June 20, 2016
With the FirstNet RFP deadline now past and speculation rampant about the outcome, one common question is, “Will LTE eventually take the place of push-to-talk LMR radio?” There are several potential answers, depending on how you qualify it.
Economies of Scale vs Technical Realities
We know the FirstNet RFP winner will have to make an aggressive sales pitch touting the features of the system in order to get buy-in from states and agencies. Unfortunately, many of the decision makers for that buy-in are non-technical politicians and administrators who may not understand the nuances between a Direct Mode LTE handset with push-to-talk using Voice-over-LTE (PTT-VoLTE) and a digital LMR handset with talk-around on simplex channels. They want simple solutions that will allow them to leverage economies of scale – if LTE is good for some use cases, why can’t it be good for all use cases?
Trying to discuss technical nuances with non-technical people is often like attempting to apply shoe polish to a cat – it makes a big mess, doesn’t produce the intended result, and you only end up making the cat angry. So, whether or not LTE actually can replace LMR, decision makers and politicians need to believe that it ultimately can or they won’t buy into the sales pitch and join FirstNet.
Willingness of First Responders to Adopt LTE
LTE was originally designed as a system to transport data – running voice over LTE is fairly new even for large commercial carriers. Plus, features like “Direct Mode” for communications between handsets without a network have yet to be proven in deployment. First responders who rely on radio to keep them safe insist on highly reliable communications, and given that their lives are on the line they have that right.
Some agencies have resisted moving from analog FM to APCO P25 – so it’s unlikely that agencies resistant to digital technologies will give up analog in favor of PTT-VoLTE any time soon. On the positive side it’s likely that features such as Direct Mode and PTT-VoLTE will find their way into commercial handsets and networks, so if they perform well in wide use they may gain more rapid acceptance in public safety.
Adoption of LTE Standards in Equipment
As the 3GPP (Third Generation Partnership Project) adds new features to the standard, the user and network infrastructure equipment must be updated to take advantage of those changes. For FirstNet this won’t be such a challenge, because the network doesn’t exist yet and there are very few handsets in deployment. Of course the equipment used for FirstNet will need for more durable than a standard smartphone, and will need to meet higher performance standards for things such as water resistance, battery life and ease of battery replacement, speaker output level, and ambient noise rejection.
Unlike the commercial world, where carriers and operators delay deploying until they know handsets are coming to market – and handset vendors hold off until they see the carriers and operators deploying updated equipment – we know fairly well what FirstNet is supposed to be, so the RFP winner(s) will begin build-out and FirstNet-capable user equipment will follow. The costs, however, are not insignificant, and agencies that have only recently paid for the transition to P25 will be reluctant to make another costly transition.
Critical Communications vs Operational Efficiencies
Public safety communications networks serve a wide variety of use cases ranging from enabling daily operational and administration functions to providing critical communications for tactical deployments during major incidents. The more critical the incident, the more likely incident commanders will be to demand proven technologies. This is why fire departments that have converted to P25 often retain analog FM channels and install analog repeaters on their incident command trucks – while not the most efficient system, analog is a known quantity proven out over decades and is less prone to complex failure modes. When LTE begins to replace LMR it will first do so in the daily operation and administration use cases, eventually gaining trust in more critical use cases.
Network capacity will also play a factor in this adoption curve. As it exists today, FirstNet’s spectrum in E-UTRA Band 14 is large enough to support a reasonable number of data-only tasks, such as full-motion video and file transfer, but if the incident is very large (e.g. on the order of Sept 11th response with impacts across a large region and multiple agencies) then the system will not be large enough for data. So, reliable PTT-VoLTE will not even be possible – which means that LMR continues to be the tool of choice until FirstNet gets more bandwidth.
Ensuring System Efficiency
Maximizing the efficiency of any LTE system involves analyzing and understanding the network’s performance on the ground, in locations where users are going to be. The Anritsu LMR Master™ S412E land mobile radio modulation analyzer (figure 1) with LTE options is a great tool for conducting this analysis. Field-tough, portable, yet powerful enough to measure critical LTE performance metrics, the LMR Master is designed to support the public safety communications of today and tomorrow.
A white paper on how to effectively test LTE for public safety is now available. It provides insight on how to test LTE broadband and P25 narrowband networks.