Furthering Electromagnetic Architecture of Buildings - An International Travel Application

The electromagnetic spectrum is a finite resource and frequency reuse is essential particularly in the mobile communications bands. Signal propagation in the built environment is notoriously complex but buildings are an environment where measures can be implemented to modify their electromagnetic architecture. Multiple occupancy commercial buildings, partitioned into offices, can in principle be electromagnetically screened internally to assist frequency reuse, and large, more open structures such as theatres can be shielded by suitable construction of the outer walls. It is common practice now, particularly in new buildings, to install aluminium foil backed layers within walls, as a fire precaution measure or for insulation purposes. Suitable screening can greatly reduce co-channel interference and our colleagues in Auckland have pointed out that an increase in the signal-to-interference ratio of just 10 or 15dB can decrease outage probability by an order of magnitude or more. At other frequencies access through the screen is necessary, especially at the emergency services band - at 400MHz in the UK, but apparently as low as 75MHz in New Zealand. In a very successful project funded by EPSRC and the National Policing Improvement Agency, we have been focussing on the application of Frequency Selective Surfaces (FSS) to the built environment with the emphasis on operation at the long wavelengths used in mobile communications. For example, a long-wavelength FSS intended to provide this emergency access while employing a minimum number of array elements has been based on simple square loop slot elements. An alternative approach is to reduce the array unit cell size, and this concept has led to a close collaboration with the Radio Systems Group at the University of Auckland who have extensive experience measuring and modelling the propagation of signals in buildings. Although FSS is an established technology, it is not well understood at mobile frequencies where the arrays are finite, elements may well be highly convoluted, layer separations are electrically small and room dimensions are comparable to the operating wavelengths. FSS design is challenging at mobile bands as they are far apart in fractional ratio terms. We have already installed in an office-type test room in Auckland a novel two layer FSS composed of highly convoluted elements. This work is ongoing, building on the work previously funded by the EPSRC. This application is for funding to enable the investigators to travel to Auckland on two separate occassions to work on three related topics: 1. to study the effect of FSS when mounted in small apertures, 2. to characterise FSS performance for high angles of incidence, 3. to assess the effect of wall mounted FSS on Wireless Computer Network performance in a specially built office-type room.

The work summarised in this travel application impacts on two main areas: 1. on the building industry and the related civil engineering 2. on the efficient use of the radio spectrum, particularly at the wavebands used by mobile communications. The UK is a world leader at present in electromagnetic effects in the built environment. This project assists in maintaining this situation and spreading experience with the application of FSS to an international audience through, amongst other things, the bilateral experimental nature of the work and the consequential interchange of ideas and experience. The Auckland Group has long standing expertise in wave propagation in buildings, while we have decades of experience with Frequency Selective Surfaces. The two groups complement each other. We will work in New Zealand to build on the impact already created there by our existing work. We will use the knowledge gained to feedback into the UK's Wireless Friendly Buildings Forum. This fits in with both the 'challenge theme' defined by the Modern Built Environment Knowledge Transfer Network as a priority need, and with the UK Digital Economy Programme, 'novel design helping to transform lives'. There is, unfortunately, in our experience, a big gap between, on the one hand, the communications industry with its need to function efficiently in buildings, and on the other, the awareness of the requirements of good Electromagnetic Architecture on the part of civil engineers and architects who fabricate the built environment. Part of the impact will be a contribution towards bridging the gap and facilitating technology transfer. This is a relatively new area of engineering application and we have been able to contribute through two EPSRC funded projects in the past decade. These focused on the incorporation of Frequency Selective Surfaces, the first leading to interest from the Radio Communications Agency (now OFCOM) where for example Professor Parker was a member of a consortium led by ERA. One of the impacts of the second was the initiation of our collaboration with the Radio Systems Group at the University of Auckland, the continuing facilitation of which is the subject of this application for travel funds. We are also striving to inform the civil engineers of the importance of Electromagnetics in the built environment and this application forms part of this effort. A few years ago we were approached by one of the governors of our local prison regarding the illicit use of mobile phones. The prison service is an area where improved electromagnetic architecture could have obvious benefits. To quote from the BBC news website (23 November 2009) David Jamieson, chairman of Wandsworth prison's Independent Monitoring Board, says illegal phones fuel prison drug trading, bullying and gang problems. Behind bars, phones can cost 400 each. He said the trade had been worth 9m in 2008, when 7,000 phones were seized. Yet another area is in the design of theatres, our New Zealand colleagues pointed out to us that the cost of theatrical productions is so high, that investing in buildings where the unwanted use of phones could be prevented whilst permitting emergency service communications is not out of the question. In summary therefore, the impact of this work is the development of the electromagnetic architecture of buildings to enhance their wireless friendliness. To assist in propagating this benefit beyond academia we are already in discussions with civil engineering companies, for example, Waterman plc., we are members of the Wireless Friendly Buildings Forum, we have contacts with the Architectural Engineering Company Buro Happold, and the Home Office Scientific Development Branch (HOSDB). To quote a comment on some of our related work in this area this work could become 'an essential component in the radio planning and radio pollution armoury'.