Evolution of the use-case

Chair of ETSI’s Technical Committee for TETRA and Critical Communications Evolution, Brian Murgatroyd, talks to Philip Mason about the future of narrowband.

COVID-19 notwithstanding, the biggest current talking point for the sector is the way in which broadband critical communications technology is beginning – slowly but surely – to steal a march on its narrowband equivalent.

As discussed elsewhere in this issue, for instance, we are already starting to see numerous examples in the public safety space, not only in relation to national roll-outs, but also individual MNO contracts. At the same time, meanwhile, we are also seeing the integral role being played by broadband in the burgeoning ‘Industry 4.0’ concept.

As exciting as all this undoubtedly is, of course, the other side of the conversation is what the future might hold for the aforementioned narrowband technology. Will organisations even be using the likes of TETRA in 10 or 20 years and, if so, what might that usage look like?

One answer to this can potentially be found in a piece of research published by IHS Markit this time last year, which concluded that demand for TETRA is actually likely to increase, at least in the short term. According to the organisation, this will be led primarily by the industrial user vertical (eight per cent compound growth by 2023), closely followed by transport, utilities and public safety.

More reassurance, meanwhile, is provided by the hard work still being carried out in order to improve TETRA as a standard going forward. This is occurring in a variety of realms, including security, as well as the interoperability necessary for successful broadband/narrowband interworking.

Focus on interworking

As chair of ETSI’s Technical Committee for TETRA and Critical Communications Evolution, Brian Murgatroyd is in a uniquely informed position to answer the questions posed above. Discussing his views on the future of narrowband technology in an increasingly complicated marketplace, he says: “It’s true that a lot of national communications systems are going over to broadband, which you can understand due to the potential for enhanced services such as streaming video.

“At the same time, that doesn’t necessarily apply to all groups of critical communications users, or indeed other TETRA users. There’s a large proportion of the market that still only requires – or indeed prefers – a narrowband service.”

He continues: “If user organisations do require broadband, meanwhile, there will still be questions to answer, such as whether that will be on its own or in conjunction with voice provided by narrowband.

“TETRA is also incredibly reliable, something which – again – could potentially be a factor if the majority of public safety broadband networks are likely to be operated off the back of pre-existing commercial offerings. This is by no means a straightforward question.”

Going back to the subject of standardisation as an indicator of future value, it is no surprise to learn – certainly given the above answer – that a key area of focus is the interworking piece. This is something which is being demonstrated across the world, whether it is the Norwegian authorities rolling out Motorola’s Kodiak solution, or the Kuwaiti government’s recent procurement of Airbus’s Tactilon Dabat device.

“Hybridisation is a natural and important part of our work going forward,” says Murgatroyd. “We need to cater for people who want to interwork TETRA and broadband, either temporarily as they install their systems, or permanently because they believe that broadband speech will lag behind data.

“The interworking functionality is intended to maintain as many services as possible across the link. One to many, many to one or many to many.”

One area of particular interest to Murgatroyd is security, something which he has been involved with throughout his career at ETSI. Discussing the ongoing evolution of this in relation to the TETRA standard, he says: “TETRA has always had air interface encryption between the base station and the device, just like you’d have on a GSM or 3G/4G network.

“At the same time, a percentage of users also require greater protection, as well as separacy of agencies using the network. Having been quite heavily involved in that, I have to say, the end-to-end encryption side of TETRA is extremely effective.

“We’re now developing new algorithms with a longer key length for air interface encryption. We haven’t had notification of any attacks on public safety TETRA, but nevertheless we need to future-proof things.”

He continues: “Going back to the subject of interoperability, the question now is how do you re-encrypt end to end across the broadband network? More to the point, how do we make sure that the standards are implemented in relation to this?

“As with everything else, it’s all very well saying what the requirements are and writing a standard, it’s a different thing to get industry to adhere to it. It’s the demand which makes the standards viable.”

Asked what he believes the main technical issues might be when it comes to standardisation, Murgatroyd suggests that one could lay in the variety of different ways there are to achieve hybridisation. Examples he gives of this include the aforementioned hybridised terminals themselves, as well as joining nets via a dispatcher patch, connecting the same audio to both systems.

Regarding encryption across broadband and TETRA networks, meanwhile, this will likely have to be solved by what Murgatroyd refers to as an “intermediate transcoding step within an interworking function [IWF]”. This is because “pure end-to-end encryption requires a straight-through connection across both the TETRA and broadband networks, while retaining synchronisation”.

According to Murgatroyd, this can be facilitated by using the TETRA codec in the broadband system. However, this would require broadband terminals to be able to use both the TETRA codec as well as the broadband one.“This may be complex to achieve, so the compromise of an intermediate transcoding in an IWF is fine, as long as the latter is contained in a secure environment,” he says.

It is obvious that TETRA currently possesses clear advantages over broadband, particularly when it comes to mission-critical push-to-talk. Indeed, it has been the gold standard for years when it comes to this area of functionality.

The same cannot be said, however, for its short data service, something which, in terms of ‘non-voice’, is essentially the narrowband equivalent of being able to send an SMS. Given the limitations of the technology in this regard, how is it likely to evolve purely from a use-case perspective? What can users expect to see over and above what they have now?

Addressing this, Murgatroyd says: “The short data service has actually been very widely used, which is something that people may not be aware of. This came to the fore particularly with location services/devices, enabling organisations to know where their resources are. Personally, I’d say this aspect of functionality has been fully developed, with the standards amended accordingly.

“This of course is not to say that the implementation of the technology itself hasn’t moved on, something that you can see in the increasing roll-out of TETRA paging. This is apparent in somewhere like Germany, where the fire brigade relies on a huge number
of volunteers.”

Lack of faith

Earlier on in the interview, Murgatroyd expressed what seemed like a potential lack of faith in commercial networks in terms of resilience. That being the case, you also have to wonder what his opinions are in relation to other crucial features such as priority and pre-emption, without which no network meant for first-responders could function. With our time coming to an end, I ask him to clarify his comments.

“I actually have an enormous amount of faith in commercial networks when it comes to mission-critical functionality,” he says. “A huge amount of resources and preparation have gone into these projects, after all, the most obvious examples being FirstNet and the Emergency Services Network.

“Nevertheless, these are still commercial networks, meaning there are factors which always need to be considered. That obviously includes priority and pre-emption, but also the physical infrastructure itself. What’s the overlap coverage like if a base station falls over? Is the contingency there to deliver the same level of service that they’re used to with TETRA?”

He continues: “This obviously applies to any national communications system, which is another reason why a lot of governments are quite cautious when it comes to just abandoning what they already have. An illustration of this is the original roll-out of TETRA in the UK, where we made a large number of assumptions which didn’t actually turn out to be quite right.

“One of these was that base stations only ever fail one at a time, which of course is not always the case. You also have to take into account the possibility of a power outage, where you could lose 30 or 40. What happens if there’s insufficient back-up power, which was precisely what happened on more than one occasion?”

If what Murgatroyd says is correct, it is clear that TETRA possesses an extremely viable future. It continues to be a solid, well-specified and well-supported technology, the use of which is as varied as the industries in which it is rolled out.

Media contact

Philip Mason
Managing Editor, Critical Communications Portfolio
Tel: +44 (0)20 3874 9216