Optimal Power and Resource Allocation for Transmit Power Minimization in OFDMA-based NOMA Networks

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Convection de Rayleigh Bénard dans l’He3 au voisinage du point critique

On étudie les scenarii de transition pour l’écoulement 2D de type Rayleigh Bénard dans l’He3 au voisinage de son point critique. Il s’agit d’une approche : à la fois théorique de stabilité linéaire et par simulation numérique directe. Pour le numérique on utilise une approximation de type anélastique des équations de Navier-Stokes compressibles et une loi d’état paramétrique. Quatre scenarii possibles de transition et la structuration spatiale des modes d’instabilité sont déterminés

Utilisation de la Radio Intelligente pour un Réseau Mobile à Faible Consommation d’Energie

The reduction of the carbon footprint of human activities is one of the current major economic and ecological challenges. Communication networks have a dual role in this reduction. On one hand,mobile networks, and in particular the base stations, are nowadays an important energy consumer. It is, thus, necessary to optimize their behavior in order to reduce their carbon footprint. On the other hand,some communication networks are necessary to better manage the electrical grid. Thanks to this bettermanagement, it is possible to improve the proportion of electricity produced by renewable energy sources.In this thesis, we look at both aspects. In a first step, we propose a solution to reduce the energy consumption of wireless mobile networks. For that purpose, we propose algorithms that optimize the power allocation when Cell Discontinuous Transmission is used by the base stations.In a second step, we propose a solution in order to improve the performance of Internet of Things networks used for the electrical grid. More precisely, we use multi-armed bandit algorithm for channel selection in IoT networks as a means of increasing the reliability of communications.La réduction de l’empreinte carbone de l’activité humaine est aujourd’hui un enjeu économique et écologique majeur. Les réseaux decommunication ont un double rôle à jouer dans cette réduction. En premier lieu, les réseaux mobiles, et en particulier les stations de base, sont un gros consommateur d’électricité. Il est donc nécessaire d’optimiser leur fonctionnement pour réduire leur empreinte carbone. Ensuite, des réseaux de communication sont désormais nécessaires pour mieux gérer la production d’électricité et ainsi pouvoir augmenter la proportion d’électricité produite par des sources d’énergie renouvelables.Dans cette thèse, nous regardons ces deux aspects.Nous commençons par proposer une solution pour réduire la consommation d’énergie des réseaux mobiles. Pour cela, nous proposons des algorithmes pour optimiser l’allocation de puissance lorsque des mécanismes de mise en veille dynamique sont utilisés.Dans un second temps, nous proposons une solution pour améliorer le fonctionnement des réseaux d’objets connectés utilisés pour la gestion del’électricité. Plus précisément, nous rendons plus fiables ces communications grâce à l’utilisation d’algorithmes de bandit multibras pour l’accèsfréquentiel

A New Lower Bound on the Ergodic Capacity of Optical MIMO Channels

International audienceIn this paper, we present an analytical lower bound on the ergodic capacity of optical multiple-input multiple-output (MIMO) channels. It turns out that the optical MIMO channel matrix which couples the mt inputs (modes/cores) into mr outputs (modes/cores) can be modeled as a sub-matrix of a m × m Haar-distributed unitary matrix where m > mt, mr. Using the fact that the probability density of the eigenvalues of a random matrix from unitary ensemble can be expressed in terms of the Christoffel-Darboux kernel. We provide a new analytical expression of the ergodic capacity as function of signal-to-noise ratio (SNR). Moreover, we derive a closed-form lower-bound expression to the ergodic capacity. In addition, we also derive an approximation to the ergodic capacity in low-SNR regimes. Finally, we present numerical results supporting the expressions derived

Upper and lower bounds for the ergodic capacity of MIMO Jacobi fading channels

International audienceIn multi-(core/mode) optical fiber communication, the transmission channel can be modeled as a complex sub-matrix of the Haar-distributed unitary matrix (complex Jacobi unitary ensemble). In this letter, we present new analytical expressions of the upper and lower bounds for the ergodic capacity of multiple-input multiple-output Jacobi-fading channels. Recent results on the determinant of the Jacobi unitary ensemble are employed to derive a tight lower bound on the ergodic capacity. We use Jensen's inequality to provide an analytical closed-form upper bound to the ergodic capacity at any signal-to-noise ratio (SNR). Closed-form expressions of the ergodic capacity, at low and high SNR regimes, are also derived. Simulation results are presented to validate the accuracy of the derived expressions

Dynamic Sleep Mode for Minimizing a Femtocell Power Consumption

International audienceThe use of power control (PC) and discontinuous transmission (DTx) can reduce the average power consumption of mobile base stations (BS). In this paper, the power consumption of a picocell or a femtocell are analyzed in a time division multiple access (TDMA) scenario. The minimization of the power consumption is viewed as a constrained optimization problem and a closed form of the compromise between transmit power and transmission time which minimizes the average power consumption is found. Moreover, we show that for a base station with a low transmit power and a sufficient power saving during sleep mode, such as picocells and femtocells, the average power consumption is minimum when the service time is minimized. Finally, numerical results show that discontinuous transmission greatly decreases the average power consumption of the base station

Mises en Veille Dynamiques pour Minimiser la Consommation d'Energie d'une Station de Base

National audienceCell DTx can reduce a base station energy consumption. We show, in this paper, that when cell DTx and power control are used, there is a trade-off between the user's instantaneous transmit power and the time during which the base station has to be switched to sleep mode in order to minimize the base station energy consumption. Furthermore, we propose an efficient algorithm which allows to find this optimum. With the proposed solution, the average base station power consumption can be reduced by 7W compared to a naive strategy. This accounts for 4% of the total base station energy consumption.La mise en veille dynamique des stations de base (cell DTx en anglais) permet de réduire leur consommation d'énergie. Nous montrons, dans cet article, que lorsque ces veilles sont utilisées avec un contrôle de la puissance d'émission, il existe un compromis entre puissance instantanée et temps de veille qui permet de minimiser la consommation de la station de base. De plus, nous proposons un algorithme efficace utilisant des expressions analytiques pour trouver cet optimum. Nous montrons que pour des macro-cellules, la solution proposée permet de réduire la puissance moyenne consommée de 7W par rapport à rapport une stratégie naïve. Cela représente 4% de l'énergie totale consommée par la station de base

Improvement of the LPWAN AMI Backhaul's Latency thanks to Reinforcement Learning Algorithms

International audienceLow Power Wide Area Networks (LPWANs) have been recently deployed for long range Machine-to-Machine (M2M) communications. These networks have been proposed for many applications and in particular for the communications of the Advanced Metering Infrastructure (AMI) backhaul of the smart grid. However, they rely on simple access schemes that may suffer from important latency, which is one of the main performance indicators in smart grid communications. In this article, we apply Reinforcement Learning (RL) algorithms to reduce the latency of AMI communications in LPWANs. For that purpose, we first study the collision probability in an unslotted ALOHA-based LPWAN AMI backhaul which uses the LoRaWAN acknowledgement procedure. Then, we analyze the effect of collisions on the latency for different frequency access schemes. We finally show that RL algorithms can be used for the purpose of frequency selection in these networks and reduce the latency of the AMI backhaul in LPWANs. Numerical results show that non-coordinated algorithms featuring a very low complexity reduce the collision probability by 14%, and the mean latency by 40%