This research addresses the concept of radio resource allocation for cellular communications systems operating in congested and contested environments with an emphasis on end-to-end quality of service (QoS). The radio resource allocation is cast under a proportional fairness formulation which translates to a convex optimization problem. Moreover, the resource allocation scheme considers subscription-based and traffic differentiation in order to meet the QoS requirements of the applications running on the user equipment in the system. The devised resource allocation scheme is realized through a centralized and a distributed architecture and solution algorithms for the aforementioned architectures is derived and implemented in the mobile devices and the base stations. The sensitivity of the resource allocation scheme to the temporal dynamics of the quantity of the users in the system is investigated. Furthermore, the sensitivity of the resource allocation scheme to the temporal dynamics in the application usage percentages is accounted for. In addition, a transmission overhead of the centralized and distributed architectures for the resource allocation schemes is performed. Furthermore, the resource allocation scheme is modified to account for a possible additive bandwidth done through spectrum sharing in congested and contested environments, in particular spectrally coexistent radar systems. The radar-spectrum additive portion is devised in a way to ensure fairness of the allocation, high bandwidth utilization, and interference avoidance. In order to justify the aforesaid modification, the interference from radar systems into the Long Term Evolution (LTE) as the predominant 4G technology is studies to confirm the possibility of the spectrum sharing. The preceding interference analysis contains a detailed simulation of radar systems, propagation path loss models, and a third generation partnership project compliant LTE system. The propagation models are Free Space Path Loss (FSPL) and Irregular Terrain Model (ITM). The LTE systems under consideration are macro cell, outdoor small cells, and indoor small cells. Furthermore, the resource allocation under channel consideration is formalized such that the resources are allocated under a congested environment and based on the quality of channel the users have in the network as well as the quality of service requirements of the applications running on the mobile devices. / Ph. D.

The radio spectrum dependent applications are facing a huge scarcity of the resource. To address this issue, future wireless systems require new wireless network architectures and new approaches to spectrum management. Spectrum sharing has emerged as a promising solution to address the radio frequency (RF) spectrum bottleneck. Although spectrum sharing is intended to provide flexible use of the spectrum, the architecture of the existing approaches, such as TV White Space [1] and Citizen Broadband Radio Services (CBRS) [2], have a relatively fixed sharing framework. This fixed structure limits the applicability of the architecture to other bands where the relationship between various new users and different types of legacy users co-exist. Specifically, an important aspect of sharing that has not been explored enough is the cooperation between the resource owner and the opportunistic user. Also in a shared spectrum system, the users do not have any information about the availability and duration of the available spectrum opportunities. This lack of understanding about the shared spectrum leads the research community to explore a number of core spectrum sharing tasks, such as opportunity detection, dynamic opportunity scheduling, and interference protection for the primary users, etc. This report proposes a Primary-Secondary Cooperation Framework to provide flexibility to all the involved parties in terms of choosing the level of cooperation that allow them to satisfy different objective priorities. The cooperation framework allows exchange of a probabilistic assurance: Spectrum Opportunity Duration Assurance (SODA) between the primary and secondary operations to improve the overall spectrum sharing experience for both the parties. This capability will give the spectrum sharing architectures new flexibility to handle evolutions in technologies, regulations, and the requirements of new bands being transitioned from fixed to share usage. In this dissertation we first look into the regulatory aspect of spectrum sharing. We analyze the Federal Communications Commission's (FCC) initiatives with regards to the commercial use of the 150 MHz spectrum block in the 3.5 GHz band. This analysis results into a Spectrum Access System (SAS) architecture and list of required functionalities. Then we address the nature of primary-secondary cooperation in spectrum sharing and propose to generate probabilistic assurances for spectrum opportunities. We use the generated assurance to observe the impact of cooperation from the perspective of spectrum sharing system management. We propose to incorporate primary user cooperation in the auctioning and resource allocation procedures to manage spectrum opportunities. We also analyze the improvement in spectrum sharing experience from the perspective of the primary and secondary users as a result of cooperation. We propose interference avoidance schemes that involve cooperation to improve the achievable quality of service. Primary-secondary cooperation has the potential to significantly influence the mechanism and outcomes of the spectrum sharing systems. Both the primary and secondary operations can benefit from cooperation in a sharing scenario. Based on the priorities of the primary and secondary operations, the users may decide on the level of cooperation that they are willing to participate. Also access to information about the availability and usability of the spectrum opportunity will result in efficient spectrum opportunity management and improved sharing performance for both the primary and secondary users. Thus offering assurances about the availability and duration of spectrum opportunity through primary-secondary cooperation will significantly improve the overall spectrum sharing experience. The research reported in this dissertation is expected to provide a fundamental analytical framework for characterizing and quantifying the implications of primary-secondary cooperation in a spectrum sharing context. It analyzes the technical challenges in modeling different level of cooperation and their impact on the spectrum sharing experience. We hope that this dissertation will establish the fundamentals of the spectrum sharing to allow the involved parties to participate in sharing mechanisms that is suitable to their objective priorities. / PHD

Emerging technologies such as wireless local area networks and cellular telephones have dramatically increased the use of wireless communications services within the last 10 years. The shortage of available spectrum exists due to increasing demand for wireless services and current spectrum allocation regulations. To alleviate this shortage, Research aims to improve spectral efficiency and to allow spectrum sharing between separately managed and non-coordinating communications systems. This thesis explores the feasibility of spectrum sharing between airborne weather radar and wireless local area networks at 9.3 GHz – 9.5 GHz. Characteristics of flight paths of aircraft using airborne weather radar and the low duty cycle of radar transmissions offer unique opportunities for spectrum sharing. But it was found that the extremely sensitive receivers provide challenges for designing a communications system meant for widespread use. The probability of causing harmful interference to airborne weather radar is too great for most types of wireless local area networks, but a direct sequence spread spectrum scheme could share spectrum with airborne weather radar. Bit errors in wireless local area network links caused by airborne weather radar interference do not significantly decrease the performance of the wireless local area network system. The distribution of interference outside of the airborne weather radar receiver by using direct sequence spread spectrum combined with the acceptable bit error rates indicate that while spectrum sharing between airborne weather radar and wireless local area network at 9.3 GHz – 9.5 GHz is not feasible, direct sequence spread spectrum systems can share spectrum with airborne weather radars under more limited assumptions. / Master of Science

Les technologies mobiles terrestre et satellite sont naturellement complémentaires. Les réseaux cellulaires terrestres sont adaptés aux villes où la densité d'utilisateurs est maximale mais perdent leur rentabilité dans les zones peu peuplées. A l'inverse, les systèmes mobile satellite permettent de couvrir de vastes zones à moindre coût mais n'assurent pas la couverture dans les zones urbaines car le signal est bloqué par les constructions. En les combinant pour assurer la couverture en ville par le réseau terrestre et dans les zones moins denses avec le satellite, on obtient un système à la couverture totale pour un coût optimal. Nous appelons un tel système intégrant une composante satellite et une composante terrestres un "système intégré" satellite/terrestre. Nul doute que d'ici quelques années, le rêve de la communauté satellite de rendre tous les terminaux mobiles capables de se connecter à un satellite sera accessible. Le satellite pourra ainsi être vu par les utilisateurs de terminaux portables comme une énième technologie d'accès à un système "intégré", aux côtés du Bluetooth, du Wifi et des technologies cellulaires (GSM, UMTS, LTE). La réutilisation du spectre satellite par les systèmes terrestres est un facteur déterminant dans le succès de cette intégration car elle permet de justifier les investissements dans le système satellite qui ne peut être rentabilisé par les abonnements seuls. Toutefois sa mise en œuvre pose de nombreux problèmes : règlementaires, commerciaux et bien entendu techniques. Cette thèse apporte des solutions sur ce dernier point et j'espère qu'elle contribuera ainsi à rendre possible ce rêve d'intégration. Nous avons adopté une approche descendante du problème du partage de spectre dans les systèmes mobiles satellite-terrestre. Nous avons tout d'abord établi une synthèse sur les aspects recouverts par l'intégration des systèmes mobiles satellite et terrestre. Nous avons ensuite dressé l'état de l'art sur la problématique de la réutilisation du spectre satellite par les systèmes terrestres, que nous avons complété par nos analyses. Nous avons décidé dans cette thèse de nous focaliser sur un des problèmes majeurs soulevés par cette réutilisation : les interférences co-fréquence du système terrestre sur le lien montant satellite. A partir de l'analyse d'une solution de partage statique de spectre par coordination des plans de fréquence (principe de zone d'exclusion), nous avons élaboré puis analysé les performances de mécanismes innovants d'allocation de ressources dans le système terrestre qui permettent de réduire de façon importante les interférences. De plus, nous proposons une méthode pour garantir au système satellite que les interférences subies sur son lien montant soient inférieures à une valeur limite. Enfin, nous définissons une architecture et les mécanismes associés qui permettent l'implantation des solutions proposées dans un système satellite-terrestre fondé sur la technologie LTE. L'étude du sujet de partage de spectre dans les systèmes mobiles satellite-terrestre est relativement nouvelle et cette thèse constitue donc un travail novateur important qui pourra être utilisé comme base à de futurs travaux. / Terrestrial and satellite mobile technologies are naturally complementary. Terrestrial cellular systems are adapted to urban areas where the user density is maximal but their cost-effectiveness is much lower in sparsely populated areas. On the contrary, mobile satellite systems cover large zones at a relatively low cost but they cannot ensure coverage in urban areas because of signal blockage due to buildings. By combining both systems for ensuring coverage in cities with terrestrial networks and in less dense areas with the satellite, we obtain a system with complete coverage for an optimal cost. Such a system is called mobile terrestrial and satellite "integrated system". It is likely that in a few years, the dream of enabling satellite connectivity on all mobile terminals will be within reach. The satellite will then be perceived for mobile terminal users as an additional access technology to an "integrated network" comparable to Wifi, Bluetooth or cellular technologies (GSM, UMTS, LTE). The spectrum reuse by terrestrial systems is a key for the success of this integration because it justifies part of the investments in the satellite systems that cannot be supported by user subscriptions only. However, implementation of spectrum sharing generates many issues: regulatory, commercial and obviously technical. This thesis brings answers on the latter and I hope it will contribute to make this dream of integration become reality. We used a descending approach of the issue of spectrum sharing in terrestrial and satellite mobile systems. First, we establish a synthesis of all the aspects covered by the integration of mobile satellite and terrestrial systems. Then, we made the state of the art on the issue of satellite spectrum reuse by terrestrial systems and we completed it with our analysis. We decided to focus our work on one of the major issues raised by this reuse: co-frequency interference generated by the terrestrial system on the satellite uplink. From the analysis of a solution proposing a static spectrum sharing by coordination of frequency plans (the exclusion zone principle), we elaborated and analyzed performances of innovative mechanisms of resources allocation in the terrestrial system that allows to reduce significantly the interferences. Moreover, we proposed a method for guaranteeing to the satellite system that interferences from the terrestrial system will not exceed a given threshold. At last, we define an architecture and the associated mechanism that allow the implementation of our solution in an integrated terrestrial-satellite systems based on LTE technology. The study of spectrum sharing in terrestrial-satellite mobile systems is rather new and this thesis represents an innovative work that may serve as a basis for future studies on this issue.

Au début des années 2000, les instances aéronautiques ont exprimé le besoin de développer un nouveau système de radiocommunication aéronautique du fait de l'augmentation du trafic aérien et de la saturation croissante des capacités de communication radio entre les aéronefs et les stations de contrôle aérien. L'une des composantes de ce système, nommée L-DACS (« L-band Digital Aeronautical Communication System »), devrait opérer dans la bande L-aéronautique (960-1164 MHz), dans laquelle fonctionnent également de nombreux autres systèmes radioélectriques. La compatibilité radioélectrique (CRE) de L-DACS avec ces systèmes est un des facteurs principaux à prendre en considération dans le développement d'un tel système.L'objectif principal de cette thèse est d'identifier les principaux problèmes reliés à la CRE et d'en étudier les cas critiques. Ces travaux sont fondamentaux en aéronautique, puisque tout dysfonctionnement dans la communication ou dans les systèmes de radionavigation peut mettre en danger la sécurité du vol. Les conclusions de cette thèse contribueront à la normalisation du système L-DACS et à la finalisation de ses spécifications.Dans une première étape, on étudie l'état de l'art dans les communications aéronautiques et en CRE. On analyse en particulier les dernières spécifications des deux systèmes candidats L-DACS. Ensuite, on propose un algorithme de calcul de brouillage dans le but d'étudier la CRE dans le domaine fréquentiel, d'en identifier et d'en traiter les cas critiques. L'analyse fréquentielle étant insuffisante dans plusieurs cas, on propose alors une approche temporelle d'étude de CRE. Après en avoir présenté les avantages, on présente un exemple d'étude de l'effet d'un système L-DACS sur un récepteur DME (« Distance Measuring Equipment ») à l'aide d'un banc de test CRE aéronautique.Cette thèse a été réalisée en collaboration avec la Direction Générale de l'Aviation Civile (DGAC), qui est un acteur principal pour la réglementation des communications et un affectataire de fréquence pour le spectre aéronautique en France. La thèse contribue aux études menées par la DGAC à l'échelle nationale et internationale.Dans les perspectives, on propose la poursuite de cette étude par une approche temporelle plus générale pour étudier la CRE entre des systèmes radioélectriques quelconques en tenant compte de paramètres supplémentaires liés à la dynamique des systèmes et aux propriétés de leurs technologies. / In the beginning of the 21th century, the aeronautical authorities expressed their need to develop a new system for aeronautical radiocommunications, because the air-traffic is increasing and that current communication systems between pilots and air-controllers are reaching their capacity limits. The L-band Digital Aeronautical Communication System (L-DACS) is the part of the future system that will be operating in a part of the aeronautical L-band (960-1164 MHz), already occupied by a large number of radio-frequency legacy systems. Consequently, it is essential to consider its radio-frequency compatibility (RFC) for the development of the future L-DACS system. This thesis aims at identifying the principal issues related to RFC and studying its critical situations. Such topics are fundamental in aeronautics, as any communication or radionavigation dysfunction may endanger flight and passengers security. Some obtained results will be used for the L-DACS standardization and its specifications finalization. We first analyze the state-of-the-art in both aeronautical communications and RFC, focalizing on updated specifications of both preselected L-DACS candidate systems. We then propose a deterministic algorithm to compute the interference level in order to study the RFC in the frequency domain under identified critical scenarios. Since the frequency-domain analysis seems to be insufficient in several cases, we develop a different methodology, called the time-frequency approach, to analyze the RFC for such situations. We apply this new approach to analyze the effect of an L-DACS interferer on a Distance Measuring Equipment (DME) receiver, using an aeronautical RFC test-bed that we implemented at SUPELEC. This work has been performed in collaboration with the French Civil Aviation Authorities (DGAC), which are an important actor in aeronautical communication regulations and aeronautical spectrum management in France. The thesis contributes to DGAC studies at national as well as international levels. For further work, we suggest to generalize the proposed time-frequency approach to analyze the RFC between any two radio-frequency systems, taking into account additional parameters related to system dynamics and their technology properties.

Device-to-device (D2D) networking enables direct discovery and communication between cellular subscribers that are in proximity, thus bypassing the base stations (BSs). In principle, exploiting direct communication between nearby mobile devices will improve spectrum utilization, overall throughput, and energy consumption, while enabling new peer-to-peer and location-based applications and services. D2D-enabled broadband communication technology is also required by public safety networks that must function when cellular networks are not available. Integrating D2D into cellular networks, however, poses many challenges and risks to the long-standing cellular architecture, which is centered around the BSs. This dissertation identifies outstanding technical challenges in D2D-enabled cellular networks and addresses them with novel models and fundamental analysis. First, this dissertation develops a baseline hybrid network model consisting of both ad hoc nodes and cellular infrastructure. This model uses Poisson point processes to model the random and unpredictable locations of mobile users. It also captures key features of multicast D2D including multicast receiver heterogeneity and retransmissions while being tractable for analytical purpose. Several important multicast D2D metrics including coverage probability, mean number of covered receivers per multicast session, and multicast throughput are analytically characterized under the proposed model. Second, D2D mode selection which means that a potential D2D pair can switch between direct and cellular modes is incorporated into the hybrid network model. The extended model is applied to study spectrum sharing between cellular and D2D communications. Two spectrum sharing models, overlay and underlay, are investigated under a unified analytical framework. Analytical rate expressions are derived and applied to optimize the design of spectrum sharing. It is found that, from an overall mean-rate perspective, both overlay and underlay bring performance improvements (vs. pure cellular). Third, the single-antenna hybrid network model is extended to multi-antenna transmission to study the interplay between massive MIMO (multi-input multiple-output) and underlaid D2D networking. The spectral efficiency of such multi-antenna hybrid networks is investigated under both perfect and imperfect channel state information (CSI) assumptions. Compared to the case without D2D, there is a loss in cellular spectral efficiency due to D2D underlay. With perfect CSI, the loss can be completely overcome if the number of canceled D2D interfering signals is scaled appropriately. With imperfect CSI, in addition to pilot contamination, a new asymptotic underlay contamination effect arises. Finally, motivated by the fact that transmissions in D2D discovery are usually not or imperfectly synchronized, this dissertation studies the effect of asynchronous multicarrier transmission and proposes a tractable signal-to-interference-plus-noise ratio (SINR) model. The proposed model is used to analytically characterize system-level performance of asynchronous wireless networks. The loss from lack of synchronization is quantified, and several solutions are proposed and compared to mitigate the loss. / text

Abstract Radio spectrum is a scarce natural resource whose efficient management has been the source of contentious debate for over a century. The mobile communication ecosystem has created a tremendous business that is reliant on the availability of spectrum for wireless networks. The growth of mobile communications has increased the rivalry between the different wireless ecosystems that compete over gaining access rights to radio spectrum. Due to the scarcity of unallocated spectrum bands without incumbent users, sharing-based governance models for spectrum management have gained increasing attention in regulation, industry and academia. Spectrum sharing allows two or more wireless systems to operate in the same spectrum band. These systems often come from different wireless ecosystems that have conflicting goals. Spectrum sharing, and specifically the development of new sharing-based governance models for more efficient management of the scarce resource, is a strategic management topic that calls for the development of rules and conditions by regulators that are agreeable to all involved stakeholders. This thesis presents a novel framework for the development of upcoming sharing-based spectrum governance models that bring together stakeholders from different wireless business ecosystems with conflicting goals. The framework is built upon the theoretical basis of governance models, stakeholder analysis, and business ecosystems. Spectrum management is here seen as governance of common pool resources, and the tool of stakeholder analysis from strategic management is formally introduced into the development of new sharing-based spectrum governance models where different business ecosystems collide. The developed three-step stakeholder analysis is applied to two case studies for mobile communications including the future use of the ultra-high frequency (UHF) band, and the licensed shared access (LSA) concept. For the UHF band case study, the thesis identifies the stakeholders, analyses their relations and saliences to reach long-term compromises between broadcasting and mobile communication ecosystems. For the LSA case study, the thesis identifies the stakeholders and their relations, and develops management actions through a work flow for the main phases and stakeholders’ tasks. It then presents the world’s first live field trial with mobile communication systems, where the conflicting requirements of all stakeholders were considered. The developed stakeholder analysis model formally introduces the strategic management of stakeholders into the spectrum management domain, and it provides regulators, industry and academia a new tool for reaching long-term compromises in spectrum management through sharing. / Tiivistelmä Radiotaajuudet muodostavat rajallisen luonnonvaran, jonka tehokas hallinta on ollut vuosikymmenten ajan kiistanalainen keskustelunaihe. Matkaviestinnän ekosysteemi on luonut suurta liiketoimintaa saamalla käyttöönsä radiotaajuuksia, joilla matkaviestinverkot voivat toimia. Matkaviestinnän kasvu on lisännyt eri langattomien järjestelmien ekosysteemien välistä kilpailua radiotaajuuksien saatavuudesta. Taajuuksien yhteiskäyttöön perustuvat hallintamallit ovat herättäneet kasvavaa kiinnostusta taajuushallinnoissa, teollisuudessa ja tutkimusmaailmassa, koska lähes kaikki radiotaajuudet on jo annettu erilaisten langattomien järjestelmien käyttöön. Taajuuksien yhteiskäyttö mahdollistaa kahden tai useamman radiojärjestelmän toiminnan samalla taajuusalueella. Usein nämä järjestelmät edustavat erilaisia langattomia ekosysteemejä, joilla on ristiriitaiset tavoitteet. Taajuuksien yhteiskäyttö ja siihen liittyvien hallintamallien kehittäminen rajallisen luonnonvaran tehokkaamman käytön mahdollistamiseksi on strategisen johtamisen aihealue, joka edellyttää, että taajuushallinnot kehittävät säännöt ja ehdot, jotka ovat hyväksyttäviä sidosryhmille. Tämä väitöskirja esittelee uuden viitekehityksen taajuuksien yhteiskäyttöön perustuvien taajuuksien hallintamallien kehittämiselle tuomalla yhteen eri sidosryhmät, jotka edustavat erilaisia langattomia liiketoimintaekosysteemejä, joilla on ristiriitaiset tavoitteet. Kehitetyn viitekehyksen teoriapohja koostuu hallintomalleista, sidosryhmäanalyysistä sekä liiketoiminnan ekosysteemeistä. Tässä työssä taajuuksien hallinta nähdään yhteisresurssien (common pool resource, CPR) hallintana, ja strategisen johtamisen työkaluista sidosryhmäanalyysi on valittu taajuuksien yhteiskäyttömallien kehittämiseen erilaisten liiketoiminta-ekosysteemien kohtauspisteessä. Työssä kehitettyä kolmiaskelista sidosryhmäanalyysiä sovelletaan kahteen matkaviestinnän tapaustutkimukseen sisältäen UHF-taajuuden tulevaisuuden käytön sekä taajuuksien lisensioidun yhteiskäytön (licensed shared access, LSA). UHF-taajuuden tapaustutkimuksessa väitöskirjassa tunnistetaan sidosryhmät ja analysoidaan niiden riippuvuuksia ja painoarvoja pitkän tähtäimen kompromissin löytämiseksi yleisradioliikenteen ja matkaviestinnän ekosysteemien välille. LSA-tapaustutkimukselle väitöskirjassa tunnistetaan sidosryhmät ja niiden riippuvuudet sekä kehitetään johtamismalleja työnkulkukaavion avulla. Lisäksi työssä esitellään maailman ensimmäinen todellisella matkaviestinjärjestelmällä tehty kokeilu, joka ottaa huomioon eri sidosryhmien ristiriitaiset vaatimukset. Työssä kehitetty malli on ensimmäinen strategisen johtamisen sidosryhmäanalyysin sovellus taajuuksien hallintaan ja tuo taajuushallinnoille, teollisuudelle ja tutkimusmaailmalle uuden työkalun pitkän tähtäimen kompromissien löytämiseen taajuuksien hallinnalle yhteiskäytön avulla.

With the ever-growing demand for higher data rate in next generation communication systems, researchers are pushing the limits of the existing architecture. Due to the stochastic nature of communication channels, most systems use some form of adaptive methods to adjust the transmitting parameters and allocation of resources in order to overcome channel variations and achieve optimal throughput. We will study four cases of adaptive transmission and dynamic resource allocation in collaborative systems that are practically significant. Firstly, we study hybrid automatic repeat request (HARQ) techniques that are widely used to handle transmission failures. We propose HARQ policies that improve system throughput and are suitable for point-to-point, two-hop relay, and multi-user broadcast systems. Secondly, we study the effect of having bits of mixed SNR qualities in finite length codewords. We prove that by grouping bits according to their reliability so that each codeword contains homogeneous bit qualities, the finite blocklength capacity of the system is increased. Thirdly, we study the routing and resource allocation problem in multiple collaborative networks. We propose an algorithm that enables collaboration between networks which needs little to no side information shared across networks, but rather infers necessary information from the transmissions. The collaboration between networks provides a significant gain in overall throughput compared to selfish networks. Lastly, we present an algorithm that allocates disjoint transmission channels for our cognitive radio network in the DARPA Spectrum Collaboration Challenge (SC2). This algorithm uses the real-time spectrogram knowledge perceived by the radios and allocates channels adaptively in a crowded spectrum shared with other collaborative networks.

As the wireless communication technologies evolve and the demand of wireless services increases, spectrum scarcity becomes a bottleneck that limits the introduction of new technologies and services. Spectrum sharing between primary and secondary users has been brought up to improve spectrum efficiency. In underlay spectrum sharing, the secondary user transmits simultaneously with the primary user, under the constraint that the interference induced at the primary receiver is below a certain threshold, or a certain primary rate requirement has to be satisfied. Specifically, in this thesis, the coexistence of a multiple-input single-output (MISO) primary link and a MISO/multiple-input multiple-output (MIMO) secondary link is studied. The primary transmitter employs maximum ratio transmission (MRT), and single-user decoding is deployed at the primary receiver. Three scenarios are investigated, in terms of the interference from the primary transmitter to the secondary receiver, namely, weak interference, strong interference and very strong interference, or equivalently three ranges of primary rate requirement. Rate splitting and successive decoding are deployed at the secondary transmitter and receiver, respectively, when it is feasible, and otherwise single-user decoding is deployed at the secondary receiver. For each scenario, optimal beamforming/precoding and power allocation at the secondary transmitter is derived, to maximize the achievable secondary rate while satisfying the primary rate requirement and the secondary power constraint. Numerical results show that rate splitting at the secondary transmitter and successive decoding at the secondary receiver does significantly increase the achievable secondary rate if feasible, compared with single-user decoding at the secondary receiver. In overlay spectrum sharing, different from underlay spectrum sharing, the secondary transmitter can utilize the knowledge of the primary message, which is acquired non-causally (i.e., known in advance before transmission) or causally (i.e., acquired in the first phase of a two-phase transmission), to help transmit the primary message besides its own message. Specifically, the coexistence of a MISO primary link and a MISO/MIMO secondary link is studied. When the secondary transmitter has non-causal knowledge of the primary message, dirty-paper coding (DPC) can be deployed at the secondary transmitter to precancel the interference (when decoding the secondary message at the secondary receiver), due to the transmission of the primary message from both transmitters. Alternatively, due to the high implementation complexity of DPC, linear precoding can be deployed at the secondary transmitter. In both cases, the primary transmitter employs MRT, and single-user decoding is deployed at the primary receiver; optimal beamforming/precoding and power allocation at the secondary transmitter is obtained, to maximize the achievable secondary rate while satisfying the primary rate requirement and the secondary power constraint. Numerical results show that with non-causal knowledge of the primary message and the deployment of DPC at the secondary transmitter, overlay spectrum sharing can achieve a significantly higher secondary rate than underlay spectrum sharing, while rate loss occurs with the deployment of linear precoding instead of DPC at the secondary transmitter. When the secondary transmitter does not have non-causal knowledge of the primary message, and still wants to help with the primary transmission in return for the access to the spectrum, it can relay the primary message in an amplify-and-forward (AF) or a decode-and-forward (DF) way in a two-phase transmission, while transmitting its own message. The primary link adapts its transmission strategy and cooperates with the secondary link to fulfill its rate requirement. To maximize the achievable secondary rate while satisfying the primary rate requirement and the primary and secondary power constraints, in the case of AF cooperative spectrum sharing, optimal relaying matrix and beamforming vector at the secondary transmitter is obtained; in the case of DF cooperative spectrum sharing, a set of parameters are optimized, including time duration of the two phases, primary transmission strategies in the two phases and secondary transmission strategy in the second phase. Numerical results show that with the cooperation from the secondary link, the primary link can avoid outage effectively, especially when the number of antennas at the secondary transceiver is large, while the secondary link can achieve a significant rate. Power is another precious resource besides spectrum. Instead of spectrum efficiency, energy-efficient spectrum sharing focuses on the energy efficiency (EE) optimization of the secondary transmission. The EE of the secondary transmission is defined as the ratio of the achievable secondary rate and the secondary power consumption, which includes both the transmit power and the circuit power at the secondary transmitter. For simplicity, the circuit power is modeled as a constant. Specifically, the EE of a MIMO secondary link in underlay spectrum sharing is studied. Three transmission strategies are introduced based on the primary rate requirement and the channel conditions. Rate splitting and successive decoding are deployed at the secondary transmitter and receiver, respectively, when it is feasible, and otherwise single-user decoding is deployed at the secondary receiver. For each case, optimal transmit covariance matrices at the secondary transmitter are obtained, to maximize the EE of the secondary transmission while satisfying the primary rate requirement and the secondary power constraint. Based on this, an energy-efficient resource allocation algorithm is proposed. Numerical results show that MIMO underlay spectrum sharing with EE optimization can achieve a significantly higher EE compared with MIMO underlay spectrum sharing with rate optimization, at certain SNRs and with certain circuit power, at the cost of the achievable secondary rate, while saving the transmit power. With rate splitting at the secondary transmitter and successive decoding at the secondary receiver if feasible, a significantly higher EE can be achieved compared with the case when only single-user decoding is deployed at the secondary receiver. Moreover, the EE of a MIMO secondary link in overlay spectrum sharing is studied, where the secondary transmitter has non-causal knowledge of the primary message and employs DPC to obtain an interference-free secondary link. Energy-efficient precoding and power allocation is obtained to maximize the EE of the secondary transmission while satisfying the primary rate requirement and the secondary power constraint. Numerical results show that MIMO overlay spectrum sharing with EE optimization can achieve a significantly higher EE compared with MIMO overlay spectrum sharing with rate optimization, at certain SNRs and with certain circuit power, at the cost of the achievable secondary rate, while saving the transmit power. MIMO overlay spectrum sharing with EE optimization can achieve a higher EE compared with MIMO underlay spectrum sharing with EE optimization. / Aufgrund der rasanten Entwicklung im Bereich der drahtlosen Kommunikation und der ständig steigenden Nachfrage nach mobilen Anwendungen ist die Knappheit von Frequenzbändern ein entscheidender Engpass, der die Einführung neuer Funktechnologien behindert. Die gemeinsame Benutzung von Frequenzen (Spektrum-Sharing) durch primäre und sekundäre Nutzer ist eine Möglichkeit, die Effizienz bei der Verwendung des Spektrums zu verbessern. Bei der Methode des Underlay-Spektrum-Sharing sendet der sekundäre Nutzer zeitgleich mit dem primären Nutzer unter der Einschränkung, dass für den primären Nutzer die erzeugte Interferenz unterhalb eines Schwellwertes liegt oder gewisse Anforderungen an die Datenrate erfüllt werden. In diesem Zusammenhang wird in der Arbeit insbesondere die Koexistenz von Mehrantennensystemen untersucht. Dabei wird für die primäre Funkverbindung der Fall mit mehreren Sendeantennen und einer Empfangsantenne (MISO) angenommen. Für die sekundäre Funkverbindung werden mehrere Sendeantennen und sowohl eine als auch mehrere Empfangsantennen (MISO/MIMO) betrachtet. Der primäre Sender verwendet Maximum-Ratio-Transmission (MRT) und der primäre Empfänger Einzelnutzerdecodierung. Für den sekundären Nutzer werden außerdem am Sender eine Datenratenaufteilung (rate splitting) und am Empfänger entweder eine sukzessive Decodierung – sofern sinnvoll – oder andernfalls eine Einzelnutzerdecodierung verwendet. Im Unterschied zur Methode des Underlay-Spektrum-Sharing kann der sekundäre Nutzer beim Verfahren des Overlay-Spektrum-Sharing die Kenntnis über die Nachrichten des primären Nutzers einsetzen, um die Übertragung sowohl der eigenen als auch der primären Nachrichten zu unterstützen. Das Wissen über die Nachrichten erhält er entweder nicht-kausal, d.h. vor der Übertragung, oder kausal, d.h. während der ersten Phase einer zweistufigen Übertragung. In der Arbeit wird speziell die Koexistenz von primären MISO-Funkverbindungen und sekundären MISO/MIMO-Funkverbindungen untersucht. Bei nicht-kausaler Kenntnis über die primären Nachrichten kann der sekundäre Sender beispielsweise das Verfahren der Dirty-Paper-Codierung (DPC) verwenden, welches es ermöglicht, die Interferenz durch die primären Nachrichten bei der Decodierung der sekundären Nachrichten am sekundären Empfänger aufzuheben. Da die Implementierung der DPC mit einer hohen Komplexität verbunden ist, kommt als Alternative auch eine lineare Vorcodierung zum Einsatz. In beiden Fällen verwendet der primäre Transmitter MRT und der primäre Empfänger Einzelnutzerdecodierung. Besitzt der sekundäre Nutzer keine nicht-kausale Kenntnis über die primären Nachrichten, so kann er als Gegenleistung für die Mitbenutzung des Spektrums dennoch die Übertragung der primären Nachrichten unterstützen. Hierfür leitet er die primären Nachrichten mit Hilfe der Amplify-And-Forward-Methode oder der Decode-And-Forward-Methode in einer zweitstufigen Übertragung weiter, währenddessen er seine eigenen Nachrichten sendet. Der primäre Nutzer passt seine Sendestrategie entsprechend an und kooperiert mit dem sekundären Nutzer, um die Anforderungen an die Datenrate zu erfüllen. Nicht nur das Spektrum sondern auch die Sendeleistung ist eine wichtige Ressource. Daher wird zusätzlich zur Effizienz bei der Verwendung des Spektrums auch die Energieeffizienz (EE) einer sekundären MIMO-Funkverbindung für das Underlay-Spektrum-Sharing-Verfahren analysiert. Wie zuvor wird für den sekundären Nutzer am Sender eine Datenratenaufteilung (rate splitting) und am Empfänger entweder eine sukzessive Decodierung oder eine Einzelnutzerdecodierung betrachtet. Weiterhin wird die EE einer sekundären MIMO-Funkverbindung für das Overlay-Spektrum-Sharing-Verfahren untersucht. Dabei nutzt der sekundäre Nutzer die nicht-kausale Kenntnis über die primären Nachrichten aus, um mittels DPC eine interferenzfreie sekundäre Funkverbindung zu erhalten.

Sharing a band of frequencies in the radio spectrum among multiple wireless systems has emerged as a viable solution for alleviating the severe capacity crunch in next-generation wireless mobile networks such as 5th generation mobile networks (5G). Spectrum sharing can be achieved by enabling multiple wireless systems to coexist in a single spectrum band. In this dissertation, we discuss the following coexistence problems in spectrum bands that have recently been raising notable research interest: 5G and Fixed Satellite Service (FSS) at 27.5-28.35 GHz (28 GHz); 5G and Fixed Service (FS) at 71-76 GHz (70 GHz); vehicular communications and Wi-Fi at 5.85-5.925 GHz (5.9 GHz); and mobile broadband communications and radar at 3.55-3.7 GHz (3.5 GHz). The results presented in each of the aforementioned parts show comprehensively that the coexistence methods help achieve spectrum sharing in each of the bands, and therefore contribute to achieve appreciable increase of bandwidth efficiency. The proposed techniques can contribute to making spectrum sharing a viable solution for the ever evolving capacity demands in the wireless communications landscape. / Ph. D.