Public Safety Advocate: Part 2 — Wireless Networks and Devices for Public Safety, Even PTT Part 2

Last week in Part 1 of this Advocate, I covered a lot of history and hopefully provided insight into how long public safety has been looking for more good voice service. This week, we will take this further and discuss where we are today in more detail and where I think we need to be in the near future.

Along the way, we must keep in mind that working on behalf of public safety means all of us involved in public safety communications are working for public safety professionals in the field and we must be responsive to their needs today and into the future.

Talking to the Network

Many, including myself, want to see FirstNet and virtually every LMR system used by public safety to be interconnected and capable of functioning on a nationwide system. Looking at what is happening in the LMR and broadband worlds, we see a shift from how LMR devices have been controlled to perhaps how they should be controlled, e.g., a trunked LMR system where the user depresses the PTT button that sends a request for communications to the system. If there is an available channel, the system usually moves the entire group of users to that channel for their communications and then back to the control channel or its equivalent depending on the type of system.

While this is close to how cellular is implemented today, there are some significant differences. A cellular network either knows exactly where a field unit is or it cannot find the unit and understands it has been turned off or is out of range. Not only does the network talk to the device, the device must be in range to talk to the network.

When using any application on FirstNet, including PTT, the network and the device must be communicating. However, a handheld has lower power than the nearest cell site so it is often easy to run out of its range. Public safety asked for, and the FCC and 3GPP approved, a higher transmit level for devices in public safety Band 14 to provide solid communications farther from a cell site.

Establishing a true unified PTT communication system including FirstNet and LMR is made more difficult today because there are so many variations of PTT. The standard developed by 3GPP that is now available on FirstNet and several other broadband systems requires that the server or core of the PTT system be located within the network it serves. With “over-the-top PTT,” the server can be in a secure cloud or some LMR providers require moving the over-the-top server into their networks.

Solving PTT and future interoperability issues has more to do with politics than technology. There are ways to interconnect the 3GPP standard version of PTT with LMR systems. However, at this point, it is not nearly as easy to deploy PTT on FirstNet using the 3GPP standard and LMR when using an over-the-top PTT system.

Politics come into play because as FirstNet was being developed there was a big push by almost everyone including public safety to establish a common standard that would become used worldwide. The 3GPP standards body was tasked with development of the standard and its delivery was very late. A number of vendors have enabled the 3GPP standard in their radios (broadband devices) but today there are still a limited number of ways to connect LMR with the 3GPP standard. I believe we could and should solve this problem with a combination standard that uses an over-the-top application to talk to a 3GPP flavor of push-to-talk over FirstNet.

A truly nationwide interoperable PTT system running across FirstNet (Built with AT&T) could change how the public safety community uses all of the available communications networks. Perhaps we could use FirstNet as the preferred PTT system for multi-jurisdictional incidents. Since this network would be connected to virtually all existing LMR systems, FirstNet could provide multiple levels of usability and redundancy. Personnel in the field would not have to change channels (or groups) on their devices and PTT would once again become a tool they use but do not have to manage.

Today, seven or eight flavors of on- and off-network PTT are being used by ten vendors. In comparison, several existing PTT over-the top-providers are using the same flavor of PTT.   Then the number of LMR and FirstNet PTT users can be further broken down by vendor (data from reliable source).

Even though we do not have definitive numbers to put with each PTT vendor, we do know that several vendors have the majority of FirstNet PTT users. However, you will find that only two vendors account for most of these types of systems. Of the types of agencies that already have PTT over FirstNet and have integrated their own LMR systems into the FirstNet network, you will also find that only two vendors account for most of these systems.

Of course, there is always a caveat, and this one cannot be fixed overnight. Broadband PTT simplex, or off-network communications, are vitally important to public safety not only in the United States but around the world. So far, attempts to implement LMR’s tried-and-true, tested PTT simplex on broadband networks have not ended well.

Some people who solve this problem by carrying two devices will be happy with a cell phone and some will need a device that provides a variety of communications levels when they are at an incident or in the field.

If we had nationwide broadband PTT, perhaps some vendors that are building the next generation of higher-capacity batteries and more extensive multiband LMR devices could come out with LMR/FirstNet handhelds with screens large enough to be usable for FirstNet. I have been at many incidents where more than one-hundred simplex channels were required. It should be possible to build an LMR device that includes enough simplex to be useful (how much is enough?) and has fully functional FirstNet broadband network capability.

I see a hand in the audience waving! “How could they build such a device at a reasonable price?” he asks. FirstNet devices are affordable because they are built to attract consumers as well as public safety, meaning vendors can produce them in larger quantities at lower prices. At the same time, AT&T worked long and hard to convince cellular to build Band 14 into their standard devices to make the most of public safety interest.

One more idea that may or may not be valid is to also build in Family Radio Service (FRS) and use the devices like family service radios are used today.


Electric companies may say, “We have the grid, now we need to light it up.” The number of users signing up for FirstNet is growing by the month and we can make their tasks easier by marrying (not pushing) LMR and FirstNet together going forward. My priorities for this are:

  • Nationwide unified PTT over FirstNet
  • Off-network PTT that meets or exceeds requirements for simplex communications being used over LMR networks.
  • Link Next-Generation 9-1-1 (NG911) to the public safety grid so additional information can be sent to responders in the field in a timely fashion.
  • Bring together the too many databases of information sitting in servers that should be nearly instantaneously available to the first responder community.

Some will say I am an optimist; we can never accomplish these goals. However, looking back at where public safety communications was in 1930, where cellular was in 1973, and where both technologies are today, my bet is on making all this work better together.

There are, of course, some hindrances standing in the way of truly unified nationwide PTT. Every FirstNet device that can talk to LMR devices on an agency basis today and on every LMR network in the United States will help the public safety community be more efficient and safer in the field. My list of must haves includes:

  • Fully unified nationwide PTT between FirstNet and LMR systems.
  • Next-Generation 9-1-1 (NG911) nationwide buildout that is compatible with all Public Safety Access Points (PSAPs) and dispatch systems in place in the United States.
  • Broadband network to broadband network interoperability may be necessary at some point but there are too many political and financial ramifications to bridging various broadband networks at the moment. This has been made much more difficult because one of the broadband network operators insisted on tying its core to the FirstNet core. I and many others don’t believe this is an efficient or safe way for networks to be able to move traffic for public safety across different broadband networks. If it was up to me, when it comes time for such interoperability, I would first look to an over-the-top PTT system with guardrails so public safety is assured that traffic that passes between networks is secure.

Of these, I believe the first goal of fully unified nationwide PTT between FirstNet and LMR systems is the most imperative. Once this is in place, application databases, video, perhaps computer-aided dispatch, etc., will need to be extended in the same way. But rather than tackling all of these at once, let’s start with PTT and provide what was promised to the public safety community prior to FirstNet was a reality. That promise was to build a public safety nationwide broadband network that is fully interoperable, secure, and provides priority and pre-emption for the public safety community.

Winding Down

Here we go again! I thought we might finally be gaining traction on nationwide FirstNet PTT interoperability. Now I wonder if it will ever happen. If you read the Advocate more than occasionally, you know how strongly I feel about a common nationwide PTT system running on FirstNet (Built with AT&T).

At last count, there were 10 certified applications for PTT over FirstNet. There are also several that are using FirstNet but are not certified and do not include the proper encryption. This makes it difficult to track all of the applications that run over FirstNet and to identify which may not be certified. Perhaps it would be better if each application was assigned a certification number that could be read by the network.

Early on, there were high expectations that the 3GPP standards body, which had been tasked with developing a worldwide PTT standard, would deliver a standard much earlier than it did. Vendors that have implemented 3GPP’s “Mission-Critical Push-To-Talk” (MCPTT) are very late to the party.

Much of the FirstNet world has moved on and chosen other vendors. With so many vendors, it is difficult for any agency to determine which FirstNet-certified PTT will best suit its needs. To make it worse, there is no way to know exactly how many agencies are using PTT over FirstNet, which vendors they have chosen, and how many agencies have integrated their LMR PTT with a flavor of FirstNet talk.

Even so, there are some clues to who is using what type of PTT application. If, for example, your agency does a lot of work in conjunction with federal agencies, that might lead to one choice. If your agency prefers a single brand of hardware for LMR and you have ISSI or the funds to put it in, another vendor should be considered. Others in the PTT business with FirstNet-certified applications may offer pricing or other benefits not available from larger vendors.

Within the last few weeks, I have identified some vendors that want to change their PTT technology and the changes will have to be certified by AT&T for use on FirstNet. In the meantime, a number of agencies are perfectly happy with their current PTT choice. The more certified FirstNet vendors there are, the more difficult it is to develop a nationwide solution.

If this was a horse race to the finish line, I would put my money on the first horse at the starting gate. This horse should have been the nationwide/worldwide standard. However, I only see two ways this first horse can finish anywhere near the rest of the pack and it is likely that the first horse would be close to last. However, that may not be so bad. When Nextel closed its doors, it had many users and most of them were unhappy nonbusiness users who really wanted Nextel to stay in business.

So, the first horse becomes an also-ran. Those with a vested interest in that horse might decide it is too late for it to be a contender after all.

In closing this metaphor, my final recommendation is that the trainer of the winning horse and the trainer of the also-ran horse work together and figure out how both of their horses can take the crown.

Until next week…

Andrew M. Seybold, Sr.
©2022, Andrew Seybold Inc.


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