Wireless coverage in buildings: Only connect

Were you one of the thousands queuing up around the block to purchase Apple’s latest iPhone 4 when it launched last month? The company sold 1.7 million in the first three days - a record. It would have sold more, it says, only it ran out of phones.

There is a lot of spurious science around and software that purports to give plots of wireless coverage in a building. It’s utterly naive and doesn’t reflect reality

Chris Yates, WFBF

Ten years ago, smart phones like these were inconceivable. Now businesses can barely function without them. At this year’s British Council for Offices (BCO) conference, Jack Pringle, senior partner with architect Pringle Brandon, referred to the Facebook generation: “They talk to 20 people at one time while playing a video game, listening to music and doing ’work’. It is this generation that will set the agenda for the office of the future.”

But forget the office of the future for a moment, what about the office of today? We’ve all experienced dodgy mobile phone reception while sitting at our desks, dashing towards the window to get a stronger signal. Is there an approach to building design that could improve the performance of the wireless systems in them?

At the moment, says Chris Yates, chairman of the Wireless Friendly Building Forum (WFBF), predicting the performance of a building to handle wireless signals is almost impossible. “There is a lot of spurious science around and software that purports to give plots of wireless coverage in a building. It’s utterly naive and doesn’t reflect reality,” he says.

One of the reasons the forum was set up at the end of last year was to co-ordinate research into the area of wireless systems in buildings. As the use of wireless devices increases, more and more issues over performance will arise, explains Yates - and there is nobody taking an interdisciplinary approach on how this performance can be improved.

With wireless looking set to be a mainstay of the way we work in the future, the WFBF ultimately wants to develop a way of defining and assessing its performance in any one building, similar to the way in which BREEAM or LEED rate a building’s environmental performance. “Then a value can be placed on it and developers and end users get interested and it becomes part of their decision-making process,” says Yates.

But until this is achieved, what should designers be doing? Here, we take a look at three wireless applications and the main implications for buildings.

Cellular

This is the technology that mobiles and smart phones such as Blackberrys and iPhones rely on for voice calls and data transfer. Cellular signals are broadcast by public masts and are actually very difficult to keep out of a building. The main path in is through the glazing, but once inside, things can start to go haywire, with signals reflected or absorbed by the building’s structure.

Columns, lift shafts and risers in particular can create blackspots where reception becomes poor or non-existent. Concrete floors cast on lightweight metal decks will block most signals, as will materials such as lead roofing and the metal foils on the back of some insulation materials.

A common way to deal with this is to boost the signal or re-broadcast it using a repeater. These systems usually use an external antenna to collect the signal, which is transmitted to an amplifier and retransmitted locally. For multistorey buildings, several transmitters might be needed.

Of course, this equipment needs to be accommodated and installed, but when this should be done is a source of some confusion. The current BCO guide to specification does not outline at what stage ICT infrastructure should be installed, but according to Yates some sort of infrastructure provision should be made at the core and shell stage, even if the active equipment isn’t installed.

Signal strength can also be significantly decreased by the use of high-performance glazing and solar shading, which are becoming commonplace with the tightening of Part L of the Building Regulations.

Mitigating action can be taken. Buro Happold’s specialist facade division, for example, is now beginning to consider the effect that facade components have on wireless performance, while also considering trade-offs in acoustic, blast, thermal performance and aesthetics.

According to Yates these trade-offs need careful consideration. Some glass options might give marginally better performance in terms of thermal behaviour, but completely ruin the wireless service, whereas another option might give negligible degradation for a similar price. “

So it is something to think about. It’s no good handing the building over and then telling them there’s no wireless signal,” warns Yates.

Wi-fi LANs

Local area networks (LANs) that you can connect to with your netbook or laptop are increasingly being used for hot desking and breakout spaces. The performance of these systems often comes down to good ICT management. Capacity - the time it takes to transfer data - is the main issue and in some public buildings, particularly libraries, providing the bandwidth for enough users is becoming a problem, particularly with the rise in audio and video files being downloaded.

Where this affects the design team of the building is the coverage. Often the requirement is to have wireless capability throughout the entire office. This can be achieved by providing enough access points, which means putting the cabling in. The rule of thumb is to position these points on a 15m grid, which is staggered on the floors above and below. This will provide the maximum capacity that a LAN can support, whatever the system or maker, says Yates. “You might not want to use all those outputs but you put the cabling in for them. You don’t really get much resistance from clients when you suggest it.”

For an office with 2,000 occupants, the number of access points would be around 200, which will cost in the region of £20,000 to £30,000. “It’s small change on a building but the benefits are substantial because you can probably meet any future requirements for a good number of years, probably until the next building refurbishment cycle, and it avoids disruption,” adds Yates.

Blackspots, such as around the building’s cores, are obvious areas for additional access points. However, concrete floors cast on metal decking can be an advantage as they shield one floor from the next and prevent “overspill”. This means that the wireless signal is contained on just one floor which helps maximise the system’s capacity.

The rest

As well as cellular and Wi-fi LANs, wireless technology is increasingly being used for sensors and controls for the building’s mechanical and electrical systems. These can typically be anything from occupancy detectors and temperature sensors to wireless light switches and dimmers. Proprietary systems such as ZigBee and Enocean are embedded into products which then communicate with one another wirelessly, often just between themselves. Generally speaking these are optimised for the specific application and can largely be left to their own devices.