Airwave: evolution in the age of revolution

25/01/2022

With UK emergency organisations still procuring Airwave devices in the time before ESN, Philip Mason reports on the ongoing development of TETRA as an operational technology.

As anyone working in UK public safety comms over recent years will be aware, much – you might even say the majority – of the focus within the sector has been directed towards the Emergency Services Network.

As important as ‘mission-critical’ broadband is going to be going forward, however, we’re not quite there yet. Indeed, it’s likely to be several years before the final transition away from Airwave, with the programme now shifting much of its attention towards user reassurance.

With that in mind, one thing that doesn’t necessarily get talked about is the current TETRA-based technology, particularly in relation to its ongoing development. This is a shame, if only because UK emergency services, ESN or no ESN, are still procuring new Airwave handsets to replace kit which in some instances is over a decade old.

It’s also a shame because TETRA is evolving, both in terms of the standard itself and the operational benefits on the frontline. Furthermore, this evolution is taking place in direct parallel with the development of emergency services broadband, as evidenced by the current emphasis on the interworking piece. 

That being the case, in this article, we’re going to examine the aforementioned evolution of TETRA via input from two different experts. The first of these – Brian Murgatroyd – will talk about the standard itself, something which he has been closely associated with since its initial creation.

We’ll also hear from Cheshire Constabulary, which has just procured a suite of new Airwave-compatible handhelds, prompted by the encroaching obsolescence of its current stock.

Brute force attack

Murgatroyd is current chair of standard organisation ETSI’s technical committee for TETRA and critical communications evolution. Probably even more relevant for readers of the BAPCO Journal, meanwhile, is that he also previously led on critical communications security at PITO (the former UK Police Information Technology Organisation), during the original roll-out of Airwave.

As such, he has a better view than most, not just on the evolution of TETRA but also the evolution of TETRA specifically as it pertains to public safety comms in the UK. Giving an overview of the current, ongoing, changes to the standard and why they are taking place, he says: “There are currently two main areas where we are seeing considerable change and development. That is, around broadband interworking, as well as increased security requirements.”

Dealing with the latter topic first, Murgatroyd says increased security measures are becoming necessary due to the development of ever-more powerful computing technology. According to him, this is symbolised in particular by the increasingly discussed but as yet unrealised phenomena known as ‘quantum computing’.

“What we are trying to do on the security side is essentially future-proof TETRA for the next 20 or so years,” says Murgatroyd. “Currently, the TETRA air interface uses an algorithm which employs 80-bit keys, something which has been the case as far back as 1996. This level of protection has been fine up until now but might not be sufficient going into the future. The plan is to increase the key length to 192 bits.”

He continues: “This increase is necessary to continue to avoid what is known as a ‘brute force attack’, during which the hostile actor essentially tries every key combination in turn with the specific aim of cracking the security code. The longer the key code, the longer an attack would take, and with 192 bits it would take several years.”

Murgatroyd illustrates this via a discussion of the American Data Encryption Standard, which used a 56-bit key. This was first ‘cracked’ in 1998 using a purpose-built machine (known as Deepcrack), developed by the Electronic Frontier Foundation. The first attempt to break the security took just over two days, while six months later a networked approach led to it being broken in 22 hours.

Surprisingly, one thing which this posited increase in security has not been prompted by, however, is the increasing need on the part of users to interoperate TETRA and broadband technology together. This is due to the fact – at least according to Murgatroyd – that within any system involving both narrowband and broadband, both discreet ‘sides’ will already be using their own well-established security protocols.

Elaborating on this, he says: “When it comes to interworking, what is ultimately required is matching levels of security on both sides. The danger would be having strong encryption on one and weak encryption on the other when they’re in the process of sharing the same message.

“Honestly, the security measures which already exist within broadband are pretty good, even before the overlay of the critical communication requirements. Interworking will not be a limiting factor when it comes to increasing security within TETRA.”

Staying with the interworking piece, Murgatroyd likens ongoing efforts to facilitate smooth communication between the two as being like the creation of a “black box” sitting inside the TETRA system.  Elaborating on this, he says: “The specification for the ‘interworking function’ shows how all appropriate services on the critical comms broadband system can be delivered to a connected TETRA system, and vice versa. Some services – like video streaming – clearly cannot be delivered by narrowband. There is a growing demand for interworking in both systems.”

A step change for Airwave?

Speaking to Murgatroyd, it is clear that sizeable efforts are taking place to evolve the TETRA standard, thereby addressing a technological environment which has moved on considerably since Airwave was first rolled out 20 years ago.

At the same time, however, changes are also taking place related to how the technology is used by those operating on the frontline. One example he gives of this is current attempts to leverage the use of group addressed packet data, thereby enabling the sending of a single message to multiple recipients. 

This potential for development on the ‘operational’ side has recently been reflected in Cheshire Constabulary’s decision to procure a suite of Motorola Solutions’ new MXP600 TETRA handsets for its officers operating across the force. According to Paul Wycherley, Airwave Manager for Cheshire Constabulary, this was done purely to provide those on the frontline with the best possible technology in the interim period before ESN transition.

Discussing this, he says: “It became apparent about a year and a half ago that we’d – quite rightly - got the maximum value out of our previous generation of handsets and it was the right time for an upgrade.”

He continues: “When exploring new technology investments, Cheshire Constabulary’s IT services team always works according to the motto that they want to give those on the frontline the very best equipment to do the job. That’s ultimately what the procurement of the new handsets was all about.”

“We were aware that several manufacturers, including Motorola Solutions, were launching new terminals, so we decided to have a look at them. We found that the MXP600 in particular had significant operational benefits in the areas which were the most important to our officers.”

According to Wycherley, one of the most important benefits was the handsets’ ability to increase radio strength, thereby enabling greater connectivity in more remote areas. There were also apparent advantages around the accuracy of the onboard GPS, something it was anticipated would come into its own during use by specialist officers during hazardous incidents.

“Following trials of the new equipment, our rural officers in particular told us they were achieving increased communication in the most remote geographic areas. Our officers also rely on the device’s intelligent and superior audio quality which allows for clear communication, even in extreme weather and noisy conditions.”

“To take one example, during attendance at the G7 in Cornwall in June, one of our sergeants who took along the MXP600 had excellent coverage in the most rural areas. That rubber stamped it for us.

“At the same time, the MXP600 also combines GPS and Galileo to provide location accuracy of 1.2 metres³. That’s vital for officer safety and decision making, for instance during incidents in which specialist firearms officers are deployed. Also, if an emergency button or ‘man down’ feature is activated on the MXP600, it enables dispatchers to pass on even more accurate location information to others on the frontline, so help can arrive faster. Being able to pinpoint a frontline worker’s location to just a few metres can make all the difference in keeping them safe and effectively managing an incident.”

The other attractive thing for Cheshire Constabulary – again, according to Wycherley - was the inclusion of Bluetooth 5.0 functionality, thereby offering potential for the devices to be used in conjunction with ESN. This goes some way to answering the next - pretty obvious - question, relating to why Cheshire would re-procure TETRA devices now with ESN seemingly around the corner.

 Answering this, he says: “We believe that the version of Bluetooth included on the MXP600 devices will be compatible with ESN. That opens up options for us to use it as a remote speaker mic connected to a broadband device carried in the officer’s pocket.

 “That in turn gives options in terms of reduced training costs, because our officers will already be used to carrying and operating the Motorola Solutions device. So, alongside the extra functionality, we believe that the radios will help us to achieve a more seamless transition to the new network.”

Wycherley is convinced that Cheshire Constabulary’s new radios represent a “step change” for Airwave TETRA handsets as used by the UK emergency services. If nothing else, the latest generation of devices prove that TETRA technology is still developing and remains relevant, both in terms of the standard itself and the operational functionality required on the frontline.

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