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White spaces are locally or temporally available frequencies that are principally reserved for primary use such as TV broadcasting. The currently prevalent view to the utilization of such spectrum resources is that white space devices must query a geolocation database to obtain information about available frequencies and related maximum transmission powers. A geolocation database is fundamentally based on field strength estimates of the primary service obtained using radio propagation models. However, field strength estimates for geographically extensive broadcast networks are typically computed for spatial resolutions of hundreds of square meters. Therefore, even with the most sophisticated propagation models currently available, the predicted values always contain errors due to the limited geographical information. To overcome such deficiency, we propose a geostatistical approach for estimating the radio environment based on universal kriging interpolation. In addition, we optimize the locations of field measurements using spatial simulated annealing, and show that it improves significantly local field strength estimates.

Summary This paper describes a licensed shared access (LSA) testbed and field trials using a live network. The testbed includes real 4G base stations and up to 1000 virtual base stations, in the spectrum sharing scenario between satellite and cellular systems. The trials focus on 5G pioneer bands 3.4–3.8 GHz and 24.25–27.5 GHz where a satellite system is operating in the downlink direction and a cellular system is accessing the same band. The designed testbed supports both frequency bands. The performance evaluation concerns evacuation and frequency change times using different types of base stations in 3.6 GHz, that is, how fast the system relinquishes the shared band to the primary user and continues transmission using another band. We show that our LSA system is scalable and able to support large number of base stations. In addition, we investigate how satellite systems could reuse International Mobile Telecommunication (IMT) bands to offer enhanced satellite communication services for land, maritime, and aeronautical applications. Preliminary simulations and analysis confirm the possibility to reuse IMT spectrum for satellite systems without causing harmful interference to the terrestrial system.

This paper focuses on evaluating the gains obtained through cooperative spectrum sensing in real-world while using cyclostationary based mobile sensors. In cooperative sensing (CS), different secondary users (SUs) in a geographical neighborhood cooperate to detect the presence of a primary user (PU). As compared to single-user sensing, cooperation provides diversity gains in the face of multipath fading and shadowing. The effectiveness of the CS is demonstrated by analyzing data acquired in two extensive field measurement campaigns. The first measurement campaign (MC-I) focuses on measurements at fixed locations while the second measurement campaign (MC-II) focuses on a scenario where measurements are taken inside a moving car. These measurements are carried out for DVB-T channels in Finland's Capital Region, which consists of urban and suburban environments. Hard decision rules such as OR, AND, MAJORITY and soft decision rule such as SUM (sum of cyclostationary test statistics) are employed and their detection performances are compared to a cyclostationary based single-user detector. A performance parameter of relative increase in probability of detection (RIPD) is used to efficiently demonstrate the cooperation gain obtained relative to local sensing. It is shown that cooperation can significantly improve the performance of a sensor severely affected by fading and shadowing effects. Furthermore, it is shown that increasing the number of collaborating users beyond few users (5-8) does not in practice bring significant improvement in terms of the expected RIPD. The performances of CS schemes evaluated from MC-I are also compared to the corresponding simulated CS results using empirical channel models and terrain data for the same experimental parameters. It is shown that the use of empirical or theoretical models may result in detection errors in practical conditions and measurements should be used to improve the accuracy in such scenarios.

Since the introduction of the idea of cognitive radio, various approaches towards spectrum sharing have been considered, for example, the Licensed Shared Access (LSA), which is considered in Europe, or Citizens Broadband Radio Service (CBRS) with Spectrum Access System (SAS) regulated by the US. This paper deals with the problem of coordinated resource allocation among a set of available base stations. A detailed definition of the problem is provided, followed by a discussion on a set of heuristics proposed for solving the problem. Four solutions are presented that are based on existing standards as well as on the approaches described in the literature. Next, new multi-selection (multi-choice) algorithm is proposed and discussed in detail. The main problem is divided in two subproblems, which are solved by using graph theorem and analytical description. The performance of the proposed solutions is analyzed in various scenarios. Finally, a trade-off between power allocation and frequency use is provided. All challenges identified during the investigation of the problem are presented.