In the literature, various Mobile Ad hoc NETwork (MANET) routing protocols proposed. Each performs the best under specific context conditions, for example under high mobility or less volatile topologies. In existing MANET, the degradation in the routing protocol performance is always associated with changes in the network context. To date, no MANET routing protocol is able to produce optimal performance under all possible conditions. The core aim of this thesis is to solve the routing problem in mobile Ad hoc networks by introducing an optimum system that is in charge of the selection of the running routing protocol at all times, the system proposed in this thesis aims to address the degradation mentioned above. This optimisation system is a novel approach that can cope with the network performance’s degradation problem by switching to other routing protocol. The optimisation system proposed for MANET in this thesis adaptively selects the best routing protocol using an Artificial Intelligence mechanism according to the network context. In this thesis, MANET modelling helps in understanding the network performance through different contexts, as well as the models’ support to the optimisation system. Therefore, one of the main contributions of this thesis is the utilisation and comparison of various modelling techniques to create representative MANET performance models. Moreover, the proposed system uses an optimisation method to select the optimal communication routing protocol for the network context. Therefore, to build the proposed system, different optimisation techniques were utilised and compared to identify the best optimisation technique for the MANET intelligent system, which is also an important contribution of this thesis. The parameters selected to describe the network context were the network size and average mobility. The proposed system then functions by varying the routing mechanism with the time to keep the network performance at the best level. The selected protocol has been shown to produce a combination of: higher throughput, lower delay, fewer retransmission attempts, less data drop, and lower load, and was thus chosen on this basis. Validation test results indicate that the identified protocol can achieve both a better network performance quality than other routing protocols and a minimum cost function of 4.4%. The Ad hoc On Demand Distance Vector (AODV) protocol comes in second with a cost minimisation function of 27.5%, and the Optimised Link State Routing (OLSR) algorithm comes in third with a cost minimisation function of 29.8%. Finally, The Dynamic Source Routing (DSR) algorithm comes in last with a cost minimisation function of 38.3%.

Cette thèse est consacrée au développement d’un outil de pré-dimensionnement par éléments finis pour l’estimation de l’endommagement par fatigue polycyclique de structures linéaires sous chargements multiaxiaux et stationnaires gaussiens. L’état de contraintes atteint dans ces structures étant aléatoire, il devient nécessaire de raisonner en terme de statistique et l’approche spectrale s’avère particulièrement adaptée pour cette situation. Dans ce travail, les méthodes spectrales sont améliorées par la prise en compte des largeurs de bande des spectres de réponses des structures soumises à des chargements nonproportionnels et de moyennes non nulles. Le critère d’endommagement de Sines est retenu. L’étude numérique de la distribution de l’endommagement résultant des incertitudes sur les paramètres matériaux et des applications dans le domaine de l’optimisation des structures sont également abordées. / This dissertation is devoted to the development of a finite element pre-designing tool for the estimation of high cycle fatigue damage for linear structure subject to multiaxial and Gaussian stationary loads. Given the random nature of the stress state, it becomes necessary to look at this problem from a statistical point of view and spectral methods appear to be the best approach. In this work, spectral methods are improved by taking into account the response spectral bandwidths of structures under non proportional and non zero mean loads; the Sines’ damage criterion is employed. The numerical analysis of the fatigue damage distribution resulting from the uncertainties of the material parameters and applications in the field of structural optimisation are also treated.