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This paper describes the current efforts underway to set up matched long-term continuously running spectrum observatories in the US (in Chicago and Blacksburg) and in Turku, Finland. The measurement equipment setup is described, along with the architecture for the networked database used to aggregate, archive and share the spectrum measurement data collected across the multiple international locations. High performance computer infrastructure to permit analysis and as appropriate fusion specific elements of the terabytes of data is described. The measurement parameters and spectrum measurement band plans are listed. Preliminary analysis results are also provided-particularly, simple occupancy statistics in Chicago and in Turku. To demonstrate the utility of the global spectrum observatory network, an interesting example is provided that compares and contrasts the very different signals that occupy the same spectral band, but in different geographic regions.

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In 2007, the Wireless Network and Communications (WiNCom) Research Center at the Illinois Institute of Technology initiated a continuous RF spectrum measurement program in the frequency range 30 MHz to 6 GHz. The data measurement collection, now multiple Terabytes, was historically stored in a flat file format on multiple hard drives which was efficient and easy to deal with from a data collection perspective, but not very effective from an analysis and sharing perspective. This paper describes the data capture structure, the new database and data storage approach that has been created to enable large scale, "safe storage", and to facilitate data queries and RF measurement analysis by researchers both inside and outside of IIT's network, and some of the application that have been implemented using this new structure.

This paper presents results from spectrum occupancy measurements in the 2.3-2.4 GHz band at Turku, Finland and Chicago, USA. The band is currently under study in European regulation and standardization for mobile communication systems. We review the recently introduced Licensed Shared Access (LSA) concept as a potential means for making the 2.3-2.4 GHz band available for mobile communications on a shared basis while protecting the rights of the incumbent spectrum users. The spectrum occupancy measurements conducted in one location in Finland show that the use of this band is rather low indicating that there might be potential for mobile communication systems to share this band with the incumbents under the LSA approach.

The MicroWave Oven (MWO) is a popular appliance that acts as an unintentional interferer for 2.4 GHz IEEE 802.11 Wi-Fi communication signals. An interference mitigation technique is developed that incorporates cognitive radio paradigms allowing Wi-Fi devices to reliably transmit information while a residential MWO is operating. This technique is applied in the experimental case where Barker spread Wi-Fi signals carry data in the presence of MWO emissions. Bit error rate is evaluated to provide a performance metric for the mitigation technique.

An RF measurement system with high time resolution is implemented to determine the statistical characteristics of various channels in the Land Mobile Radio bands. The applicability of simple statistical models to the observed data is investigated, as well as their validity over short and long periods of time. The results show that the statistics of the idle and holding times of communication on these channels vary significantly over time and demonstrate daily periodicity, requiring non-stationary models to accurately represent them. Over short durations of time however, conventional distributions such as the exponential and log-normal may adequately characterize the properties of these quantities, allowing convenient and compact representations of the data. Results based on empirical data are presented to quantify the probability of stationarity for voice traffic within a time span of given length. The findings are useful for network planning or streamlining, network simulation and modeling, and investigation of dynamic spectrum access.

Some devices not usedfor data communications radiate in the 2.4 GHz Wireless-Fidelity (Wi-Fi) band, thus causing unintentional interference that degrades the performance ofIEEE 802.11 wireless systems. An analytical model for radio emissions from one of the most common unintentional interferers, the residential microwave oven, is developedfrom laboratory measurements. Simulation of the analytical model results in a power spectral density and spectrogram that are in good agreement with experimental data. An interference mitigation technique is proposedfor the microwave oven emission.