Enhancing radio coverage inside buildings

In radio networks, cell sizes are determined by the power needed to provide an acceptable signal-to-noise ratio to a certain percentage of a given coverage zone. Propagation within buildings introduces losses to the system. If the losses can be minimised, it is possible to use lower power levels, while still covering the same region, and increase the overall spectrum efficiency of the network. Theoretical and experimental work has been performed to show that propagation within buildings can be greatly improved by using techniques based on frequency selective surfaces (FSS). A novel structure is proposed that has the potential to enhance the propagation in corridors and stairwells. The structure, mode conversion FSS (MC-FSS), is highly efficient and converts and re-radiates the specular energy in a predefined direction away from the specular direction. The structure can easily be retrofitted into existing buildings, with minimal structural impact, and can be fabricated using very low cost materials. The technology has been demonstrated at 870 MHz but could be very useful for much higher frequency applications, for example future MM-wave wireless LAN systems.