Dissertationen zum Thema „Communications 5G“

Un sistema mobile di comunicazione è un sistema di telecomunicazioni in cui è possibile mantenere la connessione o legame tra due o più utenti, anche nelle situazioni di mobilità totale o parziale degli stessi utenti. I sistemi radiomobili si stanno evolvendo dalla creazione del 1G (prima generazione) al 4G (quarta generazione). I telefoni di ogni generazione si differenziano in quattro aspetti principali : accesso radio, velocità di trasmissione dati, larghezza di banda e sistemi di commutazione. In questa tesi si affronta il tema dei sistemi 5G , negli ambienti terrestri e satellitari , in quanto sono l'ultima evoluzione dei sistemi mobili . Si introduce il passaggio dalla prima alla connessione di quarta generazione , al fine di capire perché 5G sta per cambiare la nostra vita . Quello che mi colpisce è il sito italiano www.Repubblica.it che dice : " con la nuova generazione 5 possiamo affidare le intere porzioni nette di vita". La tecnologia cellulare , infatti , ha cambiato radicalmente la nostra società e il nostro modo di comunicare . In primo luogo è cambiata la telefonia vocale , per poi trasferirsi all' accesso dati , applicazioni e servizi. Tuttavia , Internet non è stato ancora pienamente sfruttato dai sistemi cellulari. Con l'avvento del 5G avremo l'opportunità di scavalcare le capacità attuali di Internet . Il sistema di comunicazione di quinta generazione è visto come la rete wireless reale , in grado di supportare applicazioni web wireless a livello mondiale ( wwww ). Ci sono due punti di vista dei sistemi 5G : evolutivo e rivoluzionario. Dal punto di vista evolutivo, i sistemi 5G saranno in grado di supportare wwww permettendo una rete altamente flessibile come un Adhoc rete wireless dinamica ( DAWN ) . In questa visione tecnologie avanzate, tra cui antenna intelligente e modulazione flessibile , sono le chiavi per ottimizzare le reti wireless ad hoc. Dal punto di vista rivoluzionario, i sistemi 5G dovrebbe essere una tecnologia intelligente in grado di interconnettere tutto il mondo senza limiti . Un esempio di applicazione potrebbe essere un robot wireless con intelligenza artificiale .

Duplexage par division dans le temps (TDD) Massive Multiple Input Multiple Output (MaMIMO) dépend de la réciprocité de canal pour obtenir des informations d'état de canal au niveau de l'émetteur (CSIT). Toutefois, le canal numérique global de bout en bout n’est pas réciproque en raison de la présence de chaînes de transmission (Tx) et de réception (Rx), qui doivent être corrigées à l’aide de facteurs de calibration. Nous fournissons une expression simple et élégante du Cramér-Rao Bound (CRB) pour l’estimation des paramètres de calibration. Nous analysons des approches des moindres carrés existants et proposons des algorithmes optimaux. Nous considérons également la beamforming pour une liaison MIMO point à point variant rapidement dans le temps. Dans un système Orthogonal Frequency Division Multiplexing (OFDM), il en résulte une interférence entre porteuses (ICI). Avec une hypothèse de variation linéaire de canal à travers le symbole OFDM, il a été observé que le problème est similaire à celui d'une conception de beamformer MIMO par canal de diffusion à interférence (IBC). Le design du beamformer prend en compte le fenêtrage de réception en utilisant le préfixe cyclique en excès. En plus de la CSIT complète, nous étudions également des approches qui maximisent le Expected Weighted Sum Rate (EWSR) lorsque la Tx n’a qu’une connaissance partielle du canal. Premièrement, nous utilisons une approximation de système large qui fonctionne également bien pour un petit nombre d’antennes Tx et Rx. Nous analysons également la possibilité d’utiliser la métrique Expected-signal-expected-interference-WSR de signal EWSR. Enfin, les résultats expérimentaux sont présentés
Time Division Duplexing (TDD) Massive Multiple Input Multiple Output (MaMIMO) with a massive number of base station (BS) antennas relies on channel reciprocity to obtain Channel State Information at Transmitter (CSIT). However the overall end to end digital channel is not reciprocal due to the presence of Transmit (Tx) and Receive (Rx) chains which need to be corrected using calibration factors. Our work provides a simple and elegant expression of the Cramer Rao Bound (CRB) for calibration parameter estimation. We provide analysis for the existing least squares approaches and propose optimal algorithms to estimate the calibration parameters. We also consider beamforming for a rapidly time-varying point to point MIMO link. In an Orthogonal Frequency Division Multiplexing (OFDM) sytem, this results in inter-carrier interference (ICI). With an assumption of linear channel variation across the OFDM symbol, it is observed that the beamformer design problem is similar to that of a MIMO Interfering Broadcast Channel (IBC) beamforming design. The beamformer design takes into account receive windowing using the excess cyclic prefix and the window is jointly designed with the Tx beamformer. In addition to full CSIT, we also investigate partial CSIT approaches that maximize Expected Weighted Sum Rate (EWSR) where the Tx has only partial knowledge of the channel. First, we use a large system approximation that also works well for a small number of Tx and Rx antennas to derive the beamformers. In our work, we also analyze the possibility of using the Expected-signal- expected-interference-WSR metric instead of the EWSR. Finally, experimental results on the Eurecom MaMIMO testbed are presented

Ce travail de thèse a été financé par le projet FUI Mass-Start (2017-2020). Le projet ambitionne de développer une solution open source 5G pour le MIMO Massif. L’objectif est le développement d’une plateforme Hardware et Software, sur le principe du succès d’OAI en 4G (www.openairinterface.org). Les principaux livrables matériels du projet sont les sous-systèmes radio et de traitement de bande de base compatibles 5G, leur intégration dans un démonstrateur de terminal 5G basé sur OAI et le réseau d’antennes permettant les expérimentations de bout en bout du lien MIMO Massif. L'objectif de la thèse est le développement et la mesure de système antennaires qui seront utilisés dans le projet.Sur la bande 5G FR1, le travail s'est concentré sur le développement d'une méthodologie de conception antennaire combinant circuit d'adaptation et optimisation géométrique. Les contraintes en bande passante sont évaluées à partir du facteur de qualité des antennes. Le prototype final démontre qu'un système non-résonnant permet de couvrir la plupart des bandes de téléphonie mobile 5G sous les 6GHz en respectant des contraintes d'intégration très forte.Sur la bande 5G FR2, et plus précisément sur la bande n258 Européenne, différents types d'architecture d'antennes réseau ont été évalués et mesuré. La thèse s'est particulièrement concentrée sur la co-conception entre les antennes et les modules électroniques sur une technologie PCB.Les solutions proposées ont été utilisées pour quantifier et modéliser l'effet du corps humain, et plus particulièrement de la main, sur les performances sur réseau antennaire. Enfin, une solution basée sur plusieurs réseaux distribués sur un téléphone montre une meilleure robustesse aux effets de blocage du corps humain
The work in this thesis has been funded by the French FUI project MASS-START (2017-2020). The project aims at the integration of 5G compatible baseband and radio subsystems into an Over-Air-Interface-based 5G terminal and gNodeB demonstrator, and the antenna array for end-to-end Multiple Input Multiple Output link experimentation. The scope of the thesis concerns the design and assessment of antenna systems that are to be used in the project.At 5G Frequency Range 1 band, the work concentrates on the development of a methodology to design antenna with a matching circuit for mobile terminals with limited area. The bandwidth limitation is evaluated using Quality-Factor. A Particle Swarm Optimization algorithm is proposed and examined in different antenna designs for mobile terminals. The final design demonstrates a system with three non-resonating coupling elements covering most of the sub-6GHz bands of 5G. At 5G Frequency Range 2 band, more precisely band n258 of Europe, different types of array antennas are studied. The work first checks two types of feeding for a patch antenna that can be integrated into Printed Circuit Board to have a low profile antenna and ease the fabrication procedure. The designs are later fabricated and experimentally evaluated. With a Millimeter-Wave array at hand, we proceed a measurement campaign in which the effects of the user's finger at close proximity of the antenna are evaluated. The losses due to absorption, reflection, diffraction are quantified and compared with numerical estimations in literature. A system of multiple end-fire arrays placed at different locations in a terminal is also studied showing the compromising effectiveness if one array is severely blocked

Cette thèse doctorale explore l'amélioration de l'allocation des ressources sans fil dans les communications Vehicle-to-Everything (V2X), selon la norme 3GPP Release 16. Le domaine spécifique de notre recherche est la communication NR-V2X Sidelink, également connue sous le nom de communication New Radio-Vehicles to Vehicles (NR-V2V). Notre objectif est de formuler un nouveau protocole d'optimisation qui garantit non seulement des services de haute qualité (QoS) mais surpasse également les méthodologies existantes dans la communication NR-V2V.Tout d'abord, nous introduisons la Configuration Physique Adaptative (APC), un algorithme basé sur la recherche conçu pour identifier la configuration optimale de la couche physique à l'intérieur d'un ensemble de facteurs environnementaux, spécifiquement adaptée pour un schéma de communication de diffusion. Suite à cela, nous faisons évoluer l'APC vers une variante sensible à la radio (RA-APC), élargissant son champ d'action en incorporant une communication en unicast et en établissant une structure plus flexible pour les ressources PHY. Dans la phase finale, nous affinons encore RA-APC en intégrant un algorithme d'apprentissage automatique, spécifiquement un arbre de décision. Cette intégration met à jour les schémas au sein des facteurs d'entrée, augmentant ainsi à la fois la précision et l'efficacité du processus d'optimisation de l'allocation
This doctoral dissertation explores the enhancement of wireless resource allocation in Vehicle-to-Everything (V2X) communications, as specified by the 3GPP Release 16 standard. The specific area of our research is the NR-V2X Sidelink communication, also known as the New Radio-Vehicles to Vehicles (NR-V2V) communication. Our goal is to formulate a novel optimization protocol that not only guarantees high-quality services (QoS) but also outperforms existing methodologies in NR-V2V communication.Initially, we introduce Adaptive Physical Configuration (APC), a search-based algorithm designed to identify the optimal physical layer configuration within a set of environmental factors, specifically tailored for a broadcast communication scheme. Following this, we evolve APC into a Radio Aware variant (RA-APC), broadening its scope by incorporating unicast communication and establishing a more flexible structure for PHY resources. In the final phase, we further refine RA-APC by integrating a machine learning algorithm, specifically a decision tree. This integration uncovers patterns within the input factors, thereby augmenting both the accuracy and efficiency of the allocation optimization process

Future wireless communications (often referred to as 5G) are expected to operate at much higher frequencies compared to today’s wireless systems. During this thesis, we have investigated the option to use high frequency crystal oscillators, which along with a PLL, will generate the RF LO signal in the mmW range. Different topologies that consume low power and deliver low phase noise for better channel capacity have been studied and presented. In this report we provide a detailed analysis of crystal oscillator theory and designand we discuss techniques that we have used to simulate our models. During this project we have encountered various challenges such as parasitic oscillation, start-up behaviour and effects from package modeling. All these issues are discussed in detail while solutions, examples and results are demonstrated. Finally, along with the crystal oscillator we have also proceeded in the design of a buffer for a better input/output isolation. A squarer has been implemented for greater power savings.

The evolution of wireless networks towards 5G dictates the integration of a mul-titude of heterogeneous radio access technologies to the traditional macro-cell systems. Equipping the network with numerous small cell nodes, such as fem-tocell and picocell base stations (BSs), implies a spectrum efficient and network performance improving solution to support the rapidly increasing user demands. However, this can be proven to be a cost-inefficient method that increases the capital and operational expenditures of the network operators as well as the power consumption, especially in low-traffic network conditions where a number of BSs should be switched-off. To this end, device-centric solutions that leverage the potentials stemming from the proximity, mobility and increased dynamics of user devices should be considered. To this end, direct, proximity-based Device-to-Device (D2D) communication, where two close-ranged user equipments (UEs) are able to exchange data by bypassing the BS, is expected to play predominant role in improving the overall network welfare and ease part of the traffic developed on the BSs side. This thesis focuses on the soft integration of inband D2D communications in emerging cellular networks where D2D-enabled devices utilize the licensed spec-trum. In the introductory part of the thesis we highlight the merits that this communication paradigm can offer in terms of spectrum utilization, energy sav-ing, delay reduction and data rate improvement. We also provide an overview of the D2D use cases that enable opportunities for new services, its potential in improving the overall network performance as well as its offloading capability that can ease the traffic employed along the network. In the sequel, we proceed with our proposed methodology that aims at easing the coexistence of cellular and D2D users in emerging cellular networks. One of the main contributions of the thesis is the optimization of cell association for D2D UEs (DUEs). Cell association for D2D communications is an unexplored area and a rather fertile ground for research. Following the conventional motif, a user device would preferably couple with a high power macro cell BS that provides the user with the highest signal power. However, with the advent of D2D com-munications, this could be proven to be highly inefficient for users that want to communicate directly and are associated with different BSs because BS intercom-munication complexity and access delay is introduced. To this end, we propose a number of optimization formulations for D2D-based cell association that takes into consideration not only the nature of the inband D2D communications (un-derlay or overlay), but also performance-hindering factors such as user density, interference and so on. Other than the throughput enhancing and power saving attributes of the proposed framework, notable resource efficiency improvement is achieved. Indicatively, for both underlay and overlay D2D communications, more than 12% and 45% radio resource utilization mitigation is ensured compared to baseline methods. On top of optimizing cell association for D2D communications, we further investigate the problem of resource allocation in different D2D underlaying cellu-lar network scenarios where DUEs are permitted to reuse the cellular resources and, therefore, high levels of interference need to be prevented. By consider-ing different deployment scenarios, we propose a set of low-complexity heuristic algorithms with the aim to achieve high data rate performance for D2D com-munications with respect to meeting the cellular users’ quality of service (QoS) requirements. The proposed algorithms are evaluated in high-traffic networking scenarios where D2D communications underlay relay-enabled cellular networks. In aggregate, more than 10% of sum throughput performance is achieved against various resource allocation techniques. In the sequel, we explore the dynamics of virtualizing the radio resources for efficient sharing as, nowadays, we are witnessing higher network heterogeneity and the emergence of multiple stakeholders with the overarching need to significantly reduce deployment costs and achieve a sustainable network operation. Network virtualization has emerged as a promising technique to overcome the complexity of current network operation as well as facilitate inter-operators’ sharing. There-fore, disruptive approaches to manage radio and network-virtualized resources are expected to be a catalyst element of future mobile network architectures. Despite the fact that a number of solutions for radio access network (RAN) virtualization emerged over the last few years, it is worth pointing out that little attention has been placed on issues related to D2D virtualization. Therefore, based on the integration of an inter-tenant controller that enables the radio resource sharing between multiple operators, we devise a set of efficient algorithms to optimize the throughput performance of D2D communications in virtualized environments as well as reduce the utilization levels of the allocated radio resources. More than 12% of sum-rate performance improvement compared to legacy, intra-tenant ap-proaches where the radio resources are assigned based on which device initiates the communication per case. Finally, a summary of the research outcomes along with some future directions for D2D communications concludes this thesis.

The 5G Core Network architecture is modeled to include instruments that can establish networks built on the same physical infrastructure but serve different service categories for communication types with varying characteristics. Relying on virtualization and cloud technologies, these instruments make the 5G system different from previous mobile communication systems, change the user profile, and allow new business models to be included in the system. The subject of this thesis includes the study of Ultra-reliable low latency communication, which is one of the fundamental service categories defined for the 5G system, and the analysis of the techniques presented in 3GPP’s Release 16, which enhance the service parameters by modifying the core network. In the theoretical part, the 5G system and URLLC are introduced with a particular focus on the user plane on the core network. In the implementation part, redundant transmission support on the N3 interface, one of the techniques presented in the technical specification, is modeled using open source software tools (Open5GS and UERANSIM) and network virtualization instruments. As a result of the tests and measurements performed on the model, it was observed that the implemented technique enhanced the system's reliability.

The development of fifth generation mobile networks has laid the ground for the creation of new applicative scenarios, characterized by increasingly demanding requirements. In particular, to satisfy low latency requirements, an aspect to take into account is represented by the random access procedure, performed by devices for initial connection to the network or to switch to a connected state afterwards. Because of the limited amount of resources available for random access, the presence of a high number of devices requesting access at the same time can generate congestion and require multiple access attempts, increasing latency and compromising the fulfillment of the requirements. The problem was already addressed in the scientific literature, with the proposal of a series of solutions to improve the random access procedure. This thesis work aims at enriching these efforts, by leveraging device-to-device communications and the reservation of random access resources, and by proposing a dynamic strategy to alleviate performance deterioration at runtime and intervene on the system with reconfiguration operations, in order to solve possible congestions. The studied scenarios are analyzed by means of the ns-3 network simulator, extended by the additional mmWave and MilliCar modules, for the simulation of 5G networks and device-to-device communications through the cellular sidelink. The results obtained from the simulations have the objective of demonstrating the advantages introduced by the dynamic reconfiguration strategy, and of gaining useful insights on the usage of the proposed enhancements for the random access procedure.

In this dissertation, we investigate two main research directions towards net- work efficiency and green communications in heterogeneous cellular networks (HetNets) as a promising network structure for the fifth generation of mobile systems. In order to analyze the networks, we use a powerful mathematical tool, named stochastic geometry. In our research, first we study the performance of MIMO technology in single-tier and two-tier HetNets. In this work, we apply a more realistic network model in which the correlation between tiers is taken into account. Comparing the obtained results with the commonly used model shows performance enhancement and greater efficiencies in cellular networks. As the second part of our research, we apply two Cell Zooming (CZ) techniques to HetNets. With focus on green communications, we present a K−tier HetNet in which BSs are only powered by energy har- vesting. Despite the uncertain nature of energy arrivals, combining two CZ techniques, namely telescopic and ON/OFF scenarios, enables us to achieve higher network performance in terms of the coverage and blocking probabilities while reducing the total power consumption and increasing the energy and spectral efficiencies.
In this dissertation, we investigate two main research directions towards net- work efficiency and green communications in heterogeneous cellular networks (HetNets) as a promising network structure for the fifth generation of mobile systems. In order to analyze the networks, we use a powerful mathematical tool, named stochastic geometry. In our research, first we study the performance of MIMO technology in single-tier and two-tier HetNets. In this work, we apply a more realistic network model in which the correlation between tiers is taken into account. Comparing the obtained results with the commonly used model shows performance enhancement and greater efficiencies in cellular networks. As the second part of our research, we apply two Cell Zooming (CZ) techniques to HetNets. With focus on green communications, we present a K−tier HetNet in which BSs are only powered by energy har- vesting. Despite the uncertain nature of energy arrivals, combining two CZ techniques, namely telescopic and ON/OFF scenarios, enables us to achieve higher network performance in terms of the coverage and blocking probabilities while reducing the total power consumption and increasing the energy and spectral efficiencies.

Avec les avancées technologiques apportées par les réseaux 5G, une nouvelle ère de communications de Vehicle-to-Everything (V2X) est apparue, offrant des applications nouvelles et avancées en matière de sécurité, d'efficacité et d'autres expériences de conduite dans les systèmes de transport intelligents (ITS). Cependant, les nouvelles fonctionnalités s'accompagnent de nouveaux défis en matière de sécurité, en particulier dans le domaine des communications Vehicle-to-Network (V2N).Cette thèse se concentre sur l'application des systèmes de misbehavior detection dans les communications V2X au sein des réseaux 5G. Tout d'abord, nous présentons un nouveau système de misbehavior detection, intégré au réseau central 5G pour détecter et prévenir les attaques V2X. Ensuite, nous proposons un schéma de collaboration entre les nœuds de détection afin d'améliorer les résultats de la détection dans les réseaux 5G edge. Enfin, nous proposons d'utiliser le Federated Learning pour permettre un entraînement distribué et nous évaluons les performances sur une grande variété d'attaques V2X
The introduction of 5G networks has brought significant technical improvements; a new era of Vehicle-to-Everything (V2X) communications has emerged, offering new and advanced safety, efficiency, and other driving experience applications in the Intelligent Transport Systems (ITS). However, with new features come new security challenges, especially in the realm of Vehicle-to-Network (V2N) communications.This thesis focuses on the application of misbehavior detection in V2X communications within 5G networks. First, we introduce a novel misbehavior detection system integrated with 5G core (5GC) network to detect and prevent V2X attacks. Then, we propose a collaboration scheme between detection nodes to improve detection results in 5G edge networks. Last, we leverage Federated Learning to enable distributed training, and we assess the performance on a wide variety of V2X attacks

L'émergence de nouveaux cas et d’applications tels que la réalité virtuelle/augmentée, l'automatisation industrielle, les véhicules autonomes, etc. en 5G fait définir au Third Generation Partnership Project (3GPP) Ultra-reliable low-latency communications (URLLC) comme un des trois services. Pour soutenir URLLC avec des exigences strictes de la fiabilité et de la latence, 3GPP Release 15 et 16 ont standardisé des fonctionnalités d’URLLC dans le spectre sous licence. Release 17 en cours agrandit des fonctionnalités d’URLLC au spectre sans licence pour cibler des nouveaux cas dans des scénarios industriels. Dans la première partie de cette thèse du Chapitre 2 au Chapitre 4, nous nous concentrons sur URLLC dans le spectre sous licence. La première étude est confrontée au problème de garantir le nombre des répétitions dans des uplink configured-grant (CG) ressources. Ensuite, nous étudions la collision entre une eMBB UL transmission d'un UE et une URLLC UL transmission d'un autre UE sur des CG ressources. Enfin, nous recherchons la DL transmission où le feedback de la DL semi-persistent scheduling transmission est abandonné à cause du conflit entre des DL/UL symboles. Dans la deuxième partie du Chapitre 5 au Chapitre 8, nous nous focalisons sur URLLC dans le spectre sans licence. Dans le spectre sans licence, un appareil demande d'accéder au canal en utilisant load based equipment (LBE) ou frame based equipment (FBE). L’incertitude d’acquérir un canal par LBE ou FBE pourrait empêcher la URLLC transmission d’atteindre l’exigence de la latence. Par conséquent, l'étude de l'impact de LBE ou FBE sur la URLLC transmission et des améliorations de LBE et de FBE sont nécessaires
The advent of new use cases and new applications such as augmented/virtual reality, industrial automation, autonomous vehicles, etc. in 5G has made the Third Generation Partnership Project (3GPP) specify Ultra-reliable low-latency communications (URLLC) as one of the service categories. To support URLLC with the strict requirements of reliability and latency, 3GPP Release 15 and Release 16 have specified the URLLC features in licensed spectrum. The ongoing 3GPP Release 17 extends the URLLC features to unlicensed spectrum to target the new use cases in the industrial scenario. In the first part of the thesis from Chapter 2 to Chapter 4, we focus on the URLLC in licensed spectrum. The first study deals with the problem of ensuring the configured number of uplink (UL) configured-grant (CG) repetitions of a transport block. Secondly, we study the collisions of an eMBB UL transmission of a user equipment (UE) and an URLLC UL transmission of another UE on the CG resources. Thirdly, the focus of this study is the downlink (DL) transmission where the feedback of the DL semi-persistent scheduling transmission is dropped due to the conflict of the DL/UL symbols. In the second part from Chapter 5 to Chapter 8, we focus on URLLC operation in unlicensed spectrum. In unlicensed spectrum, a 5G device is required to access to a channel by using load based equipment (LBE) or frame based equipment (FBE). The uncertainty of obtaining channel access through LBE or FBE can impede the achievement of the URLLC latency requirements. Therefore, the study of impact of LBE and FBE on URLLC transmission and the enhancements of LBE and FBE are needed

Les stations de base à petite échelle (picocellules et femtocellules) seront un des leviers principaux qui permettront d'atteindre l'objectif 1000X, objectif fixé par les grands acteurs du domaine des télécommunications visant à augmenter la capacité des réseaux mobiles sans fil 5G d'un facteur 1000 par rapport aux réseaux 4G. Dans ce type de réseau, l'amplificateur de puissance (PA) est responsable de la majorité de la consommation de puissance de la station de base. Pour minimiser sa consommation de puissance, le PA est polarisé proche de sont point de compression mais avec l'augmentation des largeurs de bande, ce dernier subit des effets de mémoire accrus qui viennent s'ajouter aux problèmes classiques de non-linéarités. Les systèmes de prédistorsion numérique (DPD), et analogique/RF(ARFPD) peuvent être utilisés pour améliorer le compromis linéarité / efficacité des PAs. Cependant pour les pico-cellules et femto-cellules utilisées dans le standard 5G, les prédistorseurs conventionnels ne sont adaptés pour des raisons de complexité et de consommation de puissance.Le modèle "Memory Polynomilal" (MP) est l'un des modèles de prédistorsion les plus attractifs pour modéliser les PAs, fournissant des performances intéressantes avec peu de coefficients. Cependant, la précision de ce modèle se dégrade pour les signaux large bance. Pour palier ce problème, nous proposons un nouveau modèle, le FIR-MP qui combine un filtre FIR au modèle MP classique. Pour valider et quantifier la précision du modèle proposé, nous avons effectué des simulations avec un modèle extrait par mesure de l'amplificateur sur étagère ADL5606 (GaAs 1W HBT PA). Les résultats de ces simulations présentent des améliorations du taux de fuite des canaux adjacents (ACLR) de 7,2 dB et 15,6 dB, respectivement, pour des signaux à 20 MHz et 80 MHz par rapport au modèle MP classique. Le FIR-MP a été également synthétisé en technologie CMOS FDSOI 28 nm. Les résultats de la synthèse ont donné une puissance globale de 9,18 mW and 116,2 mW, respectivement, pour les signaux de 20 MHz and 80 MHz.Basé sur le modèle proposé de FIR-MP, une nouvelle approche à signaux mixtes pour linéariser les PAs a été aussi étudiée. En fait, le filtre numérique FIR améliore la performance de correction de la mémoire sans aucune expansion de la bande passante et la linéarisation en bande de base permet d'éviter l'utilisation de composants RF dans la linéariseur. Ainsi, les contraintes en bande passante requises pour le DAC, les filtres de reconstruction et les blocs RF de l'émetteur sont relâchées comparés aux techniques conventionnelles de linéarisation numériques et RF. Nous avons ainsi étudié l'impact des diverses non-idéalités en utilisant un signal modulé à 80 MHz afin de dériver les exigences pour la mise en œuvre du circuit. Les simulations ont montré qu'une résolution de 8 bits pour les coefficients et un SNR de 60 dB sont nécessaires pour atteindre un ACLR1 supérieur à 45 dBc. Ces résultats constituent un premier signe favorable dans l'optique d'une implémentation matérielle de la solution proposée, étape indispensable pour évaluer précisément sa consommation de puissance et sa complexité pour pouvoir la comparer à l'état de l'art des linéariseurs
Small-cell base stations (picocells and femtocells) handling high bandwidths (> 100 MHz) will play a vital role in realizing the 1000X network capacity objective of the future 5G wireless networks. Power Amplifier (PA) consumes the majority of the base station power, whose linearity comes at the cost of efficiency. With the increase in bandwidths, PA also suffers from increased memory effects. Digital predistortion (DPD) and analog RF predistortion (ARFPD) tries to solve the linearity/efficiency trade-off. In the context of 5G small-cell base stations, the use of conventional predistorters becomes prohibitively power-hungry.Memory polynomial (MP) model is one of the most attractive predistortion models, providing significant performance with very few coefficients. We propose a novel FIR memory polynomial (FIR-MP) model which significantly augments the performance of the conventional memory polynomial predistorter. Simulations with models extracted on ADL5606 which is a 1 W GaAs HBT PA show improvements in adjacent channel leakage ratio (ACLR) of 7.2 dB and 15.6 dB, respectively, for 20 MHz and 80 MHz signals, in comparison with MP predistorter. Digital implementation of the proposed FIR-MP model has been carried out in 28 nm FDSOI CMOS technology. With a fraction of the power and die area of that of the MP a huge improvement in ACLR is attained.An overall estimated power consumption of 9.18 mW and 116.2 mW, respectively, for 20 MHz and 80 MHz signals is obtained.Based on the proposed FIR-MP model a novel low-power mixed-signal approach to linearize RF power amplifiers (PAs) is presented. The digital FIR filter improves the memory correction performance without any bandwidth expansion and the MP predistorter in analog baseband provides superior linearization. MSPD avoids 5X bandwidth requirement for the DAC and reconstruction filters of the transmitter and the power-hungry RF components when compared to DPD and ARFPD, respectively.The impact of various non-idealities is simulated with ADL5606 (1 W GaAs HBT PA) MP PA model using 80 MHz modulated signal to derive the requirements for the integrated circuit implementation. A resolution of 8 bits for the coefficients and a signal path SNR of 60 dB is required to achieve ACLR1 above 45 dBc, with as little as 9 coefficients in the analog domain. Discussion on the potential circuit architectures of subsystems is provided. It results that an analog implementation is feasible. It will be worth in the future to continue the design of this architecture up to a silicon prototype to evaluate its performance and power consumption

In this thesis, components and parameters based power models (PMs) are produced to measure the power consumption (PC) of cloud radio access network (CRAN) architecture. In components PM, the power figure of each component within C-RAN is evaluated. After, this model is parametrised such that the computation complexity of each component is converted to a straightforward, but accurate method, called parameterised PM. This model compares cooling and total PC of traditional LTE architecture with C-RAN. This comparison considered different parameters such as, utilised bandwidth, number of antenna, base band units (BBUs) and remote radio heads (RRHs). This model draws about 33% reduction in power. Next, this PC model is updated to serve and exhibit the cost of integrating software defined networks (SDNs) with C-RAN. Alongside, modelling the power cost of the control plane units in the core network (CN), such as serving gateway (SGW), packet gateway (PGW) and mobility management entity (MME). Although there is power cost, the proposed model shows the directions to mitigate it. Consequently, a simplified PM is proposed for virtualisation based C-RAN. In this model, the power cost of server virtualisation by hosting several virtual machines (VMs) is shown, in a time and cost effective way. The total reduction in the PC was about 75%, due to short-cutting the number of active servers in the network. Alongside, the latency cost due to such technique is modelled. Finally, to enable efficient virtualisation technology, live migrating the VMs amongst the servers is vital. However, this advantageous situation is concurrent with VM's migration time and power cost. Therefore, a model is proposed to calculate the power cost of VM's live migration, and shows the effect of such decision upon the total PC of the network/C-RAN. The proposed work converts the complexity of other proposed PMs, to a simplified and costless method. Concurrently, the time cost is added to the imposed virtualisation's time cost to formulate the total delay expected prior to these techniques' execution.

La quinta generación de redes móviles (5G) se encuentra a la vuelta de la esquina. Se espera provea de beneficios extraordinarios a la población y que resuelva la mayoría de los problemas de las redes 4G actuales. El éxito de 5G, cuya primera fase de estandarización ha sido completada, depende de tres pilares: comunicaciones tipo-máquina masivas, banda ancha móvil mejorada y comunicaciones ultra fiables y de baja latencia (mMTC, eMBB y URLLC, respectivamente). En esta tesis nos enfocamos en el primer pilar de 5G, mMTC, pero también proveemos una solución para lograr eMBB en escenarios de distribución masiva de contenidos. Específicamente, las principales contribuciones son en las áreas de: 1) soporte eficiente de mMTC en redes celulares; 2) acceso aleatorio para el reporte de eventos en redes inalámbricas de sensores (WSNs); y 3) cooperación para la distribución masiva de contenidos en redes celulares. En el apartado de mMTC en redes celulares, esta tesis provee un análisis profundo del desempeño del procedimiento de acceso aleatorio, que es la forma mediante la cual los dispositivos móviles acceden a la red. Estos análisis fueron inicialmente llevados a cabo por simulaciones y, posteriormente, por medio de un modelo analítico. Ambos modelos fueron desarrollados específicamente para este propósito e incluyen uno de los esquemas de control de acceso más prometedores: access class barring (ACB). Nuestro modelo es uno de los más precisos que se pueden encontrar en la literatura y el único que incorpora el esquema de ACB. Los resultados obtenidos por medio de este modelo y por simulación son claros: los accesos altamente sincronizados que ocurren en aplicaciones de mMTC pueden causar congestión severa en el canal de acceso. Por otro lado, también son claros en que esta congestión se puede prevenir con una adecuada configuración del ACB. Sin embargo, los parámetros de configuración del ACB deben ser continuamente adaptados a la intensidad de accesos para poder obtener un desempeño óptimo. En la tesis se propone una solución práctica a este problema en la forma de un esquema de configuración automática para el ACB; lo llamamos ACBC. Los resultados muestran que nuestro esquema puede lograr un desempeño muy cercano al óptimo sin importar la intensidad de los accesos. Asimismo, puede ser directamente implementado en redes celulares para soportar el tráfico mMTC, ya que ha sido diseñado teniendo en cuenta los estándares del 3GPP. Además de los análisis descritos anteriormente para redes celulares, se realiza un análisis general para aplicaciones de contadores inteligentes. Es decir, estudiamos un escenario de mMTC desde la perspectiva de las WSNs. Específicamente, desarrollamos un modelo híbrido para el análisis de desempeño y la optimización de protocolos de WSNs de acceso aleatorio y basados en cluster. Los resultados muestran la utilidad de escuchar el medio inalámbrico para minimizar el número de transmisiones y también de modificar las probabilidades de transmisión después de una colisión. En lo que respecta a eMBB, nos enfocamos en un escenario de distribución masiva de contenidos, en el que un mismo contenido es enviado de forma simultánea a un gran número de usuarios móviles. Este escenario es problemático, ya que las estaciones base de la red celular no cuentan con mecanismos eficientes de multicast o broadcast. Por lo tanto, la solución que se adopta comúnmente es la de replicar e contenido para cada uno de los usuarios que lo soliciten; está claro que esto es altamente ineficiente. Para resolver este problema, proponemos el uso de esquemas de network coding y de arquitecturas cooperativas llamadas nubes móviles. En concreto, desarrollamos un protocolo para la distribución masiva de contenidos, junto con un modelo analítico para su optimización. Los resultados demuestran que el modelo propuesto es simple y preciso, y que el protocolo puede reducir el con
La cinquena generació de xarxes mòbils (5G) es troba molt a la vora. S'espera que proveïsca de beneficis extraordinaris a la població i que resolga la majoria dels problemes de les xarxes 4G actuals. L'èxit de 5G, per a la qual ja ha sigut completada la primera fase del qual d'estandardització, depén de tres pilars: comunicacions tipus-màquina massives, banda ampla mòbil millorada, i comunicacions ultra fiables i de baixa latència (mMTC, eMBB i URLLC, respectivament, per les seues sigles en anglés). En aquesta tesi ens enfoquem en el primer pilar de 5G, mMTC, però també proveïm una solució per a aconseguir eMBB en escenaris de distribució massiva de continguts. Específicament, les principals contribucions són en les àrees de: 1) suport eficient de mMTC en xarxes cel·lulars; 2) accés aleatori per al report d'esdeveniments en xarxes sense fils de sensors (WSNs); i 3) cooperació per a la distribució massiva de continguts en xarxes cel·lulars. En l'apartat de mMTC en xarxes cel·lulars, aquesta tesi realitza una anàlisi profunda de l'acompliment del procediment d'accés aleatori, que és la forma mitjançant la qual els dispositius mòbils accedeixen a la xarxa. Aquestes anàlisis van ser inicialment dutes per mitjà de simulacions i, posteriorment, per mitjà d'un model analític. Els models van ser desenvolupats específicament per a aquest propòsit i inclouen un dels esquemes de control d'accés més prometedors: el access class barring (ACB). El nostre model és un dels més precisos que es poden trobar i l'únic que incorpora l'esquema d'ACB. Els resultats obtinguts per mitjà d'aquest model i per simulació són clars: els accessos altament sincronitzats que ocorren en aplicacions de mMTC poden causar congestió severa en el canal d'accés. D'altra banda, també són clars en què aquesta congestió es pot previndre amb una adequada configuració de l'ACB. No obstant això, els paràmetres de configuració de l'ACB han de ser contínuament adaptats a la intensitat d'accessos per a poder obtindre unes prestacions òptimes. En la tesi es proposa una solució pràctica a aquest problema en la forma d'un esquema de configuració automàtica per a l'ACB; l'anomenem ACBC. Els resultats mostren que el nostre esquema pot aconseguir un acompliment molt proper a l'òptim sense importar la intensitat dels accessos. Així mateix, pot ser directament implementat en xarxes cel·lulars per a suportar el trànsit mMTC, ja que ha sigut dissenyat tenint en compte els estàndards del 3GPP. A més de les anàlisis descrites anteriorment per a xarxes cel·lulars, es realitza una anàlisi general per a aplicacions de comptadors intel·ligents. És a dir, estudiem un escenari de mMTC des de la perspectiva de les WSNs. Específicament, desenvolupem un model híbrid per a l'anàlisi de prestacions i l'optimització de protocols de WSNs d'accés aleatori i basats en clúster. Els resultats mostren la utilitat d'escoltar el mitjà sense fil per a minimitzar el nombre de transmissions i també de modificar les probabilitats de transmissió després d'una col·lisió. Pel que fa a eMBB, ens enfoquem en un escenari de distribució massiva de continguts, en el qual un mateix contingut és enviat de forma simultània a un gran nombre d'usuaris mòbils. Aquest escenari és problemàtic, ja que les estacions base de la xarxa cel·lular no compten amb mecanismes eficients de multicast o broadcast. Per tant, la solució que s'adopta comunament és la de replicar el contingut per a cadascun dels usuaris que ho sol·liciten; és clar que això és altament ineficient. Per a resoldre aquest problema, proposem l'ús d'esquemes de network coding i d'arquitectures cooperatives anomenades núvols mòbils. En concret, desenvolupem un protocol per a realitzar la distribució massiva de continguts de forma eficient, juntament amb un model analític per a la seua optimització. Els resultats demostren que el model proposat és simple i precís
The 5th generation (5G) of mobile networks is just around the corner. It is expected to bring extraordinary benefits to the population and to solve the majority of the problems of current 4th generation (4G) systems. The success of 5G, whose first phase of standardization has concluded, relies in three pillars that correspond to its main use cases: massive machine-type communication (mMTC), enhanced mobile broadband (eMBB), and ultra-reliable low latency communication (URLLC). This thesis mainly focuses on the first pillar of 5G: mMTC, but also provides a solution for the eMBB in massive content delivery scenarios. Specifically, its main contributions are in the areas of: 1) efficient support of mMTC in cellular networks; 2) random access (RA) event-reporting in wireless sensor networks (WSNs); and 3) cooperative massive content delivery in cellular networks. Regarding mMTC in cellular networks, this thesis provides a thorough performance analysis of the RA procedure (RAP), used by the mobile devices to switch from idle to connected mode. These analyses were first conducted by simulation and then by an analytical model; both of these were developed with this specific purpose and include one of the most promising access control schemes: the access class barring (ACB). To the best of our knowledge, this is one of the most accurate analytical models reported in the literature and the only one that incorporates the ACB scheme. Our results clearly show that the highly-synchronized accesses that occur in mMTC applications can lead to severe congestion. On the other hand, it is also clear that congestion can be prevented with an adequate configuration of the ACB scheme. However, the configuration parameters of the ACB scheme must be continuously adapted to the intensity of access attempts if an optimal performance is to be obtained. We developed a practical solution to this problem in the form of a scheme to automatically configure the ACB; we call it access class barring configuration (ACBC) scheme. The results show that our ACBC scheme leads to a near-optimal performance regardless of the intensity of access attempts. Furthermore, it can be directly implemented in 3rd Generation Partnership Project (3GPP) cellular systems to efficiently handle mMTC because it has been designed to comply with the 3GPP standards. In addition to the analyses described above for cellular networks, a general analysis for smart metering applications is performed. That is, we study an mMTC scenario from the perspective of event detection and reporting WSNs. Specifically, we provide a hybrid model for the performance analysis and optimization of cluster-based RA WSN protocols. Results showcase the utility of overhearing to minimize the number of packet transmissions, but also of the adaptation of transmission parameters after a collision occurs. Building on this, we are able to provide some guidelines that can drastically increase the performance of a wide range of RA protocols and systems in event reporting applications. Regarding eMBB, we focus on a massive content delivery scenario in which the exact same content is transmitted to a large number of mobile users simultaneously. Such a scenario may arise, for example, with video streaming services that offer a particularly popular content. This is a problematic scenario because cellular base stations have no efficient multicast or broadcast mechanisms. Hence, the traditional solution is to replicate the content for each requesting user, which is highly inefficient. To solve this problem, we propose the use of network coding (NC) schemes in combination with cooperative architectures named mobile clouds (MCs). Specifically, we develop a protocol for efficient massive content delivery, along with the analytical model for its optimization. Results show the proposed model is simple and accurate, and the protocol can lead to energy savings of up to 37 percent when compared to the traditional approach.
Leyva Mayorga, I. (2018). On reliable and energy efficient massive wireless communications: the road to 5G [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/115484
TESIS

This dissertation is directed towards improving the performance of 5G Wireless Fronthaul Networks and Wireless Sensor Networks, as measured by reliability, fault recovery time, energy consumption, efficiency, and security of transmissions, beyond what is achievable with conventional error control technology. To achieve these ambitious goals, the research is focused on novel applications of networking techniques, such as Diversity Coding, where a feedforward network design uses forward error control across spatially diverse paths to enable reliable wireless networking with minimal delay, in a wide variety of application scenarios. These applications include Cloud-Radio Access Networks (C-RANs), which is an emerging 5G wireless network architecture, where Remote Radio Heads (RRHs) are connected to the centralized Baseband Unit (BBU) via fronthaul networks, to enable near-instantaneous recovery from link/node failures. In addition, the ability of Diversity Coding to recover from multiple simultaneous link failures is demonstrated in many network scenarios. Furthermore, the ability of Diversity Coding to enable significantly simpler and thus lower-cost routing than other types of restoration techniques is demonstrated. Achieving high throughput for broadcasting/multicasting applications, with the required level of reliability is critical for the efficient operation of 5G wireless infrastructure networks. To improve the performance of C-RAN networks, a novel technology, Diversity and Network Coding (DC-NC), which synergistically combines Diversity Coding and Network Coding, is introduced. Application of DC-NC to several 5G fronthaul networks, enables these networks to provide high throughput and near-instant recovery in the presence of link and node failures. Also, the application of DC-NC coding to enhance the performance of downlink Joint Transmission-Coordinated Multi Point (JT-CoMP) in 5G wireless fronthaul C-RANs is demonstrated. In all these scenarios, it is shown that DC-NC coding can provide efficient transmission and reduce the resource consumption in the network by about one-third for broadcasting/multicasting applications, while simultaneously enabling near-instantaneous latency in recovery from multiple link/node failures in fronthaul networks. In addition, it is shown by applying the DC-NC coding, the number of redundant links that uses to provide the required level of reliability, which is an important metric to evaluate any protection system, is reduced by about 30%-40% when compared to that of Diversity Coding. With the additional goal of further reducing of the recovery time from multiple link/node failures and maximizing the network reliability, DC-NC coding is further improved to be able to tolerate multiple, simultaneous link failures with less computational complexity and lower energy consumption. This is accomplished by modifying Triangular Network Coding (TNC) and synergistically combining TNC with Diversity Coding to create enhanced DC-NC (eDC-NC), that is applied to Fog computing-based Radio Access Networks (F-RAN) and Wireless Sensor Networks (WSN). Furthermore, it is demonstrated that the redundancy percentage for protecting against n link failures is inversely related to the number of source data streams, which illustrates the scalability of eDC-NC coding. Solutions to enable synchronized broadcasting are proposed for different situations. The ability of eDC-NC coding scheme to provide efficient and secure broadcasting for 5G wireless F-RAN fronthaul networks is also demonstrated. The security of the broadcasting data streams can be obtained more efficiently than standardized methods such as Secure Multicasting using Secret (Shared) Key Cryptography.

The demand for higher capacity, higher data rate and larger bandwidth has driven the research and industrial world to develop next generation wireless communication technology, namely, the 5G. Among all the approaches proposed for such a high demand, only the cooperative communication approach promises to significantly improve of the performances (capacity, data rate, bandwidth, etc.) with a low cost. In this thesis, we propose a D2D communication scheme as a solution for the out-door scenario and a cooperative scheme among the access infrastructures as the in-door scenario solution. In the first part, we address the implementation of content-centric routing in a D2D architecture for Android devices based on WiFi Direct, a protocol recently standardised by the Wi-Fi Alliance. After discussing the creation of multiple D2D groups, we introduce novel paradigms featuring intra- and inter-group bidirectional communication. We then present the primitives involved in content advertising and requesting among members of the multi-group network. In addition to the communications, we also devise a mechanism to enable the devices to spontaneously establish the multi-group D2D network. Finally, we evaluate the performance of our architecture and the network formation mechanism in a real testbed consisting of Android devices. In the second part, we propose, implement and evaluate a bandwidth aggregation service for residential users that allows to improve the upload throughput of the ADSL connection by leveraging the unused bandwidth of neighboring users. The residential access gateway adopts the 802.11 radio interface to simultaneously serve the local home users and to share the broadband connectivity with neighboring access gateways. Differently from previous works, our aggregation scheme is transparent both for local users, who are not required to modify their applications or device drivers, and for neighboring users, who do not experience any meaningful performance degradation. In order to evaluate the achievable performance and tune the parameters driving the traffic balancing, we developed a fluid model which was shown experimentally to be very accurate. Our proposed scheme is amenable to efficient implementation on Linux networking stack. Indeed, we implemented it and tested in some realistic scenarios, showing an efficient exploitation of the whole available bandwidth, also for legacy cloud storage applications.

Comment rendre les villes, les usines et les maisons à la fois intelligentes et sensibles aux hommes ? Pour y parvenir il est possible d’équiper les personnes, les villes, les usines et les maisons de dispositifs radio pour communiquer des messages, grâce à l’Internet des objets. Cependant, les émissions radio permanentes s’accompagnent d’une dépense énergétique rédhibitoire.La technologie de communication par rétrodiffusion ambiante (AmBC) permet de communiquer sans émettre d’onde radio supplémentaires, en exploitant les ondes radio ambiantes (Wifi, diffusion TV ou FM, cellulaire, etc.). Les dispositifs AmBC rétrodiffusent le champ électromagnétique ambiant grâce à une antenne connectée à une impédance variable. L’information est alors communiquée à un récepteur en modulant l’impédance du dispositif AmBC. Grâce à leur très faible consommation, ils peuvent être alimentés par un système de récupération d’énergie. Cependant la portée et le débit restent encore très limités.Dans ce travail, nous nous focalisons sur l’étude des améliorations de cette technologie en tirant profit des réseaux mobiles du futur.Premièrement nous montrons que les antennes compactes reconfigurables peuvent avantageusement remplacer les antennes à impédance ajustable dans les dispositifs AmBC.Ces antennes compactes reconfigurables utilisent différents diagrammes de rayonnement et différentes polarisations pour rendre plus robuste la communication.Deuxièmement nous démontrons que les antennes existantes au sein des réseaux 5G peuvent être utilisées dans les systèmes AmBC afin d’améliorer significativement leur débit et leur portée.Dans un scénario 5G, l'antenne « massive Multiple-Input Multiple-Output » (mMIMO) de la station de base peut être utilisée comme source d'ondes ambiantes pour créer des zones de forte puissance et des zones de bonne réception grâce à la technique de précodage. Ces zones visent à améliorer les performances de la communication entre le dispositif AmBC et le récepteur. Nous démontrons également que l’antenne mMIMO peut aussi être utilisée comme récepteur pour améliorer la détection des dispositifs AmBC.Enfin nous montrons qu’une technologie émergente pour la 6G, appelée surface intelligente reconfigurable (RIS), qui permet de contrôler partiellement le canal de propagation des ondes, peut assister les systèmes AmBC. Nous montrons qu’il est possible d’exploiter la capacité de formation de faisceau de manière passive de la technologie RIS pour améliorer la performance des systèmes AmBC
How can cities, factories and homes be made both intelligent and responsive to people? To achieve this, it is possible to equip people, cities, factories and houses with radio devices to communicate messages, thanks to the Internet of things. However, permanent radio emissions result in a crippling energy expense.Ambient Backscatter Communication (AmBC) technology enables communication without the need for additional radio emission, by exploiting ambient radio waves (Wi-Fi, TV or FM broadcast, cellular, etc.). AmBC devices, named tags, backscatter the ambient electromagnetic field thanks to an antenna connected to a tunable impedance. The information is communicated to a reader by modulating the impedance of the AmBC tag. Therefore, thanks to their very low consumption, they can be powered by energy harvesting. However, the range and the data rate of these devices are still very limited.We focus this work on the study of improvements of this technology by taking advantage of the future mobile networks.Firstly, we show that the compact reconfigurableantennas can advantageously replace antenna with tunable impedance in AmBC tags. Such compact reconfigurable antennas use different radiation patterns and polarizations to make the communication more robust.Secondly, we demonstrate that existing antennas within 5G networks can be used in AmBC systems to significantly improve the data rate and the range of the AmBC tags. In a 5G scenario, the massive Multiple-Input Multiple-Output (mMIMO) antenna of the base station can be used as source of ambient waves to create hot spots and good reception spots thanks to the precoding technique. These spots aim at improving the performance of the communication from the tag to the reader. We demonstrate also that the mMIMO antenna can also be used as reader to enhance the detection of AmBC tags.Finally, we show that an emerging technology for 6G, called reconfigurable intelligent surface (RIS), which allows to partially control the wave propagation channel, can assist AmBC systems. We exploit the passive beamforming capability of the RIS technology to improve the performance of AmBC systems

La croissance rapide du trafic de données sans fil et des services intensifs en bande passante (voix sur IP, streaming vidéo, live streaming, etc.) nécessite de trouver des solutions viables pour améliorer la qualité de service et maximiser les performances du réseau. Pour s'adapter à ces applications intensives en bande passante, les réseaux cellulaires hétérogènes (HetNets) ont été introduits dans le 3GPP comme l'une des principales caractéristiques pour répondre à ces exigences avancées.Maintenant, en raison de la différence de charges de trafic de liaison montante (UL) et de liaison descendante (DL) attendues dans les prochaines générations HetNets, il devient essentiel d'ajuster dynamiquement les ressources UL/DL. Pour soutenir cette nouvelle approche, le duplexage temporel (TDD) dynamique a été proposé. Néanmoins, l'importance d'UL se pose avec l'évolution des réseaux sociaux et des solutions cloud. Par conséquent, il est très intéressant d’introduire de nouvelles techniques qui atténuent les interférences de l’UL, améliorent les débits UL et DL et permettent également une meilleure utilisation des ressources radio en fournissant un équilibrage de charge adéquat entre UL et DL. Une telle caractéristique supplémentaire est le découplage accès UL/DL.Dans notre travail, nous développons d'abord un modèle TDD dans HetNets. Dans ce modèle, nous dérivons des expressions analytiques pour la distribution de l'emplacement du brouilleur considérant tous les scénarios d’interférences possibles qui pourraient se produire dans les réseaux basés sur TDD, tout en tenant compte de l'impact nocif de cette interférence.Basé sur ce dernier résultat, nous dérivons la fonction de distribution et de génération de moment (MGF) de l’interférence intercellulaire montante et descendante considérant un réseau composé d'une macro-cellule et d'une petite cellule. Nous nous appuyons sur les expressions dérivées pour analyser la capacité moyenne de la cellule de référence dans les transmissions en liaison montante et en liaison descendante.Deuxièmement, nous développons un modèle statistique conjoint TDD/découplage pour mettre en évidence les avantages que le mode d'accès de découplage peut apporter à un système basé sur HetNet TDD. L'introduction du mode de découplage nécessite une analyse approfondie de l’étude de comparaison avec le mode d'accès couplé UL/DL conventionnel. Par conséquent, nous dérivons les statistiques du signal d'interférence et du signal d'intérêt des deux modes, puis analysons leur impact sur le performance du système.Ce travail a été étendu pour inclure le déploiement de plusieurs petites cellules, où des aperçus supplémentaires sur les avantages du mode de découplage sont fournies en termes de gains de découplage UL et DL. Suite à la mise en œuvre du modèle développé, il est démontré que le cas de découplage apporte de plus grands avantages dans la liaison montante et maintient la même amélioration dans la liaison descendante pour diverses valeurs de décalage et, ainsi, améliore les performances globales du système lorsqu'il est associé avec une technologie TDD dynamique. Il est en outre démontré que notre réseau modélisé peut être optimisé en adoptant la combinaison optimale à la fois du facteur de décalage des petites cellules et de la distance entre les petites cellules.D'un autre côté, l'évaluation des avantages d'un TDD adaptatif et du découplage dans un système basé sur HetNet en fonction des charges de trafic variant dans le temps, nécessite de trouver un simulateur de niveau système où nous pouvons présenter le motif derrière l' adoption de découplage et de TDD dynamique. À partir des scénarios de simulation mise en œuvre, il est observé que l'algorithme adaptatif proposé apporte des améliorations de performances significatives dans le débit UL et DL par rapport à un certain nombre de schémas conventionnels, principalement dans les systèmes fortement chargés
The rapid growth in wireless data traffic and bandwidth intensive services (voice over IP, video streaming, livestreaming, etc.) necessitates finding viable solutions to improve service quality and maximize thenetwork performance. To accommodate these bandwidth intensive applications, heterogeneous cellular networks (HetNets) were introduced in 3GPP as one of the main features to meet these advanced requirements. Yet, because of the difference in uplink (UL) and downlink (DL) traffic loads expected in the next HetNetsgeneration, it becomes essential to dynamically adjust UL/DL resources. To support this newapproach, dynamic time-division duplexing (TDD) has been proposed. Nevertheless, the importance of UL arises along with the evolution of social networking and cloudsolutions. Therefore, it is of great interest to introduce novel techniques that mitigate ULinterferences, improve UL and DL throughputs and allow as well, a better use of radio resources byproviding adequate load balancing among UL and DL. Such an additional feature is the decoupledUL/DL access.In our work, we first develop a TDD model in HetNets. Under this model, we derive analytical expressions for the distribution of the interferer location considering all possible interference scenarios that could occur in TDD-based networks, while taking into account the harmful impact of interference.Based on the latter result, we derive the distribution and moment generating function (MGF) of the uplink and downlinkinter-cell interference considering a network consisting of one macro cell and one small cell. We build on the derivedexpressions to analyze the average capacity of the reference cell in both uplink and downlink transmissions.Second, we develop a joint TDD/decoupling statistical model to highlight the benefits thatthe decoupling access mode can bring to a HetNet TDD based system, in terms of UL and DL spectral efficiencies and throughputs. Introducing the decoupling mode necessitates a thoroughcomparison study with the conventional coupled UL/DL access mode. Therefore, we derive the statistics of the interference signal and the signal of interest of both modes and then analyze their impact on the system performance.This work was extended to include multiple small cells deployment, where more insight into the benefits of decoupling mode is provided in terms of UL and DL decoupling gains. Further to the implementation of the developed model, it is shown that the decoupling case brings greater benefits in the uplink and maintains the same improvement in the downlink for various offset values and thus, improves the overall system performance when being combined with a dynamic TDD technology. It is further shown that our modeled network can be optimized by adopting the optimal combination of both the small cell offset factor and the distance between small cells.On the other hand, evaluating the benefits of an adaptive TDD and decoupling in a HetNet based system according to time-variant traffic loads, necessitates findinga system level simulator where we can present the motivation and accurately assess the role of both decoupling and dynamic TDD techniques in the UL/DL optimization problem. From the applied simulation scenarios, it is observed that the proposed adaptive algorithm (dynamic TDD with decoupling policies) yields significant performance improvements in UL and DL throughput compared to a number of conventional schemes, mainly in dense HetNet deployment and in highly loaded systems

When looking towards the deployment of 5G network architectures, mobile network operators will continue to face many challenges. The number of customers is approaching maximum market penetration, the number of devices per customer is increasing, and the number of non-human operated devices estimated to approach towards the tens of billions, network operators have a formidable task ahead of them. The proliferation of cloud computing techniques has created a multitude of applications for network services deployments, and at the forefront is the adoption of Software-Defined Networking (SDN) and Network Functions Virtualisation (NFV). Mobile network operators (MNO) have the opportunity to leverage these technologies so that they can enable the delivery of traditional networking functionality in cloud environments. The benefit of this is reductions seen in the capital and operational expenditures of network infrastructure. When going for NFV, how a Virtualised Network Function (VNF) is designed, implemented, and placed over physical infrastructure can play a vital role on the performance metrics achieved by the network function. Not paying careful attention to this aspect could lead to the drastically reduced performance of network functions thus defeating the purpose of going for virtualisation solutions. The success of mobile network operators in the 5G arena will depend heavily on their ability to shift from their old operational models and embrace new technologies, design principles and innovation in both the business and technical aspects of the environment. The primary goal of this thesis is to design, implement and evaluate the viability of data centre and cloud network infrastructure sharing use case. More specifically, the core question addressed by this thesis is how virtualisation of network functions in a shared infrastructure environment can be achieved without adverse performance degradation. 5G should be operational with high penetration beyond the year 2020 with data traffic rates increasing exponentially and the number of connected devices expected to surpass tens of billions. Requirements for 5G mobile networks include higher flexibility, scalability, cost effectiveness and energy efficiency. Towards these goals, Software Defined Networking (SDN) and Network Functions Virtualisation have been adopted in recent proposals for future mobile networks architectures because they are considered critical technologies for 5G. A Shared Infrastructure Management Framework was designed and implemented for this purpose. This framework was further enhanced for performance optimisation of network functions and underlying physical infrastructure. The objective achieved was the identification of requirements for the design and development of an experimental testbed for future 5G mobile networks. This testbed deploys high performance virtualised network functions (VNFs) while catering for the infrastructure sharing use case of multiple network operators. The management and orchestration of the VNFs allow for automation, scalability, fault recovery, and security to be evaluated. The testbed developed is readily re-creatable and based on open-source software.

To enable wireless control of factories, such that sensor measurements can be sent wirelessly to an actuator, the probability to receive data correctly must be very high and the time it takes to the deliver the data from the sensor to the actuator must be very low. Earlier, these requirements have only been met by cables, but in the fifth generation mobile network this is one of the imagined use cases and work is undergoing to create a system capable of wireless control of factories. One of the problems in this scenario is when all data in a packet cannot be sent in one transmission while ensuring the very high probability of reception of the transmission. This thesis studies this problem in detail by proposing methods to cope with the problem and evaluating these methods in a simulator. The thesis shows that splitting the data into multiple segments and transmitting each at an even higher probability of reception is a good candidate, especially when there is time for a retransmission. When there is only one transmission available, a better candidate is to send the same packet twice. Even if the first packet cannot achieve the very high probability of reception, the combination of the first and second packet might be able to.
För att möjliggöra trådlös kontroll av fabriker, till exempel trådlös sändning av data uppmätt av en sensor till ett ställdon som agerar på den emottagna signalen, så måste sannolikheten att ta emot datan korrekt vara väldigt hög och tiden det tar att leverera data från sensorn till ställdonet vara mycket kort. Tidigare har endast kablar klarat av dessa krav men i den femte generationens mobila nätverk är trådlös kontroll av fabriker ett av användningsområdena och arbete pågår för att skapa ett system som klarar av det. Ett av problemen i detta användningsområde är när all data i ett paket inte kan skickas i en sändning och klara av den väldigt höga sannolikheten för mottagning. Denna uppsats studerar detta problem i detalj och föreslår metoder för att hantera problemet samt utvärderar dessa metoder i en simulator. Uppsatsen visar att delning av ett paket i flera segment och sändning av varje segment med en ännu högre sannolikhet för mottagning är en bra kandidat, speciellt när det finns tid för en omsändning. När det endast finns tid för en sändning verkar det bättre att skicka samma paket två gånger. Även om det första paketet inte kan uppnå den höga sannolikheten för mottagning så kan kanske kombinationen av det första och andra paketet göra det.

Le domaine des transports intelligents repose sur une infrastructure robuste de communication véhiculaire, essentielle à la gestion du trafic, à la surveillance des routes, à l'accessibilité à l'Internet des objets (IoT) et aux informations des conducteurs/passagers. Alors que la norme conventionnelle IEEE802.11p a longtemps dominé ce domaine, l'avènement de la 5G et de ses successeurs marque un changement de paradigme.Cette thèse représente une exploration complète des technologies 5G et au-delà spécifiquement adaptées aux exigences uniques de la communication véhicule-à-tout (V2X). L'objectif principal est une analyse méticuleuse de la technologie Non-Orthogonal Multiple Access (NOMA) et des schémas de modulation multiporteuse (MCM) dans le contexte des applications V2X de nouvelle génération. Au cœur de cette exploration se trouve la recherche de stratégies de conception PHY/MAC (couches physique et de contrôle d'accès au support) transversales visant à élever les performances.Le parcours de recherche commence par une vue d'ensemble introductive, plongeant dans le contexte historique et la pertinence des communications V2X, accompagnée d'un examen des diverses exigences des groupes de cas d'utilisation V2X. Ce travail préliminaire combine des connaissances issues d'organisations normatives et des dernières publications, offrant une vue d'ensemble complète du paysage historique de la communication véhiculaire.Ensuite, la thèse navigue dans le paysage contemporain, mettant l'accent sur l'application des technologies 5G aux différents cas d'utilisation V2X. Elle cartographie la relation entre les groupes de cas d'utilisation V2X et les technologies habilitantes tout en explorant l'architecture hiérarchique 5G V2X. Cette exploration fait le lien entre les exigences actuelles de communication, les normes existantes et les directions de recherche ouvertes ainsi que les défis imminents.Le cœur de la thèse tourne autour de l'exploration des implications des schémas NOMA et MCM dans les applications V2X de prochaine génération. La culmination de cette recherche se manifeste dans un paradigme de conception transversale axé sur l'amélioration des performances et de l'adaptabilité des systèmes de communication cellulaires véhiculaires à tout (C-V2X). En disséquant les mécanismes NOMA au sein des couches physique et de contrôle d'accès au support (PHY/MAC), cette étude démontre des améliorations substantielles des performances de débit par rapport aux systèmes d'accès multiple orthogonal (OMA) conventionnels.Les résultats de cette thèse aspirent à contribuer à des solutions avancées pour les futurs systèmes de transport autonomes et connectés, avec un accent spécifique sur l'amélioration des performances des couches physique et d'accès au support dans des scénarios V2X sophistiqués
The realm of intelligent transportation hinges upon robust vehicular communication infrastructure, vital for traffic management, road monitoring, Internet of Things (IoT) accessibility, and driver/passenger information. While the conventional IEEE802.11p standard has long dominated this domain, the advent of 5G and its successors marks a paradigm shift.This thesis represents a comprehensive exploration of 5G and beyond technologies specifically tailored to the unique demands of Vehicle-to-Everything (V2X) communication. The primary aim is a meticulous analysis of Non-Orthogonal Multiple Access (NOMA) technology and Multi-Carrier Modulation (MCM) schemes within the context of next-generation V2X applications. Central to this exploration is the pursuit of cross-layer PHY/MAC (Physical Layer/Medium Access Control) design strategies aimed at elevating performance benchmarks.The research journey begins with an introductory overview, delving into the historical context and relevance of V2X communications, accompanied by an examination of the diverse requirements across V2X use case groups. This foundational groundwork combines insights from normative organizations and the latest literature, providing a comprehensive overview of the historical landscape of vehicular communication.Subsequently, the thesis navigates the contemporary landscape, emphasizing the application of 5G enabling technologies to various V2X use cases. It maps the relationship between V2X Use Case Groups and Enabling Technologies while exploring the Hierarchical 5G V2X high-level architecture. This exploration bridges current communication requirements and existing standards with open research directions and impending challenges.The core of the thesis revolves around the exploration of NOMA and MCM schemes' implications within next-generation V2X applications. The culmination of this research manifests in a cross-layer design paradigm focusing on the enhancement of performance and adaptability within cellular vehicle-to-everything (C-V2X) communication systems. By dissecting NOMA mechanisms within the Physical/Medium Access Control (PHY/MAC) layers, this study demonstrates substantial throughput performance improvements compared to conventional Orthogonal Multiple Access (OMA) systems.The outcomes of this thesis aspire to contribute advanced solutions for future autonomous and connected transport systems, with a specific emphasis on the enhancement of physical and medium access layer performance within sophisticated V2X scenarios

Les futurs réseaux sans fil devront être conçus pour répondre aux besoins hétérogènes de systèmes entièrement différents. De nouveaux services soumis à des contraintes variées coexisteront avec les utilisateurs actuels sur la même bande de fréquences. L'OFDM, la couche physique utilisée par les systèmes actuels, souffre d’un mauvais confinement spectral et ne permet pas cette coexistence. De nombreuses nouvelles formes d'onde avec une localisation spectrale améliorée ont donc été proposées. Nous étudions la coexistence de nouveaux systèmes basés sur ces formes d'onde avec des utilisateurs OFDM préexistant. Nous fournissons la première analyse théorique et expérimentale de l'interférence inter-système qui se produit dans ces scenarios. Nous appliquons ensuite cette analyse pour évaluer les performances de différentes formes d'ondes avancées et nous étudions finalement les performances d'un réseau où des utilisateurs cellulaires OFDM coexistent avec des paires D2D utilisant l'une des formes d'ondes améliorées étudiées
Future wireless networks are envisioned to accommodate the heterogeneous needs of entirely different systems. New services obeying various constraints will coexist with legacy cellular users in the same frequency band. This coexistence is hardly achievable with OFDM, the physical layer used by current systems, because of its poor spectral containment. Thus, a myriad of multi-carrier waveforms with enhanced spectral localization have been proposed for future wireless devices. In this thesis, we investigate the coexistence of new systems based on these waveforms with legacy OFDM users. We provide the first theoretical and experimental analysis of the inter-system interference that arises in those scenarii. Then, we apply this analysis to evaluate the merits of different enhanced waveforms and we finally investigate the performance achievable by a network composed of legacy OFDM cellular users and D2D pairs using one of the studied enhanced waveforms

Abstract With the unprecedented growth in mobile data traffic and network densification, the emerging fifth-generation (5G) wireless network warrants a paradigm shift with respect to system design and technological enablers. In this regard, the prime motivation of this thesis is to propose an integrated access-backhaul (IAB) framework to dynamically schedule users, while efficiently providing a wireless backhaul to dense small cells and mitigating interference. In addition, joint resource allocation and interference mitigation solutions are proposed for two-hop and multi-hop self-backhauled millimeter wave (mmWave) networks. The first contribution of this thesis focuses on a multi-user two-hop relay cellular system in which a massive antenna array enabled macro base station (BS) simultaneously provides high beamforming gains to outdoor users, and wireless backhauling to outdoor small cells. Moreover, a hierarchical interference mitigation scheme is applied to efficiently mitigate cross-tier and co-tier interference. In the second contribution, a multi-hop self-backhauled mmWave communication scenario is studied whereby a joint multi-hop multi-path selection and rate allocation framework is proposed to enable Gbps data rates with reliable communications. Using reinforcement learning techniques, a dynamic and efficient re-routing solution is proposed to cope with blockage and latency constraints. Finally, a risk-sensitive learning solution is leveraged to provide high-reliability and low-latency communications. In summary, the dissertation analyses key trade-offs between (i) capacity and latency, (ii) reliability and network density. Extensive simulation results were carried out to verify the performance gains of the proposed algorithms compared to several baselines and for different network settings. Key findings show significant improvements in terms of higher data rates, lower latency, and reliable communications with some trade-offs
Tiivistelmä Liikkuvan dataliikenteen ennennäkemättömän kasvun ja verkkojen tihentymisen seurauksena pian käyttöön tulevien viidennen sukupolven (5G) langattomien verkkojen järjestelmäsuunnittelua ja teknologisten mahdollistajien käyttöä on täytynyt lähestyä kokonaan uudesta näkökulmasta. Niinpä tämän väitöstyön johtavana ajatuksena on ehdottaa integroitua verkkoon pääsyn ja runkoverkkoyhteyden muodostamismallia, jossa käyttäjät resursoidaan dynaamisesti ja samalla muodostetaan tehokkaat runkoverkkoyhteydet piensoluille. Tätä varten tutkitaan resurssiallokaation ja häiriöiden lieventämisen yhteisratkaisuja, jotka tukevat kahden tai useamman hypyn yhteyksiä ja samanaikaista runkoverkkoyhteyden luomista millimetriaaltoalueen verkoissa. Työn alkuosa keskittyy usean käyttäjän välitinavusteiseen kahden hypyn solukkoverkkoon, jossa makrotukiasemassa käytetään suurta antenniryhmää muodostamaan samanaikaisesti suuren vahvistuksen antennikeiloja käyttäjälinkeille ja langattomalle runkoyhteysosuudelle. Lisäksi sovelletaan hierarkkista häiriönvaimennusmenetelmää saman kerroksen ja kerrosten välisen häiriön tehokkaaseen vähentämiseen. Työn seuraavassa osassa arvioidaan usean hypyn runkoverkkoyhteyden muodostuksen tutkimusongelmaa millimetrialueen kommunikaatiossa kehittämällä yhdistetty menetelmä usean hypyn monipolkuvalinnalle ja tiedonsiirtoresurssien allokoinnille. Tällä tähdätään gigabittiluokan datanopeuksiin ja luotettavaan tietoliikenteeseen millimetrialueella. Vahvistavan oppimisen tekniikan avulla esitellään dynaaminen ja tehokas uudelleenreitityskonsepti toimimaan esto- ja viiverajoitusten kanssa. Lopuksi hyödynnetään riskisensitiivistä oppimista ja antennidiversiteettitekniikoita suuren luotettavuuden ja pienen latenssin saavuttamiseksi millimetrialueen tiedonsiirrossa. Näiden avulla analysoidaan kaupankäyntiä esimerkiksi (i) kapasiteetin ja latenssin sekä (ii) luotettavuuden ja verkon tiheyden/kuormituksen välillä. Mittavien suoritettujen simulointien avulla osoitetaan ehdotettujen algoritmien suorituskykyedut suhteessa tunnettuihin verrokkeihin useissa eri skenaarioissa. Tulosten perusteella saavutetaan merkittäviä kustannussäästöjä infrastruktuurin ja runkoverkon osalta sekä päästään suuriin datanopeuksiin ja parannuksiin pienen latenssin luotettavassa tietoliikenteessä

L’augmentation exponentielle des équipements d’utilisateurs sans fil (UEs) et des services des réseaux associés aux déploiements actuels de cinquième génération (5G) pose plusieurs défis de conception sans précédent qui doivent être résolus avec l’avènement des futurs réseaux au-delà de la 5G. Plus précisément, la demande croissante de débits de données élevés ainsi que la nécessité de desservir un grand nombre d’appareils hétérogènes, allant des téléphones mobiles classiques aux objets connectés formant l’internet des objets (IoT), motivent l’étude de nouveaux schémas de traitement et de transmission du signal. À cet égard, les sorties multiples massives à entrées multiples (massive MIMO) sont une technologie d’accès bien établie, qui permet de desservir plusieurs dizaines d’UEs en utilisant lesmêmes ressources temps-fréquence au moyen de techniques de formation de faisceau hautement directionnelles. Cependant, le massive MIMO présente des problèmes d’évolutivité dans les scénarios accès massif où la population UE est composée d’un grand nombre de périphériques hétérogènes. En effet, si la disponibilité d’un grand nombre d’antennes dans les émetteurs-récepteurs massive MIMO apporte des gains de performances substantiels, elle augmente également considérablement la surcharge et la complexité du système. Plus précisément, la dimensionnalité élevée des canaux nécessite l’allocation de ressources temps-fréquence considérables pour acquérir les informations d’état de canal (CSI) et se traduit par de grandes opérations matricielles pour construire des précodeurs/décodeurs. De plus, dans le contexte de communications de multidiffusion comme, par exemple, la mise en cache périphérique sans fil ou la diffusion de messages critiques pour la mission, les techniques d’antennes multiples conventionnelles présentent des taux de disparition lorsque le nombre d’UEs augmente même dans le régime d’antenne massif. Enfin, le grand nombre de chaînes de radiofréquences (RF) associées aux émetteurs-récepteurs massive MIMO, qui sont utilisés pour contrer les pertes de propagation dans des environnements difficiles tels que, par exemple, à des fréquences d’ondes millimétriques (mmWave), se heurte au budget de puissance limité des appareils IoT. Dans cette thèse, nous proposons de nouvelles méthodes à antennes multiples évolutives pour l’amélioration des performances dans les scénarios d’intérêt susmentionnés. Plus précisément, nous décrivons le rôle fondamental joué par le CSI statistique qui peut être mis à profit pour réduire à la fois la complexité et la surcharge pour l’acquisition de CSI et pour la suppression des interférences multi-utilisateurs. En effet, lorsque les UEs sont équipés au moins de duex antennes, leurs propriétés de sélectivité spatiale peuvent être exploitées pour imposer une orthogonalité statistique parmi les transmissions interférentes. De plus, nous exploitons les communications de périphérique à périphérique (D2D) pour surmonter le goulot d’étranglement fondamental de la multidiffusion conventionnelle. En particulier, nous exploitons les capacités de précodage d’un émetteur multi-antennes pour sélectionner soigneusement les UEs dans des conditions de canal favorables, qui à leur tour agissent comme des relais opportunistes et retransmettent le message via les liaisons D2D. Enfin, dans le cadre des communications mmWave, nous explorons les avantages des surfaces intelligentes reconfigurables (RISs) récemment proposées, qui sont un catalyseur clé de l’innovation grâce à leur structure intrinsèquement passive qui permet de contrôler l’environnement de propagation et de contrer efficacement les pertes de propagation. En particulier, nous utilisons la formation de faisceaux passive au niveau du RIS, c’est-à-dire sans aucune dépense d’énergie significative, ainsi que la formation de faisceaux active conventionnelle au niveau de l’émetteur pour augmenter considérablement les performances du réseau
The exponential increase of wireless user equipments (UEs) and network services associated with current 5G deployments poses several unprecedented design challenges that need to be addressed with the advent of future beyond-5G networks and novel signal processing and transmission schemes. In this regard, massive MIMO is a well-established access technology, which allows to serve many tens of UEs using the same time-frequency resources. However, massive MIMO exhibits scalability issues in massive access scenarios where the UE population is composed of a large number of heterogeneous devices. In this thesis, we propose novel scalable multiple antenna methods for performance enhancement in several scenarios of interest. Specifically, we describe the fundamental role played by statistical channel state information (CSI) that can be leveraged for reduction of both complexity and overhead for CSI acquisition, and for multiuser interference suppression. Moreover, we exploit device-to-device communications to overcome the fundamental bottleneck of conventional multicasting. Lastly, in the context of millimiter wave communications, we explore the benefits of the recently proposed reconfigurable intelligent surfaces (RISs). Thanks to their inherently passive structure, RISs allow to control the propagation environment and effectively counteract propagation losses and substantially increase the network performance

Fifth Generation (5G) networks are expected to support emerging applications with diverse quality of service (QoS) requirements, such as reliability, latency, and age-of-information. In conventional wireless networks, orthogonal resources are allocated to different transmitters to guarantee QoS performance. As the density of networks or devices increases, we need to increase the frequency reuse factor. Thus, interference becomes one of the bottlenecks for ensuring the QoS requirements of a large number of devices with limited time-frequency resources. This thesis presents novel methods for improving QoS performance in interference-limited networks. Specifically, we consider three typical scenarios: Ultra-reliable and Low latency communications (URLLC), time-critical applications, and multi-tenant communications. In 5G networks, URLLC is one of the most challenging services with high reliability and low latency requirements. We define a new QoS metric, QoS violation probability, to measure the percentage of users without QoS guarantee. We propose a random packet repetition scheme that randomizes the interference power. The randomization is used to obtain diversity within the channel coherence time. The variation of interference can be exploited to reduce the QoS violation probability in interference-limited networks. Then, we optimize the number of reserved slots and the number of repetitions for each packet to minimize the QoS violation probability. We build a cascaded Random Edge Graph Neural Network (REGNN) to represent the repetition scheme and develop a model-free unsupervised learning method to train it. We analyze the QoS violation probability using stochastic geometry in a symmetric scenario and apply a model-based Exhaustive Search (ES) method to find the optimal solution. Simulation results show that in the symmetric scenario, the QoS violation probabilities achieved by the model-free learning method and the model-based ES method are nearly the same. In more general scenarios, the cascaded REGNN generalizes very well to wireless networks with different scales, network topologies, cell densities, and frequency reuse factors. It outperforms the model-based ES method in the presence of model mismatch. For time-critical applications, we investigate the timely updates of short packets in interference-limited networks. Specifically, we minimize a performance metric, Age-of-Information (AoI), by optimizing the power control policy that is scalable to the number of wireless links. To find the optimal policy, we develop a deep reinforcement learning algorithm, graph-based deterministic policy gradient (GDPG). The actor and critic of the GDPG are represented by two types of graph neural networks (GNNs). We design two structures to implement the GDPG in a centralized and distributed manner. Simulation results show that when the number of wireless links in the testing stage is different from that in the training stage, the average AoI achieved by the GDPG is around $25\%$ lower than the WMMSE (weighted minimize mean square error) algorithm in a hexagonal cellular network and $50\%$ lower in a random network. The proposed methods are scalable to the number of wireless links in the network. With fine-tuning, our proposed two GDPG structures can be generalized well to networks with different densities and topologies. Finally, we consider a multi-tenant network scenario, where multiple vertical industries or operators (acting as tenants) run their network on a single base station (BS). A new duality concept is developed to allocate precoding weights and transmit power at the BS so that the minimum isolation level from interference between tenants is maximized. A real-time multi-antenna multi-tenant BS (MBS) prototype is built by using commercial-off-the-shelf (COTS) software-defined-radio (SDR) boards. The over-the-air experiments show MBS provides a higher minimum isolation level and network capacity than other known algorithms. The research on improving the QoS for different applications in 5G and beyond is developing rapidly. Possible future directions include 1) developing a more flexible transmission scheme that repeats the packet transmission in different resource blocks, 2) optimizing the peak AoI with a constraint on the tail probability, and 3) proposing a general solution for improving the QoS or other queue state information metrics in 5G interference-limited networks.

The unmanned aerial vehicles (UAVs) are also known as drones. Recently, UAVs have attracted the next generation researchers due to their flexible, dynamic, and cost-effective deployment, etc. Moreover, the UAVs have a wide range of application domains, such as rescue operation in the remote area, military surveillance, emergency application, etc. Given the UAVs are appropriately deployed, the UAVs provide continuous and reliable connectivity, on-demand, and cost-effective features to the desired destination in the wireless communication system. Thus, the UAVs can be a great choice to deploy as a mobile relay in co-existence with the base stations (BSs) on the ground to serve the 5G wireless users. In this thesis, the UAV-assisted mobile relay (UAV-MR) in the next generation wireless networks has been studied, which also considers the UAV-MR physical layer security. The proposed system also considers one ground user, one BS on the ground, and active presence of multiple eavesdroppers, situated nearby the ground user. The locations of these nodes (i.e., the ground user, the BS, and the eavesdroppers) are considered fixed on the ground. Moreover, the locations of the eavesdroppers are not precisely known to the UAV-MR. Thus, this thesis aims to maximize the achievable secrecy rate, while the BS sends the secure information to the ground user via the UAV-MR. However, the UAV-MR has some challenges to deploy in wireless networks, such as 3D deployment, robust resource allocation, secure UAV-MR to ground communication, the channel modeling, the UAV-MR flight duration, and the UAV-MR robust trajectory design, etc. Thus, this project investigates the UAV-MR assisted wireless networks, which addresses those technical challenges to guarantee efficient UAV-MR communication. Moreover, the mathematical frameworks are formulated to support the proposed model. An efficient algorithm is proposed to maximize the UAV-MR achievable secrecy rate. Finally, the simulation results show the improved performance for the UAV-MR assisted next-generation networks.

Internet of Things (IoT) refers to the interconnection of uniquely identifiable smart devices which enables them to participate more actively in everyday life. Among large-scale applications, machine-type communications (MTC) supported by cellular networks will be one of the most important enablers for the success of IoT. The existing cellular infrastructure has been optimized for serving a small number of long-lived human-oriented communications (HoC) sessions, originated from smartphones whose batteries are charged in a daily basis. As a consequence, serving a massive number of non-rechargeable machine-type devices demanding a long battery lifetime is a big challenge for cellular networks. The present work is devoted to energy consumption modeling, battery lifetime analysis, and lifetime-aware network design for massive MTC services over cellular networks. At first, we present a realistic model for energy consumption of machine devices in cellular connectivity, which is employed subsequently in deriving the key performance indicator, i.e. network battery lifetime. Then, we develop an efficient mathematical foundation and algorithmic framework for lifetime-aware clustering design for serving a massive number of machine devices. Also, by extending the developed framework to non-clustered MTC, lifetime-aware uplink scheduling and power control solutions are derived. Finally, by investigating the delay, energy consumption, spectral efficiency, and battery lifetime tradeoffs in serving coexistence of HoC and MTC traffic, we explore the ways in which energy saving for the access network and quality of service for HoC traffic can be traded to prolong battery lifetime for machine devices. The numerical and simulation results show that the proposed solutions can provide substantial network lifetime improvement and network maintenance cost reduction in comparison with the existing approaches.

QC 20161103

La codificación de red (NC) ha surgido recientemente como una nueva solución para mejorar el rendimiento de la red en términos de rendimiento y fiabilidad. Sin embargo, la naturaleza multiusuario de NC y su aplicabilidad inherente a la ingeniería de flujo versátil en todas las capas de la pila de protocolos requieren nuevos enfoques de diseño de sistemas inalámbricos. El objetivo de esta tesis es estudiar el diseño de NC como una funcionalidad de red ofrecida a los diseñadores de servicios de comunicación inalámbrica 5G. El diseño facilitaría el control del rendimiento de la red, la confiabilidad y la conectividad a través de redes inalámbricas 5G. Las contribuciones de esta tesis son las siguientes. Primero desarrollamos un diseño de Funcionalidad de codificación de red como una caja de herramientas de dominios de diseño NC y mostramos cómo se puede integrar en las infraestructuras virtualizadas actuales. En segundo lugar, evaluamos el rendimiento de longitud finita de diferentes códigos de red usando matrices aleatorias vs Pascal. Modelamos el proceso de codificación, recodificación y decodificación de diferentes esquemas de codificación en notación de matriz y las correspondientes probabilidades de error. A continuación, proponemos un algoritmo de búsqueda binaria para identificar la velocidad de codificación óptima para algunas tasas de pérdida de paquetes de destino específicas dada una longitud de bloque de codificación predefinida. Nos enfocaremos en los códigos de logro de capacidad y los esquemas de codificación con la programación de escenarios representativos y mostraremos la compensación de la tasa de retardo alcanzable entre los códigos aleatorios y los códigos estructurados con la programación. En la última parte de esta tesis, validamos el diseño de NCF propuesto para un caso de uso completo para mejorar la conectividad de los dispositivos de red móvil ad-hoc (MANET) sobre las redes convergidas de nubes satelitales en aplicaciones de emergencia. La idea clave es que en un escenario de emergencia puede no haber acceso directo a la niebla o la computación en la nube, que luego se proporcionará por satélite y los únicos recursos computacionales locales disponibles son los dispositivos MANET. Para resolver esta situación, definimos un NCF a nivel de paquetes con entradas de objetivos de calidad del servicio de datos, restricciones de computación local y estadísticas por ruta. Las salidas son tasas de codificación centralmente optimizadas que equilibran los recursos computacionales por nodo y la cobertura resultante.
Network coding (NC) has recently emerged as a new solution for improving network performance in terms of throughput and reliability. However, the multi-user nature of NC and its inherent applicability to versatile flow engineering across all layers of the protocol stack, call for novel wireless system design approaches. The goal of this thesis is to study the design of NC as a network functionality offered to the 5G wireless communication service designers. The design would facilitate the control of network throughput, reliability, and connectivity over 5G wireless networks. The contributions of this thesis are the following. We first develop a design of Network Coding Functionality as a toolbox of NC design domains and show how it can be integrated in current virtualized infrastructures. Second, we evaluate the finite-length performance of different network codes using random vs Pascal matrices. We model the encoding, re-encoding, and decoding process of different coding schemes in matrix notation and corresponding error probabilities. We then propose a binary searching algorithm to identify optimal coding rate for some specific target packet loss rates given a pre-defined coding block-length. We will focus on capacity-achieving codes and coding schemes with scheduling for representative scenarios and show the achievable rate-delay trade-off between random codes and structured codes with scheduling. In the last part of this thesis, we validate the proposed NCF design for a complete use case to enhance connectivity of Mobile Ad-hoc Network (MANET) devices over converged satellite-cloud networks in emergency applications. The key insight is that in an emergency scenario there may not be direct access to fog or cloud computing, which will then be provided via satellite and the only local computational resources available are the MANET devices. To solve this situation, we define a packet-level NCF with inputs from data service quality targets, local computation constraints and per-path statistics. Outputs are centrally-optimized coding rates balancing per-node computational resources and resulting coverage.

Spectrum scarcity is one of the most important challenges in wireless communications networks due to the sky-rocketing growth of multimedia applications. As the latest member of the multiple access family, non-orthogonal multiple access (NOMA) has been recently proposed for 3GPP Long Term Evolution (LTE) and envisioned to be a key component of the 5th generation (5G) mobile networks for its potential ability on spectrum enhancement. The feature of NOMA is to serve multiple users at the same time/frequency/code, but with di erent power levels, which yields a signi cant spectral e ciency gain over conventional orthogonal multiple access (OMA). This thesis provides a systematic treatment of this newly emerging technology, from the basic principles of NOMA, to its combination with simultaneously information and wireless power transfer (SWIPT) technology, to apply in cognitive radio (CR) networks and Heterogeneous networks (HetNets), as well as enhancing the physical layer security and addressing the fairness issue. First, this thesis examines the application of SWIPT to NOMA networks with spatially randomly located users. A new cooperative SWIPT NOMA protocol is proposed, in which near NOMA users that are close to the source act as energy harvesting relays in the aid of far NOMA users. Three user selection schemes are proposed to investigate the e ect of locations on the performance. Besides the closed-form expressions in terms of outage probability and throughput, the diversity gain of the considered networks is determined. Second, when considering NOMA in CR networks, stochastic geometry tools are used to evaluate the outage performance of the considered network. New closed-form expressions are derived for the outage probability. Diversity order of NOMA users has been analyzed based on the derived outage probability, which reveals important design insights regarding the interplay between two power constraints scenarios. Third, a new promising transmission framework is proposed, in which massive multipleinput multiple-output (MIMO) is employed in macro cells and NOMA is adopted in small cells. For maximizing the biased average received power at mobile users, a massive MIMO and NOMA based user association scheme is developed. Analytical expressions for the spectrum e ciency of each tier are derived using stochastic geometry. It is con rmed that NOMA is capable of enhancing the spectrum e ciency of the network compared to the OMA based HetNets. Fourth, this thesis investigates the physical layer security of NOMA in large-scale networks with invoking stochastic geometry. Both single-antenna and multiple-antenna aided transmission scenarios are considered, where the base station (BS) communicates with randomly distributed NOMA users. In addition to the derived exact analytical expressions for each scenario, some important insights such as secrecy diversity order and large antenna array property are obtained by carrying the asymptotic analysis. Fifth and last, the fundamental issues of fairness surrounding the joint power allocation and dynamic user clustering are addressed in MIMO-NOMA systems in this thesis. A two-step optimization approach is proposed to solve the formulated problem. Three e cient suboptimal algorithms are proposed to reduce the computational complexity. To further improve the performance of the worst user in each cluster, power allocation coe cients are optimized by using bi-section search. Important insights are concluded from the generated simulate results.

Future fifth generation (5G) cellular networks have to cope with the expected ten-fold increase in mobile data traffic between 2015 and 2021. To achieve this goal, new technologies are being considered, including massive multiple-input multiple-output (MIMO) systems and millimeter-wave (mmWave) communications. Massive MIMO involves the use of large antenna array sizes at the base station, while mmWave communications employ frequencies between 30 and 300 GHz. In this thesis we study the impact of these technologies on the performance of channel estimators. Our results show that the characteristics of the propagation channel at mmWave frequencies improve the channel estimation performance in comparison with current, low frequency-based, cellular networks. Furthermore, we demonstrate the existence of an optimal angular spread of the multipath clusters, which can be used to maximize the capacity of mmWave networks. We also propose efficient noise variance estimators, which can be employed as an input to existing channel estimators.

This thesis evaluates the possibility of using millimeter waves of frequency 28GHz for the use of wireless backhaul in small cell solutions in the coming fifth generation mobile networks. This frequency band has not been used in preceding mobile networks but is undergoing a lot of research. In this thesis simulations are performed to evaluate how the high frequency waves behave inside a three dimensional grid of buildings. The simulations use highly directive antenna arrays with antenna gains of 26dBi. A main results of the investigation was that a high bandwidth of 800MHz was not enough to provide 12Gbps in non line-of-sight propagation within the simulations. Furthermore, without interference limiting techniques, the interference is probable to dominate the noise, even though the high diffraction losses of millimeter waves propose that interference should be very limited in urban areas.

In recent years, the demand for higher data rates in wireless communication networks is escalating due to widespread penetration of portable smart devices and increasing popularity of multimedia services. As these devices and applications proliferate, data traffic volume is expected to reach 11 exabytes per month in 2017, which is beyond the current fourth generation (4G) cellular system architecture's capacity, particularly when spectrum and energy efficiency, coverage and interference issues are considered. The next generation of wireless communication technology, commonly known as the fifth generation (5G) system, aims to overcome the limitations of the 4G systems. 5G systems will be formally standardised in 2018, but the early indication suggests that heterogeneous networks (HetNets) and small cell networks (SCNs) are going to be big parts of 5G systems, particularly in facilitating massive data traffic and ubiquitous connectivity for users. In HetNets, small cells of different sizes are integrated into an existing macrocell network, which helps to overcome limited spectrum and power efficiency issues. Researchers have been actively looking for solutions to further improve small cell network technology, and numerous solutions are presented in the literature. However, most of these studies focus on fixed small cell networks, which are suitable only for static users, and to support mobile users, mobile small cells are required. Mobile small cells are expected to be a key technological advancement in 5G networks, specifically to serve mobile users in vehicular environments. This thesis focuses on research challenges related to mobile small cell networks, and presents solutions for overcoming poor spectrum and energy efficiency issues. An analytical model for resource management in 5G HetNets to mitigate interference among mobile small cells with deterministic mobility (e.g., public bus/train), is also presented in this thesis. First, the analytical model in this work is modelled as a classical optimisation problem, and considering the time complexity of a classical optimisation solution, a heuristic graph colouring solution is then presented. Next, the model is extended for mobile small cells with random mobility. In addition, an optimisation and meta-heuristic solution is presented to cater for the need of mobile users moving at pedestrian speeds. The ultimate benefits of these proposed solutions include better spectrum and energy efficiency and improved data rates.

In this work, the formulation and the implementation of innovative methodological paradigms for the design of unconventional array architectures for future generation communication systems has been addressed. By exploiting the potentialities of the codesign strategy for elementary radiators in an irregularly clustered array architectures and by introducing an innovative capacity-driven design paradigm, the proposed methodologies allow to effectively design unconventional array architectures with optimal trade-offs in terms of performance and complexity/costs. The codesign synthesis strategy is proposed to solve the arising massive multi-objective design problem aimed at fitting the multiple objectives and requirements on the "free-space" performance of the array architecture. Afterward, the capacity-driven design paradigm is formulated and implemented for the design of MIMO array architectures to maximize the quality of the communication system in first place instead of considering "free-space" figures-of-merit. A set of numerical results has been provided (i) to validate the proposed paradigms in real-application scenarios and (ii) to provide insights on the effectiveness, the limitations and the potentialities of proposed design methodologies.

In this work, the formulation and the implementation of innovative methodological paradigms for the design of unconventional array architectures for future generation communication systems has been addressed. By exploiting the potentialities of the codesign strategy for elementary radiators in an irregularly clustered array architectures and by introducing an innovative capacity-driven design paradigm, the proposed methodologies allow to effectively design unconventional array architectures with optimal trade-offs in terms of performance and complexity/costs. The codesign synthesis strategy is proposed to solve the arising massive multi-objective design problem aimed at fitting the multiple objectives and requirements on the "free-space" performance of the array architecture. Afterward, the capacity-driven design paradigm is formulated and implemented for the design of MIMO array architectures to maximize the quality of the communication system in first place instead of considering "free-space" figures-of-merit. A set of numerical results has been provided (i) to validate the proposed paradigms in real-application scenarios and (ii) to provide insights on the effectiveness, the limitations and the potentialities of proposed design methodologies.

Les systèmes de communication sans fil à venir vont faire un usage intensif des transmissions de paquets courts. La norme 5G émergente en est un exemple parfait, pour lequel deux des trois principaux cas d'utilisation, les communications massives de type machine (mMTC) et les communications ultra fiables à faible latence (URLLC), reposent intrinsèquement sur des paquets courts. Un autre exemple est fourni par les récents réseaux d'accès de faible puissance (LPWAN) tels que Sigfox, LoRa, etc. et conçus pour prendre en charge l'IoT. L'utilisation de paquets courts au niveau de la couche physique peut modifier considérablement la conception des systèmes de communication numériques. En particulier, avec une longueur de bloc courte, la surcharge de l'en-tête ne peut plus être considérée comme négligeable. Plus important encore, les résultats asymptotiques de la théorie de l'information, qui ont été un guide essentiel et un moteur essentiel de la conception de systèmes de communication en constante amélioration jusqu'à présent, ne sont plus valables dans ce régime. Comment alors assurer une communication fiable sans augmenter la longueur du code puisque ce dernier n'est plus une option? Par extension et plus fondamentalement, comment concevoir la couche physique de paquets courts pour assurer des performances optimales avec l'utilisation la plus efficace possible des ressources disponibles? L'objectif de cette thèse est de revoir les techniques de conception de la couche physique pour la communication par paquets courts et de proposer de nouvelles directives de conception tirant parti des derniers résultats en matière de codage de canal dans le régime de longueur de bloc finie
Upcoming wireless communication systems are expected to make intensive use of short packet transmission. An epitome is the emerging 5G standard, for which two out of the three principal use cases, massive Machine Type Communications (mMTC) and Ultra Reliable Low Latency Communications (URLLC), are intrinsically based on short packets. Another example is provided by the recent Low-Power Wide Area Networks (LPWAN) designed to support the IoT such as Sigfox, LoRa, etc.The use of short packets at the physical layer may substantially change the way digital communication systems are designed. In particular, at short block length, header overhead may no longer be considered negligible. More importantly, asymptotic results from information theory which have been a central guide and a key driver to the design of ever-improving communication systems so far no longer hold in this regime. How, then, to ensure reliable communication without increasing the code length since the latter is no longer an option ? By extension and more fundamentally, how to design the physical layer of short packets to ensure optimal performance with the most efficient use of available resources at hand ? The focus of this PhD thesis is to revisit physical layer design for short-packet communication and to propose new design guidelines leveraging the latest results on channel coding in the finite blocklength regime

In this thesis, a fully millimetre-wave (mm-wave) generation and transmission system is proposed for futuristic communications. Significant challenges have been dealt with regarding the proposed system, including designing the mm-wave generation and transmission technique, and its application in cellular networks. These challenges are presented through five main contributions and validated via Optiwave Design Software and MATLAB simulation tools. Firstly, three novel photonic generation methods are proposed and designed based on the characteristics of Brillouin fibre laser and the Stimulated Brillouin Scattering (SBS) effects with phase modulation. The mm-wave carriers are successfully generated with a tuning capability from 5 to 90 GHz. Also, these carriers are with good Signal to Noise Ratio (SNR) up to 51 dB, and low noise signal power of about -40 dBm. The impact of these methods is obtaining stable mm-waves appropriate for Radio over Fibre (RoF) transmission systems in 5G optical networks. Secondly, a full-duplex RoF system with the generation of a 64 GHz mm-wave is proposed. Successful transmission of the mm-wave over a fibre link is achieved for up to 100 km of fibre with a data rate of 5 Gbits/s. The main impact of this system is cost reduction and performance improvement by simplifying mm-wave generation and transmission over fibre. Also, it ensures a useful communication link for small cell networks. Thirdly, a hybrid Fibre/Free-space optical (FSO) system for the generation and transmission of 64 GHz mm-wave is proposed. This optical system provides a low latency communication link and overcomes mm-wave high path losses. A successful mm-wave transmission is achieved over a 10 km fibre length, and 2 km FSO link length with a good Bit Error Rate (BER) of about 1.5×10-13 and a data rate of 10 Gbits/s. This system increases the network coverage area by transmitting the mm-wave over the FSO link to the areas with natural obstacles the laying of fibre cables impossible. Also, it can be used as an effective solution under emergency disaster conditions. Fourthly, a comprehensive study of the wireless propagation performance for different mm-wave bands (28, 60, and 73 GHz) as cellular networks is investigated and compared with the 2.4 GHz Ultra-High Frequency band (UHF). A map-based scenario is proposed for the deployment of Base Stations (BSs) within the Brunel University London Campus map to consider real blockage effects. This investigation involved specifying which mm-wave spectrum can enhance the futuristic cellular networks, by evaluating the coverage and rate trends. Comparative results show that the 73 GHz bands can achieve the higher rate with good coverage and the lowest interference effects than the other mm-wave bands. Finally, a simplified path loss model is proposed to estimate precisely the 28 GHz mm-wave performance, which is considered a key component in 5G networks in outdoor applications. The proposed path loss model captures the diffraction and specular reflection impacts on mm-wave wireless propagation.

Vehicle-related communications are a key application to be enabled by Fifth Generation (5G) wireless systems. The communications enabled by the future Internet of Vehicles (IoV) that are connected to every wireless device are referred to as Vehicle-to-Everything (V2X) communications. A major application of V2X communication systems will be to provide emergency warnings. This thesis evaluates Long-Term Evolution (LTE) and Dedicated Short Range Communications (DSRC) in terms of service quality and latency, and provides guidelines for design of cooperative LTE-DSRC systems for V2X communications. An extensive simulation analysis shows that (1) the number of users in need of warning has an effect on latency, and more so for LTE than for DSRC, (2) the DSRC priority parameter has an impact on the latency, and (3) wider system bandwidths and smaller cell sizes reduce latency for LTE. The end-to-end latency of LTE can be as high as 1.3 s, whereas the DSRC latency is below 15 ms for up to 250 users. Also, improving performance of systems is as much as important as studying about latency. One method to improving performance is using a better suitable antenna for physical communication. The mobility of vehicles results in a highly variable propagation channel that complicates communication. Use of a smart, steerable antenna can be one solution. The most commonly used antennas for vehicular communication are omnidirectional. Such antennas have consistent performance over all angles in the horizontal plane; however, rapidly steerable directional antennas should perform better in a dynamic propagation environment. A linear array antenna can perform dynamical appropriate azimuth pattern by having different weights of each element. The later section includes (1) identifying beam pattern parameters based on locations of a vehicular transmitter and fixed receivers and (2) an approach to find weights of each element of linear array antenna. Through the simulations with our approach and realistic scenarios, the desired array pattern can be achieved and array element weights can be calculated for the desired beam pattern. Based on the simulation results, DSRC is preferred to use in the scenario which contains large number of users with setup of higher priority, and LTE is preferred to use with wider bandwidth and smaller cell size. Also, the approach to find the controllable array antenna can be developed to the actual implementation of hardware with USRP.
Master of Science

Les futurs réseaux mobiles promettent des opportunités sans précédent pour l'innovation et des cas d'utilisation disruptifs. L'engagement des réseaux 5G et au-delà à fournir des applications critiques nécessite un réseau polyvalent, évolutif, efficace et rentable, capable d'adapter son allocation de ressources pour répondre aux exigences de services hétérogènes. Pour relever ces défis, le découpage du réseau s'est imposé comme l'un des concepts fondamentaux proposés pour améliorer l'efficacité des réseaux mobiles 5G et leur conférer la plasticité requise. L'idée est de fournir des ressources à différentes industries verticales en construisant plusieurs réseaux logiques de bout en bout sur une infrastructure virtualisée partagée. Chaque "tranche de réseau" ainsi définie est personnalisée pour fournir un service spécifique en adaptant son architecture et ses technologies d'accès radio.Précisément, des applications telles que l'automatisation industrielle ou les communications entre véhicules imposent aux réseaux cellulaires des exigences strictes en matière de latence et de fiabilité. Étant donné que le réseau mobile actuel ne peut pas répondre à ces exigences, les communications ultra-fiables et à faible temps de latence constituent un sujet de recherche essentiel qui a suscité un élan considérable de la part du monde universitaire et des alliances industrielles. Pour répondre à ces exigences, l'utilisation de la multi-connectivité, c'est-à-dire l'exploitation simultanée de plusieurs liaisons radio comme voies de communication, est une approche prometteuse.L'objectif du présent manuscrit est d'étudier des techniques d'allocation de resources exploitant la couverture redondante des utilisateurs, garantie dans de nombreux scénarios 5G. Nous examinons d'abord l'évolution des réseaux mobiles et discutons des diverses considérations relatives à l'architecture de découpage du réseau et de son impact sur la conception des méthodes d'allocation des ressources. Nous utilisons ensuite les outils de la théorie des files d'attente pour modéliser un système dans lequel un ensemble d'utilisateurs URLLC sont connectés simultanément à deux stations de base ayant la même bande passante ; nous appelons ce scénario le cas homogène. Nous introduisons des politiques d'allocation appropriées et évaluons leurs performances respectives en évaluant leur fiabilité. Ensuite, nous étendons les résultats du cas homogène à un cadre plus général où les interfaces physiques gèrent des bandes passantes différentes, que nous appelons le cas hétérogène. Enfin, nous fusionnons les éléments ci-dessus pour valider le choix des schémas d'allocation des ressources en tenant compte de l'architecture déployée
Future mobile networks envision unprecedented innovation opportunities and disruptive use cases. As a matter of fact, the 5G and beyond networks' pledge to deliver mission-critical applications mandates a versatile, scalable, efficient, and cost-effective network capable of accommodating its resource allocation to meet the services' heterogeneous requirements. To face these challenges, network slicing has emerged as one of the fundamental concepts proposed to raise the 5G mobile networks' efficiency and provide the required plasticity. The idea is to provide resources for different vertical industries by building multiple end-to-end logical networks over a shared virtualized infrastructure. Each network slice is customized to deliver a specific service and adapts its architecture and radio access technologies.Precisely, applications such as industrial automation or vehicular communications pose stringent latency and reliability requirements on cellular networks. Given that the current mobile network cannot meet these requirements, ultra-reliable low-latency communications (URLLC) embodies a vital research topic that has gathered substantial momentum from academia and industrial alliances. To reach URLLC requirements, employing multi-connectivity (MC), i.e., exploiting multiple radio links as communication paths at once, is a promising approach.Therefore, the objective of the present manuscript is to investigate dynamic scheduling techniques, exploiting redundant coverage of users, guaranteed in numerous 5G radio access network scenarios. We first review the evolution of mobile networks and discuss various considerations for network slicing architecture and its impact on resource allocation design. Then, we use tools from queuing theory to model a system in which a set of URLLC users are connected simultaneously to two base stations having the same bandwidth; we refer to this scenario as the homogenous case. We introduce suitable scheduling policies and evaluate their respective performances by assessing their reliability. Next, we extend the homogenous case's results to a more general setting where the physical interfaces manage different bandwidths, referred to as the heterogeneous case. Finally, we merge the above elements to validate the choice of resource allocation schemes considering the deployed architecture

Mestrado em Engenharia Electrónica e Telecomunicações
A proliferação massiva das comunicações sem os faz prever que o número de utilizadores aumente exponencialmente até 2020, o que tornar a necessário um suporte de tráfego milhares de vezes superior e com ligações na ordem dos Gigabit por segundo. Este incremento exigir a um aumento significativo da e ciência espectral e energética. Impõe-se portanto, uma mudança de paradigma dos sistemas de comunicação sem os convencionais, imposta pela introdução da 5a geração. Para o efeito, e necessário desenvolver novas e promissoras técnicas de transmissão, nomeadamente a utilização de ondas milimétricas em sistemas com um número massivo de antenas. No entanto, consideráveis desafios emergem ao adotar estas técnicas. Por um lado, este tipo de ondas sofre grandes dificuldades em termos de propagação. Por outro lado, a adoção de arquiteturas convencionais para sistemas com um número massivo de antenas e absolutamente inviável, devido ao custo e ao nível de complexidade inerentes. Isto acontece porque o processamento de sinal ao nível da camada f sica e maioritariamente feito em banda base, ou seja, no domínio digital requerendo uma cadeia RF por cada antena. Neste contexto as arquiteturas híbridas são uma proposta relativamente recente que visa simplificar a utilização de um grande número de antenas, dividindo o processamento entre os domínios analógico e digital. Para além disso, o número de cadeias RF necessárias e bastante inferior ao número total de antenas do sistema, contribuindo para obvias melhorias em termos de complexidade, custo e energia consumida. Nesta dissertação e implementada uma arquitetura híbrida para ondas milimétricas, onde cada cadeia RF está apenas conectada a um pequeno conjunto de antenas. E considerado um sistema contendo um transmissor e um recetor ambos equipados com um grande número de antenas e onde, o número de cadeias RF e bastante inferior ao número total de antenas. Pré-codificadores híbridos analógico/digital, recentemente propostos na literatura são utilizados e novos equalizadores híbridos analógico/digital são projetados. E feita uma avaliação de performance à arquitetura implementada e posteriormente comparada com uma outra arquitetura, onde todas as antenas estão conectadas a todas as cadeias RF.
The expected massive proliferation of wireless systems points out an exponential increase in the number of users until 2020, which is needed to support up to one thousand times more tra c and connections in order of Gigabit per second. However, these goals require a signi cantly improvement in the spectral and energy e ciency. As a result, it is essential to make a paradigm shift in conventional wireless systems, imposed by the introduction of fth generation (5G). For this purpose, new and promising transmission techniques will be needed, namely the use of millimeter Waves (mmWave) in systems with a massive number of antenna elements. Nevertheless, considerable challenges emerge in the adoption of these techniques. On one hand, mmWave su er great di culties in terms of propagation. On the other hand, the using of conventional architectures for systems with a large number of antennas is absolutely impracticable because of the costs and the level of complexity. This happens because the signal processing in physical layer is mostly done in baseband, which means, that one RF chain for each antenna is required. In this context the hybrid architectures are a relatively recent proposal where the aim is to simplify the use of a large number of antenna elements, dividing the processing between the analog and digital domains. Moreover, the number of RF chains needed are much lower than the total number of antenna elements of the system, which contribute to obvious improvements in terms of complexity, costs and energy consumption. In this Dissertation a hybrid mmWave based architecture, where each RF chain is only connected to a small set of antennas, is implemented. It is considered a system comprising a transmitter and a receiver both equipped with a massive number of antennas and where the number of RF chains is much lower than the number of antennas. Hybrid analog/digital precoders recently proposed in the literature are used and a new hybrid analog/digital equalizer is designed. The implemented architecture is then evaluated and compared with other architecture, where all the antennas are connected to all RF chains.

Yes
A planar dual-polarized phased array is proposed for 5G cellular communications. The array has the properties of dual-polarization, wideband and quasi end-fire radiation, which is printed on one side of a single-layer substrate. The design contains two 8-element sub-arrays including horizontally polarized end-fire dipole antennas and vertically polarized end-fire periodic slot antennas, employed on the PCB ground plane of the 5G mobile platform. Both sub-arrays provide wide bandwidth to cover 28 and 38 GHz (promising 5G candidate bands). The -10 dB impedance bandwidth of the proposed CPW-fed dipole and slot antennas are 26.5-39.5 GHz and 27.1-45.5 GHz, respectively. Moreover, for -6 dB impedance bandwidth, these values could be more than 20 GHz (24.4-46.4 GHz for the dipole antenna) and 70 GHz (22.3-95 GHz for the slot antenna). The fundamental characteristics of the proposed dual-polarized 5G antenna array in terms of the impedance bandwidth, realized gain, polarization, radiation pattern, and beam steering are investigated and good results are obtained. The clearance of the proposed dual-polarized 5G antenna array is less than 4.5 mm which is sufficient for cellular applications.
This work is partially supported by the InnovationsFonden project of Reconfigurable Arrays for Next Generation Efficiency (RANGE), AAU Young Talent Program, and European Union’s Horizon 2020 research and innovation programme under grant agreement H2020-MSCA-ITN-2016SECRET-722424.

Multiple antennas at each side of the communication channel seem to be vital for future wireless communication systems. Multi-antenna communication provides throughput gains roughly proportional to the smallest number of antennas at the communicating terminals. On the other hand, multiple antennas at a terminal inevitably increase the hardware complexity of the latter. For efficient design of such systems relevant mathematical tools, capable of capturing the most significant features of the wireless multi-antenna channel - such as fading, spatial correlation, interference - are essential. This thesis, based on the asymptotic methods from statistical physics and random matrix theory, develops a series of asymptotic approximations for various metrics characterizing the performance of multi-antenna systems in different settings. The approximations become increasingly precise as the number of antennas at each terminal grows large and are shown to significantly simplify the performance analysis. This, in turn, enables efficient performance optimization, which would otherwise be intractable. After a general introduction, provided in Chapter 2, this thesis provides four different applications of large-system analysis. Thus, Chapter 3 analyzes multi-antenna multiple-access channel in the presence of non-Gaussian interference. The obtained large-system approximation of the sum rate is further used to carry out the precoder optimization routine for both Gaussian and finite-alphabet types of inputs. Meanwhile, Chapter 4 carries out the large-system analysis for a multi-hop relay channel with an arbitrary number of hops. Suboptimality of some conventional detectors has been captured through the concept of generalized posterior mean estimate. The obtained decoupling principle allows performance evaluation for a number of conventional detection schemes in terms of achievable rates and bit error rate. Chapter 5, in turn, studies achievable secrecy rates of multi-antenna wiretap channels in three different scenarios. In the quasi-static scenario, an alternating-optimization algorithm for the non-convex precoder optimization problem is proposed. The algorithm is shown to outperform the existing solutions, and it is conjectured to provide a secrecy capacity-achieving precoder. In the uncorrelated ergodic scenario, a large-system analysis is carried out for the ergodic secrecy capacity yielding a closed-form expression. In the correlated ergodic scenario, the obtained large-system approximation is used to address the corresponding problem of precoder optimization. Finally, Chapter6 addresses a practical case of random network topology for two scenarios: i) cellular mobile networks with randomly placed mobile users and ii) wiretap channel with randomly located eavesdroppers. Large-system approximations for the achievable sum rates are derived for each scenario, yielding simplified precoder optimization procedures for various system parameters.

QC 20140901

At present, the current 4G systems provide a universal platform for broadband mobile services; however, mobile traffic is still growing at an unprecedented rate and the need for more sophisticated broadband services is pushing the limits on current standards to provide even tighter integration between wireless technologies and higher speeds. This has led to the need for a new generation of mobile communications: the so-called 5G. Although 5G systems are not expected to penetrate the market until 2020, the evolution towards 5G is widely accepted to be the logical convergence of internet services with existing mobile networking standards leading to the commonly used term “mobile internet” over heterogeneous networks, with several Gbits/s data rate and very high connectivity speeds. Therefore, to support highly increasing traffic capacity and high data rates, the next generation mobile network (5G) should extend the range of frequency spectrum for mobile communication that is yet to be identified by the ITU-R. The mm-wave spectrum is the key enabling feature of the next-generation cellular system, for which the propagation channel models need to be predicted to enhance the design guidance and the practicality of the whole design transceiver system. The present work addresses the main concepts of the propagation channel behaviour using ray tracing software package for simulation and then results were tested and compared against practical analysis in a real-time environment. The characteristics of Indoor-Indoor (LOS and NLOS), and indoor-outdoor (NLOS) propagations channels are intensively investigated at four different frequencies; 5.8 GHz, 26GHz, 28GHz and 60GHz for vertical polarized directional, omnidirectional and isotropic antennas patterns. The computed data achieved from the 3-D Shooting and Bouncing Ray (SBR) Wireless Insite based on the effect of frequency dependent electrical properties of building materials. Ray tracing technique has been utilized to predict multipath propagation characteristics in mm-wave bands at different propagation environments. Finally, the received signal power and delay spread were computed for outdoor-outdoor complex propagation channel model at 26 GHz, 28 GHz and 60GHz frequencies and results were compared to the theoretical models.

Support of many different services, approximately 1000x increase of current data rates, ultra-reliability, low latency and energy/cost efficiency are among the demands from upcoming 5G standard. In order to meet them, researchers investigate various potential technologies involving different network layers and discuss their trade-offs for possible 5G scenarios. Waveform design is a critical part of these efforts and various alternatives have been heavily discussed over the last few years. Besides that, wireless technology is expected to be deployed in many critical applications including the ones involving with daily life activities, health-care and vehicular traffic. Therefore, security of wireless systems is also crucial for a reliable and confidential deployment. In order to achieve these goals in future wireless systems, physical layer (PHY) algorithms play a vital role not only in waveform design but also for improving security. In this dissertation, we draft the ongoing activities in PHY in terms of waveform design and security for providing spectrally efficient and reliable services considering various scenarios, and present our algorithms in this direction. Regarding the waveform design, orthogonal frequency division multiplexing (OFDM) is mostly considered as the base scheme since it is the dominant technology in many existing standards and is also considered for 5G new radio. We specifically propose two approaches for the improvement of OFDM in terms of out-of-band emission and peak to average power ratio. We also present how the requirements of different 5G RAN scenarios reflect on waveform parameters and explore the motivations behind designing advanced frames that include multiple waveforms with different parameters, referred to as numerologies by the 3GPP community, as well as the problems that arise with such coexistence. On the security aspect, we firstly consider broadband communication scenarios and propose practical security approaches that suppress the cyclic features of OFDM and single carrier-frequency domain equalization based waveforms and remove their vulnerability to the eavesdropping attacks. Additionally, an authentication mechanism in PHY is presented for wireless implantable medical devices. Thus, we address the security issues for two critical wireless communication scenarios in PHY to contribute a confidential and reliable deployment of wireless technologies in the near future.

Les réseaux véhiculaires constituent une classe de réseaux mobiles à part entière présentant l’originalité de permettre aux véhicules de communiquer les uns avec les autres dans le cadre d'une mobilité spatiale élevée ainsi qu’avec les réseaux cellulaires et les réseaux de communication déployés sur l’infrastructure routière. En vue de supporter les communications des véhicules autonomes de niveau 5, ces réseaux doivent offrir une QoS adaptée aux contraintes temporelles critiques des communications tout en garantissant un haut niveau d’intégrité des données échangées. La technologie LTE utilisée dans les réseaux mobiles cellulaires et qui est dotée d’un cadre rigoureux de QoS a été choisie par le 3GPP (Release 14) pour la communication dans les réseaux véhiculaires sous la référence LTE-V2X/ cellular V2X. La Release 14 introduit deux modes (3,4) de communication LTE spécialement conçus pour les communications V2V. Dans le mode 3, la sélection des canaux radios est gérée par la station de base eNodeB. Dans le mode 4, les véhicules sélectionnent leurs ressources radio d’une manière autonome indépendamment de toute couverture du réseau cellulaire. Dans la littérature, différents algorithmes d’allocation de ressources pour les modes 3 et 4 ont été proposés.Dans la première partie de la thèse, on s’intéresse au mode 3 qui répond aux besoins du monitoring des véhicules autonomes de niveau 5 par l’infrastructure déployée sur la route et dans le Cloud. Une étude exhaustive des propositions existantes dans littérature montre que la majorité des solutions proposées ne traitent que les messages périodiques (non-safety ex. CAM) tout en assurant un minimum de sécurité. Donc, nous avons introduit les messages apériodiques (safety ex. DENM) qui sont générés dans des situations critiques (accident, bouchon). Nous avons proposé une politique d'allocation des ressources basée sur un système de priorité avec la garantie stricte d'une capacité minimale pour les applications critiques et un partage dynamique de la capacité restante avec les autres applications. Nous avons proposé également une nouvelle technique de réutilisation des ressources pour les deux types de messages (critiques et moins critiques) qui permet d’utiliser efficacement la capacité du réseau tout en satisfaisant les exigences des applications critiques sans pénaliser les applications moins critiques.La technologie LTE-V présente une étape importante vers le réseau V2X/5G. Ce réseau 5G offre, par le biais de l’URLLC, une haute intégrité et une faible latence pour les applications temps réel critiques. De plus, avec le concept du « Network Slicing », l’architecture fonctionnelle du réseau 5G offre la portabilité du réseau véhiculaire avec ses services à côté d’autres réseaux de services au sein du réseau mobile 5G. Nous avons choisi d’intégrer l’architecture du réseau véhiculaire 5G dans un même slice au niveau du réseau d’accès ce qui permet de bénéficier du gain statistique en termes de l’utilisation des ressources radios. On s'est intéressé aux couches MAC et physique NR. Nous avons étudié l’allocation dynamique des ressources radios entre les communications URLLC critiques et les communications de streaming portés dans un même Slice. L’ordonnanceur utilisé pour l’allocation des ressources est spécifié pour gérer dynamiquement les ressources spectrales entre les flux URLLC critiques et les flux de streaming échangés entre véhicules et les serveurs d’applications. Nous avons proposé plusieurs modèles statistiques de flux échangés et analysé par simulation la QoS offerte dans le réseau d’accès aux flux critiques/streaming. Nous avons également proposé un modèle analytique markovien quasi-exact de la traversée des couches MAC/Physique du flux URLLC avec comme objectif de dimensionner un mécanisme de contrôle d’admission (CAC) des flux critiques dans le slice et de garantir la QoS requise par ces flux
Vehicular networks are a class of mobile networks allowing vehicles to communicate with each other in the context of high spatial mobility, as well as with cellular networks and communication networks deployed on the road infrastructure. In order to support Level 5 autonomous vehicle communications, these networks need to provide a QoS that addresses the time-critical constraints of communications while ensuring a high level of integrity of the data exchanged. The LTE technology, used in cellular mobile networks with a strict QoS, has been selected by 3GPP (Release 14) for communication in vehicular networks under the reference LTE-V2X/ cellular V2X. Release 14 introduces two modes (3,4) of LTE communication specifically designed for V2V communication. In mode 3, radio channel selection is managed by the eNodeB base station. In Mode 4, vehicles select their radio resources autonomously regardless of any cellular network coverage. In the literature, different resource allocation algorithms for modes 3 and 4 have been proposed.In the first part of the thesis, we focus on mode 3 addressing the requirements of monitoring level 5 autonomous vehicles through the infrastructure deployed on the road and in the Cloud. An exhaustive study of the existing proposals in the literature shows that the majority of the proposed solutions only deal with periodic messages (non-safety e.g. CAM) while ensuring a minimum of security. Therefore, we introduced aperiodic messages (safety ex. DENM) which are generated in critical situations (accident, traffic jam). We proposed a resource allocation policy based on a priority system with a strict guarantee of minimum capacity for critical applications and a dynamic sharing of the remaining capacity with other applications. We also proposed a new resource reuse technique for both types of messages (critical and less critical) that allows efficient use of network capacity while satisfying the requirements of critical applications without affecting less critical applications.LTE-V technology presents an important step towards the V2X/5G network. This 5G network offers, through URLLC, high integrity and low latency for real-time critical applications. Furthermore, with the concept of "Network Slicing", the functional architecture of the 5G network offers the portability of the vehicular network with its services alongside other service networks within the 5G mobile network. We have chosen to integrate the 5G vehicular network architecture in the same slice at the access network level which allows to benefit from the statistical gain in terms of radio resources utilization. We focused on the MAC and physical NR layers. We studied the dynamic allocation of radio resources between critical URLLC communications and streaming communications carried in the same Slice. The scheduler used for resource allocation is specified to dynamically manage spectral resources between critical URLLC flows and streaming flows exchanged between vehicles and application servers. We proposed several statistical models of exchanged flows and analyzed by simulation the QoS offered in the access network to critical/streaming flows. We have also proposed a quasi-exact Markovian analytical model of the MAC/Physical layer traversal of the URLLC flow with the objective of dimensioning an admission control mechanism (CAC) of the critical flows in the slice and to guarantee the QoS required by these flows

La demande toujours croissante de connectivité et de débit de données requiert une rupture dans la conception des futurs réseaux de communication et systèmes radio. Plusieurs applications émergentes en bande millimétrique, notamment les réseaux mobiles de cinquième génération (5G) et les communications satellites, exigent des antennes large bande qui assurent une grande couverture angulaire, tout en étant à la fois compactes, facilement intégrables et à bas coût.Cette thèse propose des systèmes antennaires multifaisceaux large bande et à très grande couverture angulaire, appelés «Continuous Transverse Stub Antenna» (CTS), pour réaliser un bon compromis de l’ensemble de ces objectifs. L’architecture de l’antenne comprend un réseau de fentes longues excitées par un réseau d’alimentation en chandelier, basé sur des guides d’onde à plans parallèles. Cette structure est excitée par un formateur de faisceaux quasi-optique co-intégré. La première partie du manuscrit présent des nouveaux modèles numériques qui facilitent la conception de chaque sous-système de l’antenne et permettent l’analyse des performances globales, soit en termes d’adaptation, soit en termes de diagrammes de rayonnement. Ces outils sont exploités pour la conception d’antenne et pour étudier les limites en balayage. La thèse se poursuit en présentant de nouvelles solutions technologiques et de nouveaux design pour intégrer les antennes CTS dans des modules multicouches planaires et à faible profil. La conception et la caractérisation de deux antennes intégrées en technologie LTCC pour des points d’accès 5G à 60 GHz sont discutées. L’une des deux est à faisceau fixe, l’autre est à balayage électronique, avec une couverture de ±40°, de faibles lobes secondaires et un niveau élevé de recoupement des faisceaux. Enfin, nous proposons l’association de radomes polarisants planaires à faible profil aux antennes CTS, pour réaliser des systèmes rayonnants en polarisation circulaire. Une méthodologie systématique pour la conception de polarisateurs à très large bande est présentée, ainsi qu’un design couvrant entièrement la bande Ka pour des applications satellites
The ever-growing demand for fast and seamless connectivity shows the need of new wireless standards and technologies. Novel broadband, wide-angle scanning antennas achieving an optimal trade-off among size, gain, efficiency and costs are crucial to the development of emerging applications at millimeter waves, such as fifth-generation (5G) mobile networks and satellite communications. In this thesis, multibeam parallel-fed continuous transverse stub (CTS) array antennas are proposed as possible candidates for future mm-wave communications and are developed to tackle these requirements. The antenna architecture comprises an array of long slots, a corporate feed network based on parallel plate waveguides (PPWs) and an integrated quasi-optical beamformer. First, novel numerical models for the analysis of each subsystem and of the overall antenna, are presented, which enable an efficient and modular design of CTS antennas. These tools are exploited to derive design guidelines and assess the scanning performance. Then, novel design and technological solutions for the integration of CTS antennas in flat, low-profile multilayer modules are discussed. The design and characterization of two prototypes in LTCC technology, for 60-GHz mobile access points are presented: a fixed beam array and a switched-beam antenna with a field of view of ±40°, low SLLs and high beam overlap. Finally, planar linear-to-circular polarization converters are proposed to realize circularly polarized CTS antenna systems. A procedure to achieve an ultra-wideband, low-loss polarization conversion is outlined and a design for Ka-band satellite application is presented

Dans cette thèse, nous nous adressons le problème du contrôle de systèmes multi-agents connectés via des modèles réalistes de systèmes de communication. Nous traitons principalement les systèmes de véhicules connectés et automatisés (CAVs) communiquant via des systèmes de communication 5G qui permettent deux types de communication : la communication directe entre les nœuds, connue sous le nom de communication véhicule-à-véhicule (V2V), et la communication à travers l'infrastructure réseau, qui est la manière traditionnelle de communiquer dans les réseaux cellulaires.La thèse traite de trois problèmes : premièrement, nous analysons les propriétés de stabilité et de convergence de l'algorithme du consensus pour agents d'intégrateurs du premier ordre en utilisant un schéma d'accès multiple par répartition temporelle (TDMA) pour partager les ressources du réseau d'un canal de communication partagé. La stabilité exponentielle du système considéré est démontrée, et une borne explicite dépendant des paramètres du système de communication est fournie pour estimer la vitesse de convergence. Ensuite, nous abordons le problème du contrôle de formation d'un groupe de véhicules connectés dans un contexte de communication 5G. Nous proposons un algorithme d'allocation de ressources pour sélectionner les utilisateurs émetteurs afin d'atteindre la formation souhaitée tout en respectant les contraintes imposées par le couche de communication. Enfin, nous étudions les propriétés de stabilité des filtres de Kalman pour les systèmes hybrides, précisément, des systèmes avec une dynamique en temps continu observée à travers des mesures en temps discret. La stabilité d'entrée-à-état (ISS) est démontrée pour de tels systèmes en utilisant une fonction de Lyapunov appropriée. Ce résultat peut être considéré comme une première étape dans l'analyse de la robustesse du système global, car il permet de prendre en compte les effets des erreurs de communication sur la stabilité du système contrôlé
In this thesis, we address the problem of control of multi-agent systems connected over realistic models of communication systems. We mainly focus on systems of connected and automated vehicles (CAVs) that communicate through a 5G communication system, which allows two types of communication: direct communication between nodes, known as Vehicle-to-Vehicle (V2V) communications, and communication through the network infrastructure, which is the traditional way of communication in cellular networks.The thesis discusses three problems: first, we analyze the stability and convergence properties of the consensus algorithm of first-order integrator agents using a time-division multiple access (TDMA) scheme to share the network resources of a broadcast shared communication channel. Exponential stability of the considered system is proved, and an explicit bound depending on the communication system parameters is provided to estimate the convergence rate. Second, we treat the problem of formation control of a float of connected vehicles in a 5G communication context. We propose a resource allocation algorithm to select the transmitting users to achieve the desired formation while satisfying the constraints imposed by the communication system. Finally, we study the stability properties of Kalman filters for hybrid systems, i.e., systems with continuous-time dynamics observed through discrete-time measurements. Input-to-state stability (ISS) is proved for such systems relying on an appropriate Lyapunov function. This result can be considered as a first step in the robustness analysis of the overall system since it allows to treat the effects of communication errors on the controlled system stability

In Beyond 5G technologies, Terahertz communications will be used: frequency bands between 100 GHz and 10 THz will be exploited in order to have higher throughput and lower latency. Those frequency bands suffer from several impairments, and it is thought that phase noise is one of the most significant. Orthogonal Chirp Division Multiplexing (OCDM) might be used in Beyond 5G communications, thanks to its robustness to multipath fading: it outperforms Orthogonal Frequency Division Multiplexing (OFDM) systems. The aim of this thesis is to find a suitable model for describing phase noise in Terahertz communications, and to study the performance of an OCDM system affected by this impairment. After this, a simple compensation scheme is introduced, and the improvement that it provides is analysed. The thesis is organized as follow: in the first chapter Terahertz communications and Beyond 5G are introduced, in the second chapter phase noise is studied, in the third chapter OCDM is analysed, and in the fourth chapter numerical results are presented.