ermany’s Public Safety Digital Radio (‘BOS’) Network is the world’s largest TETRA network. As of October this year, it consisted of 4,574 base stations, covering 99 per cent of Germany. It has around 753,000 subscribers to date and about 50 million calls are made over it every month.
Given that it has been completed only recently, there is an understandable desire to get some decent mileage out of it prior to any migration to LTE, putting it at the opposite end of the spectrum to the UK’s ageing Airwave network.
Andreas Gegenfurtner (pictured above), CEO of the Federal Agency for Public Safety Digital Radio (BDBOS), says it plans to operate its current TETRA network until 2030. “Nevertheless, BDBOS has already started its modernisation process to make the existing network suitable for the future and to pioneer future broadband services.” He adds there are two aspects to this process – one is the migration of the access and core networks’ backbones from circuit switched to packet switched technology, which will result in an IP-based backbone infrastructure. The other aspect is “the modernisation of the telecommunication platform”. The first step is to update the existing TETRA network to be suitable until 2030, and the second is to realise a broadband solution either as a standalone network, as a mobile virtual network operator (MVNO) solution or as a hybrid network.
One challenge that Gegenfurtner recognises is the lack of available broadband spectrum for public protection and disaster relief (PPDR) use and “therefore a hybrid solution is probably the way to go. BDBOS prefers to use standardised solutions and a specific slice for LTE-based critical communications. Potentially this solution with all its required features will not be available before 3GPP Release 16.”
Gegenfurtner notes that the decision as to whether or not Germany should have a broadband network for public safety users is a political one and that BDBOS and the German Minister of the Interior “are currently in the preparation process for political decision-making”. BDBOS is about to finalise the planning guideline for the migration of the access network as well as the core network towards IP. “The migration of all network components to the IP world should largely be complete by 2020/2021,” Gegenfurtner says.
He adds that BDBOS assumes that this modernised network will be able to support a higher number of users, and he notes that extending its use to users who perform safety-orientated tasks “could raise the level of protection on critical infrastructures and strengthen our society’s internal security. The decision as to whether the network should be opened to ‘yellow light users’ is up to the federal government, but BDBOS would be prepared for that.”
Another challenge for a German public safety LTE network is that it would have to meet the same high standards established by the BOS Network. Over the past three years, its availability has averaged 99.95 per cent, rising to 99.97 per cent in 2016. “We have not had any serious technical incidents,” says Gegenfurtner. “Our users appreciate the extremely high level of network availability – even in case of a disaster or large-scale mission when commercial mobile radio networks have collapsed, as seen during the flooding of 2016 and the Berlin truck attack last year.”
“Technology changes, but the basic requirements – availability, integrity, reliability and redundancy for a successful network operation – will stay valid,” he says, adding that he believes a period during which TETRA and LTE will coexist will be required until the broadband technology and its applications have proven their reliability to German PMR users.
Gegenfurtner highlights the role BDBOS plays in the various industry and standard bodies. “We’re an active partner within The Critical Communications Association (TCCA), helping to define interoperability with profiles and test plans. We chair its Operator/User Association working group and we’re active in the European Telecommunications Standards Institute (ETSI), supporting the standardisation of TETRA at the international level. It was only natural for us to extend this successful approach to broadband technology and functions.
“BDBOS will be an active partner in 3GPP to support the standardisation required to support public safety LTE-based communications between PMR user equipment from different vendors. We have to ensure that the essential services and features for our PPDR users such as group communication and emergency call function become part of the specifications for standardisation and technological developments.
“So, we therefore work closely with other critical communication network operators in Europe and the US. Last month [October], we all signed a declaration that sends a very strong signal to the international standardisation community – to public as well as to commercial network operators, to vendors and manufacturers, to researchers who work on next-generation technologies, and to all users that rely on critical communications for their work. We will not let them forget how crucial and necessary it is to take public safety into account for future innovations.
“We and our international colleagues will play a vital role in standardising, implementing and rolling out broadband communications for mission-critical communications.”
The 2017 G20 Hamburg summit was attended by many world leaders, requiring absolute attention to security and their safety
A challenging task
Turning to the BOS Network as it is used today, Gegenfurtner highlights TETRA’s short call set-up time, noting that it is essential for the secure co-ordination of operations with police, fire and rescue services. He adds that low-bandwidth Short Data Services are heavily used for status and positioning reports as well as for short text messages.
“The network also enables nationwide and cross-organisational communication and simplifies the implementation of complex missions – especially in crisis and disaster situations. Even today the non-police community, the fire brigades, ambulance and disaster management services constitute more than half of our users.”
He also says that managing traffic and capacities during large-scale events is one of the most challenging tasks for a public safety radio network operator. He adds that over the past few years, BDBOS and its key partners have developed and introduced new technological features and tools, including the use of additional control channels. He adds that new technology automatically checks the utilisation of base stations’ individual control channels and selects the one in least use to improve the signalling capacity in the BOS Network.
In addition, a real-time monitoring system, which was implemented earlier this year, supports operational and tactical activities by providing both an overview of and detailed information on the BOS system, including its current usage and available capacity. This allows decisions to be made quickly during operations, thereby preventing loss and damage.
BDBOS is also looking to integrate mobile base stations connected via satellite links to boost capacity during large-scale operations and will be soon be field-testing this technology.
Securing the G20
One of the biggest tests of the BOS Network took place earlier this year in the form of the 2017 G20 Hamburg summit, which involved 25,000 PPDR users and the same number of terminals. The event was marked by an attempt by protesters to storm into the area where the summit was taking place, on the night of 6 July, only for them to be dispensed with water cannon, followed by rioting the next night that resulted in the looting of shops and the burning of dozens of parked cars, which stopped once specially armed police were deployed. It resulted in 186 arrests and an additional 225 people were taken into temporary custody.
For such large-scale operations, Gegenfurtner says BDBOS supports its users through performing radio field analysis in advance, providing temporary capacity expansions by extending TETRA base stations with additional TETRA transceivers (TTRXs) or deploying additional mobile base stations for the operation’s duration, as well as preparing a switchover to the emergency DXT as a preventative measure.
BDBOS also assists with call group planning, frequency management and audits the relevant network elements prior to the operation. During the operation, BDBOS also co-ordinates the work carried out by authorised offices and service providers such as Nokia’s technical operations team, system supplier Airbus and facility management services.
Eva-Maria Eckmann, police superintendent, head of Authorised Agency Hamburg, Federal Centre for Digital Mobile Radio Hamburg, Department of the Interior and Sport, gives her perspective on the preparations for the event and its outcome.
“Since the event location, as well as the hotels where the heads of state resided, were situated in the city centre of Hamburg, we knew the main communication among the emergency personnel would take place in a central area, covered by four to five TETRA base stations. The routes from the airport to the city centre also had to be covered.
“Therefore the base stations were fully equipped with eight TTRXs. Another part of the preparation for the summit was the creation of an entirely new group call system, which was restricted to 128 call groups in total. Ten per cent of this was reserved for everyday ‘normal’ usage. Apart from the local police, the federal police, ambulances and other emergency services were involved in the planning of the fleet-mapping right from the start. An additional difficulty was explaining the need to reduce the number of call groups to the first-responders. However, the resulting co-operation laid the ground for very successful communications during the entire event.”
Eckmann adds that the 23rd Organization for Security and Co-operation in Europe’s Ministerial Council had taken place in Hamburg relatively recently, in December 2016. “Even though it didn’t have the same political visibility, it served as a sort of test run for the G20 Summit.”
She says: “We decided that all non-resident forces shouldn’t use the GPS function of their device nor their own local call groups. They were warned that terminals not adhering to these restrictions would be barred from service and this was strictly executed during the event. Approximately 50 call groups were barred from the service immediately on arrival; terminals with GPS switched on were identified by the Authorised Office (the single point of contact for the BOS in a state) and taken out of the network, or the devices’ GPS function was switched off remotely.”
She also says that instructions for the use of the digital radio network were sent out to all organisations through the Authorised Offices in their state beforehand.
The following fall-back steps were planned for and were also implemented during the peak of network usage:
- In the planning phase, call groups were identified which would be merged in case of high network utilisation
- A third control channel was activated on two base stations, reducing their capacity by one traffic channel
- Broadcast/cell parameters were changed as follows:
- The follow-up time of each operational group call was reduced from three to two seconds
- The broadcast parameters for cell changes were adjusted during the event to minimise the load on the control channel and to cut down the number of terminals connected to one cell during a massive statically located operation.
Looking back with the benefit of hindsight, Eckmann says the Hamburg Police wouldn’t have changed the overall plan, but minor improvements could have been made by getting more staff involved in supervising the technical aspects of the operation, and having a greater number of devices where the GPS function could be turned off remotely.
The event locations had their own indoor radio coverage, while those hotels without their own coverage were temporarily equipped with DMO repeaters.
Speaking of indoor coverage, Gegenfurtner says BDBOS’s original purpose was to build a nationwide public safety radio network with a focus on outdoor rather than indoor coverage. However, with the roll-out of the BOS Network, BDBOS took measures to meet end-user organisations’ – notably fire brigades – need for indoor radio usage. Since 2008, BDBOS has developed technical options and contractual rules to provide TETRA signal feeds of different kinds for indoor use, but it is building-owners who are obligated to fund and equip distributed antenna systems.
BDBOS implemented a registration process to handle the chain of participants of indoor radio installation, such as end-user organisations, owners and builders, radio planners, Authorised Offices and the Federal Network Agency. Underlying this is a contract between BDBOS and property owners to secure enduring compliance with radio network quality. These contracts only apply for trunked mode operation and, as of this September, there were up to 200 of them. “We see this topic as an area of growing importance and one which BDBOS wants to maintain in terms of adapting technical solutions and proposing necessary amendments to federal legislation and municipal regulations,” says Gegenfurtner.
Smooth running
He explains that one of BDBOS’s priorities is working to reduce the digital radio network’s running costs and associated environmental impact. So far, it has succeeded in reducing running costs for its 64 switching centre sites by 10 per cent between 2013 and 2016, and it is targeting savings of 30 per cent from 2013’s figures.
To achieve this, “we are improving the airtightness of our data centres’ server rooms so that their oxygen reduction units operate more efficiently. We’re also trying to use as much external air cooling as possible to reduce our cooling systems’ running time. Furthermore, we’re fine-tuning how we operate our individual data centres, but we’re still working to improve our energy balance.”
The BOS Network’s sites rely on diesel generators, and each switching centre site has two of them. While planning the network’s data centres, BDBOS also considered solar panels and hydrogen fuel cells. “Due to fire safety concerns and non-optimal roof orientation, the use of solar panels was rejected and the technical capabilities of hydrogen fuel cells were not sufficient for the network’s high requirements when the planning was taking place,” Gegenfurtner says. However, he adds that some federal states are testing the use of hydrogen fuel cells on public safety radio stations.
Clearly, running the world’s largest TETRA network is not without its challenges, but so far BDBOS and its supporting organisations and vendors have risen to the challenge. Its completion has come at an awkward time in the technology cycle, with public safety LTE now looming large on the horizon. However, BDBOS is clearly planning for the future with all the diligence that would be expected, given the roughly three quarters of a million people who trust it with their lives and will be affected by the choices that it and its political overseers will make in the years to come.
