Network Design For The Department for Children, Schools & Families

About the Department for Children, Schools & Families

The headquarters for the Department of Children, Schools and Families is located in the heart of Westminster, Central London. This purpose-built 1980 office block houses 1,500 staff over 12 floors. Like many such city centre buildings, it was in need of a total refurbishment. Central to this work was a new building-wide wireless network infrastructure. This total system solution would need to work within the constraints of the building’s listed status.

Refurbishment

The DCSF is leading the drive towards creating a vibrant and sustainable working environment for the modern, technology aware civil servant, but their Sanctuary buildings HQ was not helping fulfil this. The infrastructure was just not meeting the needs of a modern government department so a building wide refurbishment was required.

Central to this work was the need for state of the art technology to provide sustainable productivity and efficiency benefits and the solution was to design and implement a high quality wireless network, providing safe, reliable and resilient communications. With a long lifetime and capable of acting as a core utility, this building-wide wireless infrastructure would help all staff, from administrators to senior civil servants, fulfil their mandate in this newly formed government department.

affini worked with Cap Gemini to design, install and commission an enterprise-class wireless solution, taking complete responsibility for the network and delivery of the system. Cap Gemini recognised that working with a partner with high Health and Safety standards would deliver additional benefits. affini’s unparalleled expertise in wireless technology and their ability to deliver the tangible benefits of wireless systems, whilst considering the issues of wireless radiation levels, safety and security, would satisfy any potential customer, employee or public concerns.

The demanding requirements on the wireless network were:

Future Proof & High Quality Wireless Network capable of being a core utility for the building.

Robust System Supporting Data & VoIP over Wi-Fi for visitors and government employees.

Reliable Connectivity for Mobility Users with support for hot desk facilities and home workers (anyone can work at any desk, so coverage had to be excellent in all occupied areas).

Ensured security with no discernible wireless leakage outside the building.

The whole system had to conform to CESG guidelines, the Government Gold Standard for IT Security. To make this more challenging, the work would take place during the refurbishment, so working in close co-operation with other suppliers on-site, affini’s flexibility and strong project management control would be put to good use.

As a high-profile project for a prestigious government department there were high expectations of affini to deliver a world class Wi-Fi solution – & get it right, first time.

Creating the Wi-Fi Design

A Wi-Fi design has three inter related aspects – Radio, Physical and IT – and each of these must be addressed if the applications are to work as required.

RF – the foundation of a successful Wi-Fi network, RF covers the number and exact locations of Access Points, associated antenna types and pointing directions, power and channel settings.

Physical – build-related elements of the Wi-Fi network such as cable routes, antenna positioning and LAN cabinets.

IT – creates a seamless, integrated solution by specifying network settings & IT infrastructure.

Design Methodology

The design methodology was three steps:

  1. Customer Requirements Capture: ensures the solution proposed will meet operational and technical needs. This was achieved by analysing aspects such as coverage mobility, latency, throughput and desired user access.
  2. Customers Site Survey & Audit: to accurately capture and measure the site’s RF propagation characteristics, establishing and locating potential sources of interference. Also used to assesses building’s characteristics for radio, equipment or implementation issues or constraints.
  3. Detailed Design: provides a comprehensive report of all the RF and Physical Wi-Fi aspects including plots of predicted throughput and coverage for each Access Point. The RF design used affini’s own Red-Predict software, which takes the audit data as a baseline to help ensure the most accurate, high quality wireless design possible.

The Wi-Fi Design

The design was based on the provision of VoIP over wireless within the required areas of the building. Operating in the 802.11 b/g (2.4 GHz) band, it required a total of 368 Access Points (AP’s) over twelve floors. All AP locations, types and power/channel settings were specified as part of the design.

To ensure security, leakage of Wi Fi signals was kept to a minimum and the system provided a limited level of redundancy from surrounding APs providing basic connectivity (1 Mbps) in the event of a single AP failure. To enable mobility among users, the network allowed a user to roam each floor and onto other floors whilst maintaining application connectivity.

Capacity was specified for meeting and conference rooms, but there were no specific requirements for the system as a whole.

Network Infrastructure – The system design used two Cisco switches on each floor, linked to a Cisco Catalyst Switch, linked to the central data network.

Discrete Installation – Cisco Access Points, mounted above ceiling tiles, were installed on each floor, with a low profile omnidirectional antenna mounted on the underside of the tile. Discrete cabling was installed to provide connectivity between the AP’s and the LAN.

Minimising Co-Channel Interference – using three separate bands within the operating frequency channel.

Increased Coverage – installing two antennas and using splitters/combiners and RF feeder cables.

Minimised Equipment Inventory – installing stand alone Power Injectors or integrated Power over Ethernet (POE) cards minimising the need for individual power supplies.

Implementing the Solution – The Wireless network was deployed on ten floors (leaving the two basement levels). As the refurbishment progressed, affini delivered a full turnkey solution one floor at a time.

The solution included:

Total Project Management Service – closely interacting with Capgemini, DCSF and other suppliers.

Supply & Installation – all cabling and hardware (cabling, network equipment, APs and antennas).

Integration – into the central data network with commissioning and final configuration of APs.

Post-Installation RF Testing – to measure the achieved coverage of the Wi-Fi system showing it fully meets network requirements.

Acceptance Testing – using subjective data tests using client devices.

Summary

The Wi-Fi solution delivered has proved to be a great success, fully meeting the DCSF’s requirement of providing flexible, secure and reliable voice and data communications across the diverse site.