PTT-over-cellular solutions make compelling case for LMR replacement, webinar speakers say

Trials of mission-critical push-to-talk (MCPTT) services meeting the 3GPP standard are expected to begin next year, but push-to-talk-over-cellular (PoC) solutions have evolved enough during the past year to be considered as an LMR replacement for non-public-safety users, panelists said yesterday during a webinar exploring the topic.

Efforts by wireless carriers and PTT vendors to make PoC solutions more reliable during the past year have made them a viable alternative to LMR networks—and they are available immediately, according to Emil Olbrich, president of the Primelime consulting group, who spoke during a webinar sponsored by Anritsu, Avtec, ESChat and Zetron.

“The PTT [services] offered on wireless networks today are radically different, and this has really happened in the past year—it’s far beyond what has been offered previously,” Olbrich said during the webinar. “The PTT services that are offered now on LTE networks and devices can not only be instantiated, but they can be operated and maintained as a software module as a virtualized function—or a VNF—in the network.

“This is not something that is coming in the future or is a proposed item. It’s actually happening now with live traffic. So, virtualized PTT systems are operating in a cloud-hosted environment serving multiple operators … in the United States and Korea.”

One PoC example is in Fairfax County, Va., which has transitioned its non-public-safety government workers from an analog LMR system—public-safety users still depend on a P25 system for primary communications—to a PoC solution offered by AT&T, according to Michael Newburn, wireless manager for Fairfax County. By moving to the PoC solution, Fairfax County expects to save more than $15 million in upfront costs to build a new LMR network and about $2 million per year in annual operating expenses, he said.

But the key to the move was the fact that Fairfax County officials were comfortable with the coverage and performance of the carrier network, which had been used for eight years to transmit data for the county’s public-safety users, Newburn said.

“That’s the driving factor, obviously,” Newburn said during the webinar. “If you’re going to do any of the push-to-talk services today, you’ve got to have a reliable network to do that.”

Making the decision easier was the fact that the cellular network provides Fairfax County’s general-government users with greater capacity and coverage—particularly indoors—than an LMR system would, as well as the ability to leverage encryption, workforce-management and location-based applications on broadband cellular devices that were purchased previously, Newburn said.

“Our two-way radio system today does only one thing, and that’s push to talk,” he said. “So, it was a natural fit for them [Fairfax County’s general-government employees] to take that same device that they already carry and add push to talk on top of it to give them a full package.”