Public Safety Advocate: Public Safety Networks Past and Future

The public safety community has been using wireless communications (wireless, land mobile radio, and digital technologies) since the early 1930s. For most of that time, public safety was struggling to find enough radio spectrum to meet its needs across the US. Radio systems typically connected back to dispatch centers using analog telephone wires furnished by various telephone companies. This enabled voice transmission, and radio transmitters and receivers could be located on towers distant from dispatch centers. As two-way radio became Land Mobile Radio (LMR), new technologies including digital broadband were added, and the method for connecting dispatch to radio sites improved dramatically.

Today, many LMR systems are still providing primarily voice communications. This resulted in having to find new and better ways to connect LMR or broadband radio systems with increasingly more complex dispatch centers and radio systems.

Two-way communications improved over time and the number of technologies grew, resulting in a variety of ways to increase remote capabilities. Standard single pairs of wires that were run point-to-point, but not connected to a telephone, led to a more modern approach known as T1, point-to-point, or point to many-point systems. Though still based on copper wires, T1 provides improved access to and from a dispatch center or Emergency Communications Center (ECC) and, theoretically, priority service with a dedicated connection to public safety service.

Typical copper connections enabled one dispatch console to use one remote base station over a single radio channel. As demand grew, multiple channels using a variety of signaling technologies were deployed over copper wire pairs to increase the number of channels that could be used over the pair. The first way to control a channel on one pair of copper wires was to reverse positive and negative voltages of the pair. Next came tones to change channels and provide other signaling functions. The tones were relayed to the base station to initiate a change from, for example, channel 1 to channel 2.

Today, public safety has more spectrum and capabilities than ever before. However, that does not mean it has all it will need now and into the future. LMR has been augmented with FirstNet and broadband. In some areas, Next Generation 9-1-1 (NG911) for incoming dispatch notifications has already been rolled out and hopefully will be built out for the entire US in the next few years.

All of these networks are being connected. This will be much easier when they can be tied together using Internet Protocol (IP-based connectivity). We are currently using IPv4 but are on our way to IPv6, which will add more capabilities.

If the vendor and public safety communities can move toward implementing IP as a common connectivity technology, all of today’s networks and what may become available will provide more ways to use communications services.

As wireless technology continued to be upgraded, and users required more features and functions, vendors and phone companies continued to work with copper wires for point-to-point and point-to-multipoint systems.

However, there were places where copper was not available. Commercial wireless solved this problem by installing analog and digital microwave point-to-point/multipoint systems and public safety systems followed the model. The placement of radio towers and base stations in these systems resulted in larger coverage areas and more flexibility. Most analog LMR systems still in operation continue to use point-to-point copper or microwave for connectivity between the access point and the radio transmitter/receiver.

Telephone companies that had provided copper connectivity for many years have been moving away from copper and have upgraded their systems with fiber. In many parts of the US, it is no longer possible for a public safety agency to order installation of one or more types of copper connectivity.

New ways to provide connectivity without using direct point-to-point technologies had to be found. For analog systems, the primary choice today is to move from copper to Voice-over-IP (VoIP) services. VoIP connectivity is provided in a digital format that is converted back to standard analog signaling once it reaches the transmitter.

As back-end services have matured along with LMR and broadband technologies such as FirstNet, features and functions offered by new radio technologies including P25 conventional, P25 simulcast, P25 trunked, and Digital Mobile Radio have, for the most part, continued to use point-to-point connectivity.

Public Safety Networks Today

Several areas still using analog technologies continue to be served by phone companies with one or another form of copper connectivity. However, while the Federal Communications Commission (FCC) has not set an end-of-life for copper connectivity, it is certainly open to existing wireline vendors to move fiber, satellite, and microwave connectivity options.

FirstNet and Internet Protocol

When the FirstNet Authority awarded the contract to build out a nationwide public safety broadband network to AT&T. At that time, LTE, or 5G were chosen for over-the-air connectivity. Internet Protocol has been used in the wireless community for many years as network capabilities continued to be expanded and IP offered many advantages. Today, we use IPv4 but we are told the transition to IPv6 is well underway. The need to move is primarily because at some point we will run out of IP addresses and will be forced to move to IPv6.

IP Advantages

Using IP back-end connectivity makes a lot of sense. First, most IP systems use multiple connectivity points and redundant network cores (central brains of an IP system). Even so, many LMR systems are not using IP for their networks nor do most APCO P25 trunked systems. These usually have a single network core that feeds the entire trunked network.

Upcoming Network Back-Ends Using IP

As we draw closer to moving to digital, communications will be delivered via fiber or high-speed digital microwave. This will enable incoming calls to the dispatch center to include pictures, video, text, voice, push-to-talk and other features and functions. The reporting party will be able to give dispatch more information than with voice or text. Therefore, at some time after NG911 has been funded and is being rolled out, we will have two of the three types of public safety networks with IP back-end services.

The first, of course, is FirstNet (Built with AT&T), the public safety broadband network. Then NG911 will also be IP-based. These two networks will provide many ways to interface both incoming and dispatch calls. Thus, public safety will be able to provide more detailed incident information better and faster.

Where that Leaves Radio

Today’s LMR systems management needs to be looking ahead to when they will have no choice but to move to IP-based connectivity. As an increasing number of phone companies cease to offer copper-based services including analog copper (many have already begun), LMR will have to find alternatives. Some can be replaced with digital microwave and point-to-multipoint and some may be replaced with 5G. Moving from the copper world to the digital world will open access to benefits that will provide better and faster services for the public safety community.

IP for Land Mobile Radio

As mentioned above, most of today’s newest types of land mobile radio including P25 trunked are not using an IP system for the back-end.

A few years ago, I was asked to write a white paper about Johnson’s (part of the Kenwood family of products) Dallas-Fort Worth airport installation of a P25 trunked system. Instead of a single core or server, Johnson’s system uses multiple cores and servers at each cell site built out from the network. The advantage to this, even back then, was that the cell site tower, server, radio equipment, and back-end of the system were 100-percent IP-based. The redundancy for the entire system was many times better, and cores at each location can greatly improve redundancy of the network.

Since that time, things have been quiet in the LMR back-end arena with a few exceptions. Kenwood has convinced a number of agencies to install P25 trunked or simulcast systems, or both, with cores at every site. If you read the white paper, you will see that there are a number of ways this combination can be P25 trunked and cores at each camera location can greatly improve redundancy of the network.

Within the last few months, Kenwood started racking up wins using this technology. For example, Santa Barbara County, California, has awarded a contract to Kenwood to install a combination UHF 700-MHz simulcast trunked system based on Sheriff and other County services between UHF and 700-MHz systems depending on where the units are located. The idea is to deploy 700-MHz systems in metro areas within the UHF system covering suburban and rural areas. [An aside: This system will use ESChat PTT, the application the county has been using for a number of years.]

Delaware County, Pennsylvania Sylvania, was my home county and where I worked as a dispatcher in the County Police Department many years ago, also awarded a contract to Kenwood for its IP-based redundant P25 trunked phone network. And there are many others including a YouTube film made in Australia about the advantages of this type of IP-back-end P25 trunked system (YouTube: Kenwood P25 Trunked Radio System.

I find it interesting that other vendors claim they can provide the same type of network connectivity by using a core at each camera location. However, so far, I have not seen any other vendor bidding on this type of network as their prime offering to an agency in the last year or so.


We are heading toward an all-IP world. FirstNet is already there, NG911 is on its way, and a number of LMR systems are moving toward an all-IP back-end that can provide higher levels of redundancy than those available today.

I will be watching how long it takes the vendor community and agencies running public safety communications systems that choose only IP-based back-end connectivity.

If your LMR system is due for an upgrade, and your agency and/or local government understands that the best combination of communications services for your community is Next-Generation 9-1-1, FirstNet, and IP-based LMR, you might want to take a look at what Kenwood offers.

As we head into the future, it will become more of an IP world and there will be more ways to thread these networks together. The all-IP vision I wrote about a few years ago will be easier to achieve, as will the capability to deliver content and services.

It will be interesting to see how many more IP-based LMR systems contracts are awarded to various vendors between now and the end of the year. My guess is that at year-end, the number of IP-based LMR systems will outpace all other options.

Winding Down

According to the calendar, it is March already. That means in only a few weeks many of us will meet in Las Vegas at the IWCE conference. This conference has been around for many years and it is a must-attend for me. While there are many other very good conferences throughout each year, IWCE is the one that is dedicated to public safety and business radio services.

Monday and Tuesday will be sessions only with no exhibit areas open. However, the panels for these two days are generally longer and more detailed. On both days, I, along with a number of very knowledgeable people, will be taking part in panels on Push-To-Talk (PTT). Wednesday and Thursday, I will be attending some of the sessions I am interested in and spending as much time as I can on the show floor. This year I expect to see a number of new devices and software applications to enhance both LMR and FirstNet.

I hope to see many of you there. Please stop and say, “hello,” and let me know what types of articles and topics you would like to see in future Advocates.

Until next time,

Andrew M. Seybold Sr.
CEO and Principal Consultant
©2023, Andrew Seybold, Inc.


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