Half-Duplex Multiuser Multiple-Input Multiple-Output (HD MU-MIMO) systemscurrently employed in communication systems are not experiencing the selfinterference(SI) problem but they are not optimal in terms of efficiency and interms of resources used (time and frequency resources). Ignoring the effect of largescalefading, we start by explaining the uplink (UL) and downlink (DL) parts ofthe MU-MIMO system and how the sum-rate is calculated. We also introduce thethree linear receivers/precoders, Maximum-Ratio Combining (MRC)/Maximum-Ratio Transmission (MRT), Zero-Forcing (ZF), and Minimum Mean-Square Error(MMSE) and which of the three types is going to be used in the study of Full-Duplex Multiuser Multiple-input Multiple-output (FD MU-MIMO) system. Thenwe introduce FD MU-MIMO system, and how the equation used to calculate thesum-rate of the UL part changes when the SI occurs, and why SI problem is notpresent in the DL part. Next, we introduce the spectral efficiency (SE), and howto calculate it and why it is taken as a parameter to compare HD and FD systems.Also the effect of SI on FD MU-MIMO system is presented through simulationgraphs, then we move to show how to reduce SI effect by increasing the number ofantennas in the base-station (BS). Lastly, we take the effect of large scale fading inorder to reach a simple statistical model in the form cumulative distribution function(CDF) graph for different values of SI and compare those of FD MU-MIMOsystem to HD MU-MIMO. The results show that FD MU-MIMO together withmassive MIMO technology is very promising and would save time and frequencyresources which means an increase in the SE but SI must be below a certain level.

La facilité de déploiement et la flexibilité des technologies sans fil ont permis une évolution considérable des normes IEEE 802.11. L'arrivée de la fibre optique à la maison a également motivé des études de recherche pour accroître les débits et la capacité. Dans ce contexte, la dernière norme IEEE 802.11ac ratifiée en 2014 a normalisé de nouvelles technologies pour atteindre des débits maximaux au-dessus de 1Obit/s. En particulier, 802 llac propose le Multiple Input Multiple Output Multi-Utilisateurs (MIMO-MU) et le Transmit Beamforming (TxBF). Ces technologies d'antennes intelligentes supposent un diagramme d'antenne d'émission qui dépend de la position des utilisateurs et des caractéristiques du canal de propagation multi-trajets correspondant. Cependant, les outils d'ingénierie et de planification radio actuels simulent une carte de couverture fixe et indépendante de tout traitement d'antennes adaptatives côté émission. Cette thèse étudie l'impact de ces techniques MIMO-MU et TxBF et propose des solutions adaptées pour l'ingénierie radio et l'optimisation du système ainsi que pour les outils de planification radio. En effet, la première partie de cette thèse consiste à affiner les gains de capacité en identifiant les configurations et les paramètres système optimaux. La deuxième partie aborde les gains de beamforming en termes du gain sur le rapport signal à bruit (SNR) et sur la réduction du niveau d'interférence pour avoir une modélisation réaliste de la couverture radio. / The deployment facility and flexibility of wireless technologies have allowed considerable evolution of IEEE 802 .11 standards. The arrival of the optical fiber to the home has further motivated the research studies to increase data rates and capacity. ln this context, the latest IEEE 802.l lac standard ratified in 2014 proposes new technologies to achieve maximum data rates above 1 Gbit/s. ln particular, 802.l lac includes the Multi-User Multiple Input Multiple Output (MU-MIMO) and Transmit Beamforming (TxBF). These smart antenna technologies assume a variable transmit antenna pattern in function of the users' position and the corresponding multipath propagation channel characteristics. However, the actual radio planning tools give a fixed coverage map in dependent of any adaptive or smart antenna processing. This thesis studies the impact of the MU-MIMO and TxBF techniques on radio engineering, system optimization as well as radio planning tools. Indeed, the first part of this thesis deals with refining the sum rate capacity gains by identifying interesting system configurations and optimal system parameters. The second part addresses the beamforming gains in terms of the Signal-to-Noise Ratio (SNR) gain and interference level to have realistic radio coverage modeling.

Spectral efficiency is one of the most important measures of the performance of wireless communication systems owing to scarcity and cost of the radio spectrum. The increase in spectral efficiency provides higher data rates to the user, lower network cost to the operator, coverage extension and higher service reliability as well. Intercell interference due to frequency reuse is one of the key impairments in wireless systems. Multiple-input multiple-output (MIMO) technique has been developed to enhance the desired signal power (and hence mitigating the effects of intercell interference) and with employing simple linear signal processing technique, can strongly mitigate the interference resulting from co-channel users. This technique is mainly used to achieve spatial diversity for boosting the communication link reliability by combating fading, and providing spatial multiplexing to increase data rates without extra bandwidth by exploiting multipath. Distributed antenna system (DAS) has recently gained substantial interest due to its ability to reduce transmitted power thereby lowering the out-of-cell interference effects, maximise the coverage and improve the spectral efficiency. The combination of MIMO techniques with DAS, so-called distributed MIMO (D-MIMO) systems, is now being exploited and largely succeeded to fulfil the services of the fourth generation (4G) wireless systems. Very recently, one of crucial significance approach to reducing the radiated power and improving spectral efficiency to cope with fifth generation (5G) wireless systems is the use of large-scale MIMO (also referred to as massive MIMO) technology, which utilizes a large number of antennas, i.e., tens to hundreds, typically at the base station (BS) side. Presently, in the light of the rapid evolution of wireless systems into 5G, the integration of wireless power transfer (WPT) with newly wireless systems has seen a great deal of attention as a potential solution for powering energy-constrained wireless systems, especially with shortening communication links by emerging new technologies, e.g., D-MIMO and massive MIMO. This thesis is devoted to investigating and comparing the performance of three different MIMO systems. More specifically, the thesis focuses on analysing the spectral efficiency of a comprehensive model of self-powered MU-MIMO systems employing linear ZF technique at the BS for both perfect and imperfect channel state information (CSI) cases. The results demonstrate the impact of practical channel impairments, e.g., spatial correlation, shadowing and co-channel interference (CCI), and system parameters, e.g., the number of BS and user antennas, signal to noise ratio (SNR) and channel estimation error, on the spectral efficiency of the system. Besides, from a spectral efficiency perspective, a proposed model of a combination of MIMO and massive MIMO technologies with DAS in the presence of linear receivers at the processing unit (PU) is considered and compared to a centralised MIMO (CMIMO) system. The obtained results provide a wide range of insights into the effects of system parameters on the spectral efficiency and reveal that the proposed distributed MIMO system outperforms the C-MIMO system. In the context of wireless powered MIMO systems, this work investigates the performance of a power beacon (PB)-assisted wireless powered C-MIMO system, including one multi-antenna BS and a number of single-antenna users powered by randomly deployed PBs in the presence of ZF receiver at the BS. Also, two modes for radiation from the PBs are assumed and compared, one is the beamforming radiation mode (BRM), and the other is the isotropic radiation mode (IRM).

<p>The growing demand for faster, more reliable wireless connectivity has brought about the development of the 802.11ax (Wi-Fi 6/6E) amendment, which aims to satisfy the increasing need for seamless wireless connectivity and improved traffic handling. The 802.11ax amendment introduces noteworthy improvements to the 802.11 wireless standard that should greatly improve the efficiency of wireless networks. The body of existing research has seen several simulated 802.11ax environments and found great success, however, these additions remain largely untested in physical environments. This thesis undertakes the testing for 802.11ax MU-MIMO to determine if these simulated successes translate into real-world improvements. By using a classroom scenario, the study investigates the performance improvements purported by 802.11ax, specifically the updated and expanded DL and UL MU-MIMO in an environment with high client numbers and density. </p>

Yes / Beamforming in multi-user MIMO (MU-MIMO) systems is a vital part of modern wireless communication systems. Researchers looking for best operational performance normally optimize the problem and then solve for best weight solutions. The weight optimization problem contains variables in numerator and dominator: this leads to so-called variable coupling, making the problem hard to solve. Formulating the optimization in terms of the signal to leakage and noise ratio (SLNR) helps in decoupling the problem variables. In this paper we study the performance of the SLNR with variable numbers of users and handset antennas. The results show that there is an optimum and the capacity curve is a concave over these two parameters. The performances of two further variations of this method are also considered.

La croissance phénoménale du trafic pousse les opérateurs mobiles à différencier leurs plans de tarification en se basant sur la bande passante consommée. Afin de maximiser la monétisation du trafic de données, les opérateurs devront envisager des approches plus intelligentes tout en améliorant leurs réseaux actuels ou en déployant de nouvelles infrastructures. Les Small Cells sont une partie intégrante des réseaux cellulaires matures 3G/4G et futurs 5G. Les Small Cells peuvent être de facto déployées dans des architectures hétérogènes pour la densification des réseaux macrocellulaires, ou de façon homogène pour une couverture en haut débit. Pour le deuxième cas de déploiement, de nouveaux défis doivent être résolus: un réseau de collecte fiable et économique est vital pour les déploiements des Small Cells. Le réseau de collecte est spécifiquement plus contraignant pour les déploiements des Small Cells dans les zones dites green-field, où les infrastructures de transport sont absentes ou présentes mais ne peuvent être contrôlées par l'opérateur. En d'autres termes, l'opérateur mobile souhaite garantir une bonne qualité d'accès aux services haut débit en se basant uniquement sur des Small Cells, tout en réduisant le coût global de l'installation. Dans cette thèse, nous nous focalisons sur des solutions de réseau de collecte rentables qui peuvent fournir les capacités minimales requises par les utilisateurs finaux. Notre première contribution vise à assurer une capacité suffisante aux réseaux Small Cells 4G. Tout d'abord, nous proposons une méthode rentable qui minimise les coûts du réseau de collecte tout en respectant les contraintes de : 1) demande de trafic dans le réseau d'accès, et de 2) caractéristiques technologiques des liens de collecte. Cette méthode permet d'obtenir des solutions sur mesure de réseau de collecte à coûts optimal pour un réseau d'accès donné, basé sur des Small Cells; ces solutions sont constituées de différentes technologies de liaison. Deuxièmement, nous analysons l'impact de l'activité des utilisateurs finaux sur le trafic généré à la fois sur les deux interfaces logiques S1 et X2 d'une Small Cell, tout en tenant compte les différentes composantes de trafic moyen d'un utilisateur final. Cette analyse permet d'avoir un aperçu très utile pour la sélection des solutions nécessaires au réseau de collecte. Dans notre deuxième contribution, nous nous focalisons sur l'amélioration des capacités des systèmes WLAN. Nous concevons un protocole d'ordonnancement MAC pour les transmissions uplink multi-utilisateurs : il permet un échange minimal des trames de contrôle requises pour la mise en place des transmissions entre les multiples émetteurs et le récepteur. Les résultats d'analyse et de simulations révèlent des performances améliorées, d'un point de vue du système et de l'utilisateur. / The recent phenomenal traffic growth is driving mobile operators to tier their pricing plans based on consumed bandwidth. To maximize data traffic monetization, operators will need to consider smarter approaches while upgrading their current networks or deploying new ones. Small Cells are an integral part of both mature 3G/4G and future 5G cellular networks. Small Cells may be de facto deployed in heterogeneous architectures for Macro cells densification, or homogeneously for minimum broadband coverage. In this respect, emerging challenges must be tackled: a reliable and economical backhaul is vital for Small Cells deployments. It is specifically more constraining for Small Cells deployments in green-field areas, where transport infrastructure are absent or non-owned. In other words, the mobile operator wants to ensure good quality access to broadband services based only on Small Cells, while reducing overall installation cost. In this thesis, we focus on cost-efficient backhaul solutions that may provide the minimum capacities required by end users. Our first contribution targets the provisioning of 4G Small Cells networks with sufficient capacity. Firstly, we provide a cost-efficient method that minimizes backhaul cost while respecting the constraints of access network traffic demand and connecting technologies characteristics. This method provides with customized cost-optimal backhaul solutions for a given Small Cells access network; those solutions are made up of different linking technologies. Secondly, we analyze the impact of end users activity -i.e. data exchange- on generated traffic on both a Small Cell logical interfaces S1 and X2; by taking into account different traffic components of an end user device. The analysis supplies with valuable insights on selecting the needed backhaul solutions. In our second contribution, we focus on improving capacity in WLAN systems. We design a MAC scheduling scheme for uplink multi-users transmissions: it enables to exchange minimal control frames required for the establishment of transmissions between the multiple transmitters and the receiver. Both analytic results and conducted proof-of-concept simulations show improved efficiency for both system and user oriented performances.

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Nowadays, multiuser Multiple-In Multiple-Out systems (MU-MIMO) are used in a new generation wireless technologies. Due to that wireless technology improvement is ongoing, the numbers of users and applications increase rapidly. Then, wireless communications need the high data rate and link reliability at the same time. Therefore, MU-MIMO improvements have to consider 1) providing the high data rate and link reliability, 2) support all users in the same time and frequency resource, and 3) using low power consumption. In practice, the interuser interference has a strong impact when more users access to the wireless link. Complicated transmission techniques such as interference cancellation should be used to maintain a given desired quality of service. Due to these problems, MU-MIMO with very large antenna arrays (known as massive MIMO) are proposed. With a massive MU-MIMO system, we mean a hundred of antennas or more serving tens of users. The channel vectors are nearly orthogonal, and then the interuser interference is reduced significantly. Therefore, the users can be served with high data rate simultaneously. In this thesis, we focus on the performance of the massive MU-MIMO downlink where the base station uses linear precoding techniques to serve many users over Rayleigh and Nakagami-m fading channels.

京都大学 / 0048 / 新制・課程博士 / 博士(情報学) / 甲第20032号 / 情博第627号 / 新制||情||109(附属図書館) / 33128 / 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 梅野 健 / 学位規則第4条第1項該当 / Doctor of Informatics / Kyoto University / DFAM

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