Public Safety Advocate: PTT Interoperability—Sweet Spot for FirstNet?

First, let me be very clear, this is NOT about Mission-Critical PTT (which may someday be available and used for dispatch, day-to-day patrols, and local incidents). This is about FirstNet as a platform to provide interoperable push-to-talk during multi-jurisdictional incidents that is in keeping with the premise that motivated the public safety community and others to seek a solution for interoperable communications starting in the 1990s and culminating with the law creating FirstNet, setting aside the D-Block for additional broadband spectrum, and providing a starter kit of $7 billion.

The primary purpose of FirstNet has always been to provide interoperable communications between and among agencies that have different Land Mobile Radio (LMR) systems and, therefore, cannot communicate directly with others at the same incident. This lack of interoperability has been a problem for more than thirty years and even after 911, Katrina, and Sandy revealed to the public, the press, and elected officials that there was a huge problem, it still took the public safety community with support from others until 2012 to establish FirstNet and another five years to become a reality.

FirstNet was designed to provide interoperable data and video, with voice to remain on LMR for many years to come. However, during the time FirstNet was organizing and issuing its RFP for a commercial partner, there were a number of developments in the world of Push-To-Talk voice. The first was that companies such as Qualcomm (QChat), Kodiak (now owned by Motorola), Harris, and ESChat entered the market to provide PTT over broadband.

The Public Safety Communications Research Division (PSCR) of the National Institute of Standards and Technology (NIST) jumped on the bandwagon and began lobbying the 3GPP standards organization to standardize PTT over cellular. The good news is this goal was accomplished with a great deal of assistance from network operators and the public safety community. The bad news is that 3GPP made the mistake of labeling this standard as “Mission-Critical PTT.” The issue, of course, is that the standard, when implemented, will only provide for half of the equation. The missing half is a mission-critical or public safety-grade network over which the standard will run. FirstNet (Built by AT&T) may, in fact, become a mission-critical network but not now and not for a while. It takes time and a lot of money to add the prerequisite redundancy.

With redundancy in place, LMR networks are a lot closer to being mission-critical. Not only have many already been hardened, many have dual communications capabilities to and from the tower sites. Further, LMR systems are more resilient because they can fall back to other modes of voice communications including trunking to standalone repeaters, standalone repeaters to simplex, and finally, simplex to simplex for one-to-one and one-to-many. FirstNet has committed to moving toward providing a public safety-grade network but until it is completed and proven, Mission-Critical Push-To-Talk remains a misnomer.

Even so, that does not mean PTT over FirstNet is not ready to be used when it is needed. In reality, FirstNet PTT can be the catalyst that provides PTT interoperability between agencies working on the same incident. A very simple example, which pre-dates FirstNet, can be found in Santa Barbara County, Calif. The Sheriff and City of Santa Barbara Police are on UHF analog channels and do share common channels with each other. County Fire, City Fire, and other fire agencies within the County are all on VHF analog and can and do coordinate easily with other fire agencies up and down the coast. The problem becomes evident when there is a major event such at the Holiday Fire, which is still burning and has destroyed homes in the area. The Sheriff, Police, and CHP are charged with evacuating the neighborhoods but they are not always working from the latest evacuation orders issued by the fire departments and they are not always able to assess the danger to themselves as they clear an area.

A few years ago, an ESChat system was installed in the County for all agencies that wanted to take part. The result is that those in command of the various services are able to talk to each other during common incidents and also be connected via a bridge to their own LMR system. This has proven to be extremely beneficial. Santa Barbara County is not the only place this is happening, nor is ESChat the only company providing these services. Kodiak, Qualcomm, Harris, and others are providing similar services and the number of PTT vendors continues to grow. During the recent Plugfest, held in Texas, there were more PTT companies attending and taking part than ever before.

Wait for the Future or Act Today?

Those at the PSCR, Plugfest, and elsewhere all seem to believe that in due time all interoperability issues with PTT over FirstNet and other first responder broadband systems in other parts of the world will be solved and all of these PTT programs will co-exist happily ever after. Obviously, I don’t agree. I think a lot can be done now to move this along. Plugfest, the 3GPP standard, and the interest level is all great, but I think with a little extra effort we could develop an interoperable PTT-over-FirstNet system that could be temporarily or permanently attached to LMR systems and activated when needed.

Think about the benefit. During a wildfire when agencies are sending in strike teams from cities, counties, and other states that cannot communicate with those already on the scene via LMR, they could communicate over FirstNet PTT, even while a state away, and receive orders and other valuable information to prepare them for their tasks once they arrive. Think about a police chase up a freeway (there are too many—hopefully, drones will take over) and the many different jurisdictions that need to be notified and provided with further information. FirstNet PTT is not limited in range the way LMR systems are, so a PTT conversation during the incident might shorten the incident and save lives. I am sure there are hundreds of other examples.

What needs to be done to make this happen? Well, some think we simply have to wait until things are ready and then implement them. My view of this is that workarounds can be used to make this happen today. First, you need to ensure that each and every PTT program certified for use on FirstNet is fully compatible with any and all of the others so regardless of which PTT option an agency has (within reason) it can communicate with others on the network without a lot of expensive hardware. Perhaps the most difficult issue to solve is how to be able to quickly connect an LMR system’s PTT system to the FirstNet PTT services. Today there are a number of ways this is being done starting with a simple radio-over-IP bridge. While this type of connection does not pass location and user ID information, it does work.

Some are in favor of a P25 interface known as ISSI but depending on the vendor, ISSI is proprietary and/or too expensive. Devices that can facilitate the interconnection are being made by companies such as JPS and Mutualink but it is probably not practical for each department to have to purchase a bridge to reach FirstNet. Suppose we took a chapter from the Motorola PAC-RT (pack-rat)? What is a pack-rat? Well, in LMR speak it is a small, low-powered radio receiver and transmitter that is interconnected with the mobile radio in a vehicle. and a handheld outside the vehicle, its signal is received by the pack-rat and then fed to the mobile unit where it is repeated at the much higher power of the mobile radio. This increases range and is widely used by the public safety community to help extend LMR coverage. Today the largest PAC-RT vendor is Pyramid communications.

What if LMR radios installed in vehicles had a way to cross-connect to the FirstNet modem in the vehicle? Then, during an incident that included differing agencies, any agency in range of its own LMR network could quickly and easily patch that network together with the FirstNet PTT services. There are some issues with this of course, one being that if I am not within my own LMR coverage I cannot cross-connect. However, if there is also a bridge at your dispatch center or Public Safety Answering Point (PSAP), the connection could be completed that way. I don’t believe building this capability into a mobile radio would add much to the cost. Further, I know of at least one vendor that will be building FirstNet modems into their LMR mobiles soon. Editor’s note: I have dubbed this interface device the Next-Gen PAC-RT and have filed a provisional patent on the concept.

This could work today using the Harris XL-200 multi-band radio with FirstNet broadband built in. I wonder if a simple software change could empower this radio to be used as a belt-worn LMR-to-LTE repeater or even to plug into existing bridge systems. Again, this idea does not solve all the interconnection issues between LMR and LTE PTT but it would certainly help in many instances.

I don’t think waiting for very smart engineers to develop a solution to this interoperability issue and establish a standard makes sense. A number of years ago, a software engineer and entrepreneur went to visit his wife who was in labor with their first child. As he was sitting there, he thought about how great it would be if he had a camera on his phone. After the birth he came back with a StarTAC phone with a digital camera soldered to it and took pictures of his daughter and sent them to his friends. I received one and still have it. He did not wait for someone somewhere to build the perfect camera for a phone, he did what he had to do to make it work and triggered the movement to include cameras in phones. (Thank you, Philippe Kahn.)

In March of 2018, AT&T announced it was releasing an RFP for a second PTT vendor to serve FirstNet. I have not heard any more about this RFP nor have I heard when the responses were due back or if a vendor was ever chosen.

An Incentive

FirstNet now has more than 1,000 agencies signed up while others are waiting for various reasons. Some are still concerned about coverage, some have been offered a better deal by a different vendor, and others are waiting and watching. Agencies that have joined FirstNet are still learning the ropes, seeing what the network will do, how many applications are out there, and how to integrate FirstNet into their communications systems. Interoperable PTT services might provide an incentive to drive other agencies to join FirstNet sooner rather than later.

The purpose of FirstNet is to provide interoperability between and among agencies. It is probably too soon but I have not heard or read any success stories about better interoperability, better incident management, or any other story that indicates FirstNet is being viewed as a valuable addition to public safety communications. If FirstNet/LMR interoperable PTT, NOT Mission-Critical PTT, became a reality, would that entice more agencies to join? AT&T has delivered early on the promise of FirstNet and continues to exceed the requirements set forth by FirstNet the Authority for build-out and other milestones. I would like to see AT&T dedicate itself to making interoperable PTT a reality sooner rather than later. After all, nationwide interoperability is the charter of FirstNet. We thought in the beginning it would be mostly about data and video, but others had a different vision and added dial-up, text, and PTT to the system’s capabilities. Data and video are up and running everywhere, how long do we have to wait for PTT to become the voice interoperability tool to make the difference during multi-jurisdictional incidents?

Winding Down

The western United States is on fire, heat waves seem to be everywhere, and hurricane season is upon us in the east. FirstNet stands ready with its COWs, drones, and other ways to beef up FirstNet during any ensuing incidents. How difficult would it be for each COW to interconnect with the LMR system being used for voice at the incident to provide PTT voice over FirstNet for all of the agencies?

I have been involved in wireless data and broadband for many years. I worked on the first paramedic radios in the early 1970s (the BioPhone), observed the first wireless email service come to life (RadioMail), played a small role in designing the BlackBerry, and much more. In the relatively short history of commercial wireless, the products and services were built and put into operation because there was a need for the service, feature, or function—often before there was a standard.

I do not believe we can wait for more Plugfests and more grants to more organizations to work on solving PTT issues sometime in the future. We need to take the first steps and recognize PTT-over-FirstNet for what it can be today: Today, it can be a very effective PTT interoperability tool when multiple agencies are working together on a common incident.

Andrew M. Seybold
©2018, Andrew Seybold, Inc.


2 Comments on "Public Safety Advocate: PTT Interoperability—Sweet Spot for FirstNet?"

  1. Bravo!

  2. I want to revert back to the significance of the beginning of your article and FirstNet’s primary mission, Interoperability! To-date we have two FirstNet approved PTT vendors, neither of which can directly talk with one another. I realize that there is no common gateway/server that is hosting Interoperability LTE talk groups to make this happen right now, and there is a rush to get agencies on the air via LTE/LMR gateways on either of those apps. Before we get too far into this, at minimum a common interoperability standard should be put in place and a vendor must comply before FirstNet approves their app. True that we may have encryption issues, however we should be able to (for now) allow non-encrypted traffic on anything that has a LMR/LTE gateway attached and revert to LTE only talk groups for sensitive traffic. I revert back some 50 yrs. and perhaps today we should let NLETS setup and handle regional and national common LTE Interoperability talk groups, in keeping with their mission but now moving voice data. I see that they have a virtualized data center with an AT&T backbone besides. Much work to do, my hat off the NPSTC working groups.

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