Fonctionnelle de vraisemblance moyennée et statistiques d'ordre supérieur

Cet article traite de l'approximation de la fonctionnelle de vraisemblance moyennée dans le contexte gaussien. Cette fonction, utilisée dans le cas de la classification ou de l'estimation à hypothèses composées, est obtenue en prenant la moyenne de la vraisemblance par rapport aux paramètres aléatoires dont on connaît la densité de probabilité. Nous montrons qu'il est possible d'exprimer cette fonction par un développement faisant intervenir explicitement des statistiques d'ordre supérieur. L'expression obtenue s'interprète comme la somme pondérée d'une intercorrélation entre des «moments intégrés» du signal de référence et des moments estimés de l'observation. Elle permet d'obtenir simplement des tests pratiques à mettre en oeuvre et nous montrons ici à titre d'exemple comment obtenir les équations du détecteur multicycle à l'ordre quatre

Joint Channel and Power Allocation in Tactical Cognitive Networks: Enhanced Trial and Error

National audienceIn tactical networks the presence of a central controller (e.g., a base station) is made impractical by the unpredictability of the nodes' positions and by the fact that its presence can be exploited by hostile entities. As a consequence, self-configuring networks are sought for military and emergency communication networks. In such networks, the transmission parameters, most notably the transmission channel and the power level, are set by the devices following specific behavioural rules. In this context, an algorithm for self-configuring wireless networks is presented, analysed and enhanced to meet the specific needs of tactical networks. Such an algorithm, based on the concept of trial and error, is tested under static and mobile situations, and different metrics are considered to show its performance. In particular, the stability and performance improvements with respect to previously proposed versions of the algorithm are detailed

Channel and power allocation algorithms for ad hoc clustered networks

978-1-4673-1422-0International audienceIn the context of mobile clustered ad hoc networks, this paper proposes and studies a self-configuring algorithm which is able to jointly set the channel frequency and power level of the transmitting nodes, by exploiting one bit of feedback per receiver. This algorithm is based upon a learning algorithm, namely trial and error, that is cast into a game theoretical framework in order to study its theoretical performance. We consider two different feedback solutions, one based on the SINR level estimation, and one based on the outcome of a CRC check. We analytically prove that this algorithm selects a suitable configuration for the network, and analyse its performance through numerical simulations under various scenarios

Combinaison de moments d'ordre 2 et 4 pour la classification de modulations linéaires

Cet article traite de la classification des modulations linéaires de phase à 4 états (MDP4) et d'amplitude sur porteuse en quadrature à 16 états (MAQ16). Celle-ci est réalisée par la reconnaissance d'une forme construite par une combinaison de moments d'ordre 4 et d'ordre 2 du signal stationnarisé, optimisée pour maximiser la probabilité de classification correcte. Ce système est une extension du système proposé dans [1] dans lequel la forme discriminante est une tranche de cumulant d'ordre 4. Les performances théoriques et expérimentales du système sont présentées pour différents rapports signal sur bruit et comparées à celles obtenues dans [1]. Un taux de classification correcte de 99% est atteint pour un rapport signal sur bruit de 0 dB et seulement 500 symboles transmis

Distributed Power Allocation with SINR Constraints Using Trial and Error Learning

978-1-4673-0436-8International audienceIn this paper, we address the problem of global transmit power minimization in a self-configuring network where radio devices are subject to operate at a minimum signal to interference plus noise ratio (SINR) level. We model the network as a parallel Gaussian interference channel and we introduce a fully decentralized algorithm (based on trial and error) able to statistically achieve a configuration where the performance demands are met. Contrary to existing solutions, our algorithm requires only local information and can learn stable and efficient working points by using only one bit feedback. We model the network under two different game theoretical frameworks: normal form and satisfaction form. We show that the converging points correspond to equilibrium points, namely Nash and satisfaction equilibrium. Similarly, we provide sufficient conditions for the algorithm to converge in both formulations. Moreover, we provide analytical results to estimate the algorithm's performance, as a function of the network parameters. Finally, numerical results are provided to validate our theoretical conclusions

Achieving Pareto Optimal Equilibria in Energy Efficient Clustered Ad Hoc Networks

International audienceIn this paper, a decentralized iterative algorithm able to achieve a Pareto optimal working point in a clustered ad hoc network is analysed. Here, radio devices are assumed to operate above a minimal signal to interference plus noise ratio (SINR) threshold while minimizing the global power consumption. A distributed algorithm, namely the optimal dynamic learning (ODL), is presented and shown to be able to dynamically steer the network to an efficient working point, by exploiting only minimal amount of information. This algorithm aims at implementing a Pareto optimal solution for a large proportion of the time, with high probability. Conversely, existing solutions aim at achieving individually optimal solutions (Nash equilibria), which might be globally inefficient. The gain is shown to be larger when the amount of available radio resource is scarce. Sufficient analytical conditions for ODL to converge to the desired working point are provided, moreover through numerical simulations the ability of the algorithm to configure an interference limited network is shown. The performance of ODL and those of a Nash equilibrium reaching algorithm are numerically compared, and their performance as a function of available resources studied

Self-Organization in Decentralized Networks: A Trial and Error Learning Approach

International audienceIn this paper, the problem of channel selection and power control is jointly analyzed in the context of multiple-channel clustered ad-hoc networks, i.e., decentralized networks in which radio devices are arranged into groups (clusters) and each cluster is managed by a central controller (CC). This problem is modeled by game in normal form in which the corresponding utility functions are designed for making some of the Nash equilibria (NE) to coincide with the solutions to a global network optimization problem. In order to ensure that the network operates in the equilibria that are globally optimal, a learning algorithm based on the paradigm of trial and error learning is proposed. These results are presented in the most general form and therefore, they can also be seen as a framework for designing both games and learning algorithms with which decentralized networks can operate at global optimal points using only their available local knowledge. The pertinence of the game design and the learning algorithm are highlighted using specific scenarios in decentralized clustered ad hoc networks. Numerical results confirm the relevance of using appropriate utility functions and trial and error learning for enhancing the performance of decentralized networks

CORASMA Program on Cognitive Radio for Tactical Networks: High Fidelity Simulator and First Results on Dynamic Frequency Allocation

International audienceThis paper reports some preliminary results of the "cognitive radio for dynamic spectrum management" (CORASMA) program that is dedicated to the evaluation of cognitive solutions for tactical wireless networks. It presents two main aspects of the program: the simulator and the the cognitive solutions proposed by the authors. The first part is dedicated to the simulator.We explain the rationale used to design its architecture, and how this architecture allows to assess and compare different cognitive solutions in an operational context. The second part addresses the dynamic frequency allocation topic that is part of the cognitive solutions tackled in the program CORASMA. We first give an overview of the challenges attached to this problem in the military context and then we expose the technical solutions studied by the authors for this purpose. Finally, we present some results obtained from the simulator as an illustration