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Avec l’émergence rapide des applications Internet, il est prévu que le trafic mobile mondial augmente de huit fois entre fin 2018 et 2022. En même temps, les futurs systèmes de communication se devront aussi d’améliorer l'efficacité spectrale des transmissions, le temps de latence et l’équité entre utilisateurs. À cette fin, une technique d’accès multiple non orthogonal (NOMA) a été récemment proposée comme un candidat prometteur pour les futurs accès radio. La technique NOMA est basée sur un nouveau domaine de multiplexage, le domaine des puissances. Elle permet la cohabitation de deux ou plusieurs utilisateurs par sous-porteuse ou sous-bande de fréquence. Cette thèse aborde plusieurs problèmes liés à l’allocation de ressources basée sur NOMA afin d'améliorer les performances du réseau en termes d'efficacité spectrale, de débit et/ou d’équité entre utilisateurs. Dans ce sens, des solutions théoriques et algorithmiques sont proposées et des résultats numériques sont obtenus afin de valider les solutions et de vérifier la capacité des algorithmes proposés à atteindre des performances optimales ou sous-optimales. Après une étude bibliographique des différentes techniques d’allocation de ressources présentée dans le premier chapitre, on propose dans le deuxième chapitre plusieurs stratégies d’allocation de ressource où une réduction de la bande utilisée par les utilisateurs est ciblée. Les résultats de simulation montrent que les stratégies proposées améliorent à la fois l’efficacité spectrale et le débit total des utilisateurs par rapport aux systèmes basés uniquement sur des techniques d’accès orthogonales. Quant au troisième chapitre, il étudie la performance du Proportional Fairness (PF) Scheduler tout en considérant que la bande passante est disponible en totalité. Dans ce sens, plusieurs améliorations basées sur le PF sont proposées, qui offrent au système NOMA des avantages en termes de débit, d’équité entre utilisateurs et de qualité de service. Dans le quatrième chapitre, nous proposons plusieurs techniques d’allocation de ressources qui donnent aux utilisateurs la possibilité de favoriser le débit par rapport à l’équité entre utilisateurs et vice versa. Dans le dernier chapitre, différentes techniques permettant une transmission hybride broadcast/broadband sur la même bande de fréquence sont proposées et comparées à l’état de l’art. / With the proliferation of Internet applications, between the end of 2016 and 2022, total mobile traffic is expected to increase by 8 times. At the same time, communications networks are required to further enhance system efficiency, latency, and user fairness. To this end, non-orthogonal multiple access (NOMA) has recently emerged as a promising candidate for future radio access. By exploiting an additional multiplexing domain, the power domain, NOMA allows the cohabitation of two or more users per subcarrier, based on the principle of signal superposition. This dissertation addresses several radio resource allocation problems in mobile communication systems, in order to improve network performance in terms of spectral efficiency, through put, or fairness. Theoretical analysis and algorithmic solutions are derived. Numerical results are obtained to validate our theoretical findings and demonstrate the algorithms ability of attaining optimal or sub-optimal solutions. To this direction, the second chapter of this thesis investigates several new strategies for the allocation of radio resources (bandwidth and transmission power) using NOMA principle, where the minimization of the total amount of used bandwidth is targeted. Extensive simulation results show that the proposed strategies for resource allocation can improve both the spectral efficiency and the cell-edge user throughput, especially when compared to schemes employing only orthogonal signaling. A context where the total bandwidth is available has also been studied, in the 3rd chapter where we investigate the performance of the proportional fairness (PF) scheduler, and we propose modifications to it, at the level of user scheduling and power allocation that show to improve the system capacity, user fairness and QoS. In the 4th chapter, we proposed new pairing metrics that allow to favor the fairness at the expense of the throughput and vice versa. The proposed metrics show enhancements at the level of system capacity, user fairness, and computational complexity. Different techniques that allow a hybrid broadcast/multicast transmission on the same frequency platform are proposed in the last chapter and compared to the state of the art.

<p>The use of relays is seen as a promising way to extend cell coverage and increase rates in LTE Advanced networks. Instead of increasing the number of base stations (BS), relays with lower cost could provide similar gains. A relay will have a wireless link to the closest BS as only connection to the core network and will cover areas close to the cell edge or other areas with limited rates.</p><p>Performing transmissions in several hops (BS-relay & relay-user) requires more radio resources than using direct transmission. This thesis studies how the available radio resources should be allocated between relays and users in order to maximize throughput and/or fairness. Time and frequency multiplexed backhaul is investigated under a full buffer traffic assumption. It is shown that the system will be backhaul limited and that the two ways of multiplexing will perform equally when maximising throughput and/or fairness. The analysis results in a set of throughput/fairness suboptimal solutions, dependant on how many relays are used per cell. The results are verified by simulations, which also show the limiting effects on throughput caused by interference between relays.</p><p>It is also analysed how the resource allocation should be done given non-fullbuffer traffic. A resource allocation that minimises packet delay given a certain number of relays per cell is presented. The analysis is based on queuing theory.</p><p>Finally some different schedulers and their suitability for relay networks are discussed. Simulation results are shown, comparing the throughput and fairness of Round Robin, Weighted Round Robin, Proportional Fairness and Weighted Proportional Fairness schemes. It is shown that allocating the resource among the relays according to the number of users served by the relays improves the fairness.</p>

The use of relays is seen as a promising way to extend cell coverage and increase rates in LTE Advanced networks. Instead of increasing the number of base stations (BS), relays with lower cost could provide similar gains. A relay will have a wireless link to the closest BS as only connection to the core network and will cover areas close to the cell edge or other areas with limited rates. Performing transmissions in several hops (BS-relay &amp; relay-user) requires more radio resources than using direct transmission. This thesis studies how the available radio resources should be allocated between relays and users in order to maximize throughput and/or fairness. Time and frequency multiplexed backhaul is investigated under a full buffer traffic assumption. It is shown that the system will be backhaul limited and that the two ways of multiplexing will perform equally when maximising throughput and/or fairness. The analysis results in a set of throughput/fairness suboptimal solutions, dependant on how many relays are used per cell. The results are verified by simulations, which also show the limiting effects on throughput caused by interference between relays. It is also analysed how the resource allocation should be done given non-fullbuffer traffic. A resource allocation that minimises packet delay given a certain number of relays per cell is presented. The analysis is based on queuing theory. Finally some different schedulers and their suitability for relay networks are discussed. Simulation results are shown, comparing the throughput and fairness of Round Robin, Weighted Round Robin, Proportional Fairness and Weighted Proportional Fairness schemes. It is shown that allocating the resource among the relays according to the number of users served by the relays improves the fairness.

We investigate, in this thesis, the use of Hierarchical Modulation (HM), a physical layer technique that enables to exploit multiuser diversity, for resource allocation in OFDMA-based systems with and without use of relaying, so as to improve the system capacity. HM allows the sharing of the resources, namely subcarriers and power, between users of different radio conditions by sending an additional stream to a user with good radio conditions on a subcarrier that was initially allocated to carry an original stream to a user with lower radio conditions. And this, without affecting the original user's rate nor the total amount of power assigned to the shared subcarrier. In the literature, most of the works that consider the use of HM focus solely on the physical layer performance, notably in terms of the bit error rate. And this for a static user scenario,i.e., with a fixed number of users in the system, each with an infinite service duration. This configuration however does not reflect the real system behavior where the number of users is dynamic, i.e., the users come to the system at random time epochs and leave it after a finite duration, corresponding to the completion of their services. The study of the system at the flow-level, as opposed to the packet level, for a dynamic user configuration, enables us to investigate the realistic relationship between capacity and demand and to quantify several system-level performance metrics, such as mean transfer times and blocking rates, which are meaningful both to the user and the network operator/provider.

Nous proposons dans cette thèse d'exploiter la Modulation Hiérarchique (MH) dans un système OFDMA avec et sans utilisation des relais en vue d'améliorer d'avantage la capacité du système en tirant profit de la diversité d'utilisateurs. MH permet de transmettre un flux supplémentaire à un utilisateur de bonnes conditions radio sur une sous-porteuse initialement allouée à un utilisateur de mauvaises conditions radio. Ceci est différent des techniques classiques d’allocation de ressources proposées dans la littérature qui respectent une orthogonalité parfaite lors de l'allocation : une sous-porteuse est allouée à un seul utilisateur et aucun autre utilisateur ne pourra l'utiliser en même temps. Dans la littérature, la plupart des travaux qui se sont intéressés à l'utilisation de la MH se sont concentrés seulement sur les performances en termes de couche basse avec un nombre fixe d'utilisateurs dans le système correspondant à une configuration statique. Toutefois, cette configuration ne reflète pas la dynamicité du nombre d'utilisateurs dans un tel système, où les utilisateurs arrivent selon une loi aléatoire et partent après avoir fini leurs services. Dans cette thèse, nous exposons l'étude des performances de l'utilisation de la MH avec des configurations dynamiques d'utilisateurs correspondant à une étude au niveau flux. Cela nous permet d'évaluer les performances en termes de nouvelles métriques à savoir le temps moyen de transfert et la probabilité de blocage qui sont importantes pour l'utilisateur et pour l'opérateur. / We investigate, in this thesis, the use of Hierarchical Modulation (HM), a physical layer technique that enables to exploit multiuser diversity, for resource allocation in OFDMA-based systems with and without use of relaying, so as to improve the system capacity. HM allows the sharing of the resources, namely subcarriers and power, between users of different radio conditions by sending an additional stream to a user with good radio conditions on a subcarrier that was initially allocated to carry an original stream to a user with lower radio conditions. And this, without affecting the original user's rate nor the total amount of power assigned to the shared subcarrier. In the literature, most of the works that consider the use of HM focus solely on the physical layer performance, notably in terms of the bit error rate. And this for a static user scenario,i.e., with a fixed number of users in the system, each with an infinite service duration. This configuration however does not reflect the real system behavior where the number of users is dynamic, i.e., the users come to the system at random time epochs and leave it after a finite duration, corresponding to the completion of their services. The study of the system at the flow-level, as opposed to the packet level, for a dynamic user configuration, enables us to investigate the realistic relationship between capacity and demand and to quantify several system-level performance metrics, such as mean transfer times and blocking rates, which are meaningful both to the user and the network operator/provider.

<p>In this thesis we study radio resource management (RRM) in two types of CDMA-based wireless networks, cognitive radio networks (CRNs) and cooperative communication networks. In the networks, all simultaneous transmissions share the same spectrum and interfere with one another. Therefore, managing the transmission power is very important as it determines other aspects of the network resource allocations, such as transmission time and rate allocations. The main objective of the RRM is to efficiently utilize the available network resources for providing the mobile users with satisfactory quality of service (QoS).</p> / Doctor of Philosophy (PhD)

<p>In this thesis we study a wireless mesh network (WMN), where a number of access points (APs) form a wireless infrastructure and provide communications to the mobile stations (MSs). Different APs share the same frequency channel. We study how to provide fair throughput for the MSs while efficiently utilizing the channel resources through effective handoff management and channel timeline allocations.</p> <p>In the first part of the thesis, we assume that the channel time allocations at the AP level are given, and jointly consider the handoff management of the MSs and the channel time allocations at the MS level. An optimization problem is formulated based on long-term proportional fairness (PF) and solved. A heuristic distributed scheme is then proposed, which can be easily implemented in a practical WMN.</p> <p>In the second part, we jointly study the channel time allocations at the AP level and the MS level together with the MS handoff management. An optimization problem is first formulated and solved as a benchmark. Two distributed schemes are proposed by decoupling the handoff management and time allocations. The HO-CA scheme performs heuristic handoff decisions for the MSs and then optimizes the channel time allocations. The CA-HO scheme allocates the channel time to individual APs based on the neighboring relationship of the APs, and then makes handoff.</p> <p>Numerical results indicate that our proposed distributed schemes can achieve close-to-optimum fairness, improve the network utilization and balance the traffic load under uneven MSs geographical distributions.</p> / Master of Applied Science (MASc)

This thesis presents various studies on energy efficient design of wireless networks. It starts with a survey on recent shortest path based energy efficient routing algorithms developed for ad hoc and sensor networks, making a comprehensive classification for these algorithms. In addition to energy efficient design, sustainable and environmentally friendly deployment of wireless networks demands increased use of renewable energy. However, this calls for novel design principles to efficiently utilize the variation in the availability of the energy. The thesis continues with an investigation of state-of-the-art resource management and scheduling algorithms developed for energy harvesting wireless sensor networks. Building on the stateof- the-art, the main contribution of this thesis is to formulate and solve a utility maximizing scheduling problem in a multiuser broadcast channel with an energy harvesting transmitter. The goal is to determine the optimal power and time allocations to users between energy arrivals. The structural properties of the problem are analyzed, and its biconvexity is proved. A Block Coordinate Descent (BCD) based algorithm is developed to obtain the optimal solution. Two simple and computationally scalable heuristics, PTF and ProNTO, which mimic the characteristics of the optimal policy, are proposed. Finally, an online algorithm, PTF-On,that will bypass the need for offline knowledge about the energy harvesting statistics, is developed. PTF-On uses a Kalman filter based energy harvesting prediction algorithm, developed in this thesis, to predict the energy that will arrive in the future.