and match different traffic across different core networks.”

Whether an opt-out state should be allowed to partner with a vendor that used a separate LTE core for public-safety traffic was a hot topic in the FCC’s recent interoperability proceeding regarding the agency’s review of opt-out applications. Ultimately, the FCC deferred the issue to the National Telecommunications and Information Administration (NTIA), which is the federal-government organization that oversees FirstNet.

“Essentially, [the core decision is] with FirstNet, and FirstNet’s made it clear that there will be one nationwide, interoperable core, period,” Sambar said. “That’s the assumption that we’re operating under. Any other details on that is a FirstNet question.”

Earlier in the week at APCO 2017, FirstNet CTO Jeff Bratcher said that “there’s no core interconnect between the big carriers right now” and emphasized the importance of the dedicated FirstNet LTE core to public-safety subscribers.

“It’s critical for the security of public safety’s traffic,” Bratcher said during an interview with IWCE’s Urgent Communications following a presentation on the APCO 2017 show floor. “It will be secure from the device, based on that network identifier, to our core. So, we will know and secure all public-safety traffic—both the user traffic and the control-plane traffic.

“The rest of the commercial networks on the other identifiers, we don’t have to worry about. That’s the way we’re implementing this with that multi-operator core network. AT&T’s operating the FirstNet core and their commercial core in parallel. So, commercial traffic goes to its core, public safety to our core. Should something happen on one of our core elements for FirstNet, it will fail over and we can leverage the commercial backup side, if we need to.”

Sambar echoed this sentiment.

“[FirstNet public-safety traffic is] on a secure evolved packet core with encryption, which is very important,” Sambar said. “But, if [traffic] leaves the FirstNet network, you’re taking your chances.”

Sambar’s comments came the day after Verizon announced that it will build a dedicated public-safety LTE core network for its first-responder customers in 2018, as well as provide public safety with prioritized—and eventually preemptive—access across its network beginning this year.