ESChat, Tait and Avtec demonstrate LMR-LTE full-featured interoperability via P25 ISSI, CSSI gateways

Lober acknowledged that communications between a P25 and the ESChat LTE-based PTT solution can experience some latency, because the LTE users may be connecting to the P25 system from a remote location and the PTT server may be housed in another remote location. However, the latency is not great enough to disrupt normal communications, he said.

“There is approximately 400 milliseconds of additional delay through the LTE network,” Lober said. “But, for the most part, it’s not perceivable for users, unless they’re sitting in a room with both a radio and an LTE device. In that case, they’ll hear a slight delay coming through the LTE device.”

Meanwhile, the potential benefits of leveraging broadband PTT are considerable. Lober noted that ESChat was utilized on Los Angeles Regional Interoperable Communications System (LA-RICS) 700 MHz Band 14 public-safety LTE system during the Rose Parade on New Year’s Day to offload non-mission-critical voice from the LMR network. That meant more tactical channels were left available to public-safety users on that network, if a large incident had occurred.

Lober said that he believes that discussions of utilizing LTE-based PTT solutions for mission-critical communications in the near future are premature.

“We are not pushing mission-critical use on the network. It’s not the right time—the devices aren’t ready, the networks aren’t ready, regardless of whether there’s a 3GPP spec or not,” Lober said. “But what you can do for non-mission-critical users [is] you can offload traffic from your radio network, allowing more channels to be available [for LMR communications].”

Leveraging LTE-based PTT effectively expands the coverage footprint of a P25 network, as well as allowing remote users in other states or countries to communicate with LMR users, Mazza said. If proper connectivity is in place LTE-based PTT solutions can provide different types of deployment scenarios, he said.

“The push-to-talk servers can either be also deployed in the premise, connected directly to the radio systems over ISSI and console systems there, or it can be deployed in the cloud—included in that option is really the ability to do cloud-based ISSI gateway,” Mazza said. “Tait’s been working with ESChat to be able to virtualize that as a server-based deployment that will be scalable to the gateway capabilities across the links and give deployment options to customers, which is really important as they choose whether it’s premise- or cloud-based communications.

“Oftentimes, the use is going to be over a short period of time or additional use for an event-based scenario, where they want to deploy it quickly and then tear it down to another deployment. Cloud-based communications gives you that option, as well operational cost models and things like that.”