The Evolution of Public Safety: FirstNet and LTE

By Don Bishop

September 5, 2017

LTE’s designers made provisions for functions that have appeal for use with public safety communications. Manufacturers probably will include them when they make devices for use on the FirstNet public safety broadband wireless network.

With AT&T’s construction of a nationwide public safety broadband network on behalf of the First Responder Network Authority, or FirstNet, everyone in the United States will have network availability, according to Christopher Schenck, director of legal for Dali Wireless. The Long Term Evolution (LTE) high-speed wireless data network will use Band 14 700-MHz radio-frequency spectrum for a subscriber-based system. “Any state can opt into it or opt out of it,” Schenck said. “But states that opt out have to offer a state network compatible with the nationwide network.”

AT&T may use the Band 14 spectrum for commercial cellular traffic when it isn’t being used for public safety communications. Schenk said a lot of thought has to go into making sure that first responders have access to the network during an emergency. Steps to take include preempting commercial communications to give priority and access control to first responders.

“If the network is down and I need to get in touch with other first responders wherever I am, that’s where proximity services and direct communication among devices come in. With direct discovery, our devices can figure out that we’re both there. You can communicate one-to-one or one-to-many.”

— Christopher Schenck, director of legal for Dali Wireless.

Several municipalities and other areas built early versions of 700-MHz LTE systems, and none shares spectrum with commercial network operators. Schenck said he learned that during the 2016 Rose Parade in Pasadena, California, the Los Angeles Regional Interoperable Communications (LA-RICS) public safety broadband network saw no degradation of its accessibility and throughput. Yet, on the commercial networks, coverage levels went down when floats went by and observers would send video they recorded. According to the LA-RICS website, the organization’s broadband network will migrate to the FirstNet network, eventually.

With LTE proximity services (ProSe), public safety devices can initiate communication without performing a discovery procedure, because it is assumed that public safety personnel know each other’s whereabouts and can thus determine whether the other person is reachable for direct communication. Source: Nokia

Schenck said the LTE technology the FirstNet network will use a global alternative to APCO Project 25 digital radio communications and the Trans-European Trunked Radio (TETRA), which are not compatible with one another. He said LTE is a proven, secure system that is already in use with cell phones — and that’s part of its appeal, because public safety agencies may be able to use market power for better pricing on public safety products.

LTE’s high data rates enable critical features that Schenck said public safety agencies can use to their advantage. He said one such function would be location tracking — every first responder would have a location tracker on him or her when carrying LTE devices. Video capability will allow dispatchers and commanders at the station to watch events unfold in the field through body cameras. “Officers will be able to share video with one another, so everybody knows what’s going on from every different perspective,” Schenck said.

The ability for sensors worn by firefighters to send biometric information will help in monitoring their health and safety while they fight fires, Schenck said. Health care providers with patients in ambulances can send health information to the hospital for doctors to evaluate.

“The state of Ohio has a FirstNet group with a website where they made a video game with some augmented reality that allows participants to see what firefighters see,” Schenck said. “The game provides a map of a burning building and thermal imaging. You can see what firefighters face without such information, and then pop up the map and the thermal imaging to see the huge difference it makes in navigating the building.”

Proximity Services

Schenck identified two functions added to LTE specifically for public safety because they’re not part of the typical commercial architecture. One is proximity services. “If the network is down and I need to get in touch with other first responders wherever I am, that’s where proximity services and direct communication among devices come in.” Schenck said. “With direct discovery, our devices can figure out that we’re both there. You can communicate one-to-one or one-to-many.”

A second public safety function is relay services. The example Schenck gave is that if one person’s LTE device cannot reach a radio access point, such as a tower outside of a building, a second LTE device in the hands of another person could relay the signal if the second person’s LTE device can reach the tower. And, nearby LTE devices can relay among themselves if none of them can reach the network.

Schenck said that so far as he knows, none of the wireless device manufacturers are building units with the relay capability, but it is written into the LTE specification. “The relay capability is necessary for LTE to really do the job that it needs to do,” he said. “Another thing that was added for LTE is group communications. When you think about first responders, you think a lot about push-to-talk and the need for one first responder to talk with everyone else on the team, so LTE’s designers added functions for groups.”

With group communication comes the need for priority, preemption and control, Schenck said. “If I’m a regular firefighter and my boss wants me to shut up and wants to say something else, he’s got to be able to do that,” he said. “You have to be able to give people access and give people priority over other people, and all that is built into LTE.”

Mission critical push-to-talk is another special function that Schecnk said the LTE specification includes for public safety. It mimics the push-to-talk function in P25 and TETRA technology. A FirstNet testing laboratory in Boulder, Colorado, will focus on testing public safety features on LTE devices. “They want to make sure the mission-critical push-to-talk function and other public safety functions really work,” he said.

In partnership with NIST, the test lab will issue certifications for individual devices. Schenck said the lab also will provide training for first responders to use the various LTE devices.

Schenck spoke of an early adopter of LTE for public safety communications in Ohio, saying that it took about four months to set up the three sites involved. In view of how long it took to set up three sites, he questioned how long it would take to set up a nationwide network. He said the nationwide network would take time because it will be complicated and expensive.

Meanwhile, Schenck described tests conducted with the Ohio system, including a simulation of a response to a report of a missing person in a shopping mall. “With LTE, they were able to share a picture of the person with all the cops in the mall almost immediately, transmitting from one cop to all of the rest of them,” he said. “They were able to find the missing person in four minutes. In the old days, the search would have involved handing out printed photos to everyone or using a verbal description over voice radio, which isn’t quite the same thing.”

A second test simulated a park employee in a national forest pressing the man-down button on the LTE device. “Because the LTE device revealed the person was in a forest, instead of just sending an ambulance, they sent an emergency medical technician on an all-terrain vehicle,” Schenck said.

Schenck reported that the participants in the Ohio test said they liked the ability to share videos directly with each other instead of having to go through dispatch. He said they liked the speed of the data and the clarity of the images in the video. “Everything is high-definition 4K video, basically, so it’s awesome,” Schenck said. “What they disliked was the short battery life. Using so much data draws down the battery. They also complained about background noise when using the LTE devices outdoors. That probably was because the equipment had not been optimized. LTE has more than enough capability to deal with that.”

The Ohio system, which was sponsored by the state government and the Greene County government, has since been decommissioned to vacate the frequencies that the FCC designated for the FirstNet network.

Among other considerations that Schenck mentioned were the National Fire Protection Association’s fire code requirements for indoor wireless coverage, the potential for interference between FirstNet operations in the 700-MHz band and cellular operations in nearby bands, and whether distributed antenna systems should carry both commercial and public safety communications.

Schenck said he hopes to see some construction of the national network and the roll-out of LTE devices as early as next year. “The market has to get to the point where it makes sense for people to do it, and it’s not there yet,” he said. “It is going to take time, and there will be some overlap between the new network and existing P25 and TETRA systems that provide functionality already. As time goes by, public safety communications can shift over to LTE.”

On March 27, Christopher Schenck, director of legal for Dali Wireless, spoke at the International Wireless Communications Expo’s Network Infrastructure Forum during the in-building wireless session moderated by the author.

Don Bishop is the executive editor of AGL Magazine. He joined AGL Media Group in 2004. He was the founding editor of AGL Magazine, the AGL Bulletin email newsletter (now AGL eDigest) and AGL Small Cell Magazine.

A frequent moderator and host for AGL Conferences, Don writes and otherwise obtains editorial content published in AGL Magazine, AGL eDigest and the AGL Media Group website.