During this project we have designed a new type of antenna that uses an array of antenna elements in order to emit electromagnetic radiation as signals and to be able to control the beam. After an extended time the design yielded a simulation which had the correct characteristics. After printing and constructing a prototype of the antenna it was tested in an anechoic chamber at Uppsala University. The array was divided into two different sub-arrays: the upper and the lower sub-arrays. Each of these consisted in itself of two sides: the long and the short sides. Each side had seven radiating elements, during the tests only one of the two sub-arrays (upper or lower) was running. Both sub-arrays are excited via a rat-race or 90 degree coupler. While the antenna was running it had 14 radiating elements and two phase shifters, two per sub-array and two per side. The idea was for a signal to travel passing the radiating elements and the phase shifter which would steer the induced electromagnetic signal in one direction, a traveling-wave array. This direction could be changed since the phase shifters were configurable in three different states per phase shifter, hence the induced electromagnetic beam was steerable. The beam was also steerable through the feed which was re-configurable, since there were two feeds per sub-array a phase shift could be introduced between the long and the short side. The beam steering range was between -2 degrees and 11 degrees oriented as 0 degrees would be a perpendicular line from the array to the receiving end. The design itself worked which could be stated from the results in the upper part of the array, the test results from the lower part however did not match the simulated results. This is likely due to an error in the construction of the antenna rather than the theory since the upper and lower part of the array was mirrored versions of each other. The phase shifters worked as intended in the bigger picture but were slightly different in the simulations compared to the physical ones, likely due to the same type of error source as regarding the full antenna.

Massive MIMO (Multiple-Input Multiple-Output) base stations have proven, both in theory and in practice, to possess many of the qualities that future wireless communication systems will require.  They can provide equally high data rates throughout their coverage area and can concurrently serve multiple low-end handsets without requiring wider spectrum, denser base station deployment or significantly more power than current base stations.  The main challenge of massive MIMO is the immense hardware complexity and cost of the base station—each element in the large antenna array needs to be individually controllable and therefore requires its own radio chain.  To make massive MIMO commercially viable, the base station has to be built from inexpensive simple hardware.  In this thesis, it is investigated how the use of low-end power amplifiers and analog-to-digital converters (ADCs) affects the performance of massive MIMO.  In the study of the signal distortion from low-end amplifiers, it is shown that in-band distortion is negligible in massive MIMO and that out-of-band radiation is the limiting factor that decides what power efficiency the amplifiers can be operated at.  A precoder that produces transmit signals for the downlink with constant envelope in continuous time is presented to allow for highly power efficient low-end amplifiers.  Further, it is found that the out-of-band radiation is isotropic when the channel is frequency selective and when multiple users are served; and that it can be beamformed when the channel is frequency flat and when few users are served.  Since a massive MIMO base station radiates less power than today's base stations, isotropic out-of-band radiation means that low-end hardware with poorer linearity than required today can be used in massive MIMO.  It is also shown that using one-bit ADCs—the simplest and least power-hungry ADCs—at the base station only degrades the signal-to-interference-and-noise ratio of the system by approximately 4 dB when proper power allocation among users is done, which indicates that massive MIMO is resistant against coarse quantization and that low-end ADCs can be used. / Massiv-MIMO-basstationer (eng: Multiple-Input Multiple-Output) har visats, både i teori och praktik, besitta många av de egenskaper som framtida trådlösa kommunikationssystem kommer att behöva.  De kan tillhandahålla enhetligt höga datatakter i hela täckningsområdet och simultant betjäna flera enkla mobilenheter utan att använda bredare spektrum, tätare basstationsplacering eller betydligt mer effekt än dagens basstationer.  Huvudutmaningen med massiv MIMO är basstationens enorma hårdvarukomplexitet och -kostnad – varje element i den stora gruppantennen skall kunna kontrolleras individuellt och kräver sålunda sin egen radiokedja.  För att massiv MIMO skall bli kommersiellt attraktiv, måste basstationen byggas av billig, enkel hårdvara.  I denna avhandling undersöks hur enkla effektförstärkare och analog-till-digital-omvandlare (AD-omvandlare) påverkar massiv-MIMO-systemets prestanda.  I studien av signaldistorsionen från enkla förstärkare visas det att inband-distorsionen är försumbar i massiv MIMO och att utombandsstrålningen är den begränsande faktorn som bestämmer vid vilken verkningsgrad förstärkarna kan arbeta.  En förkodare som åstadkommer nerlänks-sändsignaler som har konstant envelopp i kontinuerlig tid presenteras för att möjliggöra användandet av enkla förstärkare med hög verkningsgrad.  Vidare konstateras det att utombandsstrålningen är isotrop när kanalen är frekvensselektiv och när flera användare betjänas; och att den kan lobformas när kanalen är frekvensflat och när få användare betjänas.  Eftersom en massiv-MIMO-basstation utstrålar mindre effekt än dagens basstationer, betyder isotrop utombandsstrålning att enkel hårdvara med sämre linearitet än vad som krävs idag kan användas i massiv MIMO.  Det visas även att användandet av enbits-AD-omvandlare – de enklaste och mest strömsnåla AD-omvandlarna – i basstationen endast minskar signal-till-interferens-och-brus-förhållandet med 4 dB när tillbörlig effektallokering mellan användarna utförs, vilket indikerar att massiv MIMO är motståndskraftig mot grov kvantisering och att enkla AD-omvandlare kan användas. / 大規模多輸入多輸出基站，無論從理論上或實際上，皆已經證明具有許多未來無線通訊系統所需的特質。比如：在其整個覆蓋區域均一地提供高數據傳輸速率、在同一時間頻率資源上服務多個簡單的終端設備，而無需佔用更多頻譜資源或更密集地部署基站，亦無需提高基站的功耗。實現大規模多入多出系统的主要挑戰在於硬件複雜度及基站成本——大規模天線陣列中的每一個天線元必須單獨可控，因此需要其自身的射頻鏈路。爲使大規模多入多出基站有商業吸引力，基站必須以簡單低成本的硬件來建造。本論文探討簡單的功率放大器與模擬數字轉換器對大規模多入多出性能的影響。對低端功放信號失真的研究表明，帶內失真對大規模多入多出的性能影響幾乎可以忽略，而帶外泄露是限制功放效率的決定因素。爲使用高功率效率低端功放，本文提出能產生具有恆定包絡連續時間信號的預編碼。本文指出，在頻率選擇性衰落信道上服務多個用戶時，帶外泄露呈現各向同性；而在平坦衰落信道上服務少數用戶時，帶外泄露可呈現波束賦形。由於大規模多入多出基站比現用基站輻射較少功率，帶外泄露各向同性意味著大規模多入多出基站可使用低端硬件，其線性要求不比現有基站的高。另外表明，如果進行合理的多用戶功率分配，基站使用單比特模擬數字轉換器——最簡單低耗的轉換器——僅使系統的信干噪比降低約４分貝。以此可見，大規模多入多出系統對非精確量比較穩定，低端模擬數字轉換器可於此類系統中使用。

京都大学 / 0048 / 新制・課程博士 / 博士(情報学) / 甲第20741号 / 情博第655号 / 新制||情||113(附属図書館) / 京都大学大学院情報学研究科通信情報システム専攻 / (主査)教授 原田 博司, 教授 守倉 正博, 教授 大木 英司 / 学位規則第4条第1項該当 / Doctor of Informatics / Kyoto University / DFAM

The evolution to 5G and its use cases is driven by data-intensive applications requiring higher data rates over wireless channels. This has led to research in massive multiple input multiple output (MIMO) techniques and the use of the millimeter wave (mm wave) band. Because of the higher path loss at mm wave frequencies and the poor scattering nature of the mm wave channel (fewer paths exist), this thesis first proposes the use of the sphere decoding (SD) algorithm, and the semidefinite relaxation (SDR) detector to improve the performance of a uniform planar array (UPA) hybrid beamforming technique with large antenna arrays. The second contributions of this thesis consist of a low-complexity algorithm using the gradient descent for hybrid precoding and combining designs in mm wave systems. Also, in this thesis we present a low-complexity algorithm for hybrid precoding and combining designs that uses momentum gradient descent and Newton’s Method for mm wave systems which makes the objective function converge faster compared to other iterative methods in the literature; the two proposed low-complexity algorithms for hybrid precoding and combining do not depend on the antenna array geometry, unlike the orthogonal matching pursuit (OMP) hybrid precoding/combining approach. Moreover, these algorithms allow hybrid precoders/combiners to yield a performance very close to that of the optimal unconstrained digital precoders and combiners with a small number of iterations. Simulation results verify that the proposed hybrid precoding/combining scheme that uses momentum gradient descent and Newton’s Method outperforms previous methods that appear in the literature in terms of bit error rate (BER) and achievable spectral efficiency with lower complexity. Finally, an iterative algorithm that directly converts the hybrid precoding/combining in the full array (FA) architecture to subarray (SA) architecture is proposed and examined in this thesis. It is called direct conversion of iterative hybrid precoding/combining from FA to SA (DCIFS) hybrid precoding/combining. The proposed DCIFS design takes into consideration the matrix structure of the analog and baseband precoding and combining in the design derivation. Moreover, it does not depend on the antenna array geometry, unlike other techniques, such as the orthogonal matching pursuit (OMP) hybrid precoding/combining approach, nor does it assume any other constraints. Simulation results show that the proposed DCIFS hybrid design, when compared to the FA hybrid designs counterpart, can provide a spectral efficiency that is close to optimum while maintaining a very low complexity and better spectral efficiency than the conventional SA hybrid design with the same hardware complexity.

The complexity of advanced antenna techniques used in the new generation of wireless networks (5G) makes communication between experts and non-technical staff more difficult than ever. As cooperation between network vendors and network operators affects the adoption of the new standard, a need for a new tool has emerged to make technical presentations more engaging and compelling. This thesis presents an exploratory study that aims to examine various design options for an interactive visualization of radiowave propagation to be used by advanced antenna systems experts. Through a Research-oriented Design, functional and non-functional requirements were identified with the help of domain expert. Later, an interactive prototype was designed and developed using a participatory design approach. Qualitative and quantitative data was gathered through usability testing, System Usability Scale (SUS) questionnaires and semi-structured interviews conducted with 12 researchers and engineers at Ericsson AB a multinational telecommunication company. User evaluation proved that such a tool could facilitate communication between technical experts and non-technical staff. The developed prototype was considered intuitive and useful by the majority of study participants as measured by interviews and the SUS survey. Future research is encouraged to include the target audience representatives in order to measure their engagement while using the tool. / Komplexiteten hos avancerade antenntekniker som anvnds i den nya generationen av mobilntverk (5G), gr kommunikationen mellan experter och icke-teknisk personal svrare n ngonsin. Eftersom samarbetet mellan telekommunikationsfretag och ntoperatrer pverkar anpassningen av den nya standarden, har behovet av ett nytt verktyg uppsttt fr att gra tekniska presentationer mer engagerande och vertygande. Avhandlingen presenterar en underskande studie som syftar till att underska olika designalternativ fr en interaktiv visualisering av radiovgsfrkning som anvnds av avancerade antennsystems experter. Genom en forskningsinriktad design identifierades funktionella och icke-funktionella krav med hjlp av en domnexpert. Senare konstruerades och utvecklades en interaktiv prototyp med hjlp av en co-operativ designmetod. Kvalitativa och kvantitativa data samlades in genom anvndbarhetstester, System Usability Scale (SUS) frgeformulr och halvstrukturerade intervjuer med 12 forskare och ingenjrer p Ericsson AB ett multinationellt telekommunikationsfretag. Anvndarutvrdering visade att ett sdant verktyg skulle underltta kommunikationen mellan tekniska experter och icke-teknisk personal. Den utvecklade prototypen ansgs intuitiv och anvndbar av majoriteten av studiedeltagarna, mtt genom intervjuer och SUS-underskningen. Framtida forskning uppmuntrar till att inkludera mlgruppsrepresentanterna fr att mta deras engagemang medan de anvnder verktyget.

Yes / Recent studies and research have centred on new solutions in different elements and stages to the increasing energy and data rate demands for the fifth generation and beyond (B5G). Based on a new-efficient digital beamforming approach for 5G wireless communication networks, this work offers a compact-size circular patch antenna operating at 60 GHz and covering a 4 GHz spectrum bandwidth. Massive Multiple Input Multiple Output (M–MIMO) and beamforming technology build and simulate an active multiple beams antenna system. Thirty-two linear and sixty-four planar antenna array configurations are modelled and constructed to work as base stations for 5G mobile communication networks. Furthermore, a new beamforming approach called Projection Noise Correlation Matrix (PNCM) is presented to compute and optimise the fed weights of the array elements. The key idea of the PNCM method is to sample a portion of the measured noise correlation matrix uniformly in order to provide the best representation of the entire measured matrix. The sampled data will then be utilised to build a projected matrix using the pseudoinverse approach in order to determine the best fit solution for a system and prevent any potential singularities caused by the matrix inversion process. The PNCM is a low-complexity method since it avoids eigenvalue decomposition and computing the entire matrix inversion procedure and does not require including signal and interference correlation matrices in the weight optimisation process. The suggested approach is compared to three standard beamforming methods based on an intensive Monte Carlo simulation to demonstrate its advantage. The experiment results reveal that the proposed method delivers the best Signal to Interference Ratio (SIR) augmentation among the compared beamformers

Yes / The need to achieve high data rates in modern telecommunication systems, such as 5G standard, motivates the study and development of large antenna and multiple-input multiple-output (MIMO) systems. This study introduces a large antenna-order design of MIMO quasi-orthogonal space-time block code (QO-STBC) system that achieves better signal-to-noise ratio (SNR) and bit-error ratio (BER) performances than the conventional QO-STBCs with the potential for massive MIMO (mMIMO) configurations. Although some earlier MIMO standards were built on orthogonal space-time block codes (O-STBCs), which are limited to two transmit antennas and data rates, the need for higher data rates motivates the exploration of higher antenna configurations using different QO-STBC schemes. The standard QO-STBC offers a higher number of antennas than the O-STBC with the full spatial rate. Unfortunately, also, the standard QO-STBCs are not able to achieve full diversity due to self-interference within their detection matrices; this diminishes the BER performance of the QO-STBC scheme. The detection also involves nonlinear processing, which further complicates the system. To solve these problems, we propose a linear processing design technique (which eliminates the system complexity) for constructing interference-free QO-STBCs and that also achieves full diversity using Hadamard modal matrices with the potential for mMIMO design. Since the modal matrices that orthogonalize QO-STBC are not sparse, our proposal also supports O-STBCs with a well-behaved peak-to-average power ratio (PAPR) and better BER. The results of the proposed QO-STBC outperform other full diversity techniques including Givens-rotation and the eigenvalue decomposition (EVD) techniques by 15 dB for both MIMO and multiple-input single-output (MISO) antenna configurations at 10−3 BER. The proposed interference-free QO-STBC is also implemented for 16×NR and 32×NR MIMO systems, where NR≤2. We demonstrate 8 x 16 and 32 transmit antenna-enabled MIMO systems with the potential for mMIMO design applications with attractive BER and PAPR performance characteristics.

[pt] Este trabalho de dissertação de mestrado apresenta uma comparação de algumas das técnicas de detecção de sinais mais promissoras para a viabilização de sistemas MIMO de grande porte em termos de desempenho, taxa de erro de bit e complexidade, número médio de flops requeridos por vetor de símbolos recebido. Com este objetivo foram também consideradas as técnicas de detecção clássicas, visando assim ressaltar o desempenho das novas técnicas com relação as antigas. Além disso foram propostas e investigadas novas estruturas para detectores SIC baseados em lista (i.e., com múltiplos ramos) que resultaram em melhor desempenho com menor complexidade quando comparados aos detectores deste tipo já propostos. Na comparação dos algoritmos, foram considerados três cenários diferentes: (i ) monousuário, com ganhos de canal gaussianos complexos independentes e identicamente distribuídos, ou seja, uma propagação que só considera a presença de desvanecimento de Rayleigh; (ii ) múltiplos usuários com canais correlatados e que considera as perdas de propagação de pequena e larga escala num sistema com antena centralizada; e (iii ) múltiplos usuários com canais correlatados e que considera as perdas de propagação de pequena e larga escala num sistema com antena distribuída. / [en] This work dissertation presents a comparison of some of the signal detection techniques most promising for the viability of large MIMO systems in terms of performance, bit error rate, and complexity, average number of flops required by transmitted symbol vector. For this purpose it was also considered classical detection techniques, thus aiming to highlight the performance of new techniques with respect the old. Also it has been proposed and investigated new structures to SIC detectors based on list (i.e., with multiple branches) resulting in better performance with less complexity compared to detectors of this kind already proposed. In the comparison of algorithms, three different scenarios were used: (i ) single user, with channel gains independent and distributed identically complex Gaussian, that is, a spread that only considers the presence of Rayleigh fading; (ii ) multiple users, with correlated channels, and considers the short and large scale path loss in a system with centralized antenna; e (iii ) multiple users, with correlated channels, and considers the short and large scale path loss in a system with distributed antenna.

Owing to its ability to improve both spectral and energy efficiency of wireless networks, massive multiple-input multiple-output (mMIMO) has become one of the key enablers of the fifth-generation (5G) and beyond communication systems. For successful integration of this promising physical layer technique in the upcoming cellular standards, it is essential to have a comprehensive understanding of its network-level performance. Over the last decade, stochastic geometry has been instrumental in obtaining useful system design insights of wireless networks through accurate and tractable theoretical analysis. Hence, it is only natural to consider modeling and analyzing the mMIMO systems using appropriate statistical constructs from the stochastic geometry literature and gain insights for its future implementation. With this broader objective in mind, we first focus on modeling a cellular mMIMO network that uses fractional pilot reuse to mitigate the sole performance-limiting factor of mMIMO networks, namely, pilot contamination. Leveraging constructs from the stochastic geometry literature, such as Johnson-Mehl cells, we derive analytical expressions for the uplink (UL) signal-to-interference-and-noise ratio (SINR) coverage probability and average spectral efficiency for a random user. From our system analysis, we present a partitioning rule for the number of pilot sequences to be reserved for the cell-center and cell-edge users that improves the average cell-edge user spectral efficiency while achieving similar cell-center user spectral efficiency with respect to unity pilot reuse. In addition, using the analytical approach developed for the cell-center user performance evaluation, we study the performance of a small cell system where user and base station (BS) locations are coupled. The impact of distance-dependent UL power control on the performance of an mMIMO network with unity pilot reuse is analyzed and subsequent system design guidelines are also presented. Next, we focus on the performance analysis of the cell-free mMIMO network, which is a distributed implementation of the mMIMO system that leads to the second and third contributions of this dissertation. Similar to the cellular counterpart, the cell-free systems also suffer from pilot contamination due to the reuse of pilot sequences throughout the network. Inspired by a hardcore point process known as the random sequential adsorption (RSA) process, we develop a new distributed pilot assignment algorithm that mitigates the effect of pilot contamination by ensuring a minimum distance among the co-pilot users. This pilot assignment scheme leads to the construction of a new point process, namely the multilayer RSA process. We study the statistical properties of this point process both in one and two-dimensional spaces by deriving approximate but accurate expressions for the density and pair correlation functions. Leveraging these new results, for a cell-free network with the proposed RSA-based pilot assignment scheme, we present an analytical approach that determines the minimum number of pilots required to schedule a user with probabilistic guarantees. In addition, to benchmark the performance of the RSA-based scheme, we propose two optimization-based centralized pilot allocation schemes using linear programming principles. Through extensive numerical simulations, we validate the efficacy of the distributed and scalable RSA-based pilot assignment scheme compared to the proposed centralized algorithms. Apart from pilot contamination, another impediment to the performance of a cell-free mMIMO is limited fronthaul capacity between the baseband unit and the access points (APs). In our fourth contribution, using appropriate stochastic geometry-based tools, we model and analyze the downlink of such a network for two different implementation scenarios. In the first scenario, we consider a finite network where each AP serves all the users in the network. In the second scenario, we consider an infinite network where each user is served by a few nearby APs in order to limit the load on fronthaul links. From our analyses, we observe that for the finite network, the achievable average system sum-rate is a strictly quasi-concave function of the number of users in the network, which serves as a key guideline for scheduler design for such systems. Further, for the user-centric architecture, we observe that there exists an optimal number of serving APs that maximizes the average user rate. The fifth and final contribution of this dissertation focuses on the potential improvement that is possible by the use of mMIMO in citizen broadband radio service (CBRS) spectrum sharing systems. As a first concrete step, we present comprehensive modeling and analysis of this system with omni-directional transmissions. Our model takes into account the key guidelines by the Federal Communications Commission for co-existence between licensed and unlicensed networks in the 3.5 GHz CBRS frequency band. Leveraging the properties of the Poisson hole process and Matern hardcore point process of type II, a.k.a. ghost RSA process, we analytically characterize the impact of different system parameters on various performance metrics such as medium access probability, coverage probability, and area spectral efficiency. Further, we provide useful system design guidelines for successful co-existence between these networks. Building upon this omni-directional model, we also characterize the performance benefits of using mMIMO in such a spectrum sharing network. / Doctor of Philosophy / The emergence of cloud-based video and audio streaming services, online gaming platforms, instantaneous sharing of multimedia contents (e.g., photos, videos) through social networking platforms, and virtual collaborative workspace/meetings require the cellular communication networks to provide high data-rate as well as reliable and ubiquitous connectivity. These constantly evolving requirements can be met by designing a wireless network that harmoniously exploits the symbiotic co-existence among different types of cutting-edge wireless technologies. One such technology is massive multiple-input multiple-output (mMIMO), whose core idea is to equip the cellular base stations (BSs) with a large number of antennas that can be leveraged through appropriate signal processing algorithms to simultaneously accommodate multiple users with reduced network interference. For successful deployment of mMIMO in the upcoming cellular standards, i.e., fifth-generation (5G) and beyond systems, it is necessary to characterize its performance in a large-scale wireless network taking into account the inherent spatial randomness in the BS and user locations. To achieve this goal, in this dissertation, we propose different statistical methods for the performance analysis of mMIMO networks using tools from stochastic geometry, which is a field of mathematics related to the study of random patterns of points. One of the major deployment issues of mMIMO systems is pilot contamination, which is a form of coherent network interference that degrades user performance. The main reason behind pilot contamination is the reuse of pilot sequences, which are a finite number of known signal waveforms used for channel estimation between a user and its serving BS. Further, the effect of pilot contamination is more severe for the cell-edge users, which are farther from their own BSs. An efficient scheme to mitigate the effect of pilot contamination is fractional pilot reuse (FPR). However, the efficiency of this scheme depends on the pilot partitioning rule that decides the fraction of total pilot sequences that should be used by the cell-edge users. Using appropriate statistical constructs from the stochastic geometry literature, such as Johnson-Mehl cells, we present a partitioning rule for efficient implementation of the FPR scheme in a cellular mMIMO network. Next, we focus on the performance analysis of the cell-free mMIMO network. In contrast to the cellular network, where each user is served by a single BS, in a cell-free network each user can be served by multiple access points (APs), which have less complex hardware compared to a BS. Owing to this cooperative and distributed implementation, there are no cell-edge users. Similar to the cellular counterpart, the cell-free systems also suffer from pilot contamination due to the reuse of pilot sequences throughout the network. Inspired by a hardcore point process known as the random sequential adsorption (RSA) process, we develop a new distributed pilot assignment algorithm that mitigates the effect of pilot contamination by ensuring a minimum distance among the co-pilot users. Further, we show that the performance of this distributed pilot assignment scheme is appreciable compared to different centralized pilot assignment schemes, which are algorithmically more complex and difficult to implement in a network. Moreover, this pilot assignment scheme leads to the construction of a new point process, namely the multilayer RSA process. We derive the statistical properties of this point process both in one and two-dimensional spaces. Further, in a cell-free mMIMO network, the APs are connected to a centralized baseband unit (BBU) that performs the bulk of the signal processing operations through finite capacity links, such as fiber optic cables. Apart from pilot contamination, another implementational issue associated with the cell-free mMIMO systems is the finite capacity of fronthaul links that results in user performance degradation. Using appropriate stochastic geometry-based tools, we model and analyze this network for two different implementation scenarios. In the first scenario, we consider a finite network where each AP serves all the users in the network. In the second scenario, we consider an infinite network where each user is served by a few nearby APs. As a consequence of this user-centric implementation, for each user, the BBU only needs to communicate with fewer APs thereby reducing information load on fronthaul links. From our analyses, we propose key guidelines for the deployment of both types of scenarios. The type of mMIMO systems that are discussed in this work will be operated in the sub-6 GHz frequency range of the electromagnetic spectrum. Owing to the limited availability of spectrum resources, usually, spectrum sharing is encouraged among different cellular operators in such bands. One such example is the citizen broadband radio service (CBRS) spectrum sharing systems proposed by the Federal Communications Commission (FCC). The final contribution of this dissertation focuses on the potential improvement that is possible by the use of mMIMO in the CBRS systems. As our first step, using tools from stochastic geometry, we model and analyze this system with a single antenna at the BSs. In our model, we take into account the key guidelines by the FCC for co-existence between licensed and unlicensed operators. Leveraging properties of the Poisson hole process and hardcore process, we provide useful theoretical expressions for different performance metrics such as medium access probability, coverage probability, and area spectral efficiency. These results are used to obtain system design guidelines for successful co-existence between these networks. We further highlight the potential improvement in the user performance with multiple antennas at the unlicensed BS.

Avec l'augmentation du trafic de données, la multiplication des objets connectés et la diversification des types de communication, la cinquième génération de réseaux cellulaires (5G) doit relever un grand nombre de défis. Dans ce contexte, les systèmes« massive MIMO » présentent de nombreux avantages en utilisant un grand nombre d'antennes combiné à des techniques de traitement de signal adaptées. De plus, l'utilisation de la modulation FBMC/OQAM au lieu de la modulation OFDM pourrait améliorer la performance des systèmes dans ce11aines situations. En premier lieu, cette thèse se centre sur des scénarios véhiculaires. En par1iculier, les systèmes« massive MIMO » sont proposés dans le but de combattre les interférences dues à l'effet Doppler pour la voie montante. Nous montrons ainsi de manière analytique que l'augmentation du nombre d'antennes implique une réduction drastique de l'impact de l'effet Doppler. De plus, les performances des modulations OFDM et FBMC/OQAM sont comparées dans ce contexte pour des environnements« Non-Line-Of-Sight » (NLOS) et« Line-Of-Sight » (LOS). Le second scéna1io étudié dans cette thèse considère les communications dans des zones mal desservies. Dans ce contexte, les systèmes« massive MIMO » permettent de créer un lien sans-fil longue-po11ée de type« backhaul » entre deux stations de base. Ainsi, le coût de déploiement des réseaux r cellulaires est réduit. Dans cette thèse, un nouveau précodeur « massive MIMO » est proposé dans le but d'utiliser la même bande de fréquence pour le liens accès et« backhaul ». De plus, l'impact d'une désynchronisation entre les liens d'accès et le lien « backhaul » est étudié et l'utilisation de la modulation FBMC/OQAM pour le lien« backhaul » est examinée. / ESUME DE LA THESE EN ANGLAIS With the increase of the global data tmffic, the multiplication of co1mected devices and the diversification of the communication types, the fifth generation of cellular networks (5G) has to overcome a se1ies of challenges. In this context, massive MlMO systems hold a wide range of benefits by using a large number of antennas combined with appropriate signal processing techniques. Additionally, the use of the FBMC/OQAM modulation instead of the classical OFDM modulation may enhance the performance of the systems in cer1ain situations. Firstly, this thesis focuses on vehicular scenarios. In par1icular, massive MIMO systems are proposed to overcome the interference due to the Doppler effect for the uplink. We thus analytically highlight that increasing the number of receive antermas induces a drastic reduction of the impact of the Doppler effect. Moreover, the perfonnance of the OFDM and the FBMC/OQAM modulations are compared in this context for Non-Line-Of-Sight (NLOS) and Line-Of-Sight (LOS) environments. The second scenario investigated in this thesis considers communications in wide underse1ved areas. In this context, massive MIMO systems allow to create a long-range wireless back.haul link between two base stations. Thereby, the cost of deployment of the cellular networks is reduced. In this thesis r a new massive MLMO precoding technique is proposed in order to use the same fequency band for the backhaul link and the access links. Moreover, the impact of a desynchronization between the back haul link and the access links is studied and the use of the FBMC/OQAM modulation for the backhaul link is discussed.