TETRA radio manufacturers are divided on whether to make their devices more like smartphones or stick with traditional form factors. Richard Martin weighs up the pros and cons of each approach

Did you get a smartphone for Christmas? Smartphone technology continues to advance with better screens, larger memory, and a bewildering array of applications. At the same time, mobile data speeds increase with 4G and 5G service. As a result, we can watch movies on the train to work, message and email at will, and join interactive games. But can technologies from the smartphone benefit the radios that are still needed for specialist users?

Discussing this question with many of the TETRA radio manufacturers reveals two approaches. One is to add new large-screen smartphone format radios to the portfolio that support both TETRA and LTE. Airbus and Hytera are in this group. Other manufacturers have chosen to continue with the more traditional PMR-like format of a modest screen size with a keypad; Sepura (TETRA with an LTE ready option) and Motorola Solutions (TETRA-only, with a separate LTE-only offering) are in this category. Leonardo is somewhere in between, offering TETRA and hybrid TETRA-LTE devices in both touchscreen and keyboard formats.

Starting with the traditional approach, Peter Hudson, head of technology and innovation at Sepura, says: “The key things about the technology are getting more quality and user benefit for a lower cost; it’s all about meeting user requirements, both functional and financial. For example, users expect better coverage to enhance their communications capabilities and ensure improved audio quality and potentially minimise the number of base stations needed to provide this service.”

Motorola Solutions is a strong believer in the collaborative approach to TETRA/LTE. It believes integrating both technologies into one radio will dilute the advantages of a dedicated TETRA portable. The smartphone and the TETRA radio have very different lifecycles, which makes combining them problematic.

As an example of the smartphone approach, Airbus introduced the Tactilon Dabat, combining TETRA and LTE. Bruno Milard, head of terminal product business management, Secure Land Communications at Airbus, says: “TETRA provides the coverage users need, along with voice applications. With so many things to carry, the end-users need a single unit for TETRA and LTE, combining secure voice with the applications for everyday working. It must have a large screen but still meet the PMR fundamentals. We need to ensure that the user can roam between TETRA and LTE to ensure the highest possible availability in all conditions, usable in the toughest environments for long shifts of up to 12 hours. Users frequently wear gloves so the interface has to be designed to suit this.”

The touchscreen
Consumers now expect their phones to have large touchscreens, and this is where we see the clearest difference in approach between manufacturers.

“A large screen is needed for many applications,” says Airbus’s Milard. “We have used one of the largest screens on this type of device and still achieved a 1.5m drop without breakage and IP67, together with best-in-the-market power consumption. It can be viewed in all light conditions, even bright daylight, and can be used by someone wearing gloves.” Leonardo has used a commercial smartphone screen in its new radios, hardened with strong protective glass to also meet IP67.

Sepura has taken a different approach, as Hudson explains. “We need to make sure that screens can be read in all conditions. We don’t use large screens in our TETRA radios. But we have screen clarity and safety as priorities. They should be visible in all lighting conditions, and if the screens break under exceptional conditions there should be no danger from pieces of glass. The bezel on our radios gives extra protection in all but the most unusual cases.”

Motorola Solutions also prioritises ruggedness and battery life, and for that reason uses smaller screens. It takes the view that for writing a long report in the field, end-users will need a different device and so a large screen is not needed on a TETRA radio.

Processors and radio technology
While the smartphone industry is regularly rolling out new and more powerful chips for processing and memory, their use in TETRA and mission-critical radios is limited. New generations of components in the cellular industry come around in just a few years, sometimes as soon as 18 months. “Cellular technology moves quickly, we need to be able to provide long-term-support products and our requirements are very different,” says Hudson. “We have to find critical components we can rely on for many years, not just in terms of manufacture but also long-term support.”

Leonardo takes two approaches. First, it may be able to purchase components ahead in sufficient numbers for the lifetime of the radio. Alternatively, the component supplier may be able to offer a roadmap where any new versions will be fully comparable both in terms of the physical and electrical specification, as well as the operating software. Industrial-grade chip manufacturers can offer TETRA developers the functionality and the longer-term supply that is needed. Leonardo offers users a high level of software stability and limits the number of upgrades for end-users.

“The Tactilon Dabat radio includes LTE, TETRA, Wi-Fi and Bluetooth transmitters and so good RF design was critical in ensuring that they work together without problems, especially for TETRA, which must always work,” says Airbus’s Milard. “In general, the latest silicon designs use less power and are more compact, and can deliver better RF performance. We have also ensured the audio performance is at the highest level. It is clear and powerful in noisy backgrounds. The audio performance is definitely outstanding when compared to the standard smartphone.”

Sepura’s Hudson says: “When it comes to using components, PMR volumes are much smaller than those of the public cellular market, so we cannot always influence suppliers or take full advantage of the relevant technologies in the way we would like. The major players in the cellular industry are not necessarily the best comparison; suppliers in that market are driven by their large-volume business. We on the other hand are able to influence a smaller silicon supplier designing for the cellular market if we get in early. We are having success with suppliers making components for automotive or industrial markets, which have similar volume and lifecycle requirements to our own. Some of these manufacturers are looking harder at the more specialised lower-volume business, as margins are better for them.”

“RF interference is becoming even more important,” he adds. “With TETRA, Wi-Fi, Bluetooth, and in some cases P25 or LTE, in the same unit, we need tight RF design. We strive for the best layout inside the radio, as well as good blocking on the receivers.”

Batteries and power
Battery technology moves on and this was crucial in the development of radios with a large screen. Milard states: “The battery gives up to 12 hours of use and is easily changed at the end of a shift. We have paid special attention to this and it is different from the batteries used in the mass market. It will withstand temperatures from -20°C to 60°C.” Leonardo notes that to power several radio systems, a large-capacity 5100mAh battery is used to give around 18 hours of usage in the standard profile with Wi-Fi on and Bluetooth off. The software is optimised to minimise power use by disabling unnecessary functions; for example, some Android features.

Hudson adds: “We are looking at hot swappable batteries, but the best approach is to extend battery life on one charge for as long as possible, in our case up to 20 hours.”

While lithium-oxygen and lithium superoxide battery developments are under way and reported in the press, their use in the public cellphone market is not expected for some years. With the TETRA market needing stringent safety and environmental testing, we can assume they will be deployed even later here.

Leonardo’s Puma T4 series includes both conventional TETRA handsets and those with support for LTE in both touchscreen and keyboard formats

Applications and security
Android and Bluetooth are now being included in some of the new TETRA/LTE units. Can the security that users expect be maintained, especially as developers can produce applications to be loaded onto the radios?

Airbus’s Milard says: “In the Tactilon Dabat we have work applications running in the same unit as the TETRA radio. We must never compromise the TETRA assets, such as the lists of users and key messages.”

Android 5.1 is used by Leonardo as the operating system in its latest radios, but is hardened for public safety and mission-critical use. Leonardo is keen for end-users to have access to a smartphone user interface to minimise training. This opens up many possibilities for application development, but needs to be controlled. Leonardo will certify these with a digital signature before they can be used on the radios. Applications run in a ‘sandboxed’ environment so they cannot access TETRA features and secure data. Data ports can be disabled to prevent unauthorised downloads or access.

Sepura’s Hudson has a different view. “Considering the use of LTE is stimulating organisations to consider a wider range of uses for their communications, but in fact many applications can and do run effectively over the data service that TETRA supports. Our latest radios are more akin to a computing platform using a standard operating system, which means it is much easier to add applications to a radio in much the same way as you can with your smartphone. This enables us to add applications that help users in their daily tasks, either simplifying what they have to do or enhancing their safety.”

Bluetooth opens up the possibility of other applications. Hudson describes one example. “A Bluetooth-linked gun holster sensor will alert controllers when a firearm is drawn and active, or if separated from its user.” But when it comes to Bluetooth security Hudson observes that “some [public safety] users are still nervous about Bluetooth. Wired accessories are still seen as more secure.”

Small TETRA radios
The Motorola Solutions ST7000 is a compact unit aimed at hospitality users and others requiring a more unobtrusive radio. “We introduced the OLED display with touchscreen to provide the perfect solution for customers with less demanding needs in terms of ruggedness,” says Graeme Loughrey, product manager at Motorola Solutions. “Yet the design provides suitable strength for typical operation in airports, offices, hotels and many other environments with no compromise on radio or audio performance.”

Airbus has also been innovating with the TH1N and the P8GR TETRA pager for a number of users. Milard says: “These small units require advanced RF technology and the investments we have made in design [have paid off], ensuring good radio coverage.”

I asked Hudson about different radio designs such as thin TETRA radios for hospitality or security staff. “We see a market for this type of radio, but due to its requirements is often catered for by some of the non-mission-critical communication standards. Our SC21 radio is small but still has a good screen, it is robust and has full functionality. Even hospitality or security users need good environmental protection, secure communications and may need the screen to be big enough to display images or other rich information to perform work management tasks. There is a middle ground where smaller but fully functional TETRA radios fit. We see this as a large market and the SC21 fits into this.”

ATEX and intrinsic safety
Milard, when asked about the challenges in designing radios for use in explosive environments, explains: “These are more conventional PMR radio designs and not like smartphones. It’s about the basics, longer battery life, better audio, coverage and displays. The environment demands excellent audio performance as background noise can be very loud; the latest audio digital signal processor (DSP) components are helping us here. We have to pay attention to accessory design, testing and batteries. On our ATEX radio you can change the battery quickly without having to leave the risk area.”

Motorola Solutions states that its latest TETRA ATEX product is the MTP8500EX Series, which combines its “heritage along with extensive customer feedback. It meets the particular physical man-machine interface demands as well as extending coverage with a Class 3L transmitter. Audio is improved with the 2W solution as well as Bluetooth.”

Intrinsically safe devices present manufacturers with considerable design challenges

Some closing observations
Iain Ivory, formerly of Motorola Solutions, is the director of Hermitage Communications. He has years of experience in TETRA dating back to its early days and has reservations about the smartphone format for TETRA. “The TETRA smartphone units we have seen are high-tier products and have value in generating publicity, but I’m not sure there is a sizeable market. I believe the bulk of the market for TETRA will be for PMR form factor radios for many years.” Ivory believes that focusing on the basics is still essential. “Batteries need to be powerful enough to give a suitable life. High audio output will use power; when you add this to a power-hungry, large backlit screen, you either limit shift time or you need a large battery.”

Ivory adds: “The smart integration and migration strategy for TETRA and broadband is based at the switch, not hybrid devices. This allows users to optimise the choice of device for voice and data, and enables communication across networks as services gradually migrate.” On developments in silicon in TETRA radio, he says: “As the operating systems have become abstracted, it is much easier to migrate to new generations of silicon, also making product variants easier and more cost-effective.”

So will the TETRA radio turn into a smartphone? To some extent it is already happening. A number of TETRA manufacturers are offering smartphone-like designs incorporating LTE in their high-end units, with more traditional-format TETRA radios still offered. These radios have been engineered to meet the environmental and security requirements of users. Others are focusing on the more traditional form factor and improving audio, coverage and usability. Which all means users have the benefit of being able to choose which way to jump – which has to be a good thing.

Author: Richard Martin