MCX interoperability: Going far together

The work to ensure that user organisations get the interoperable mission-critical broadband ecosystem they require continues to progress, despite one significant stumbling block. Sam Fenwick explains

2013 was a memorable year for many reasons – the death of Nelson Mandela, the birth of Prince George, and the Boston Marathon Bombing, to name just a few. However, from our industry’s perspective, the most memorable event – and the one with the most long-term ramifications – took place on 31 October. TCCA’s signing of the 3GPP Partnership Agreement was the first clear step on the road we have been travelling for the past six years. It marked the start of the unceasing work to standardise the features that are required if mission-critical two-way radio users are to fully benefit from the wider telecommunications ecosystem and eventually replace their radios with broadband equivalents.

However, it must be remembered that standards are not the only piece of the puzzle. For there to be an ecosystem of mission-critical devices, servers and applications that allows government agencies and end-user organisations to buy with confidence, they need to know that they will not be tied to a single vendor due to technical issues such as ambiguities in how to implement the mission-critical standards.

For this reason, ETSI has been running its MCX Plugtests series, which brings together vendors and industry observers. The third such event (which involved remote testing only via ETSI’s HIVE virtual private network) took place earlier this year and was based on 3GPP Release 14. Over two months, 1,000 test cases and more than 150 sessions were run between 26 vendors, and the event achieved a 92 per cent success rate.

Saurav Arora, project manager (MCX Plugtests and 3GPP WG CT3), says the observations and results from the event were compiled and sent to ETSI and 3GPP TSG SA WG6 (the working group focused on mission-critical applications). This process was driven by FirstNet, and Arora says it will take 3-4 months to receive all the answers to the queries that were generated, and of the 20-25 issues that were identified, there were no stumbling blocks from a hardware perspective, although there were “some minor issues [and] some issues related to affiliation. There are a lot of clarifications, but no blocking point, some of them are improvements.”

The fourth MCX (MCPTT, MCData and MCVideo) Plugtest will take place from 23-27 September at the Savonia University of Applied Sciences in Kuopio, Finland, after two and half months of remote testing. It is being organised by ETSI, in partnership with Erillisverkot, with the support of TCCA and the European Commission. The event will mainly focus on tests with radio equipment (eNodeBs, user equipment, and evolved packet cores) with Unicast and Multicast support, but will also allow over-the-top testing of mission-critical servers and clients.

Arora says: “The biggest challenge is that we still haven’t seen much progress on MCData and MCVideo interoperability testing. I’m looking forward to seeing more support from the vendors [in these areas] – they’re quite new as they were introduced in Release 14, so we might have to wait a bit. I’m hoping that during September’s Plugtest we might see more MCData and MCVideo testing and implementations, but the priority will still be MCPTT.”

Harald Ludwig, chairman of TCCA’s Technical Forum, highlights the number of vendors that have signed up for September’s Plugtest – 35 – indicates the vendor community “are all aware of the importance of interoperability and conformance to standards. The vendors are all aware that this is important and [of] the need to go [down] this route.”

Ludwig says we might see implementations of Release 15 MCX functionality in time for next year’s Plugtest. “We always need to give vendors time to implement the standards. For Release 15 it’s maybe too early in September. [There’s] very high demand from the user side and also now from the vendor side to test interworking between MCPTT and TETRA/P25, but the standards are not ready yet.”

According to a blog by Dean Prochaska, FirstNet’s senior director of standards, which summarised the recent 3GPP meetings in Newport Beach, California, the target end dates for the completion of the work on MCPTT and MCData interworking between LMR and 3GPP have been adjusted by three months to reflect delays and, as a result, they are now expected to be completed by September. Despite this delay, according to Arora, ETSI is still seeking to test LMR/3GPP interworking next year. He adds that 3GPP held an ad hoc meeting on 17-19 July at ETSI’s HQ to complete the interworking standards.

One of the complications here is the number of vendors that could be involved in such testing (the number of possible testing combinations increases exponentially with the number of participants). While Ludwig says TCCA has yet to look into the logistics of LMR/LTE interoperability testing, he would like to see the creation of a European equivalent of FirstNet’s testing laboratory in Boulder, Colorado.

The push for certification
As I mentioned in my previous article on this subject (in our October 2018 issue), participation in the ETSI MCX Plugtests isn’t the only activity that is occupying the industry’s attention in this area. For both user organisations and vendors, there needs to be some form of MCX certification. “It gives vendors confidence that their implementations are according to the standard, they’re compliant and they’re interworking with other implementations,” says TCCA’s Ludwig. “[This in turn gives] the users confidence [and tells them that] they are not buying a proprietary solution. [This is] very important at the beginning of a [technology’s lifecycle].”

Tony Gray, TCCA’s chief executive, adds that mission-critical broadband needs to have the same or greater level of interoperability certification as TETRA (which is delivered via TCCA’s TETRA IOP programme), partly as “the diversity of vendors and solutions and functions that are now coming out of all the standards work that we’ve been so successful in doing in 3GPP gives greater opportunity but also greater risk of things falling through the gaps”.

Business case needed
As discussed back in October, the preferred plan is for MCX certification to be handled by the Global Certification Forum (GCF), which currently handles certification for consumer broadband devices. However, one sticking point remains – the automated approach that GCF employs requires the MCX test scripts to be supported by test and measurement equipment and, according to Gray, “we haven’t been successful to date in persuading any mainstream T&M manufacturer to incorporate those test [scripts]”.

However, Lars Nielsen, general manager, GCF, says this issue is exactly “why we [should] start with TCCA and [its] members to define how mission-critical certification should work, because if [the test equipment suppliers] see that certification is coming there [will] be more interest from [them] to provide solutions”.

Ludwig says he has “spoken to some test and measurement equipment vendors already and their approach is always ‘we [need] to have a business case for whatever tests we implement’. I don’t know if they don’t see the business case for mission-critical tests or if [they expect that we] present the business case to them – it’s difficult [and] it’s also new for us because we have not been in this business [before].”

Chris Hogg, programme manager at GCF, says: “If we can bring people together in conjunction with TCCA in a series of web conferences where we can start to get the customers for certification, the mission-critical operators and the manufacturers involved and get them to work together to define the scope of certification then we would [be in] a better position because then the vendor T&M industry will see that there’s something happening.”

Nielsen adds: “I expect governments want to be involved in the decision of which labs verify the compliance of mission-critical devices for their country’s law enforcement and emergency response forces.”

It is worth noting here that the GCF has created a membership category specifically for mission-critical operators and Nielsen says he is keen for the work to define the MCX certification regime to begin as quickly as possible. While he believes there could be up to 10 members in that category within the next two years, he highlights the way in which the mission-critical communications industry moves slower than its consumer counterpart, partly due to the way it is driven by government procurements.

A twin-pronged approach
In the meantime, TCCA is pursuing two other initiatives. “[We’re] trying to catalyse a pre-certification programme and we’ve got quite a reasonable level of support from interested vendors in pursuing that,” says Gray. “TCCA would engage an independent test house [to manually] analyse [the] test traces [from the MCX Plugtests] and pre-certify people’s equipment as being conformant to the standards and being interoperable to other conformant equipment. We hope to be able to start to do that soon after the fourth MCX Plugtest in September.”

Obviously, this approach is less than ideal, given that the manual nature of this testing may create capacity issues, and Ludwig is currently trying to determine “how many interested vendors are there, how many implementations [they] want to test and how many test cases we need to test to get some confidence in standards compliance”. He adds that capacity is an issue with the TETRA IOP testing programme, as that’s also done manually and “this has resulted in test sessions of several weeks and months for one infrastructure manufacturer”. However, Ludwig adds that TCCA only sees the pre-certification programme as an interim solution.

The second approach is that the Public Safety Communications Research (PSCR) division of the US National Institute of Standards and Technology (NIST) “has quite a substantial budget of investment funds that it wants to spend on getting the mobile broadband solutions available and active in the world, and it has recently come out with a call for proposals for incorporation of mission-critical voice testing in test equipment,” says Gray. “That would essentially do what I mentioned before of getting one or more test equipment manufacturer to provide the suitable test cases in their test kit. We’re working with several potential partners in being involved in that in much the same way as we are involved in the MCOP [Mission Critical Open Platform] programme, which is funded under the same NIST/PSCR budget.

“So, we’re hopeful that with these two strands running more or less in parallel, we can ultimately end up with a regime and approach that provides the quality of interoperability and conformance testing and certification that the industry needs.”

The commercial factor
It is also worth noting that interoperability isn’t just a technical issue. The decision to allow different MCPTT-based applications and also users on different cellular networks, either using the same or different apps to talk to each other, is largely a commercial one. Gray says the pressure needed to ensure that this is enabled “has to come from the bottom up – unless there’s a compelling reason then the individual carriers will probably want to lock their users into only using their service”. He adds that the “compelling reason” is precisely what led to the creation of FirstNet. In other words, the need for a nationwide, single operable solution that in situations involving multiple agencies from multiple areas – and potentially on different carriers – allows them to communicate and work seamlessly together.

“If the ecosystem allows it to just go on developing in a disparate and unharmonised way, they’ll end up looking back and thinking ‘oh dear, we’ve recreated all the problems we had with [LMR] interoperability… purely for political and commercial reasons.” He adds that “the open market has its advantages”, but it still has to be regulated so interoperability is enforced.

Similarly, political and commercial considerations will have a big role to play once interworking between MCX and LMR (TETRA and P25) has been standardised. “3GPP can develop an interoperable connection towards LMR (TETRA and P25) just as ETSI and ATIS can for TETRA and P25 respectively. But whether any or all manufacturers actually implement those is a completely separate discussion, it’s totally their commercial decision as to whether they think it’s worthwhile or whether they want to try to promote their own proprietary approach,” says Gray. “As TCCA, we would always very strongly promote and require the standardised approach since it’s the only way to maintain an open, competitive market.”

Of course, interoperability is not the only thing that is dear to the hearts and minds of end-user organisations. As Ludwig points out, performance metrics such as call set-up time and voice delay “will be a key criterion for users moving to broadband MCPTT because they have to be at least as good as they are in TETRA or P25; if they are not, users will have no motivation to move to broadband”. He understands that PSCR in the US is working to define test set-ups and measure these key performance indicators.

He also highlights the scale of the challenge, given that there are so many different types of equipment involved – “It’s the set-up of the whole LTE network, of the radio access, of the MCPTT server, the devices, the MCPTT software, and all this needs to be optimised across all the systems.”

ETSI’s Arora adds that so far, call latency and packet loss have not been tested at the MCX Plugtests events, “but [these kind of performance tests cases are] something that we might consider adding”.

We have seen that the work to iron out any kinks in the mission-critical standards is progressing well, and while the test and measurement certification roadblock remains, the industry is working hard to address this, both through engagement with T&M vendors and through pursuing several other approaches. That said, there is no cause for complacency – if user organisations are serious about interoperability, constant and concerted pressure needs to be applied to prevent the industry from sleep-building the next Tower of Babel.