Wireless interference networks refer to communication systems in which multiple source–destination pairs share the same transmission medium, and each source’s transmission interferes with the reception at non-intended destinations. Optimizing the transmission of each source–destination pair is interrelated with that of the other pairs, and characterizing the performance limits of these networks is a challenging task. Solving the problem of managing the interference and data communications for these networks would potentially make it possible to apply solutions to several existing and emerging communication systems. Wireless devices can carefully coordinate the use of scarce radio resources in order to deal effectively with interference and establish successful communications. In order to enable coordinated transmission, terminals must usually have a certain level of knowledge about the propagation environment; that is, channel state information (CSI). In practice, however, no CSI is a priori available at terminals (transmitters and receivers), and proper channel training mechanisms (such as pilot-based channel training and channel state feedback) should be employed to acquire CSI. This requires each terminal to share available radio resources between channel training and data transmissions. Allocating more resources for channel training leads to an accurate CSI estimation, and consequently, a precise coordination. However, it leaves fewer resources for data transmissions. This creates the need to investigate optimum resource allocation. This thesis investigates an information-theoretic approach towards the performance analysis of interference networks, and employs signal processing techniques to design transmission schemes for achieving these limits in the following scenarios. First, the smallest interference network with two single-input single-output (SISO) source–destination pairs is considered. A fixed-rate transmission is desired between each source–destination pair. Transmission schemes based on point-to-point codes are developed. The transmissions may not always attain successful communication, which means that outage events may be declared. The outage probability is quantified and the ε-outage achievable rate region is characterized. Next, a multi-user SISO interference network is studied. A pilot-assisted ergodic interference alignment (PAEIA) scheme is proposed to conduct channel training, channel state feedback, and data communications. The performance limits are evaluated, and optimum radio resource allocation problems are investigated. The analysis is extended to multi-cell wireless interference networks. A low-complexity pilot-assisted opportunistic user scheduling (PAOUS) scheme is proposed. The proposed scheme includes channel training, one-bit feedback transmission, user scheduling and data transmissions. The achievable rate region is computed, and the optimum number of cells that should be active simultaneously is determined. A multi-user MIMO interference network is also studied. Here, each source sends multiple data streams; specifically, the same number as the degrees of freedom of the network. Distributed transceiver design and power control algorithms are proposed that only require local CSI at terminals. / <p>QC 20141201</p>

Les communications sans fils sont devenues un outil fondamental pour les sociétés modernes. Les réseaux cellulaires sont le moyen préféré pour l’accès à Internet. L’augmentation de la capacité du réseau est étroitement liée au problème des interférences. Les réseaux coopératifs ont été largement étudiés dans les années récentes. Cette thèse porte sur deux techniques de coopération dans la voie descendante :La première partie étudie les effets de quantification et délais sur les informations de retour nécessaires pour la mise en opération des différentes techniques d’émission coordonnée, connues sous le nom de CoMP (Coordinated Multipoint Transmission). Cette technique qui promet des augmentations importantes sur la capacité du réseau en conditions idéales, or ses vrais résultats sous le feedback limité doivent être encore décrits de manière analytique. En particulier, pour les modes d’émission connus comme JT (Joint Transmission) et CBF (Coordinated Beamforming), des expressions analytiques ont été déduites pour calculer la capacité du réseau et la probabilité de succès de transmission.Finalement une nouvelle technique de coopération de réseau pour les récepteurs avancés du type SIC (Successive Interference Cancellation) est présentée. La condition mathématique qui garantit des gains de capacité grâce à l’utilisation des récepteurs SIC est obtenue. Pour en profiter, une méthode de coopération est nécessaire pour assurer une adaptation de lien adéquate pour que l’interférence soit décodable et le débit somme soit supérieur à celui atteint avec des récepteurs traditionnels. Cette technique montre des gains importants de capacité pour des utilisateurs en bordure de cellule. / Wireless communications have become a fundamental feature of any modern society. In particular, cellular networks are essential for societal welfare but the increasing demand for data traffic set enormous scientific challenges. Increasing the network capacity is closely related to the problem of interference mitigation. In this regard, network cooperation has been studied in recent years and several different techniques have been proposed. In the first part, different transmission techniques commonly referred to as Coordinated Multi-Point Transmission (CoMP), are studied under the effect of feedback quantization and delay, unequal pathloss and other-cell interference (OCI). An analytical framework is provided, which yields closed-form expressions to calculate the ergodic throughput and outage probabilities of Coordinated Beamforming (CBF) and Joint Transmission (JT). The results indicate the optimal configuration for a system using CoMP and provide guidelines and answers to key questions, such as how many transmitters to coordinate, how many antennas to use, how many users to serve, which SNR regime is more convenient, whether to apply CBF or prefer a more complex JT, etc. Second, a new coordination technique at the receiver side is proposed to obtain sum-rate gains by means of Successive Interference Cancellation (SIC). The conditions that guarantee network capacity gains by means of SIC at the receiver are provided. To take advantage of these conditions, network coordination is needed to adapt the rates to be properly decoded at the different users involved. This technique is named Cooperative SIC and is shown to provide significant throughput gains for cell-edge users.