Public Safety Advocate: FirstNet PTT Interoperability

A few weeks ago, I wrote about the need to find better, open-standard ways to bridge the gap between Land Mobile Radio (LMR) and FirstNet for Push-To-Talk (PTT). The Public Safety Technology Alliance (PSTA) has completed phase one of its work and plans to publish its findings soon. Next is the need to similarly address two other solutions discussed in the report: Dispatch Fixed Station Interface (DFSI) and Radio over Internet Protocol (RoIP). Meanwhile, the PSTA committee and others will be back at work focusing on providing open-standard, less-expensive solutions to tie LMR and FirstNet (or broadband) systems together.

For public safety, this means when an agency puts out a call for help from neighboring agencies or even agencies many states away, those responding to the incident will be able to use FirstNet to communicate with the local agency by bridging their LMR systems to the FirstNet network. The primary reason so many fought for FirstNet was to enable interoperability between networks. Today, first responders are able to communicate with each other. The number of public safety officials, vendors, contractors, and others who came together for a common cause that resulted in the passing of a law establishing FirstNet speaks highly for the public safety community.

However, the ability to cross-communicate between LMR and FirstNet or other broadband systems is only one part of the solution. The other part is to figure out how to enable the various FirstNet push-to-talk systems to communicate with each other. I have been assured by FirstNet (Built with AT&T) that it is fully committed to providing only open standards on the FirstNet network. Even so, if you look at where we are today with interconnectivity over LTE (FirstNet), you will find three that companies are certified to provide PTT over FirstNet. The first is Kodiak Networks (now owned by Motorola) with a network-based technology. The second is ESChat with an over-the-top application, meaning it can operate on multiple LTE networks and all common groups can be tied together regardless of the network being used. Orion is the third approved vendor, also with an over-the top-application. As with ESChat, Orion claims to be network-agnostic and, for the most part, device-agnostic and can provide LTE-to-LTE PTT (and WiFi) between networks.   

Interconnectivity over LTE is important since many agencies that have signed up with FirstNet still maintain a relationship with at least one other network. This is because while FirstNet is being built out quickly, there are still some areas where another provider currently offers better coverage. Another reason is that some agencies are moving slowing into the FirstNet world to test the waters. For the moment, they are retaining their other carrier for some of their activities. 

Now let’s turn our attention to the current state of PTT over FirstNet. Rumors persist that another vendor will be approved in the near future. I have written about my concern that this vendor, if my information is correct, has built a robust Mission Critical Push-to-Talk. One reason it is “great” is because the application has been built into its chipset. If true, using this new PTT will mean you will be limited to one brand of phone while the other three vendors provide PTT over many different brands and types of devices. The next thing on my agenda is to set up a meeting with this vendor to find out if the information I have received is accurate.

I have discussed this issue with a few people and received mixed reactions. One person stated that Kodiak is not an open standard and to emphasize this, pointed to the fact that the Verizon flavor and AT&T flavor of Kodiak are not compatible with each other. Others believe ESChat and Orion are not open standards either. My conclusion is that what matters more than a discussion about if and who has a proprietary PTT solution approved for FirstNet is how and how soon these PTT solutions will be capable of interoperability.

I consider PTT interoperability to be as vital as LMR-to-FirstNet integration. If an agency calls for assistance from three or four different agencies outside their jurisdiction and each is using a different PTT-over-FirstNet technology, have we really solved the central issue brought up by the 9/11 Commission, which is how to make communications for all public safety agencies interoperable?

The PSTA has a committee working on interoperable PTT, the 3GPP is finalizing a “standard” to enable cross-vendor PTT, and The Critical Communications Association (TCCA) has held numerous “Plug Fests.” However, from what I have seen all this effort is focused on PTT systems that must be embedded directly into the network. This means ESChat and Orion, and perhaps the new rumored PTT provider, will not meet the MCPTT standard.

If the standard does not accommodate both cross-vendor and cross-network PTT services, we will have missed the mark for public safety. Think about LTE becoming nationwide for public safety, then think about what happened when a major earthquake hit the South Island of New Zealand a number of years ago. New Zealand was first to respond and assistance came from Australia, the United States, and elsewhere. As it happened, Tait Communications had people at the airport giving out handheld radios that were compatible with New Zealand’s communications system. A few years into the future, what would happen if agencies from other areas arrived only to discover their LTE PTT was not compatible with the home system?

According to the 3GPP and TCCA, this would not happen, but I have to believe there is and will continue to be a need for over-the-top PTT applications that can be easily and quickly installed in LTE devices when and as needed. If you showed up in Santa Barbara County, Calif., with your Motorola Kodiak PTT, you would find the County using ESChat tied to its LMR networks. While I know FirstNet should be the main focus for nationwide public safety communications, there are still public safety users on other networks. Only over-the-top PTT applications can help solve the problem of multi-network PTT. They are more versatile and better suited for true interoperability in today’s world. 

Some progress is being made today. ESChat can, in fact, interoperate with Kodiak’s PTT system and can and has integrated P25 trunking systems using its own flavor of ISSI. According to TCCA, at last count more than thirty vendors passed TCCA interoperability tests. Some are PTT vendors, others are back-end or on-network vendors. I would prefer to see a much smaller number of approved PTT vendors and I am in favor of both on-network and over-the-top vendors, especially if the on-network vendors can be convinced to work with other networks to cross-connect PTT.

Many years before FirstNet, Nextel was purchased by Sprint and went with Qualcomm’s QChat while Kodiak won AT&T and then Verizon. As I have pointed out before, if we look back at history, we will find fast growth in the cellular industry occurred only after one network finally permitted subscribers to call people on other networks, and text messaging languished until it was available from network to network. While I agree FirstNet should continue without allowing core sharing or network sharing, in the case of PTT, I believe it is important to provide bridges between all LTE networks at least for the near future. At the same time, we also need to be mindful that each LTE network is somewhat different from the others. With every 3GPP release of a next version of LTE, each network operator is free to pick and choose which new features and functions to use in its network. Some differences are minor, some not. In spite of any differences, over-the-top PTT applications seem to work well from network to network and cross-network.

Someday FirstNet will be the primary public safety broadband network in the United States. Network deployment is far ahead of schedule and coverage differences are closing fast, but there are other reasons to maintain cross-network PTT capabilities. In a major disaster there will be second responders along with state and federal government personnel who arrive with non-FirstNet phones. If software can be quickly and easily installed in their devices to enable them to communicate with the other teams, our responses will be better coordinated and more effective. 

Winding Down

San Jose, Calif., made a big splash when it joined FirstNet as the first metro area to go all-in by including all its first responders and other government personnel on the FirstNet network. I had thought some other cities had already joined on an all-in basis, but if not, San Jose should stand out as a model for other cities to follow. Congratulations to San Jose! 


SpaceX says most of its little Low Earth Orbit satellites (LEOs) are in operation and it will soon be running tests on fifty or so to determine actual data speeds and system latency. Its press release states that five-percent of its Starlink satellites have failed and it plans to take two out of orbit and let them burn up as they enter the Earth’s atmosphere to prove they won’t contribute to more space junk over time. This is the first time I heard about this plan but it sounds like it could be a good idea. SpaceX’s other news is that in addition to orbiting 11,000 little LEOs, it plans to build up to a million Starlink earth stations. Called “Starlink Services,” they will be built by another company and design plans call for a flat-panel phased-array system to transmit and receive signals in the KU-Band for the Starlink constellation.

Drones (Unmanned Aerial Vehicles, UAVs)

I now have my second drone, this one with automatic homing. I have applied for and received an FAA Small Drone Registration ($5) in spite of the FAA site being very confusing. The first site I was sent to says you can register more than one drone and buy ID stickers for them, but that site did not work. I filled in the information three times and three times it went into limbo. Then I found, sent in my $5, and received my Small UAS Certificate of Registration. I am not sure if it covers both of my drones, perhaps the public safety UAS guru can help me here. In the meantime, I am looking for a simulator I can run on my Windows PC. There are many out there but most cost more than my drones (several cost more than one drone). If anyone knows of a good simulator for UAS flight, please let me know.

I am reading more and more about how UAVs are being used in the public safety community. Some are used as advance scouts, some carry water, and some are outfitted with radio packages. Many carry cameras for aerial views of incidents, lifeguards use them to drop life vests, and the EMS community has found a variety of uses for them. The availability of UAVs will continue to challenge the imagination and revamp public safety responses and activities. It is surprising, or perhaps not, how fast UAVs have “taken off,” so to speak. I hope to see some at APCO but if not, I’m sure there will be a number of UAVs on display at the IACP show later in the year.

Until Next Week

Andrew M. Seybold
©2019, Andrew Seybold, Inc.


Leave a comment

Your email address will not be published.