Plans for FirstNet MCPTT unveiling ‘all on track,’ AT&T’s Sambar says

BALTIMORE—AT&T testing of 3GPP-compliant mission-critical-push-to-talk (MCPTT) technology is “going really well” and the carrier plans to offer the service later this year from multiple providers that will be announced separately, according to an AT&T executive.

Earlier this year, AT&T stated that FirstNet users will be able to subscribe to MCPTT services from multiple vendors that are “fully compliant” with the 3GPP standard during the second half of next year. Chris Sambar, AT&T’s senior vice president for the FirstNet program, said those plans are still in place.

“[FirstNet users] will have multiple choices,” Sambar said during an interview with IWCE’s Urgent Communications. “We’re going to have one launch, and then we’re going to have another one after that.”

AT&T will reveal the identity of its two MCPTT vendors in separate announcements, although no specific dates have been released yet, Sambar said, expressing particular enthusiasm about the vendor that will be the subject of the first MCPTT announcement.

“Internally, all of the dates that we’ve laid out over the past year with our MCPTT provider, nothing has changed—it’s all on track,” Sambar said during an interview with IWCE’s Urgent Communications. “They’re doing a very nice job. I’m very excited actually. I’m trying not to get too excited about it, … but I’m really excited about it.

“The vendor we’re working with, they are … very focused on this space and developing solutions for this space—apps, devices and software … They’re putting a lot of energy [into it], and they’re very enthusiastic about getting into this space. They’re very serious about it.”

Sambar said he is encouraged by the results of MCPTT testing to date.

“The testing is going well,” he said. “I actually saw the app on someone’s device the other day—it looks really good. There are still some minor tweaks to make, but it’s going really well overall.”

Sambar said he is confident that public safety will like the voice quality of MCPTT, as well as the heightened security associated with the service.

“On our EPTT product today, the voice quality on that’s better than LMR,” Sambar said. “MCPTT is going to be even better than that. I don’t want to confuse it with priority and preemption, but it’s prioritized through the network.

“When you build it within the actual core of our network, which is what we’re doing, … you’ve got the direct connections between the equipment [in the core]. You’re going to have a lot better voice quality and a lot higher security, because now it’s riding on the FirstNet core with enhanced security. It’s going to be really nice.”

Sambar said the FirstNet MCPTT offerings will be compliant with the 3GPP standard for the technology.

“It definitely will,” Sambar said. I can tell you that the first one that’s going to launch definitely will. And, if anyone makes one that’s not, it will not be a FirstNet-approved app.”

Sambar clarified that FirstNet users will not be prohibited from using other push-to-talk applications.

“That’s not to say that you can’t use it on FirstNet—you still can use any over-the-top app,” Sambar said. “You use whatever apps you want. You can put whatever apps you want on your device—it’s fine. But it won’t be a FirstNet-sanctioned app, if it’s not 3GPP-compliant.

“And our people will tell the customer, ‘You can use that app, if you want, but just understand that it’s not 3GPP-compliant.’ But anything that we launch officially that’s embedded in our network will be 3GPP-compliant. That’s very important to us, and we’ve been saying that for two-and-a-half years now.”

Two of the biggest challenges associated with delivering MCPTT have been enabling direct-mode communications and large group calls. Proximity Services (ProSe) is the 3GPP standard for direct-mode communications between LTE devices without the need for connectivity to the network core. Broadcast services to support efficient group calling are enabled by the 3GPP specification for Evolved Multimedia Broadcast Multicast Services (eMBMS).

Sambar said that FirstNet MCPTT services will support both features, although not necessarily when they are first unveiled.

“ProSe will come a little bit later, and eMBMS will come a little bit later than that,” Sambar said. “The eMBMS isn’t required at the initial launch—once the service scales is when you really need eMBMS, for large broadcast calling in dense areas.

“ProSe is a challenging feature. It’s never been done before on a phone—it has been, but it’s not been done en masse, like we’re trying to do it. We will launch that, and I think that’s going to be really good. It’s going to be a game changer for public safety, I think.”

One difficulty associated with ProSe is the lack of chipsets available in the industry that support the function. Samsung has publicly stated that it has a ProSe chip that has been used in South Korea, but no information about the performance of ProSe has been released to date.

And the performance of ProSe has been a topic of considerable scrutiny within the public-safety community. Even if the technology works, ProSe’s usefulness to first responders has been questioned. After all, an LTE device with an internal antenna that typically transmits with 200 milliwatts of power is not expected to provide the type of direct-mode range that first responders have today with LMR portable devices that feature large external antennas and maximum power levels of 3 watts and 5 watts.

However, proponents of MCPTT have noted that the need for direct-mode communications for first responders could decrease in the future, as LTE and 5G networks increasingly become more available. In addition to larger terrestrial buildouts, the prevalence of various deployable technologies—from COWs and COLTs to “bring the network with you” solutions in Pelican cases and backpacks—could significantly reduce the need for direct-mode communications from LTE devices.