Central Pierce Fire & Rescue Testing Integrated LMR/VOIP PTT

By James Careless

Push-to-Talk (PTT) is a vital function for first responder communications systems, be they on land mobile radio (LMR), commercial wireless (5G/4G/LTE), or Voice-Over-IP (VOIP via commercial wireless carriers and available Wi-Fi).

The problem is that each of these communications platforms has their limits for first responders due to range and reception issues. Fortunately, commercial wireless tends to cover gaps in LMR coverage, while LMR (and satellites) can reach into areas outside of commercial wireless footprints. This is why a communications platform that includes LMR, commercial wireless, and Wi-Fi (and satellite phone if need be) can be a powerful solution for first responders.

This fact has been seized upon by Central Pierce Fire & Rescue (CPF&R), which serves an 84 square mile area encompassing the communities of Parkland, Midland, Spanaway, South Hill, Puyallup, Summit and Frederickson in Washington State. Not only have CPF&R chosen a combined LMR/VOIP over commercial wireless platforms for their EMS/fire vehicles and officers, but the department is also testing an integrated PTT solution for their users, allowing them to go from one system to another as needed to ensure connectivity.

“One of the nearby LMR network owners is the City of Tacoma, who runs an 800 MHz system,” explained CPF&R Deputy Chief Brent VanKeulen. “I noticed that Tacoma Radio had deployed ESChat, which is a PTT over IP solution, and connected it to their 800 MHz core. This allows their radio users to communicate with cellphones and vice versa. I myself have ESChat on my work cell phone. I can listen to all of our radio traffic and transmit across their 800 MHz system.”

This deployment got him and CPF&R Fire Chief Dustin Morrow thinking: What if there was a way to integrate their existing LMR system with VOIP over commercial wireless, and provide unified access to it all via integrated PTT? “After all, once you get the voice into the internet, then really it opens the door for interoperability: It breaks down all the barriers between ‘am I in the state of Washington or am I in the state of Texas?’” said Deputy Chief VanKeulen. “So anywhere there’s an internet connection, you can have PTT, as well as bridging any gaps in LMR coverage.”

That’s not all: Adding VOIP means using wireless broadband channels, which can be used to transmit life-saving data to and from CPF&R vehicles. “And it’d be really great if we could stream video around as well,” he said. “So that wondering led us to a solution where we actually have all three cell carriers inside of the fire apparatus — because all three have their coverage weaknesses — ensuring that our vehicles are connected to Dispatch at all times. They, in turn, could support integrated PTT.”

This is why CPF&R selected wireless communications equipment from Dejero, which can support multiple SIM cards in a single unit. “Then we have a FirstNet, Verizon, and T-Mobile SIM cards inside of a gateway that blends that connection into a single IP address,” said Deputy Chief VanKeulen. “That’s what connects us to the outside world for our integrated PTT tests.”

Of course, making this happen — and authorizing the funding for it — required approval at the highest level. “We’re governed by a five-member board of directors who’s responsible ultimately for CPF&R’s finances,” Chief Morrow said. “So we first had to seek authorization from them about the expenditure to acquire the test equipment, which in the state of Washington has some unique aspects of how we procure and purchase. But we did gain authorization from our Board, and worked through our Legal Counsel in the process to procure the equipment.”

This test equipment includes the Dejero 211 GateWays for connecting CPF&R vehicles to Dispatch via commercial wireless, plus small Kymeta satellite dishes that link them to the OneWeb low Earth orbit (LEO) satellite constellation as a backup. “Overall, we’re really relying on the commercial network to provide us with high speed data,” said Deputy Chief VanKeulen. “And where there’s high speed data, there’s critical PTT, which we’re rebroadcasting from our Battalion Chief units to our firefighters via LTE. We’re also testing LTE commercial boosters to solve our in-building penetration problems.”

As for CPF&R’s firefighters? “Each will carry a Tait Axiom radio that has a SIM card in it, and a PTT lapel microphone,” he said. “It’s small, it’s light, and has just three controls on it: A PTT button, a scroll button, and a volume channel selector. It’s the right form factor for our Firefighters, who aren’t going to carry cell phones or pager-like devices for PTT.”

So far, CPF&R’s integrated PTT solution is flying through its testing phase, with a high likelihood of full deployment in the future. “We’ve been talking about the collision between LMR and LTE in first response for decades, and now here it is,” said Chief Morrow. “The integrated technology does truly work, and it works in a way that is really robust and brings many, many other benefits to the table.”