The UK is in the process of moving its emergency services communications onto a 4G LTE network in a ‘big bang’ approach. Unlike most other countries, it intends to switch off its dedicated mission critical voice network.
Not only that, it has also chosen to run the service on a commercial mobile operator’s network. Some 300,000 UK emergency service personnel will share UK operator EE’s network with 30 million consumers.
It’s a bold move that has understandably caused some nervousness among the UK emergency services, but there is little question that moving to broadband systems is the way mission critical networks for first responders are moving – with the UK going first.
As such, the UK is the object of a great deal of interest from other countries that are curious to see how such a radical move plays out. However, details of how the £1bn Emergency Services Network (ESN) will work have been few and far between. But we do know a bit more following the British APCO 2016 conference and exhibition in Telford in February.
Steve Whatson, deputy director Delivery, Emergency Services Mobile Communications Programme (ESMCP) – the organisation within the UK Home Office procuring ESN – assured delegates that ESN will match the existing dedicated Airwave emergency services communication network in terms of coverage for roads, outdoor hand portable devices and marine coverage. Air to ground (A2G) will extend its reach from 6,000ft to 12,000ft.
Whatson also pointed out that coverage is not one single piece, but will comprise a number of different elements, which all need to mesh into one seamless network run by the ESN Lot 3 Mobile Services (main 4G network) provider – EE.
This includes: EE’s main commercial 4G network; Extended Area Services (hard-to-reach areas of the UK where new passive sites are to be built under a separate contract and then equipped with EE base stations); air-to-ground; London Underground; Crossrail; marine coverage (to 12 nautical miles); and special coverage solutions.
EE is currently rolling out new 4G sites – it will eventually have some 19,500 sites – and is upgrading others with 800MHz spectrum, which propagates over longer distances and is better at penetrating buildings than its other 4G spectrum holdings. Crucially for ESN, it is also switching on a Voice over LTE (VoLTE) capability, starting with the UK’s main cities.
Availability and resilience
Mission critical networks must be always available and have levels of resilience far in excess of commercial networks. Speaking exclusively to Wireless in early May, Tom Bennett, group director Technology Services, Architecture & Devices at EE, said: ‘We already achieve a very high availability level, but what the Home Office was asking for effectively was about a 0.3% increase against our existing commercial availability levels.
‘Now for every 0.1% increase in availability there is a significant investment because you are at the extreme top end of the curve where it is harder and harder to make a noticeable difference.’
There are very specific requirements for coverage and availability of the ESN network for the UK road system. Bennett says: ‘Mobile is based on a probability of service. No more than 1% of any constabulary’s roads are allowed to be below 75% availability, and on major roads it is 96% availability. A coverage gap in this context is no more than 1km.’
The current Airwave network has approximately 4,000 sites, many with back-up generators on site with fuel for seven days of autonomous running if the main power is cut, along with a range of resilient backhaul solutions.
Bennett says that out of EE’s 18,500 sites it has about the same number of unique coverage sites (ie. no overlapping coverage) – around 4,000. ‘As part of our investment programme, those unique coverage sites will need a significant investment in the causes of unavailability – ie. resilient backhaul and back-up batteries.’
He explains that EE has undertaken a lot of analysis of what causes outages on its network, and it has combined that data with the Home Office’s data on where the natural disasters in the UK have occurred over the past 10 years.
From this, EE is able to make a reasonable assessment of which sites are likely to be out of action due to flooding or other disasters for more than three or four days. ‘For those sites – and it is less than 4,000 – you need generators too, because you may not be able to physically access the sites for some days,’ says Bennett.
For obvious reasons, the unique coverage sites are mostly in rural areas. But as Bennett points out, the majority of cases where the emergency services are involved is where people are – suburban and urban areas.
‘In these areas EE has overlapping coverage from multiple sites to meet the capacity requirements, so if a site goes down, in the majority of cases we have compensation coverage. A device can often see up to five tower sites in London, for example,’ he says.
Having adequate backhaul capacity – and resilient backhaul at that – is vital in any network. Bennett says EE is installing extra backhaul, largely microwave and fibre, but other solutions will also be used including satellite and LTE relay from base station to base station – daisy chaining. On 9 May 2016, EE announced a deal with satellite provider Avanti to provide satellite backhaul in some areas of the UK.
Additional coverage and resilience will be offered by RRVs (rapid response vehicles), which EE already has in its commercial network today, for example, to provide extra capacity in Ascot during the racing season.
‘We would use similar, although not exactly the same technology for disaster recovery and site/service recovery, but with all the backhaul solutions,’ says Bennett. ‘Let’s say we planned some maintenance or upgrade work that involved taking the base station out for a while.
‘We’d talk to the chief inspector before the work commences. If he says, there’s no chance of doing that tonight, we can put the RRV there, and provided we maintain coverage, we can carry out the work. RRVs are a very good tool for doing a lot of things.’
At the British APCO event, Mansoor Hanif, director of Radio Access Networks at EE said it was looking at the possibility of using ‘airmasts’ to provide additional coverage. Meshed small cells, network in a box and repeater solutions are becoming available for these ‘airmasts’, which will provide coverage from balloons, or UAVs – tethered drones with power cables and optical fibre connected to them.
Priority and pre-emption
The ability to prioritise some users over others and, if necessary, clear the network to give them access, is a key feature of mission critical networks, and something very dear to the police in particular.
Addressing this, Bennett says: ‘ESN is predicated on priority and pre-emption. We will pre-empt users with ESN Sims against all others; and we will prioritise their services. Even if it is an important high priority user, if he is checking Facebook, we don’t care. If he is using critical voice, then that service is prioritised above everything else.
‘Ruthless pre-emption, where you push people off the network, is available to us too. We know these mechanisms work and we have categorically proved that, but the point here is to enable co-existence of both ESN personnel and consumers. Voice services have a higher priority than basic data services.’
EE is also building separate network cores for ESN. ‘We don’t need to do this’ says Bennett, ‘but we are because it is easier for them. We have six core sites and we are adding two specifically for ESN.’
However, the HSS (home subscriber service) and packet core for the mission critical services lies with Motorola Solutions, the ESN Lot 2 User Services provider. ‘It is like a full MVNO,’ says Bennett. ‘It is our radio network with our packet core interfaced with Motorola’s packet core and HSS. Users do not have an EE Sim; they have an ESN Sim.’
Public safety applications sit with Motorola and it decides on who and what gets priority. ‘We enable that prioritisation and pre-emption and that is part of the integration work and interoperability work we do with Motorola,’ says Bennett.
He says that knowledge of the subscribers and what they are doing isn’t for EE to know; it will just do what it is asked to. ‘We have the use cases, we know that much, as we need to make sure that it does work when it happens – and that is our joint responsibility with Motorola. But the accountability sits firmly with Motorola, as they are the ones facing the control rooms,’ says Bennett.
In terms of its 4G rollout and existing network upgrade, Bennett says it is business as usual, but with more aggressive timings. EE has to acquire and build out some 880 sites. ‘Once done, we must get the resilience right, but building the site is no different, and the upgrade programme is a continuation of the work we have been doing over the past four years.’
‘The key thing for end users is that they are not going to see a linear growth of coverage. What happens is that we do all the build and transmission work where they won’t see an impact and then you’ll get all the activations, so there will be a big rush of coverage additionally at the end,’ explains Bennett.
‘We’ve got to acquire and build the site or modernise existing ones, then add the tin, swop out the antennas and then you’ve got to deal with the transmission. We’ve actually got three factories operating for this and a fourth dealing with activation.’
Bennett points out that ESN will be able to smoothly evolve to keep up with developments in mobile technologys. ‘We are at LTE Release 10 now, but for ESN we will be at Release 12, and at some time during the life of the contract we’ll have to go to Release 13 with Motorola. Release 14 is probably the first release that might have aspects of 5G in it – but it is software.’
He adds that the service needs to be ready for operational testing by around April 2017. ‘Then major operational trials with end users start and go on for six months rolling on to the go-live September 2017 start date when the first users will start transition.’
Initial User Device Detailed Specifications (UDDS) have been available for some time, which provide some information on: handheld devices (ruggedised and standard commercial off the shelf); remote speaker units; tablets; vehicle mounted devices; gateways; and managed services. However, at the time of writing, revised specifications, particularly with regard to form factor, are still being awaited.
Wireless understands the cost of certification is £25,000 per devices and, while that may be a digestible sum for the larger players, privately some small device manufacturers have suggested that the cost may be prohibitive for them. If so, that will inevitably restrict the breadth of the device ecosystem available to end users.
Applications also need to be certified, and that will cost too. Any changes to devices or applications mean going back through the certification process. Some commentators have suggested that while such a move is understandable and perhaps necessary from a security point of view, it may negate some of the main advantages of moving to ‘commercial’ style broadband systems, where upgrades are a daily event.
ESMCP’s Steve Whatson reported in February that work on direct mode operation (DMO) was progressing, but he said: ‘There are reasonable questions over whether it will be in handsets by the time users start transitioning. We may need back-up ideas – dual-mode devices.’