The solution

In 2016 a Distributed Antenna System (DAS) providing a 2G, 3G and 4G mobile connectivity network indoors was implemented and provides 95% coverage at both Addenbrookes and the Rosie Hospitals.

To read more about indoor mobile connectivity solutions, including DAS and other technical options, see Introduction to in building mobile coverage.

At the point of the business case for implementation of the DAS solution this Wi-Fi network infrastructure was being refreshed across the hospital sites.

3 years prior to implementing the current DAS solution a passive DAS proposal was commissioned. Whilst this proved useful in addressing some of the trust's requirements there were two issues that meant this would not have been a future proof investment.

Firstly, this was a single operator solution limiting the connectivity availability for users on other mobile networks. Secondly, this was a passive DAS solution, which was designed to be optimised for a single frequency and as such would have required re-engineering to add on additional services. This meant that changes to accommodate new buildings would have resulted in considerable effort, disruption and infrastructure challenges.

Cambridge University Hospitals (CUH) then conducted further technical and market research, looking at network agnostic options and researching both digital and analogue active DAS systems. This research ultimately led to the implementation of an Active Analogue DAS solution in 2016.

The implementation project, managed by the trust’s estates team, involved collaboration between:

• mobile network operators (MNOs) - O2, EE, 3UK and Vodafone special projects teams
• the service integrator (Cellnex)
• the organisation providing the DAS hardware (Zinwave)

The service integrator’s role is in bringing all parties together to co-ordinate the installation of the new service. This requires specialist knowledge of the mobile industry, experience of working with special projects leads from the MNOs, and meeting industry required Joint Operators Technical Specification (JOTS) compliance standards.

JOTS standards were created to enable mobile operators and their partners to deploy shared wireless solutions for their customers, including capabilities such as avoiding interference between indoor systems and public wide-area networks.

Mobile data via the DAS provides a complementary, yet separate, connectivity infrastructure from the Wi-Fi network. this ensures the necessary connectivity resilience as connectivity becomes more critical for applications such as Teams, Epic SecureChat, Outlook and other Office 365 and cloud services.

The trust uses the 4G network for data and connectivity. Whilst the DAS equipment is capable of 2G and 3G connectivity there are no devices or applications on the network that are dependent on 2G connectivity. No issues were reported to the trust following the switch off of 3G connectivity by mobile network operators - all staff devices are 4G capable and have Voice over Long-Term Evolution (VoLTE) capability, so can make voice calls using 4G data.

Where services or applications can operate over internet, they can use both the mobile connectivity of the DAS and Wi-Fi networks, increasing overall availability. The decision on which connectivity to use is managed at the device and user level, with devices automatically switching to mobile when Wi-Fi connectivity is unavailable (based on legacy device assumptions that Wi-Fi is less likely to be metered) or according to users enabling or disabling Wi-Fi or mobile data settings.

The trust has not implemented any mobile device management (MDM) on devices issued to staff. All mobile devices in use by staff are considered as 'untrusted' over the trust's Wi-Fi network and they cannot access the trust's wide area network (WAN) or network resources.

In practice, this means that staff using mobile phones can only connect to services available over the internet. This emphasises the importance of health applications and services being designed to be internet facing, as these critical services can be made more accessible and more resilient if they are set up to be accessible via the internet.

Responsibility for maintaining the DAS service and managing service incidents sits with the estates and facilities teams, with 3rd party support from the service integrator, Cellnex. The network operators have responsibility for management and maintenance of their owned network equipment in the dedicated on-site base station hotel (BSH).

Monitoring of the DAS is carried out in real-time and if any issues or faults are identified, such as a unit not responding, an automatic alert is sent to the service integrator to investigate. This pro-active monitoring allows faults and issues, such as equipment being unplugged accidently by staff carrying out building work, to be reported and investigated quickly.

Day to day user experience and service management is the responsibility of the estates and facilities team within the trust, who operate the service desk and manage any incidents reported by users relating to connectivity or telephony. If an incident with the DAS is identified they will triage this to either resolve in-house or to report to the service integrator. The service integrator is supplied with data on the fault or issue to support resolution.

The estates and facilities team have their own monitoring capabilities for the DAS, using equipment from 3rd party supplier Metricell. The Metricell devices allow for constant monitoring of all network’s performance on site, gathering data in real time and transmitting this to a dashboard which can be accessed by the team. This dashboard shows performance and coverage data for all networks, allowing issues with coverage to be identified and for supporting data to be pulled out and sent to aid escalation to the network providers via Cellnex.

The trust is currently moving away from these devices, due to concerns around battery usage and the requirement for them to be physically moved to a location to test coverage. These are being replaced with an application-based solution from the same supplier which is installed to staff mobile devices and crowdsources the data in real time.

The network operators themselves have monitoring capabilities for their networks and have access to the BSH for scheduled maintenance and fault resolution on their equipment. To report issues to the network operators the trust contacts the service integrator, who then escalate the issue to the network provider.

The trust invested £450k in implementation of the system, with the MNOs performing the required work to upgrade at their own cost, as with any other changes to their macro network. Support costs for the DAS (at the time of writing) are approximately £40k per year. The MNO O2, as the corporate mobile contract holder at CUH, funded their own base transceiver stations (BTS) connection.

Collaboration with other campus partners and shared use of the infrastructure was beneficial and sharing costs made the solution more affordable. Astra Zeneca are a Vodafone Corporate client with sites on the campus. They funded the hospitals’ Vodafone connection and have Zinwave equipment connecting into the shared BSH.

Royal Papworth Hospital (RPH) also use the campus and have Zinwave DAS equipment installed there, connecting into the CUH BSH. CUH own and manage the BSH but hosting the Astra Zeneca and RPH connections enables sharing of some recurring infrastructure support costs, making this more affordable for all organisations involved.

Unified communications within the trust are managed by Capital Estates and Facilities Management and are not part of the wider IT function. Estates ownership of this work meant they had to work across functions and teams to identify and address any conflicts with clinical IT priorities and associate IT budgets. This helped the investment case for DAS as it became a key part of the strategy to enable a move off of the legacy telephone infrastructure. The DAS supported mobile Voice over Internet Protocol (VoIP) calling meaning there wouldn’t be a reliance on all services using desk-based VoIP due to poor mobile coverage.

Addenbrookes and The Rosie are situated across multiple buildings of varying age, with some dating back to the 1960’s. Implementation of the DAS solution was, by necessity, a phased roll out across the hospital campus. One of the trust's first considerations was how to design the network and where to locate network equipment, including remote units and the BSH itself.

In some of the newer buildings at the hospital the necessary copper and fibre cabling for the DAS equipment was already in place, whereas older buildings required new cabling for the remote units. To make the implementation less disruptive and to make maintenance throughout its lifespan easier, the DAS was designed to keep the amount of secondary hub locations low. A further design consideration was that these locations required power resilience and a secondary power supply, conditions which were not in place across all buildings and locations at the time of implementation.

These considerations, and responsibility for scheduling cabling and installation works, were managed by a dedicated project manager. This allowed a single point of contact for planning and scheduling these works and minimised disruption. As a result, there was no impact on clinical time and no downtime requirement for wards or other clinical areas, with as much of the work as possible being scheduled during already planned activities such as deep cleans.

Due to the design of the DAS much of the cabling installation was in hospital corridors, where drilling and other work did not impact patient care. Many of the antennae for the DAS were situated in underground hospital tugways (dedicated pathways to transport medical supplies and other equipment around the hospital) alongside existing cabling and pipework. This presented a challenge in some instances as access to space was limited, and the proximity of other equipment, reflective surfaces and metals negatively affected performance of the antennae.

As a result, more antennae than initially estimated had to be installed to resolve performance issues, particularly in older buildings where the infrastructure is not designed to support telecoms interfaces in locations where antennae placement would be optimal.

Implementation considerations included:

Fibre infrastructure, providing network bandwidth and resilience for the network operators, with diverse backhaul routes to two different Openreach exchanges for resilience.

A base station hotel (BSH) for the service running 24/7, monitored and supported by Cellnex (previously Herbert In-Building Wireless).

The BSH station uses a base transceiver station (BTS) to facilitate hosting multiple MNOs equipment (EE, Vodafone, O2 and Three UK), so that all networks are provided, and users can access connectivity regardless of their provider.

A wide bandwidth of services (150MHz-2.7GHz) covering the mobile spectrum for 2G, 3G, 4G and also supports radio and other services (CUH extend digital radio to areas not covered by main transmitters – such as emergency department porters for instance).

The Zinwave solution to extend radio waves over single mode fibre to over 300 remote units via secondary hubs. The strategically positioned secondary hubs to ensure high levels of resilience.

Awareness of all applicable legislation, including the Telecommunications Act and the Joint Operator Technical Specification (JOTS) which defines the specification for infrastructure and specifies the performance, coverage and reliability of wireless systems shared between UK mobile operators.

Laying the foundations for extension of the network as the hospital campus grows. At CUH this included extending outside the building in crucial locations (with agreement from MNOs) such as the ambulance yard offering high bandwidth 4G to incoming paramedics.

Some buildings on site, particularly older ones that have been converted from their original purpose, have issues with asbestos, and as such it has not been possible to extend the DAS solution to them as this would require additional cabling causing safety and environmental issues. These buildings are served by Wi-Fi connectivity only.

Ensuring the mobile network complemented the existing Wi-Fi network at the trust. The design considered how Wi-Fi could be combined with the 4G network to provide resilience and fallback, for example when maintenance of networks is required.

Commercial macro services (standard mobile network connectivity) are available at CUH but do not penetrate the buildings. For connection to the DAS the network operators deployed BTS sectors scaled to support a footfall of 20,000 per day.

CUH also utilises two Unify OpenScape 4000 hybrid private branch exchanges (PBXs) and one OpenScape Voice Session Initiation Protocol (SIP) PBX. All public switched telephone network (PSTN) services are now migrated to SIP. SIP trunk packages with inclusive mobile minutes were adopted early in the DAS project in the knowledge that calls to mobiles would increase.

Extending DAS coverage is now assumed in all capital projects, including the two new hospitals at the Biomedical Campus – the Cambridge Children’s’ and Cancer Research Hospitals.