Public Safety Advocate: Unanswered Questions

Last week I attended and moderated a panel at the IWCE LTE Communications forum in Dallas. The event was well attended, the panel sessions were very good and informative, and I was able to meet and spend time with more Advocate readers and others. All in all, it was a good trip and well worth it. However, during the forum I asked two questions and neither was answered to everyone’s satisfaction. The answers were vague and did not address what I consider to be the current needs of the public safety community.

The first question had to do with why, after all this time, 5G will still be asynchronous (faster from the cell site to the device than from the device to the cell site). The second question concerned open standards and the ability for public safety agencies to make use of Push-To-Talk (PTT) applications they currently use or want to use. The questions were asked during different panels but the answers were similar and what I consider to be non-answers. During one of the breaks I was approached by a number of people who said they had the same questions and the responses they heard did not provide them with any real answers.

Based on the responses I received and the other attendees’ expressions of frustrations, I decided I would highlight these questions and discuss why the responses do not address the communications needs of the public safety community today. Both responses dealt with things becoming better sometime in the future (unspecified how long). Also in both cases, it was clear that no one is considering near-term solutions to help with day-to-day operations of the public safety community. Even after the final standards are published, there will have to be some tweaks to make today’s solutions compatible.

Data Speeds

The gentleman whose presentation was about the future of 5G was very clear. He painted a picture of what we should expect, when it will arrive, what needs to be done with devices to make them 5G-compatible, and realistic data speeds to start out with, of course, increasing over time. What I heard was that at first, data speeds we could expect via 5G are somewhere around 400 Mbps down to devices and up to 50 Mbps from the device to the network. This is the way 3G and 4G have worked for years—more downlink speed, less uplink speed.

When I asked why 5G was not being designed for download and upload speeds closer to each other, the response was that those in charge of the specifications are still thinking in terms of what I consider to be the OLD Internet model where people were consuming more data from the Internet than they were sending back to the Internet. I don’t believe this is a valid model for today’s wireless broadband users, nor is it a valid model for the public safety community where uplink (back to the system) data and video services will be in high demand, especially for EMS tasks such as ultrasounds.

In 2012 when my team ran a series of tests on a 5X5-MHz public safety system in Alameda County, our results, and the paper we prepared and filed with both the FCC and Congress, looked at the number of videos and other forms of data that could be sent and received within a single cell sector. We chose a single cell sector since after we discussed the broadband needs with many in the public safety community, we came to the conclusion that most incidents happen in a fixed location that may be served by only one or two cell sectors. We also knew data rates vary in a cell sector depending on how far you are from the actual cell site.

The total capacity of the entire network does not matter for public safety. What matters most is the capacity and data speeds they have access to during an incident. In many cases, this means within a single to several cell sectors. Granted, AT&T has provided a much larger pipe than the 20 MHz of spectrum licensed to FirstNet, but pipe size restrictions could still be an issue. Further, if you look at today’s consumer users, many more are pushing as much or more data in the form of videos up to the network to share. They may still be consuming many streaming videos, but now they are also sending them. I maintain, therefore, that the “old” Internet model of more, faster data down and less up is no longer a valid model for wireless systems design.

I was disappointed when I heard the answer because 5G brings with it huge amounts of spectrum and small cells. It seems to me this combination would lend itself to replicating the fiber model that normally provides the same data speeds in both directions. The presenter answered my question by reciting that wireless standards are based on Internet data flow. There was no time for a follow-up question so I politely listened to what he said. Toward the end of his response I heard that perhaps, maybe, someday, those who define wireless standards will look at a new uplink versus downlink model, but don’t hold my breath.

Push-To-Talk over FirstNet

The panel about interoperability of PTT over FirstNet/AT&T also provided answers that were not here and now but far into the future. FirstNet has stated over and over again that it will only accept open standards on the network. The PTT speakers basically hid behind that statement explaining that PTT interoperability would come with LTE Release 15 from the 3GPP. If you visit the 3GPP website or query LTE release timelines using a search engine, you will find the work on Rel. 15 is to begin at the end of 2017 (this year). The site was updated October 14, 2017, but it still says the start of Rel. 15 is in the last part of this year, which is almost over.

There are no other working dates available and no tentative release date. Reading the text for what is being considered for Rel. 15, it is difficult to determine whether Mission Critical Push-To-Talk interoperability will even be considered. We are told it will be, but that is not evident from the website. Even if it is included in Rel. 15 it won’t be finalized for some time. After it is, the release will have to be reviewed by each network to see which components operators want to add to their own LTE network. Over the years, network operators have not always implemented everything in every release into their networks.

So, my questions that seem to remain unanswered are when, in fact, will 3GPP Rel. 15 be published in its final form, and how long after that will network operators incorporate Rel. 15 into their own networks? Further, since Rel. 15 will be the first release covering 5G as well, will it require all new mobile devices in order to work? Long-range plans do not help in the near term yet we have an issue that needs to be solved now. AT&T is adding states to the opt-in side of the ledger and offering them access to the entire AT&T network and then FirstNet’s Band 14 as it is built out. Are agencies expected to opt in for data and video services only and wait (patiently or not) for the 3GPP standard to be released?

Those pushing PTT over LTE as the be-all, end-all of PTT and the future death of LMR systems don’t seem to want to turn their attention to the here and now. They seem to accept that standards wend their way through the process and are then adopted. Perhaps this works for some parts of LTE but when it comes to the FirstNet network that has been made available by AT&T in more than half the states (31) to date, will they be told that if they want PTT services today it will be from only one vendor and only one flavor. The other options are to not permit any PTT over LTE until the standards are available, which would mean those who want to use PTT over LTE for interoperability between agencies on a major incident will be out of luck, or do we use some of the technologies that are available today to bridge the gap until the standard is ready?

The panel’s interoperability discussion had to do with LMR to LTE PTT use and how the two networks can be tied together to enable PTT over LTE to become part of an existing LMR system and PTT over LTE can be used as the common PTT platform at a combined agency incident to provide PTT services between agencies, multiple LMR systems, and the FirstNet broadband system. When it comes to off-network voice communications, some presenters were still saying LTE ProSe (peer-to-peer) systems would be fully capable. Assuming those who made the statements are not directly involved in public safety are correct, when will it be ready and how will it function both on and off the network and both within and outside network coverage? There are many unanswered questions and even the UK LTE system is not waiting and will come online in the future with simplex or off-network communications being handled via Tetra (Terrestrial Trunked Radio).

Then there is the unanswered question of Multicast and which networks are capable of providing it to their customers. Multicast is a 3GPP standard that enables a network to transmit to multiple devices all at once instead of having to send information sequentially to each device. This is great for sending video and other data to an incident and it would have been helpful during the Boston bombings to enable pictures of the bombers to be sent to all public safety units in the field at once. As important, I am told by a number of LTE engineers that multicast is required if you will have a lot of PTT traffic in a localized area where the number of cell sectors is limited. Further, and this is the point I have not been able to verify, I have been told that the AT&T network is not, for some reason, capable of multicast but Band 14 is. Does that mean PTT at local incidents will have to be handled on Band 14 only? I certainly hope this information is not accurate.

Back to PTT today. If a number of departments in a state or next to each other in different states are on the FirstNet network and want to experiment with PTT over FirstNet, how is this to happen, especially given FirstNet’s statement of only open standards being permitted on the network? Today there are ways of cross connecting PTT from one vendor to another on a common network. For example, take a look at Mutualink’s interoperability solutions, some of the ISSI bridges designed for P25 interoperability that will also work for PTT services and, of course, other bridges including those made by JPS. The trick will be to make the PTT systems co-exist on the FirstNet network without adding any or much delay to the PTT sessions. The “don’t shoot” test must still be met for cross connections to be useful, but they can be made today.

If we are forced to wait for a standard that has not been created, then wait for that standard to be incorporated into the various PTT solutions, and then wait for it to be deployed by network operators, we will be waiting for a very long time. Let’s find a way to make interoperable PTT work today. While there are more than sixty different flavors of PTT over LTE, only a few have gained traction with the public safety community. Those already on the AT&T network are probably using the Kodiak/Motorola solution. Then there is Harris BeOn which, I am told can operate across networks as an over-the-top PTT application or by being imbedded into the network. The last one I am aware of that has captured market share in the public safety community is ESChat, an over-the-top application that has been deployed both as a hosted and on-premise system. If there are others I apologize to the vendors, these are the ones I am familiar with in the public safety space. It should not be difficult to work out a way these three (or more) different PTT services can be interconnected to make them interoperable. Again, why do we have to wait?

If Congress really enforces the T-Band giveback, and if FirstNet really someday starts to replace LMR systems, the sooner we address cross-connectivity of PTT on the network the better. Why are we waiting for a standard when PTT is already providing interoperability services in existing systems such as Harris County and LA-RICS, which have successfully shown that PTT over LTE interconnected with LMR systems is a great way to provide interoperability in the short term. However, if multiple agencies report to an incident and each has a different flavor of PTT installed, they will not be able to communicate with others at the incident, at least in voice mode.

Either we need to go back to the original premise of a network that was discussed well before FirstNet existed that was data and video only without any voice services, or we solve the PTT interconnection problem now and not wait for the upcoming, sometime in the future, 3GPP standard. Banning PTT altogether or making PTT systems work together today are the only choices that make sense. If we bend the rules so one vendor’s proprietary PTT system is the only one permitted on the network until the standard is finished, the entire concept of FirstNet permitting only open standards on the network will have been compromised.

There will be no Public Safety Advocate next week. We will be traveling to spend the week with family.  Happy Thanksgiving to all of you and a special thanks to all of the first responders who will be working that day!

Andrew M. Seybold
©Andrew Seybold, Inc.


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