Public Safety Advocate: Another MCPTT Vendor? FirstNet Coverage, Drive Tests

Southern Linc, which replaced its Integrated Digital Enhanced Network (iDEN) with an LTE network built by Ericsson, originally chose Motorola’s Wave for its Push-To-Talk (PTT) solution. Now Southern Linc has announced it will replace Wave and phase in Ericsson’s Mission Critical Push-To-Talk (MCPTT). Many Southern Linc customers work for the Southern Linc utility, but it also welcome citizens and has been making a play for public-safety users as well. 

This could turn out to be a bad decision for Southern Linc, its current public-safety users, and others it is trying to entice to its MCPTT. I have not tried Ericsson MCPTT but I am sure it works well. Its first attempt at push-to-talk was a total failure but since it claims its new PTT meets the 3GPP standards for Mission Critical PTT, I am sure it will work over the Southern Linc network and provide satisfactory PTT services for its customers. 

However, I question whether this is the best decision Southern Linc could have made if, in fact, it is truly interested in serving the public-safety community. To my knowledge, Ericsson’s PTT is not certified for use on FirstNet and it would introduce yet another deviation from the goal of a single, nationwide, fully-interoperable network for public safety. The Critical Communications Association (TCCA) has held a number of “plug fests” to determine MCPTT interoperability and according to its reports more than thirty vendors have passed plug fest tests for interoperability. 

Even if thirty MCPTT application vendors and servers passed these tests, is not realistic to think any one public-safety broadband network would permit as many PTT vendors that ask on its network, especially since the MCPTT criteria is that any MCPTT application be on-network-based as opposed to over-the-top. On its Government Solutions portion of its website, Southern Linc not long ago touted Wave in this way: “Our Push-To-Talk (PTT) private 2-way radio technology provides the best PTT solution available. And, public sector customers have the opportunity to take advantage of the highest level of PTT (dispatch) trunking which gives priority queuing across the network in an emergency. Whatever branch, department or division you need to keep in touch with, Southern Linc can keep you connected.” Its switch to Ericsson’s MCPTT means it found something better than Wave for its customers. However, I do not believe that because it chose yet another MCPTT vendor, it has not provided a path for interoperability between its network and FirstNet or, for that matter, any other broadband network that offers priority and pre-emption services for first responders.

FirstNet PTT

Meanwhile, as we wait for the next approved PTT vendor on FirstNet (expected to be announced soon), there is no clear path to PTT compatibility between the existing approved FirstNet PTT providers. I believe the PTT interoperability issue will be resolved and public-safety agencies will have a FirstNet network those who worked with Congress to create had envisioned. And I, for one, believe FirstNet will fulfill its goals and more and more departments will join as they become aware of the new and expanded coverage being built out by FirstNet in many areas of the United States.

I believe the term “Mission Critical” as in “Mission Critical Push-To-Talk” will soon fall out of favor. Calling something “Mission Critical” elicits comments from within the public-safety community that lead to questioning the capabilities of broadband PTT and soon other so-called Mission-Critical capabilities. I prefer the term “public-safety grade” that NPSTC used in its report on network hardening. I believe this is a much more realistic way to refer to a network designed for public safety and any feature or function that runs across a public-safety grade network. 

At this time, I am a proponent of over-the-top PTT services such as those provided by ESChat and Orion among others. My reasons are two-fold. First, over-the-top PTT provides interoperability with many of the departments already on FirstNet AND it can be used as an adjunct to existing network-based PTT solutions. For example, I have both Kodiak-Motorola PTT and ESChat PTT on my current iPhone. I can switch between them as needed, and when a PTT call comes in, the phone indicates which of the two PTT solutions is active. The only disadvantage I have found in using both is that only one can be assigned to the device’s PTT button; the other has to be controlled by a screen-based PTT button. Wouldn’t it be better if Kodiak and ESChat were interoperable? Then I would only need one application to have PTT sessions with many more agencies. 

The second reason for my over-the-top PTT preference at this point is to make it easier for agencies that want to transition to FirstNet from another broadband network in an orderly manner, replacing devices over time and as FirstNet coverage in their jurisdictions continues to improve.

While having two PTT clients on a device may cost a little more, if your agency is using a network-based push-to-talk solution and your neighbors are using an over-the top-application, by installing the second PTT app you will gain interoperability with those around you. Tango Tango, a solution provider using ESChat technology, is concentrating on small departments. After one sign-up in a state, it calls on surrounding small agencies and in short order, a group of small agencies close to each other are using the same PTT application and the entire area has FirstNet PTT interoperability. 

Over the many years since P25 “standard” began being deployed, and for many years after, there was no common platform since each P25 vendor made sure its version of P25 differed just enough so only its own base stations, servers, mobiles, and portables would work on its systems. There has been a lot of push-back for this scheme and today the problem of P25 interoperability has been solved for the most part. I hope we can reach the same conclusion with PTT and that it won’t take fifteen or twenty years, which is how long it took the P25 world to make a standard a real standard. 

FirstNet Coverage

A year ago, many public-safety agencies in Maricopa County, Arizona, home to Phoenix, were sticking with their broadband providers because of both real and perceived concerns about FirstNet coverage. However, within the last year, agency after agency has run extensive coverage comparison tests comparing their broadband provider and FirstNet (Built with AT&T) and many have signed on to FirstNet while others are beginning to make the move. 

In other areas of the United States, some agencies are keeping their existing broadband providers until they see proof that FirstNet coverage is as good if not better than what they have today. Still other areas have developed a dual-network approach using in-vehicle routers by Cradlepoint, Sierra Wireless, or a few others. These routers are capable of operating on two or more networks and switching between them to provide the best possible signal in the field. While using two networks means not always having access to all FirstNet applications, security, and other features and functions when the router switches to the other network, it does provide a higher level of coverage where FirstNet has not completed its build-out.

One way this can be done is to sign up with FirstNet for full service and sign up for another contract that includes data on an as-needed basis with a second broadband supplier. Since dial-up and PTT voice are really data when it comes to LTE and soon 5G, this works well for the departments. And because coverage of both networks is available, when FirstNet coverage is sufficient the modems would rarely or never switch to the other network and the agency will know it is time to switch over to FirstNet exclusively. 

Coverage Testing

Testing to determine where there is FirstNet coverage and how it compares with one or more other broadband providers is not difficult. You can ask a vehicular modem company to run tests for you, or you can request a few of its modems, install them in your own vehicles, and run your own tests, or hire an independent company to run the tests.

There are a number of ways to run tests. The best way is to use vehicular modems and run tests over a period of months. There are also applications such as Cell Info (only available for Android devices), and speed tests such as Speedtest by Ookla, which seems to be the most used within the industry. 

All these are good and when used together, they can provide some great information. Unfortunately, factors such as the number of users within the same cell sector and the amount of data traffic being sent and received are not being measured. This will vary depending on time of day, day of the week, and other dynamics. It is clear from our observations of both broadband networks and our cable provider that come 3:00pm weekdays when schools let out, the number of users and amount of data being sent is much higher than at 10:00am. And, of course, use and amount of data go off the chart during major events. AT&T measured data usage at the Superbowl event at over 10 Terabytes! 

The point here is that when testing for network coverage, drive tests need to be conducted at different times of day and night and, if possible, data speeds should be measured. This is why the best tests employ more than a vehicular modem and some data-speed results. It is better to have a few modems installed in active patrol vehicles and/or EMS rigs. This way coverage statistics can be collected in the same area multiple times of the day and on weekdays and weekends. 

Even with all this it may not be possible to determine data speeds during a major incident or event. Recently, Scottsdale, Arizona held its annual golf tournament and the crowd size was somewhere between 170,000 and 200,000 people in a relatively small area. Three years ago, public-safety agencies were unable to use their cell phones at this event. Last year, FirstNet came in with some Cells On Wheels (COWs) and beefed up its LTE and Band 14 coverage in the area and was able to add even more capacity to the network. For the past two years, public safety has been able to use their FirstNet devices without any interruption of service for the entire event. 

Because FirstNet users have access not only to Band 14 but to all of AT&T’s LTE and soon 5G spectrum, there are fewer times when full-up pre-emption is needed, but at major events such as the Superbowl, major league games, or golf tournaments there will be a need to add capacity. It is easier to pre-plan for additional capacity than to adjust for an incident that grows in size and scope and requires more capacity. That is when COWs, COLTs, COWs with wings, and now the FirstNet blimp come into play. So far, FirstNet’s track record for quickly providing coverage where it is needed is very good. 

The unknown in drive tests is the amount of data traffic in a specific cell sector as you pass through it. Sometimes using a streaming service while drive testing will show more, but cell-sector loading changes from minute to minute, hour by hour, and day by day. Because FirstNet has so much more broadband spectrum available to it than was planned back in 2012, the issue of overcrowding a cell sector during a major event is considerably less than we feared it would be.

Winding Down

As mentioned last week when I was urging everyone to pick up the phone and call your Congressional Representatives and Senators to ask them to support the Repeal the T-band bill and the $12 billion in funding for Next-Generation 9-1-1 (NG911), calling is the best way to at least be counted. When you call, a staffer with a tally sheet will verify you are within their district and then record your support for these two bills. I also mentioned I had written to one Arizona Senator about repealing the T-band and received a thank-you for my inquiry into the impeachment. This week, I received a response from the other Senator, from the other party, and guess what. It too was a canned letter thanking me for my thoughts on impeachment. It is clear from this exercise that these two Senator’s staffers are not paying attention to emails they receive about an issue different from what they are expecting. It is sad that those we elect cannot do better and have someone actually read emails they receive. 

Following Texas’ lead, California is now considering a law to up-lift Emergency Communications Center (ECC) personnel to a status that reflects their role as an essential part of our public-safety systems. Other states are also considering this up-lift and I think we need this on a national level. I am sure those within organizations that represent these great people are working for a federal law and I support them. 

As during the FirstNet quest and as we work to support the T-Band repeal legislation and NG911 funding bill, we do not enjoy the clout of organizations that can donate substantial funds to Congress Members. This makes it more difficult for our voices to be heard but this means we need to speak louder and make sure decision-makers in Washington know that public safety sticks together. And we need to make sure they know that, for the most part, the Sheriffs in this nation win more votes within their counties than do Representatives and Senators. 

If there was ever a time to make your voices heard it is now, during an election year! 

Until next week…

Andrew M. Seybold
©Andrew Seybold, Inc.


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