In the expanding spectrum marketplace, there has been a long term evolution towards more market€“oriented mechanisms, such as Opportunistic Spectrum Access (OSA), enabled through Cognitive Radio (CR) technology. However, the potential of CR technologies to revolutionize wireless communications, also introduces challenges based upon the potentially non€“deterministic CR behaviour in the Electrospace. While establishing and enforcing compliance to spectrum etiquette rules are essential to realization of successful OSA networks in the future, there has only been recent increased research activity into enforcement. This dissertation presents novel work on the spectrum monitoring aspect, which is crucial to effective enforcement of OSA. An overview of the challenges faced by current compliance monitoring methods is first presented. A framework is then proposed for the use of random spectral sampling techniques to reduce data collection complexity in wideband sensing scenarios. This approach is recommended as an alternative to Compressed Sensing (CS) techniques for wideband spectral occupancy estimation, which may be difficult to utilize in many practical congested scenarios where compliance monitoring is required. Next, a low€“cost computational approach to online randomized temporal sensing deployment is presented for characterization of temporal spectrum occupancy in cognitive radio scenarios. The random sensing approach is demonstrated and its performance is compared to CS€“based approach for occupancy estimation. A novel frame€“based sampling inversion technique is then presented for cases when it is necessary to track the temporal behaviour of individual CRs or CR networks. Parameters from randomly sampled Physical Layer Convergence Protocol (PLCP) data frames are used to reconstruct occupancy statistics, taking account of missed frames due to sampling design, sensor limitations and frame errors. Finally, investigations into the use of distributed and mobile spectrum sensing to collect spatial diversity to improve the above techniques are presented, for several common monitoring tasks in spectrum enforcement. Specifically, focus is upon techniques for achieving consensus in dynamic topologies such as in mobile sensing scenarios.

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / Automatic spectrum management and monitoring systems are very useful to manage frequencies at test ranges and assure interference-free transmission of telemetry signals. Spectrum management systems assign telemetry frequencies using database information on available and occupied channels and analysis tools which can determine whether a data link will support telemetry. Modern, DSP-based spectrum monitoring systems, in fixed or mobile configurations, automate the process of performing spectrum occupancy to verify clear channels and identify and locate sources of interference; they are integrated with and utilize the management system database. Such systems are important to assure reliable communications channels for telemetry.

Goal of this thesis is to develop portable monitoring station for radio spectrum monitoring and its controlling application for use by Czech Telecommunication Office. The station is based on Software Defined Radio (SDR) and capable of monitoring in the range of 1 MHz - 6 GHz. Developed application controls not only the SDR but also the external RF unit (including choice of receiving antenna, filter, optional amplification/attenuation and azimuth of antenna rotator). Measurement processed by computer and displayed graphically in form of spectrum diagram and waterfall diagram. Furthermore, the application will perform spectral measurement in compliance with requirements of International Telecommunication Union. The application is also capable of recording into the file and of analyzing historical data from the previous measurement.

Dynamic spectrum access (DSA) is a powerful approach to mitigate the spectrum scarcity problem caused by rapid increase in wireless communication demands. Based on architecture design, DSA systems can be categorized as centralized and distributed. To successfully enable DSA, both centralized and distributed systems have to deal with spectrum management issues including spectrum sensing, spectrum decision, spectrum sharing and spectrum mobility. Our work starts by investigating the challenges of efficient spectrum monitoring in centralized spectrum sensing. Since central controllers usually require the presence information of incumbent users/primary users (IUs) for decision making, which is obtained during spectrum sensing, privacy issues of IUs become big concerns in some DSA systems where IUs have strong operation security needs. To aid in this, we design novel location privacy protection schemes for IUs. Considering the general drawbacks of centralized systems including high computational overhead for central controllers, single point failure and IU privacy issues, in many scenarios, a distributed DSA system is required. In this dissertation, we also cope with the spectrum sharing issues in distributed spectrum management, specifically the secondary user (SU) power control problem, by developing distributed and secure transmit power control algorithms for SUs. In centralized spectrum management, the common approach for spectrum monitoring is to build infrastructures (e.g. spectrum observatories), which cost much money and manpower yet have relatively low coverage. To aid in this, we propose a crowdsourcing based spectrum monitoring system to capture the accurate spectrum utilization at a large geographical area, which leverages the power of masses of portable mobile devices. The central controller can accurately predict future spectrum utilization and intelligently schedule the spectrum monitoring tasks among mobile SUs accordingly, so that the energy of mobile devices can be saved and more spectrum activities can be monitored. We also demonstrate our system's ability to capture not only the existing spectrum access patterns but also the unknown patterns where no historical spectrum information exists. The experiment shows that our spectrum monitoring system can obtain a high spectrum monitoring coverage with low energy consumption. Environmental Sensing Capability (ESC) systems are utilized in DSA in 3.5 GHz to sense the IU activities for protecting them from SUs' interference. However, IU location information is often highly sensitive in this band and hence it is preferable to hide its true location under the detection of ESCs. As a remedy, we design novel schemes to preserve both static and moving IU's location information by adjusting IU's radiation pattern and transmit power. We first formulate IU privacy protection problems for static IU. Due to the intractable nature of this problem, we propose a heuristic approach based on sampling. We also formulate the privacy protection problem for moving IUs, in which two cases are analyzed: (1) protect IU's moving traces; (2) protect its real-time current location information. Our analysis provides insightful advice for IU to preserve its location privacy against ESCs. Simulation results show that our approach provides great protection for IU's location privacy. Centralized DSA spectrum management systems has to bear several fundamental issues, such as the heavy computational overhead for central controllers, single point failure and privacy concerns of IU caused by large amounts of information exchange between users and controllers and often untrusted operators of the central controllers. In this dissertation, we propose an alternative distributed and privacy-preserving spectrum sharing design for DSA, which relies on distributed SU power control and security mechanisms to overcome the limitations of centralized DSA spectrum management. / Doctor of Philosophy / Due to the rapid growth in wireless communication demands, the frequency spectrum is becoming increasingly crowded. Traditional spectrum allocation policy gives the unshared access of fixed bands to the licensed users, and there is little unlicensed spectrum left now to allocate to newly emerged communication demands. However, studies on spectrum occupancy show that many licensed users who own the license of certain bands are only active for a small percentage of time, which results in plenty of underutilized spectrum. Hence, a new spectrum sharing paradigm, called dynamic spectrum access (DSA), is proposed to mitigate this problem. DSA enables the spectrum sharing between different classes of users, generally, the unlicensed users in the DSA system can access the licensed spectrum opportunistically without interfering with the licensed users. Based on architecture design, DSA systems can be categorized as centralized and distributed. In centralized systems, a central controller will make decisions on spectrum usage for all unlicensed users. Whereas in distributed systems, unlicensed users can make decisions for themselves independently. To successfully enable DSA, both centralized and distributed DSA systems need to deal with spectrum management issues, such as resource allocation problems and user privacy issues, etc. The resource allocation problems include, for example, the problems to discover and allocate idle bands and the problems to control users' transmit power for successful coexistence. Privacy issues may also arise during the spectrum management process since certain information exchange is inevitable for global decision making. However, due to the Federal Communications Commission's (FCC) regulation, licensed users' privacy such as their location information must be protected in any case. As a result, dynamic and efficient spectrum management techniques are necessary for DSA users. In this dissertation, we investigate the above-mentioned spectrum management issues in both types of DSA systems, specifically, the spectrum sensing challenges with licensed user location privacy issues in centralized DSA, and the spectrum sharing problems in distributed DSA systems. In doing so, we propose novel schemes for solving each related spectrum management problem and demonstrate their efficacy through the results from extensive evaluations and simulations. We believe that this dissertation provides insightful advice for DSA users to solve different spectrum management issues for enabling DSA implementation, and hence helps in a wider adoption of dynamic spectrum sharing.

Dynamic Spectrum Access (DSA) is now a commonly used spectrum sharing paradigm to mitigate the spectrum shortage problem. DSA technology allows unlicensed secondary users to access the unused frequency bands without interfering with the incumbent users. The key technical challenges in DSA systems lie in spectrum allocation problems and spectrum user's security issues. This thesis mainly focuses on spectrum monitoring technology in spectrum allocation and incumbent users' (IU) privacy issue. Spectrum monitoring is a powerful tool in DSA to help commercial users to access the unused bands. We proposed a crowdsourcing-based unknown IU pattern monitoring scheme that leverages the power of masses of portable mobile devices to reduce the cost of the spectrum monitoring and demonstrate the ability of our system to capture not only the existing spectrum access patterns but also the unknown patterns where no historical spectrum information exist. Due to the energy limit of the battery-based system, we then leverage solar energy harvesting and develop an energy management scheme to support our spectrum monitoring system. We also provide best privacy-protection strategies for both static and mobile IUs in terms of hiding their true location under the detection of Environmental Sensing Capabilities system. In this thesis, the heuristic approach for our mathematical formulations and simulation results are described in detail. The simulation results show our spectrum monitoring system can obtain a high spectrum monitoring coverage and low energy consumption. Our IU privacy scheme provides great protection for IU's location privacy. / Master of Science / Spectrum relates to the radio frequencies allocated to the federal users and commercial users for communication over the airwaves. It is a sovereign asset that is overseen by the government in each country to manage the radio spectrum and issue spectrum licenses. In addition, spectrum bands are utilized for various purposes because different bands have different characteristics. However, the overly crowded US frequency allocation chart shows the scarcity of usable radio frequencies. The actual spectrum usage measurements reflect that multiple prized spectrum bands lay idle at most time and location, which indicates that the spectrum shortage is caused by the spectrum management policies rather than the physical scarcity of available frequencies. Dynamic spectrum access (DSA) was proposed as a new paradigm of spectrum sharing that allows commercial users to access the abundant white spaces in the licensed spectrum bands to mitigate the spectrum shortage problem and increase spectrum utilization. In DSA, two of the key technical challenges lie in how to dynamically allocate the spectrum and how to protect spectrum users’ security. This thesis focuses on the development of two types of mechanisms for addressing the above two challenges: (1) developing efficient spectrum monitoring schemes to help secondary users (SU) to accurately and dynamically access the white space in spectrum allocation and (2) developing privacy preservation schemes for incumbent users (IU) to protect their location privacy. Specifically, we proposed an unknown IU pattern monitoring scheme that leverages the power of masses of portable mobile devices to reduce the cost of common spectrum monitoring systems. We demonstrate that our system can track not only the existing IU spectrum access patterns but also the unknown patterns where no historical spectrum information exists. We then leverage the solar energy harvesting and design energy management scheme to support our spectrum monitoring system. Finally, we provide a strategy for both static and mobile IUs to hide their true location under the monitoring of Environmental Sensing Capabilities systems.

The thesis describes methods for spectrum monitoring, which are used by the Czech telecommunication office. The thesis describes a design of an RF unit for a portable monitoring station and its potential use. The RF unit consists of several devices, which are connected. Devices like an antenna, a rotator, a rotator control unit, coaxial switches, an amplifier and attenuator were chosen as commercially available devices. It is also described, why were these devices chosen. Other devices such as filters, a control unit for the RF unit and a power supply were designed. The RF unit is controlled by a computer. A software for spectrum monitoring contains a graphical user interface for the RF unit control.

Precise and robust positioning through Global Navigation Satellite Systems (GNSS) is instrumental to a wide gamut of modern systems. The integrity of GNSS signals is increasingly compromised by Radio Frequency (RF) interference, presenting a substantial threat to the performance of GNSS receivers. This vulnerability is of particular concern for Unmanned Aerial Vehicles (UAVs), whose critical functionalities depend heavily on reliable GNSS positioning. Given their complex designs and high maneuverability, UAVs present a distinctive and powerful platform for the exploration and mitigation of GNSS RF interference. This work investigates two complementary but related aspects: (i) the detection of internal RF interference with the GNSS receiver and (ii) the localization of external RF interference sources, utilizing the advanced capabilities of UAV platforms. The detection methodology (i) synthesizes insights from existing literature by selecting RF interference detection methods compatible with observables from standard GNSS receivers. It also innovatively employs ideal spectral masks to estimate the impact of interference. In addition, the localization methodology (ii) introduces a novel UAV-centric technique that leverages the characteristics of GNSS antennas and UAV maneuverability. A concept of radiation heatmap has been developed to transform the antenna’s radiation pattern into a heatmap, indicating a possible bearing toward an RF interference source. Subsequently, a concept of triangular intersection is introduced to fuse multiple radiation heatmaps into a single localization heatmap, indicating the locations of interfering transmitters. Through this work, a comprehensive framework has been established, allowing UAVs equipped with GNSS receivers to detect internal interference and localize external RF interference sources. This dual approach contributes significantly to the monitoring of the GNSS spectrum and enhances the performance of GNSS-dependent applications. / Exakt och robust positionering genom Globala Navigationssatellitsystem (GNSS, från engelskans Global Navigation Satellite Systems) är avgörande för en mångfald av moderna system. Integriteten hos GNSS-signaler hotas alltmer av interferens från radiofrekvenser (RF, från engelskans Radio Frequency), vilket utgör ett betydande hot mot prestandan hos GNSS-mottagare. Denna sårbarhet är särskilt bekymmersam för obemannade luftfartyg (UAV, från engelskans Unmanned Aerial Vehicle), vars kritiska funktioner är starkt beroende av tillförlitlig GNSS-positionering. Med tanke på deras komplexa konstruktioner och höga manövrerbarhet utgör UAV:er en distinkt och kraftfull plattform för utforskning och mitigering av GNSS RF-interferens. Detta arbete undersöker två kompletterande men relaterade aspekter: (i) detektion av intern RF-interferens i GNSS-mottagaren och (ii) lokalisering av externa källor till RF-interferens, med användning av avancerade UAVplattformar. Metoden för detektion (i) syntetiserar insikter från befintlig litteratur genom val av metoder för upptäckt av RF-interferens som är kompatibla med observerbar data från standarden för GNSS-mottagare. Den använder dessutom “ideala spektralmasker” (från engelskans “ideal spectral masks”) innovativt för att uppskatta interferensens påverkan. Dessutom introducerar lokaliseringstekniken (ii) en ny UAV-centrerad teknik som utnyttjar egenskaperna hos GNSS-antenner och UAV:ers manövrerbarhet. Ett koncept för strålningsvärmekarta har utvecklats för att omvandla antennens strålningsmönster till en värmekarta, vilket indikerar en möjlig riktning mot en källa till RF-interferens. Därefter introduceras ett koncept för triangulär skärning för att sammanfoga flera strålningsvärmekartor till en enskild lokalisationsvärmekarta, vilket indikerar placeringen av störande sändare. Genom detta arbete har ett omfattande ramverk etablerats, vilket möjliggör för UAV:er utrustade med GNSS-mottagare att upptäcka intern interferens samt lokalisera externa källor till RF-interferens. Denna dubbla strategi bidrar avsevärt till observationen av GNSS-spektrumet och förbättrar prestandan för GNSS-beroende applikationer. / Presné a robustné určovanie polohy pomocou globálnych navigačných satelitných systémov (GNSS, z angl. Global Navigation Satellite System) je kľúčové pre široké spektrum moderných systémov. Integrita signálov GNSS je čoraz viac ohrozovaná vysokofrekvenčnou elektromagnetickou (RF, z angl. Radio Frequency) interferenciou, čo predstavuje významnú hrozbu pre výkonnosť prijímačov GNSS. Táto zraniteľnosť je obzvlášť znepokojujúca pre bezpilotné lietadlá (UAV, z ang. Unmanned Aerial Vehicle), ktorých kritické funkcionality sú vo veľkej miere závislé od spoľahlivého určenia polohy. Vzhľadom na ich zložitý dizajn a vysokú manévrovateľnosť, UAV predstavujú výnimočnú a bohatú platformu pre skúmanie a mitigáciu RF interferencie. Táto práca skúma dva komplementárne, ale súvisiace aspekty: (i) detekciu vnútornej RF interferencie s využitím prijímača GNSS a (ii) lokalizáciu zdrojov vonkajšej RF interferencie s využitím pokročilých schopností UAV platformy. Metodika detekcie (i) syntetizuje poznatky z existujúcej literatúry výberom metód detekcie RF interferencie, ktoré sú kompatibilné s pozorovaniami zo štandardných prijímačov GNSS. Taktiež inovatívne využíva ideálne spektrálne masky na odhad vážnosti vplyvu interferencie. Okrem toho, metodika lokalizácie (ii) predstavuje nový prístup zameraný na UAV, využívajúci charakteristiku antén GNSS a manévrovateľnosť UAV. V rámci tejto práce bol vyvinutý koncept radiačnej teplotnej mapy, ktorý transformuje radiačný vzor antény na teplotnú mapu, indikujúcu smer k možnému zdroju RF interferencie. Následne bol predstavený koncept trojuholníkovej priesečnosti, spájajúci viaceré radiačné teplotné mapy do jednej lokalizačnej teplotnej mapy, indikujúcej polohy rušiacich vysielačov. Prostredníctvom tejto práce bol vytvorený komplexný rámec, umožňujúci UAV, ktoré sú vybavené prijímačmi GNSS, detekovať vnútornú interferenciu a lokalizovať zdroje vonkajšej RF interferencie. Tento duálny prístup významne prispieva k možnosti monitorovania GNSS spektra a zvyšovania výkonnosti aplikácií závislých od GNSS.