Sophie Gault

Bio-inspired algorithms for dynamic resource allocation in cognitive wireless networks

Regulation will experience enormous changes in the near future resulting in seamless connectivity by spectrum borders. A promising approach in this context is dynamic spectrum allocation which leads to a more flexible access to spectral resources by employing intelligent radio devices called cognitive radios. This paper is concerned with bio-inspired approaches that exploit distribution in multi-radio environments where many users have to share a finite resource harmoniously. Three applications of bio-inspired techniques are described. The first one deals with the detection of spectrum holes whereas the second one describes resource allocation in orthogonal frequency division multiple access based systems. The third one is concerned with distributed resource auctioning.

Bio-Inspired Algorithms for Dynamic Resource Allocation in Cognitive Wireless Networks

Regulation will experience enormous changes in the near future resulting in seamless connectivity by bluring spectrum borders. A promising approach in this context is dynamic spectrum allocation which leads to a more flexible access to spectral resources by employing intelligent radio devices called cognitive radios. This paper is concerned with bio-inspired approaches that exploit distribution in multi-radio environments where many users have to share a finite resource harmoniously. Three applications of bio-inspired techniques are described. The first one deals with the detection of spectrum holes and the second one describes resource allocation in orthogonal frequency division multiple access based systems. The third one is concerned with distributed resource auctioning.

Distributed power allocation game for uplink OFDM systems

In this paper, we consider the uplink of a single cell network with K users simultaneously communicating with a base station using OFDM modulation over N carriers. In such a scenario, users can decide their power allocation based on three possible Channel State Information(CSI) levels, which are called complete, partial and statistical. The optimal solutions for maximizing the average capacity with complete and statistical knowledge are known to be the water-filling game and the uniform power allocation respectively. We study the problem in the partial knowledge case. We formulate it as a strategy game, where each player (user) selfishly maximizes his own average capacity. The information structure that we consider is such that each player, at each time instant, knows his own channel state, but does not know the states of other players. We study the existence and uniqueness of Nash equilibrium. We find the optimal solution for the symmetric case considering two positive channel states, and we show the optimization problem for any L states.

Evolution of Wireless Communication Systems Towards Autonomously Managed, Cognitive Radio Functionalities

This contribution presents key functionalities and design approaches of a distributed system architecture as it is studied in the framework of the European E2R II project. An emphasis is laid on policy based self-governance, distributed reconfiguration concepts and corresponding cognitive support functionalities; this support is necessary to assure context awareness in the equipment in order to facilitate (enable) distributed decision making. The idea is to distribute decision making functionalities among network and user equipment elements in order to (i) limit the required calculation complexity on the network and user side for the determination of the optimum resource selection strategy, (ii) increase the reactivity of the equipment to any context change minimizing the required amount of human interaction and (iii) minimize the signaling overhead by broadcasting generic policy rules applicable to all users instead of targeting a user-by-user based reconfiguration approach. A simple use case illustrates how Game Theoretic tools can be used in order to derive suitable policies and how to perform decisions.

Adaptive resource management platform for reconfigurable networks

Users’ expectations towards technology, in terms of quality, service availability and accessibility are ever increasing. Aligned with this, the wireless world is rapidly moving towards the next generation of systems, featuring cooperating and reconfiguring capabilities for coexisting (and upcoming) Radio Access Technologies (RATs), so that to improve connectivity and reduce costs. In this respect, conventional planning and management techniques ought to be replaced by advanced schemes that consider multidimensional characteristics, increased complexity and high speeds. To this effect, means are needed capable to support scalability and to cater for advanced service features, provided to users at high rates and cost-effectively. This article provides a scheme to optimize resource management in future systems, by describing a platform that accommodates engineering mechanisms that deal with dynamic, demand driven planning and managing of spectrum and radio resources in reconfigurable networks. To do so, it first discusses the fundamentals and the approach followed in the proposed architecture and then investigates the basic functional modules. The architecture is validated through a set of use-cases that exemplify the operational applicability and efficiency in a wide range of communication scenarios.

Autonomic communications: exploiting advanced and game theoretical techniques for RAT selection and protocol reconfiguration

The Autonomic Communications concept emerges as one of the most promising solutions for future heterogeneous systems networking. This notion implies the introduction of advanced mechanisms for autonomic decision making and self-configuration. To this end, this paper proposes an integrated framework that facilitates autonomic features to capture the needs for RAT selection and device reconfiguration in a Composite Radio Environment. Specifically, a game theoretical approach targeted to the definition of appropriate policies for distributed equipment elements is presented. Thus, the user terminals are able to exploit context information in order to i) identify an optimum trade-off for (multiple) Radio Access Technology (RAT) selection and ii) adapt the protocol stack and respective protocol functionality using a proposed component based framework for transparent protocol component replacement. Simulation and performance results finally show that the proposed mechanisms lead to efficient resource management, minimizing the complexity on the network and terminal side as well as keeping the required signaling overhead as low as possible.

Iterative Mercury/Waterfilling for Parallel Multiple Access Channels

This paper describes a multiuser power allocation strategy for fixed constellation over parallel Gaussian channels (e.g. OFDM systems). The criterion under consideration is mutual information, given arbitrary input distributions over users and over subcarriers. The algorithm achieves with very low complexity the multi-user aggregate sum mutual information upper bound. The algorithm is based on an iterative Mercury/waterfilling procedure. Moreover, we extend the framework to a decentralized scenario using a linear approximation of the MMSE function. We show, in particular that each user can, under certain assumptions, independently determine the power allocation without knowing the channel information of other users. Simulation results validate the theoretical claims.

Advanced reconfiguration framework based on game theoretical techniques in autonomic communication systems

The Autonomic Communications concept forms one promising solution to accommodate the increased complexity of legacy and emerging systems, fostering the automation and minimizing the need for human intervention. This notion implies the introduction of advanced mechanisms for autonomic decision making and self-configuration. The focus of this work is on the introduction of an advanced reconfiguration framework for the support of the following functionalities: i) efficient strategies of terminal attachment to heterogeneous wireless systems are proposed dependent on the evaluation of input stimuli from the surrounding telecom environment. ii) it is shown how to enable optimized selection and attribution of resources, iii) the application of new device configuration is examined, proposing a framework for dynamic protocol stack adaptation. It is indeed necessary to introduce a framework that will enable, policy based reconfiguration decisions supporting dynamic and optimal discovery, download and replacement of necessary protocol functionality. In this context, legacy management and control mechanisms should be enriched with such features operating in either terminal or network equipment. Namely, this contribution discusses cognitive reconfiguration management issues by introducing two basic reconfiguration units encapsulated in a unified management and control architecture: i) the component based protocol stack reconfiguration framework and ii) the resource usage optimization unit. Simulation and performance results presented in the paper prove the technical feasibility of the proposed mechanisms as well as the optimization of reconfiguration actions.RésuméLe concept de communications autonomes constitue une solution prometteuse qui permet la coexistence de systèmes dont la complexité ne cesse d’augmenter, en particulier les systèmes traditionnels et les systèmes émergents/de nouvelle génération. Ce concept, fondé sur l’auto-organisation et qui a pour avantage de diminuer la nécessité de toute intervention humaine, requiert la définition de mécanismes avancés pour la prise de décision distribuée et l’ auto-configuration. Nous présentons ici un système de reconfiguration avancé ayant les fonctionnalités suivantes: i) le système est muni de stratégies efficaces pour l’accès d’un terminal aux ressources de réseaux sans fil hétérogènes, ces stratégies étant fonction de certains paramètres de l’environnement, éventuellement évalués par mesure, ii) nous fournissons également des méthodes pour optimiser la sélection et l’ attribution de ces ressources, iii) enfin, nous nous intéressons à la configuration du terminal et proposons une adaptation dynamique de la pile de protocole. Dans ce cadre, il faudra également considérer des décisions de reconfiguration basées sur des règles qui permettront la découverte, le chargement et le remplacement éventuel de certaines fonctionnalités du protocole de façon dynamique et optimale. Dans ce contexte, les mécanismes de management et de contrle doivent inclure ces caractéristiques, soit au niveau du terminal, soit au niveau du réseau. Cette contribution traite des problèmes de gestion de la reconfiguration cognitive et introduit deux éléments de reconfiguration basiques réunis dans une architecture de management et contrle unifiée: i) le système de reconfiguration de la pile protocolaire à base de composants et ii) le système d’optimisation de l’usage des ressources. Les résultats de simulation illustrent la faisabilité technique des mécanismes proposés ainsi que l’optimisation de l’opération de reconfiguration.