Study Item to Standardize PMR/LMR to LTE Interworking Moves to 3GPP SA6
Monday, April 18, 2016 | Comments
An industry group is working to standardize two-way radio and Long Term Evolution (LTE) interworking capabilities and submitted a study item to the Third Generation Partnership Project (3GPP) SA6 for potential inclusion in LTE Release 14 or 15.

The study item is the first step in pushing the issue of interworking professional mobile radio (PMR)/LMR and LTE networks higher on the priority list for 3GPP LTE public-safety requirements.

An Alliance for Telecommunications Industry Solutions (ATIS) ad hoc LMR/LTE interworking group, which submitted the study item, was formed last October and is discussing the transition of Project 25 (P25) and TETRA networks to LTE technology. The work on TETRA updates interworking requirements outlined in a European Telecommunications Standards Institute (ETSI) work item, said Malcolm Quelch, chairman of the ETSI working group on requirements for TETRA and critical communications evolution (TC TCCE).

In addition to the study item, the group will submit a terminology document and a gap analysis document providing insight into what interworking between the technologies is needed, in addition to the 3GPP SA1 requirements already captured. The terminology document addresses differences among P25, TETRA and 3GPP mission-critical push to talk (MCPTT) “so when we talk about emergency calls and user IDs, we’re all on the same page,” Quelch said.

“In the United States and Europe, the need was recorded, but essential MCPTT functionality came first; now that is being addressed, and we wanted to push this up in priority,” Quelch said.

The specifications work for MCPTT was completed at 3GPP meetings in March in Gothenburg, Sweden, and will be included in LTE Release 13.

The terminology document includes identity translation and call-routing scenarios. The TETRA + Critical Communications Association (TCCA) encouraged ETSI to include TETRA technology in the work.

“We can put in place a common terminology so that we understand what it means in each technology,” Quelch said. “There is good overlap between TETRA and P25, but slight differences in how things are named, and more differences in MCPTT.”

Interworking requirements were included in the requirements written in 3GPP SA1 some time ago, but they hadn’t found their way into standards released in SA6, the working group within 3GPP that defines specifications for critical communications. The gap analysis tracks updated requirements since the original SA1 document was developed. The document highlights the need for short data service (SDS) interworking for TETRA specifically.

A solicitation letter was sent to eight European organizations requesting updates on requirements for interworking, and six groups responded. Quelch said there is debate in the public-safety communications industry about whether interworking standards are necessary. Some organizations, such as the U.K. Home Office, plan a “big bang change” with plans to switch directly from TETRA to LTE.

“Most other organizations think that’s really too risky,” he said. “Many users expect to have TETRA alongside LTE for quite some time. We do need some interworking.”

He cited the Scandinavian countries, which plan to have TETRA and LTE working together for some time, and there will likely be different groups with different technologies operating at emergency scenes.

“There’s a view that legacy systems will stay in place for some time,” Quelch said. “That would be sensible because putting a new technology in place isn’t just about whether the technology is there and available — and it isn’t there yet — but changing the working practices to use the new technology will take some time. It makes sense to standardize the interworking with as much functionality as we can put into 3GPP.”

Quelch said there is an outside chance LMR/LTE interworking will be included in LTE Release 14, but it’s more likely to be part of Release 15. He said even with a 3GPP standard, there will likely be local adaption for either TETRA or P25 standards.

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Sandra Wendelken is editor of MissionCritical Communications and RadioResource International magazines. Contact her at

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