Ericsson announces MCPTT support, including eMBMS LTE broadcast, IOPS functionality

Ericsson has announced a new critical-communications portfolio that includes two key capabilities needed for 3GPP-standard mission-critical push to talk (MCPTT) to become a viable alternative to LMR: LTE broadcast and the ability for a cell site to support local communications without connectivity to the main network core.

Jason Johur, Ericsson’s strategy and market-development director for mission-critical and private networks, said that Ericsson’s Critical Communications Broadband Networks initiative launched last week is the result of the vendor’s efforts deploying critical-LTE solutions in recent years for customers like Southern Linc, the communications arm of the Southern Company utility in the southeastern U.S.

“We began deploying those back in 2017,” Johur said during an interview with IWCE’s Urgent Communications. “What we did last year is take the learnings from those deployments and make further enhancements, which we have been pushing through the standards. Those enhancements, in turn, are part of our portfolio this year.”

One key capability implemented at Southern Linc that is of particular interest to the public-safety community is Evolved Multimedia Broadcast Multicast Services (eMBMS), which is also known as LTE broadcast, Johur said.

With eMBMS, a network provider can broadcast communications—notably for public safety, MCPTT group calls—much more efficiently than it could by connecting to each group user separately via unicast technology. In fact, many industry experts have asserted that MCPTT could not be considered as an LMR alternative until eMBMS.

“We’ve integrated eMBMS,” Johur said. “There are at least three customers that are using that who need that in order to deliver mission-critical push to talk.”

Another technical challenge for MCPTT is the fact that LTE communications require each device to link back to the LTE network core—the evolved packet core (EPC)—or the device effectively became useless.

Carriers have become better about distributing EPC functionality in geographically diverse locations, but the potential for a device to lose all functionality when connection to the core is lost has been a big concern. That’s particularly true for users of land-mobile-radio (LMR) systems with base-station sites that support a “graceful degradation” to repeater mode when connection to the central controller is lost. While in repeater mode, an LMR site lets users within the site’s coverage area to continue communicating with each other, although they cannot talk with the broader network until the central-controller link is re-established.

This LMR-like repeater functionality was established within LTE by 3GPP in a standard known as Isolated E-UTRAN Operation for Public Safety (IOPS), but it has not been announced publicly as being deployed in real-world settings on LTE base stations (eNodeBs).

Johur said Ericsson is prepared to change that by making IOPS commercially available.

“We’ll have IOPS toward the tail end of this year,” Johur said. “We’ll have a number of early deployments of that, so that will be an important first there.”

At the heart of the IOPS solution is the notion that LTE network operators “push out some of that core capability out to the site, and that capability will support multiple eNodeBs,” Johur said.

Theoretically, an LTE network operator could install this IOPS core capability at every cell site, but that may not be practical, Johur said. With this in mind, the IOPS core functionality is designed to support not only communications at a given cell site but also those at surrounding cell sites that also may have lost connectivity to the main network core, he said.

“Provided that you’ve got transmission connection between multiple eNodeBs, you can use one of these distributed cores, so to speak, to support multiple eNodeBs with IOPS capability,” Johur said. “So, you can host locally a push-to-talk application and other applications that are needed at a local level.”

Johur said that Ericsson is deploying critical-communications LTE networks with quality-of-service class identifier (QCI) technology that lets network providers designate the quality of service, priority and preemption (QPP) for each packet on the network, as dictated by policy.

“[QCI is] basically the mechanism that gives you quality of service over the network,” Johur said. “There is an identifier that is given for every stream of information that runs over the network and different quality-of-service characteristics associated with that, such as an acceptable bit-error rate, reliability and latency, so the network will guarantee that the information is maintained at that service level.”

As an example, voice communications likely will have one of the highest service levels and be given high priority on most LTE systems, while other applications that are less latency-sensitive or of less importance could be transmitted at lower priority levels, Johur said.

“You can basically partition your applications across the network across those different QCIs, depending on priority, so you know that the network is always prioritizing the most important traffic over that network,” he said. “That traffic could be application-specific, or it could be user-specific or role-specific, so there are a number of tools there that you have.”

Johur said the combinations of these capabilities is promising for Ericsson, network operators and end users of critical-communications solutions like MCPTT in the future.

“eMBMS is here; IOPS is here,” Johur said. “We’ve also implemented the full suite of mission-critical QCIs, as well. We have that as of the end of last year.

“To fully implement mission-critical push to talk, you need the QCIs. And, unless you’re operator has hundreds of megahertz of spectrum, you also need eMBMS. With those two combined and compliance with 3GPP Release 13 and above, we have a strong offering there.”

Ericsson has participated in face-to-face MCPTT plugtests during the past two years and plans to do so again this year, Johur said. Meeting the demanding key performance indicators (KPIs) outlined in the MCPTT standard is difficult, but Ericsson’s LTE networking knowledge has positioned the company well, he said.

“You have to optimize both the network and the device to get the KPIs that we know our customers demand,” Johur said. “We have integration labs where we put that together and validate it, so we know that we can meet the KPIs from the customer.

“It’s not possible to do it from over-the-top applications. Over-the-top applications are fine for certain customers with slightly more relaxed requirements for performance. But, when it comes to mission-critical customers, the performance needs to be at another level.

“It requires these mission-critical QCIs to be in place in the network. You need an application that can use those QCIs and have the relevant interfaces into the network. You also need the application running, optimized on the device. Only when you’ve done all of that can you meet the SLAs that we know we need to hit.”

Ericsson has built Southern Linc’s critical LTE network, but the utility is utilizing a “third party” push-to-talk-over-cellular solution, Johur said. Ericsson is in the process deploying a pilot in two regions of Spain that will support a fully compliant MCPTT service, he said.

Johur identified Ericsson’s clear path to meeting MCPTT requirements for performance when an LTE device is connected to the network EPC or an IOPS core. As for addressing the need for MCPTT to support direct-mode or device-to-device communications, Ericsson is pursuing multiple paths in search of solutions, he said.

Johur said the first is LTE proximity services (ProSe), which is part of the 3GPP LTE standard for device-to-device communications. Ericsson is working with vendors like Samsung—a vendor that has publicly announced that it has a chipset that supports ProSe—to help develop a useful solution, he said.

“We continue to work with those vendors, and I am very positive about further developments this year,” Johur said. “From Ericsson’s perspective, we are working with those device vendors that are trying to bring that capability to market, to commercial release. Hopefully, there will be some new news on that later on this year.”

But many public-safety advocates question whether ProSe could ever provide a direct-mode voice alternative to LMR, which typically features devices that boast a large external antenna and transmit with 3 watts to 5 watts of power. By comparison, most LTE devices have an internal antenna and transmit at 0.25 watts, so any LTE device-only direct-mode solution would have to overcome a significant physics disadvantage in comparison to LMR.

Meanwhile, Ericsson is working with LMR vendors that have multimode LTE devices—and are seeking more partners willing to develop such solutions, Johur said.

“We’ve worked with some existing PMR vendors that have a multimode device—LTE capability and DMR capability,” Johur said. “Some of those device vendors have launched that product a number of years ago, but the two functions within the device were not integrated well together.

“We’ve worked with them to integrate those capabilities to make them as seamless as possible to the end user. So, the end user now has a multimode device—it will operate in LTE or DMR, in this respect. Behind the scenes, we’ll work between those two, depending on which of those two connections are available. We’ve worked with some device vendors in that space to prove that is possible. We can do the same with TETRA or P25 device vendors; we’ll happily work with them on that.”

Meanwhile, some industry sources have pointed to 3GPP standards progress in the vehicle-to-X (V2X) standard and wondered whether that technology could be adapted to meet public safety’s need for an effective LTE direct-mode voice technology. Johur acknowledged the conversations but said that considerable work would need to be done before V2X could be a considered a voice alternative.

“I know everyone is looking at V2X, including FirstNet,” he said. “That would need to evolve, in order for it to be suitable for voice. Those in the industry know that, so I think there is discussion going on within the standards around that. But still, a number of customers in public safety are pushing for enhancements to ProSe and then making that a reality.”