A spectrum of new mobile possibilities
Demand for new spectrum is a challenge as the airwaves are becoming increasingly crowded. Governments are reallocating bandwidth previously reserved for TV and radio broadcasting, but this is still not enough. Another promising option is to share some underutilised spectrum reserved for other purposes, such as military applications, when it is not being used for its primary application. In the past, this was not possible but today the technology exists to automatically utilise these temporarily free or underused channels. For instance, cognitive radio can exploit underutilised spectrum without interfering with primary users. 'Wireless sensor networks for cognitive software radios' (WISERNETS) was an EU-backed project that studied a spectrum cartography approach to cognitive radio. The project developed wireless terminals that were capable of evaluating transmission opportunities for local or cooperative communications. WISERNETS' prototype system collaborates with a network of wireless sensors to map the local airwaves to work out the available spectrum. Based on this map, terminals can cooperatively calculate the best use of spectrum, whether via base stations or mobile–to–mobile. The project also utilised ultra-wideband (UWB) technology to keep the transmission power of secondary users below the noise level of primary users. It also managed the interference caused by other UWB cognitive users. Once exploited, WISERNETS technology will be able to help create local, tailored solutions to meet growing demand for spectrum.