Public Safety Advocate: FirstNet Interoperability, More on MegaRange™ Test Drives

Last week’s Advocate discussing the difference between FirstNet and commercial networks that concluded that FirstNet needs to continue to stand alone and not become part of a network of networks was one of the most viewed and commented on Advocates I have written in a while. Most of the comments agreed that FirstNet is different from a typical commercial broadband network from The FirstNet Authority down to the public-safety professionals whose network it is. 

Commercial network operators want FirstNet to be converted into a network of networks, partly because they continue to believe FirstNet is AT&T and AT&T is FirstNet. I wrote about this a few months ago, trying to make the point that FirstNet is a public/private partnership (perhaps the most successful of all attempts). AT&T won the twenty-five-year contract to build and operate the network under the direction of The FirstNet Authority, but the network belongs to our public-safety community. 

To be clear, AT&T is far more than simply a contractor. Much of the FirstNet team within AT&T has supported public safety since well before there was a FirstNet and the entire FirstNet (Built with AT&T) team is dedicated solely to public safety and making sure our first responders have the best possible broadband network in place and operational. This team goes the extra mile whenever needed. While there is still work to be done, more sites to be built, more devices to be certified, and more applications to be approved, AT&T continues to be well ahead of schedule in all facets of the network build-out.

Lack of Interoperability

In last week’s Advocate, while I made a case for keeping FirstNet an independent network that belongs to public safety under the auspices of a not-for-profit organization (The FirstNet Authority), I did mention that interoperability even within the FirstNet network it is still lacking. I believe the Push-To-Talk (PTT) situation is the most significant unresolved interoperability issue. There is neither full interoperable and compatible PTT within the FirstNet Network nor a clear path to FirstNet and Land Mobile Radio (LMR) PTT interoperability.  

For a number of years, we have been told that once the 3GPP standards body created Mission-Critical Push-To-Talk (MCPTT) standards we would see true network and cross-network (FirstNet to LMR) interoperability. Today there are at least seven different FirstNet-approved PTT vendors. Three of these use a common PTT platform but all the others are different and, so far, these vendors have resisted interoperability with other PTT vendors. As a result, we still do not have a common platform for push-to-talk on FirstNet nor do we have a standard interface for integrating FirstNet PTT with LMR PTT.

Mission-Critical Push-To-Talk came to FirstNet a year ago. Today it is only available on a few Android phones and no Apple iOS phones. Yet when I visit fire and police stations, I see many Apple FirstNet devices in use. We were also told that the 3GPP has a standard for the integration of broadband PTT and LMR PTT (InterWorking Function, IWF) but we still await its implementation. We are told MCPTT is evolving and it will all come together real soon now. In the meantime, it appears that more and more local, state, and federal agencies using FirstNet are not waiting for MCPTT. They are instead signing contracts for other FirstNet-approved PTT services. 

As I have said before, waiting for standards to be developed and implemented when there is a pressing need does not make much sense when there are vendors that provide a solution today. 

I am sure FirstNet PTT will reach a point where it is more widely available on more devices and, at some point, there will be a good, solid, inexpensive way to integrate with LMR PTT. However, the need is now. Will most of the FirstNet user-community already have chosen another PTT path to pursue by then? Small companies sometimes recognize needs and can respond to them more quickly than larger companies. We should not simply dismiss smaller companies because they are smaller; we should talk to them and understand what they are seeing in the field and how they are responding. 

A number of smaller companies are becoming principal suppliers of services or devices. Not many people paid attention to Sonim when it first came on the scene, yet Sonim has established itself as a major player in the hardened broadband-device market. For a while, its products were being resold by major public-safety vendors that had not yet developed their own products. Fast-moving smaller companies can respond to the needs they see more quickly than most larger companies.

When I was at Biocom and we were deploying our BioPhone 3502 paramedic radio, the company’s owner and I went to a bid opening in a major city in Florida. We were the lowest bidder, but the competitor had a removable battery on its paramedic unit and ours was inside the case and not accessible. We flew back to California and spent the week-end modifying a radio with an external, removable battery and flew back to the city on Monday with the sample. We won the bid and delivered a number of paramedic radios to the city’s EMS folks and sold a number of consoles to hospitals in the area. We beat the big guys because we were fast on our feet. 

PTT is not the only area with interoperability issues. There are other areas that I think will be more difficult to resolve. One is the lack of common applications and data files that can be sent from one agency to another. This issue is more difficult to resolve since many agencies have their own favorite applications their people have been using for a long time and they know and like them. Further, not only are field applications not necessarily compatible with other applications used by different agencies, there is a lack of compatibility between Computer-Aided Dispatch (CAD) files at Emergency Communications Centers (ECCs) and Dispatch facilities. This precludes one ECC from being able to send files to another ECC unless they are using the same CAD system or they have invested in software to convert one format to another. 


I know I have said this before but I think it deserves repeating. Public safety spent years convincing Congress, the Executive Branch, the Federal Communications Commission (FCC), and others that public safety needed a fully interoperable nationwide broadband network. Now that we have this network, units from California, for example, can travel to New York and communicate with New York’s agencies as well as their home ECCs. This network has been put together faster and better than we thought possible. Now the interoperability issues that remain have more to do with what the network carries across it than the network itself. I think resolving this issue should be a next, most pressing priority for both the network contactor (AT&T) and The FirstNet Authority, which oversees the network. Waiting for standards may not be the best solution and we should not be afraid to consider other options. Today, many agencies are not waiting because their need is immediate. 


The day before publishing this Advocate I will have taken part in a webinar put together by the Public Safety Broadband Technology Alliance (PSBTA) on the topic of MegaRange. During this webinar, Chief Harlin McEwen (Ret) and I will have presented details about a number of drive tests using MegaRange devices made by Assured Wireless and Airgain. The results clearly show that the MegaRange devices add both range and data speed to FirstNet Band 14 but what may not be quite as obvious is that neither MegaRange device is set up only for high-power Band 14 operation. They also include all the AT&T LTE spectrum bands available to FirstNet users. 

Because MegaRange systems are new and we are still learning about them, when we first received our MegaRange devices and began running drive tests, it became obvious that since these MegaRange devices include both Band 14 and all the AT&T LTE bands, and because they are added to our mobile routers as a Wide-Area Network (WAN), the router cannot tell which band the MegaRange device has selected at any given point in time. Band 14 is given priority whenever it is available and there is currently no way to record which band the MegaRange device has selected.

When adding MegaRange devices to a fleet, it does not matter which portion of LTE spectrum the MegaRange device is operating on, only that it is connected and communicating. When on Band 14, coverage of a Band-14 cell site increases and data capabilities are improved in the mobile-to-cell site direction. Our tests indicate that the MegaRange device evens out coverage for the mobile unit regardless of which portion of LTE spectrum it has selected. 

After a discussion with Assured Wireless toward the end of our recent drive tests (which we plan to continue), I was sent a new injector, which is the device that records input from the MegaRange device and provides its power and connections to a mobile router, laptop, or tablet. The data this new injector sends to the cloud includes which band the MegaRange device has chosen. Since the AirgainConnect antenna using the Assured Wireless module is my MegaRange device, the injector is able to send data from my latest drive test up to the cloud.

I received a copy of the drive test results in an Excel spreadsheet and some very astute engineers at Sierra Wireless were able to incorporate the data indicating which portion of the LTE network was selected and correlate it with the actual drive-test data normally reported in the cloud-based information collected from the Sierra Wireless MG-90. This was a lot of work for a lot of people to be able to collect information that is only needed for our goal of validating statements of performance from the two MegaRange vendors. As a result, we could see when the MegaRange system was connected to Band 14 and when our FirstNet radio in the MG-90 was indicating we were in a cell on a different LTE band. 

This Drive Test seems to indicate that FirstNet and HPUE coverage are about the same in this metro area (Phoenix)
This shows the actual FirstNet signal strength during the drive
Notice that in some areas where the router is connected to standard FirstNet band 14
There are areas of very week signal–the HPUE provides better coverage overall
This is the same drive test laid in on Google showing the FirstNet bands the router was attached to during this test.

Data from this latest drive test reinforced the manufacturers’ test results showing MegaRange makes a significant difference in both coverage and data access on the Band-14 network. Above are a several of maps that were created by combining this data. Again, the purpose was to be able to confirm that MegaRange performs on FirstNet (Built with AT&T) as both vendors have claimed. Their claims about the advantages of MegaRange have been borne out by these drive tests.

In case you missed it, the webinar was recorded and can be found at . The full set of PowerPoint presentations from Chief McEwen, Bob LaRose of Assured Wireless, Larry Greenstein of Airgain, and me can be downloaded for reference. 

Over the next few months or more, I am sure there will be more drive tests conducted by others including agencies that have adopted MegaRange and there will most likely be more devices built for the MegaRange platform and more devices based on the Assured Wireless AW12 module. My personal preference at the moment is to combine a MegaRange device with any FirstNet-approved vehicular router. This is because most routers are able to establish a WiFi hotspot around the vehicle, which enables handheld smartphones and tablets with WiFi to connect to the WiFi bubble and, therefore, back to the vehicle where their signals will be sent via the MegaRange device up to the network. 

Until next week…

Andrew M. Seybold
©2021, Andrew Seybold, Inc.


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