Allocation de ressources distribuée dans les réseaux OFDMA multi-cellulaires

La thèse étudie des méthodes d'allocation de ressources, distribuées par station de base (BS) dans les réseaux OFDMA multi-cellulaires. L'objectif est de fournir la Qualité de Service (QdS) requise par chaque utilisateur, quelle que soit sa localisation dans la cellule. Les travaux portent d'abord sur la coordination causale de réseaux. Deux BSs forment un lien MIMO virtuel pour les utilisateurs localisés en bordure de cellule. Ces utilisateurs bénéficient d'un gain de diversité et d'une diminution de l'interférence inter-cellulaire. L'efficacité de la méthode d'allocation de ressources associée dépend de l'équité du contrôle de puissance. En conséquence, la coordination de réseaux est utilisée pour les utilisateurs à Débit Contraint (DC), mais pas pour les utilisateurs Best Effort (BE), dans un algorithme permettant de gérer conjointement les deux objectifs de QdS. La thèse étudie ensuite les réseaux totalement distribués. Pour les utilisateurs DC, une méthode d'allocation de ressources incluant une allocation de puissance itérative est déterminée pour résoudre le problème Margin Adaptive. Cette méthode est étendue aux utilisateurs DC en MIMO, lorsque le transmetteur connaît tout l'information de canal, ou uniquement ses caractéristiques statistiques. Pour les utilisateurs BE, enfin, l'objectif est de maximiser la somme des débits pondérés, le poids de chaque utilisateur étant proportionnel à la longueur de sa file d'attente. Une méthode d'allocation de sous-porteuses, déduite d'un graphe d'interférence, et une méthode de contrôle de puissance distribuée sont proposées pour résoudre ce problème d'optimisation

Comparison of distributed space and frequency interference alignment

This paper addresses multiple access in MIMOwireless networks. It compares two distributed interferencealignment techniques, in space and in frequency, that bothaim at removing interferences through orthogonalization. Thetheoretical advantages and drawbacks of each technique arehighlighted. Then, the multiplexing gain and the computationalcomplexity are analytically evaluated. It is shown that frequencyinterference alignment achieves a higher multiplexing gain thanspace interference alignment in realistic network conditions,and always requires a lower computational complexity. Finally,the performances of both algorithms with varying number ofinterfering links are assessed via numerical simulations. Spaceinterference alignment fulfills complete interference suppression,and consequently provides the same spectral efficiency to alllinks, regardless of the number of interfering links. Frequencyinterference alignment is less efficient in terms of INR, and thespectral efficiency per link thus decreases when the number oflinks increases. Nevertheless, the spectral efficiency is alwayshigher with frequency interference alignment than with spaceinterference alignment

Allocation de ressources distribuée dans les réseaux OFDMA multi-cellulaires

La thèse étudie des méthodes d'allocation de ressources, distribuées par station de base (BS) dans les réseaux OFDMA multi-cellulaires. L'objectif est de fournir la Qualité de Service (QdS) requise par chaque utilisateur, quelle que soit sa localisation dans la cellule. Les travaux portent d'abord sur la coordination causale de réseaux. Deux BSs forment un lien MIMO virtuel pour les utilisateurs localisés en bordure de cellule. Ces utilisateurs bénéficient d'un gain de diversité et d'une diminution de l'interférence inter-cellulaire. L'efficacité de la méthode d'allocation de ressources associée dépend de l'équité du contrôle de puissance. En conséquence, la coordination de réseaux est utilisée pour les utilisateurs à Débit Contraint (DC), mais pas pour les utilisateurs Best Effort (BE), dans un algorithme permettant de gérer conjointement les deux objectifs de QdS. La thèse étudie ensuite les réseaux totalement distribués. Pour les utilisateurs DC, une méthode d'allocation de ressources incluant une allocation de puissance itérative est déterminée pour résoudre le problème Margin Adaptive. Cette méthode est étendue aux utilisateurs DC en MIMO, lorsque le transmetteur connaît tout l'information de canal, ou uniquement ses caractéristiques statistiques. Pour les utilisateurs BE, enfin, l'objectif est de maximiser la somme des débits pondérés, le poids de chaque utilisateur étant proportionnel à la longueur de sa file d'attente. Une méthode d'allocation de sous-porteuses, déduite d'un graphe d'interférence, et une méthode de contrôle de puissance distribuée sont proposées pour résoudre ce problème d'optimisation.The thesis studies resource allocation methods, distributed per base station (BS) in multi-cellular OFDMA networks. The objective is to provide the Quality of Service (QoS) requested by each user, whatever its location in the cell. First, it investigates causal network coordination in distributed networks. Two BSs form a virtual Multiple Input, Multiple Output (MIMO) array for the users located at the border of cells. These users thus benefit from a diversity gain, and from inter-cell interference mitigation. The efficiency of the associated resource allocation method depends on the fairness of the power control objective. Thus, network coordination is used for Rate Constrained (RC) users, but not for Best Effort (BE) users, in a proposed algorithm that jointly manages both QoS objectives. The thesis next considers the more general perspective of fully distributed networks. For RC users, a resource allocation process with iterative interference-based power allocation is determined to solve the Margin Adaptive problem. It includes a distributed constraint that guarantees power control convergence. The proposed method is extended to RC users in MIMO, both when full Channel State Information is available at transmission, and when only the statistical properties of the channel are available at transmission. Finally, for BE users, the objective is to maximize the weighted sum throughput, where the weight of each user is proportional to its queue length. A subcarrier allocation method, deduced from a network-wide interference graph, and a distributed power control method are proposed for that optimization problem.PARIS-Télécom ParisTech (751132302) / SudocSudocFranceF

Cooperative allocation for underlay cognitive radio systems

This paper proposes a resource allocation and decodingstrategy at the secondary systems for underlay and interweavemulti-carrier cooperative cognitive radio. The objective isto maximize the sum rate of both primary and secondary systems,taking into account the interference threshold constraint and thefact that the primary receiver always considers interference asnoise. The decoding strategy at the secondary receivers is eitherSuccessive Interference Cancellation or treating interference asnoise, depending on their channel gains. The sum rate andsecondary rates are highly improved, compared with otherresource allocation algorithms. The proposed algorithm benefitsfrom multi-user diversity when the number of secondary cellsincreases

Adaptive resource allocation and decoding strategy for underlay multi-carrier cooperative cognitive radio systems

International audienc

Power allocation for the multi-carrier two-user Gaussian Interference Channel

This paper studies the multi-carrier two-user Gaussian InterferenceChannel (G-IFC) with an adaptive strategy dependingon the channel gains. The decoding strategy at each receiver iseither Successive Interference Cancellation or treating interferenceas noise, depending on whether interference is strongor weak. The transmit strategy may also rely on FDMA whenrequired. Then, an iterative power allocation algorithm is proposedin order to maximize the sum rate when considering allcarriers jointly. By splitting power allocation at both transmitters,the initial optimization problem can be turned into aseries of convex optimization problems. The proposed algorithmconverges very rapidly and provides a sum rate increasecompared to FDMA and to a strategy where interference is alwaysconsidered as noise

Lattice-based coding scheme for MIMO bi-directional relaying with three nodes

This paper proposes a general method for bi-directional relaying with three nodes over four time intervals, composed of alternate MAC phases and broadcast phases. Different nodes transmit in MAC phases, and the data stored in broadcast phases allows decoding of all information. The physical layer network coding strategy for this relaying protocol is a lattice-based coding scheme combined with power control, so that the relay receives an integer linear combination of the nodes codewords. This strategy is analyzed for MIMO with $2$ receive and transmit antennas. Analytical expressions of the exchange rate and transmit powers under high SNR approximation are provided, and numerically validated with respect to the general SNR mode. The proposed method is then compared with Amplify-and-Forward. It is shown that lattice-based coding provides a gain of 4.5 dB in average SNR on the achievable exchange rate, and is totally fair, contrary to Amplify-and-Forward

Weigthed sum throughput maximization in multi-cell OFDMA networks

This paper addresses resource allocation forweighted sum throughput maximization (WSTM) in multicell orthogonalfrequency-division multiple-access (OFDMA) networks.Two suboptimal algorithms with polynomial-time complexity areprovided. First, we determine a graph-based subcarrier allocationalgorithm allowing joint transmission of two interferinglinks whenever such a transmission fulfills the pairwise WSTMobjective. An analytical expression of the optimal power allocationwith two interfering cells in single-carrier transmissionis obtained, and the capacity region study serves as the basis tobuild the interference graph. Second, we present a distributedpower-control algorithm suitable for any signal-to-interferenceplus-noise ratio (SINR) regime. It rejects users and subcarrierswith weighted SINR that is too low before operating in the highSINR regime for the remaining users and subcarriers. Bothalgorithms and their combination are assessed via dynamicsimulations, where the weight of each user is proportional to itsqueue length. They are shown to significantly decrease resourceconsumption and efficiently balance users? queue lengths

Wireless Telecommunication Systems

Wireless telecommunication systems generate a huge amount of interest. In the last two decades, these systems have experienced at least three major technological leaps, and it has become impossible to imagine how society was organized without them. In this book, we propose a macroscopic approach on wireless systems, and aim at answering key questions about power, data rates, multiple access, cellular engineering and access networks architectures.We present a series of solved problems, whose objective is to establish the main elements of a global link budget in several radiocommunications systems