Most expect eventual public-safety transition to MCPTT over LTE, but timing remains in doubt

Sambar has stated that AT&T plans to complete its deployment of the nationwide FirstNet system in most of the country much sooner than the five-year schedule in the contract would suggest. AT&T expects to install equipment supporting service on 700 MHz Band 14—the spectrum licensed to FirstNet—on about one-third of all AT&T sites by the end of this year.

Most industry analysts believe MCPTT can be an effective solution for mission-critical voice when users are connected to a broadband system with QPP, such as FirstNet. However, there are significant doubts whether the proximity services—the 3GPP standard for direct-mode operations—will meet public safety’s needs, particularly in terms of the coverage range from a LTE device that operates at a fraction of the power used by LMR portables.

LTE device manufacturer Sonim Technologies recently introduced new rugged smartphones that support a module that enables direct-mode communications on 900 MHz unlicensed frequencies that leverage LoRa technology at up to 1 watt of power—more than commercial LTE devices but still less than most LMR portables.

While the Sonim direct-mode module showcased a new technological possibility—previously, most LTE direct-mode discussions had been limited only to the proximity-services standard—many noted that the solution utilizes a spectrum frequency and a technological protocol that public safety does not use today for mission-critical voice, limiting its practical use in the near term.

Bob Escalle, vice president of Sonim Technologies’ public-safety market segment, acknowledged that the 900 MHz module is less than ideal for first responders and said Sonim Technologies is pursuing development of a direct-mode solution that leverages P25, the LMR technology standard for U.S. public safety.

“We’ve actually taken a P25 module and put it onto a smartphone,” Escalle said during an IWCE 2018 session. “We’ll be supporting multiple bands on a smartphone device as an option. So, we have 900 MHz ISN unlicensed band direct-mode capability, and we will also have a P25 option, as well.”

Another key issue facing MCPTT is interoperability, both within the broadband arena and with legacy LMR systems.

Currently, there are multiple PoC solutions, and many of them have been linked to LMR networks via gateways based on standards such as inter RF subsystem interface (ISSI), console subsystem interface (CSSI), bridging systems interface (BSI) and radio over IP (RoIP). However, the PoC offerings now do not support inherent interoperability between vendor solutions—or even within a vendor, if the PoC service is offered by different carriers.

MCPTT is expected to address this issue, which will be critical to adoption, according to Kris Patel, Motorola Solutions’ vice president of unified communications.

Patel said he has been tasked with overseeing development of Motorola Solutions’ MCPTT efforts. Although Motorola Solutions will deploy its WAVE 7000 broadband and Kodiak Networks—the company co-founded by Patel that was purchased by Motorola Solutions last year—push-to-talk solutions separately “to make sure we fulfill our customer commitments” in the near term.

Meanwhile, Motorola Solutions has started the process of taking “the best of both breeds and [integrating] them into a single platform” and offer packages geared to meet the specific needs of a vertical sector, Patel said.