There has been a steady growth in the traffic generated by Mobile Network Operators (MNOs), and by 2020 it is expected to overload the existing licensed spectrum capacity and lead to the problem of scarce resources. One method to deal with this traffic overload is to access unlicensed and shared spectrum bands using an opportunistic approach. The use of Licensed Shared Access (LSA) is a novel approach for spectrum sharing between the incumbent user (i.e., the current owner of the shared spectrum) and the LSA licensee (i.e., the temporary user of frequencies, such as an MNO). The LSA system allows the incumbent users to temporarily provide the LSA licensee with access to its spectrum resources. However, licensees must adopt vertical handover and traffic steering procedures to vacate their customers from the LSA band without causing interference, whenever this is required by the incumbent. These procedures should be carried out, de facto, before the base station is turned off as a part of a rapid release of unscheduled LSA band facing evacuation scenarios. Thus, in this dissertation, a cognitive mechanism is proposed to make decisions in advance to find the best target network(s) for evacuated customers in connected mode and with active traffic per class of service. On the basis of these decisions, the vertical handover and traffic steering procedures are carried out for the best target network(s), which are selected in advance and undertaken immediately to avoid interference between the licensee and incumbent services. Furthermore, this guarantees the seamless connectivity and QoS of evacuated customers and their traffic respectively, during and after the unscheduled evacuation scenarios. A performance evaluation conducted in a simulating scenario consisting of one LTE-LSA and three Wi-Fi networks, demonstrated that the proposed solution could be completed within the time required for the unscheduled evacuation, as well as, being able to ensure the QoS and seamless connectivity of the evacuees. The total execution time obtained during the performance evaluation of the proposed solution was around 46% faster than of two related works and could thus avoid interference between the licensee and incumbent services.

Cette thèse s'intéresse aux problèmes d'allocations des ressources et de puissance dans les réseaux cellulaires de quatrième génération (4G). Pour faire face à la demande continuellement croissante en débit des utilisateurs mobiles, les opérateurs n'ont d'autre choix que de densifier leurs infrastructures d'accès au réseau radio (RAN), afin de maximiser l'utilisation de la bande passante disponible dans l'espace. Un des défis de cette nouvelle architecture est la coexistence de nombreuses cellules voisines et la gestion des interférences co-canal qu'elles génèrent entre elles. De telles contraintes ont amené la communauté scientifique à s'intéresser aux réseaux auto-organisés et auto-optimisés (SON), qui permettent aux réseaux de s'optimiser localement via des décisions décentralisées (sans planification statique). L'intérêt principal de tels réseaux est le passage à l'échelle des algorithmes distribués et la possibilité de s'adapter dynamiquement à de nouveaux environnements. Dans cette optique, nous proposons l'étude de deux problèmes d'allocation de ressources. La première partie de cette thèse se concentre sur l'optimisation de l'usage des ressources, dans un contexte de transmission coordonnée par plusieurs stations de base (CoMP). Les performances de la coordination de stations de base sont évaluées, selon le critère de capacité uniforme, ainsi que le compromis entre l'efficacité spectrale et l'équité entre les utilisateurs. Nous proposons également une méthode généralisée et distribuée de sélection de l'ensemble de stations en coopération, afin d'optimiser le compromis efficacité-équité. Dans une seconde partie, nous nous intéressons à l'optimisation de l'allocation des ressources et de puissance, dans le but de minimiser la consommation électrique du réseau. Nous présentons deux algorithmes dont les décisions sont décentralisées. Le premier est basé sur une optimisation stochastique (via l'échantillonneur de Gibbs) et permet une optimisation globale du système. Le second quant à lui est basé sur l'adaptation de la théorie du contrôle et utilise des modèles prédictifs et la poursuite de cibles pour allouer les ressources et les puissances dans un contexte de canaux et d'interférences dynamiques. Dans de nombreux cas, plusieurs objectifs concurrents sont à considérer pour évaluer les performances d'un réseau (capacité totale, équité, consommation électrique, etc.). Dans le cadre de cette thèse, nous nous efforçons à présenter les résultats sous la forme de compromis multi-objectifs.

This work concentrates on the application of diversity techniques and space time block coding for future high speed mobile wireless communications on multicarrier systems. At first, alternative multicarrier kernels robust for high speed doubly-selective fading channel are sought. They include the comparisons of discrete Fourier transform (DFT), fractional Fourier transform (FrFT) and wavelet transform (WT) multicarrier kernels. Different wavelet types, including the raised-cosine spectrum wavelets are implemented, evaluated and compared. From different wavelet families, orthogonal wavelets are isolated from detailed evaluations and comparisons as suitable for multicarrier applications. The three transforms are compared over a doubly-selective channel with the WT significantly outperforming all for high speed conditions up to 300 km/hr. Then, a new wavelet is constructed from an ideal filter approximation using established wavelet design algorithms to match any signal of interest; in this case under bandlimited criteria. The new wavelet showed better performance than other traditional orthogonal wavelets. To achieve MIMO communication, orthogonal space-time block coding, OSTBC, is evaluated next. First, the OSTBC is extended to assess the performance of the scheme over extended receiver diversity order. Again, with the extended diversity conditions, the OSTBC is implemented for a multicarrier system over a doubly-selective fading channel. The MIMO-OFDM systems (implemented using DFT and WT kernels) are evaluated for different operating frequencies, typical of LTE standard, with Doppler effects. It was found that, during high mobile speed, it is better to transmit OFDM signals using lower operating frequencies. The information theory for the 2-transmit antenna OSTBC does not support higher order implementation of multi-antenna systems, which is required for the future generation wireless communications systems. Instead of the OSTBC, the QO-STBC is usually deployed to support the design of higher order multi-antenna systems other than the 2-transmit antenna scheme. The performances of traditional QO-STBC methods are diminished by some off-diagonal (interference) terms such that the resulting system does not attain full diversity. Some methods for eliminating the interference terms have earlier been discussed. This work follows the construction of cyclic matrices with Hadamard matrix to derive QO-STBC codes construction which are N-times better than interference free QO-STBC, where N is the number of transmit antenna branches.

There has been a steady growth in the traffic generated by Mobile Network Operators (MNOs), and by 2020 it is expected to overload the existing licensed spectrum capacity and lead to the problem of scarce resources. One method to deal with this traffic overload is to access unlicensed and shared spectrum bands using an opportunistic approach. The use of Licensed Shared Access (LSA) is a novel approach for spectrum sharing between the incumbent user (i.e., the current owner of the shared spectrum) and the LSA licensee (i.e., the temporary user of frequencies, such as an MNO). The LSA system allows the incumbent users to temporarily provide the LSA licensee with access to its spectrum resources. However, licensees must adopt vertical handover and traffic steering procedures to vacate their customers from the LSA band without causing interference, whenever this is required by the incumbent. These procedures should be carried out, de facto, before the base station is turned off as a part of a rapid release of unscheduled LSA band facing evacuation scenarios. Thus, in this dissertation, a cognitive mechanism is proposed to make decisions in advance to find the best target network(s) for evacuated customers in connected mode and with active traffic per class of service. On the basis of these decisions, the vertical handover and traffic steering procedures are carried out for the best target network(s), which are selected in advance and undertaken immediately to avoid interference between the licensee and incumbent services. Furthermore, this guarantees the seamless connectivity and QoS of evacuated customers and their traffic respectively, during and after the unscheduled evacuation scenarios. A performance evaluation conducted in a simulating scenario consisting of one LTE-LSA and three Wi-Fi networks, demonstrated that the proposed solution could be completed within the time required for the unscheduled evacuation, as well as, being able to ensure the QoS and seamless connectivity of the evacuees. The total execution time obtained during the performance evaluation of the proposed solution was around 46% faster than of two related works and could thus avoid interference between the licensee and incumbent services.

There has been a steady growth in the traffic generated by Mobile Network Operators (MNOs), and by 2020 it is expected to overload the existing licensed spectrum capacity and lead to the problem of scarce resources. One method to deal with this traffic overload is to access unlicensed and shared spectrum bands using an opportunistic approach. The use of Licensed Shared Access (LSA) is a novel approach for spectrum sharing between the incumbent user (i.e., the current owner of the shared spectrum) and the LSA licensee (i.e., the temporary user of frequencies, such as an MNO). The LSA system allows the incumbent users to temporarily provide the LSA licensee with access to its spectrum resources. However, licensees must adopt vertical handover and traffic steering procedures to vacate their customers from the LSA band without causing interference, whenever this is required by the incumbent. These procedures should be carried out, de facto, before the base station is turned off as a part of a rapid release of unscheduled LSA band facing evacuation scenarios. Thus, in this dissertation, a cognitive mechanism is proposed to make decisions in advance to find the best target network(s) for evacuated customers in connected mode and with active traffic per class of service. On the basis of these decisions, the vertical handover and traffic steering procedures are carried out for the best target network(s), which are selected in advance and undertaken immediately to avoid interference between the licensee and incumbent services. Furthermore, this guarantees the seamless connectivity and QoS of evacuated customers and their traffic respectively, during and after the unscheduled evacuation scenarios. A performance evaluation conducted in a simulating scenario consisting of one LTE-LSA and three Wi-Fi networks, demonstrated that the proposed solution could be completed within the time required for the unscheduled evacuation, as well as, being able to ensure the QoS and seamless connectivity of the evacuees. The total execution time obtained during the performance evaluation of the proposed solution was around 46% faster than of two related works and could thus avoid interference between the licensee and incumbent services.

Les changements philosophiques et techniques qui ont accompagné l’avènement de notre civilisation «moderne » laissent dans leurs sillages un cortège de bouleversements physiques, chimiques etbiologiques à l’échelle du globe. Aujourd’hui les preuves sont nombreuses pour affirmer que cechangement global modifie le fonctionnement de la « Nature ». La nécessité d’appréhender et decomprendre ce fonctionnement a conduit à interroger les processus de reconfiguration des diversescomposantes et fonctionnalités des éco-sociosystèmes sous l’influence des changements globaux.Concentrant aujourd’hui près de 75 % de la population humaine, les écosystèmes estuariens et côtierssont particulièrement vulnérables, de plus en plus exploités et contaminés et leur biodiversité estlargement impactée. L’estuaire de la Gironde, un des plus grands estuaires d’Europe de l’Ouest, montredepuis au moins trois décennies des signes de ce changement global. C’est dans ce contexte que cettethèse décrit la trajectoire fonctionnelle de l’écosystème estuarien au cours des trente dernières années.Trois aspects du fonctionnement y sont décrits, analysés et discutés. L’étude de la dynamiqueinterannuelle du cortège ichtyologique a permis, tout d’abord, de mettre en avant trois périodes defonctionnement distinctes dans les dernières décennies. L’exploration des rythmes saisonniers despoissons et de leurs proies zooplanctoniques dans chacune d’elle a ensuite permis de montrer desmodifications de la phénologie de ces espèces à même d’engendrer, pour certaines, desdésynchronisations temporelles entre proies et prédateurs questionnant, par conséquent, la stabilité desrelations trophique et la capacité trophique du milieu. Enfin, un modèle holistique du réseau trophique aété réalisé pour chacune des trois périodes. La comparaison des propriétés de chacun d’eux a permisde conclure à une augmentation du stress de l’estuaire de la Gironde et à remettre en question sacapacité à durablement jouer son rôle de nourricerie pour les stocks de poissons marins du Golfe deGascogne. Quatre scénarii d’évolutions prospectifs synthétisent les conclusions de cette étude etdonnent à voir des avenirs possibles de cet écosystème. / The philosophical and technical changes associated with the emergence of our "modern" civilizationcaused numbers of physical, chemical and biological changes those led to changes in the functioning of"Nature". The necessity to understand this functioning has led to question the reconfiguration process ofthe various eco-sociosystems’ components and features under the influence of Global Change. TheGironde estuary, one of the largest estuaries in Western Europe, has shown since three decades, signsof this Global Change. In this context, this study highlights the functional trajectory of this estuarineecosystem during the last thirty years. Three aspects of its functioning are described, analyzed anddiscussed. First, the study of the inter-annual fish community evolution highlighted three periods withdistinct functioning. The exploration of the seasonal patterns of the fish and zooplankton dynamicsduring each period shows phenological changes able to cause, in some cases, prey-predator mismatch.This leads to question the stability of trophic interactions and the trophic capacity of the ecosystem forfish. Finally, within each of these three periods, the estuarine food web was modeled within a holisticframework. The comparison of the functional properties of each model highlighted an increase in thestress of the Gironde estuary and questioned the sustainability of its nursery function for Bay of Biscaymarine stocks. Four forecasting scenarios summarize conclusions of this study and let see possiblefutures of this ecosystem.

Scheduling has always been an indispensable part of resource allocation in wireless networks. Accurate information about channel-state is assumed as a modeling simplification. However, in a real-life network ,e.g., Long Term Evolution(LTE) or IEEE 802.16e WiMAX, the channel-state information feedback to the transmitter can have uncertainty. The primary reason being that although resource allocation is done at the finer granularity of a Physical Resource Block (PRB), channel-state information is still feedback at the coarser granularity of a sub band, which is a group of PRBs. This is done to reduce the feedback traffic from the users to the Base Station. However, this averaging causes information loss and hence, the resulting uncertainty at the scheduler. Moreover, uncertainty might be present in the channel-estimates because of the very process of estimation. In the first part of the thesis, we model the channel-estimate in accuracy and characterize the network stability region. Compared to earlier works, we allow the channel estimates to have dependence among themselves, which is a more realistic situation in a modern LTE or WiMax network. We then propose two simple Max Weight based scheduling schemes that achieve any rate in the interior of the stability region. We also derive an asymptotically tight upper bound on the mean queueing delay in our system under one of the throughput-optimal policies we propose. The above policies ensure stability of the network and we have also obtained bounds on the mean queueing delays. However, different applications may require certain quality of service which may not be satisfied by these policies. Thus, we also propose a throughput-optimal policy for the network under traffic with heterogeneous QoS constraints and present some numerical results studying its performance. In the second part of the thesis, we study the problem of energy-efficient scheduling under average delay constraint. For wireless access technologies, the largest power consumer is the Base Station(BS). Any reduction in the power consumption in a BS will reduce carbon footprint from the Information and Communication Technology sector. We concentrate on the problem of minimizing the total non-renewable power consumed in a Green BS, that is powered by renewable energy sources ,e.g., solar/wind energy and may also be connected to the power grid or diesel generators. Specifically, we consider the problem of minimizing the average grid power consumption of a Green BS downlink in scheduling multiple users with average delay constraints. We have a packetized model for the data packets (i.e., the packets cannot be fragmented) which is a more realistic model for packet-switched networks. The power function is a non-decreasing convex function of the queue-lengths and only one user is allowed to transmit in a slot. We prove the existence of a power optimal policy under delay constraints for multiple users. We analyse the problem and provide some structural results for the optimal policy.

Orthogonal frequency division multiplexing (OFDM) in next generation wireless systems provides high downlink data rates by employing frequency-domain scheduling and rate adaptation at the base station (BS). However, in order to control the significant feedback overhead required by these techniques, feedback reduction schemes are essential. Best-m feedback is one such scheme that is implemented in OFDM standards such as Long Term Evolution. In it, the sub channel (SC) power gains of only the m strongest SCs and their corresponding indices are fed back to the BS. However, two assumptions pervade most of the literature that analyze best-m feedback in OFDM systems. The first one is that the SC gains are uncorrelated. In practice, however, the SC gains are highly correlated, even for dispersive multipath channels. The second assumption deals with the treatment of unreported SCs, which are not fed back by the best-m scheme. If no user reports an SC, then no data transmission is assumed to occur. In this thesis, we eschew these assumptions and investigate best-m feedback in OFDM systems with correlated SC gains. We, first, characterize the average throughput as a function of correlation and m. A uniform correlation model is assumed, i.e., the SC gains are correlated with each other by the same correlation coefficient. The system model incorporates greedy, modified proportional- fair, and round robin schedulers, discrete rate adaptation, and non-identically distributed SC gains of different users. We, then, generalize the model to account for feedback delay. We show in all these cases that correlation degrades the average throughput. We also show that this effect does not arise when users report all the SC power gains to the BS. In order to mitigate the reduction in the average throughput caused by unreported SCs, we derive a novel, constrained minimum mean square error channel estimator for the best-m scheme to estimate the gains of these unreported SCs. The estimator makes use of the additional information, which is unique to the best-m scheme, that the estimated SC power gains must be less than those that were reported. We, then, study its implications on the downlink average cell throughput, again for different schedulers. We show that our approach reduces the root mean square error and increases the average throughput compared to several approaches pursued in the literature. The more correlated the SC gains, greater is the improvement.

This work concentrates on the application of diversity techniques and space time block coding for future high speed mobile wireless communications on multicarrier systems. At first, alternative multicarrier kernels robust for high speed doubly-selective fading channel are sought. They include the comparisons of discrete Fourier transform (DFT), fractional Fourier transform (FrFT) and wavelet transform (WT) multicarrier kernels. Different wavelet types, including the raised-cosine spectrum wavelets are implemented, evaluated and compared. From different wavelet families, orthogonal wavelets are isolated from detailed evaluations and comparisons as suitable for multicarrier applications. The three transforms are compared over a doubly-selective channel with the WT significantly outperforming all for high speed conditions up to 300 km/hr. Then, a new wavelet is constructed from an ideal filter approximation using established wavelet design algorithms to match any signal of interest; in this case under bandlimited criteria. The new wavelet showed better performance than other traditional orthogonal wavelets. To achieve MIMO communication, orthogonal space-time block coding, OSTBC, is evaluated next. First, the OSTBC is extended to assess the performance of the scheme over extended receiver diversity order. Again, with the extended diversity conditions, the OSTBC is implemented for a multicarrier system over a doubly-selective fading channel. The MIMO-OFDM systems (implemented using DFT and WT kernels) are evaluated for different operating frequencies, typical of LTE standard, with Doppler effects. It was found that, during high mobile speed, it is better to transmit OFDM signals using lower operating frequencies. The information theory for the 2-transmit antenna OSTBC does not support higher order implementation of multi-antenna systems, which is required for the future generation wireless communications systems. Instead of the OSTBC, the QO-STBC is usually deployed to support the design of higher order multi-antenna systems other than the 2-transmit antenna scheme. The performances of traditional QO-STBC methods are diminished by some off-diagonal (interference) terms such that the resulting system does not attain full diversity. Some methods for eliminating the interference terms have earlier been discussed. This work follows the construction of cyclic matrices with Hadamard matrix to derive QO-STBC codes construction which are N-times better than interference free QO-STBC, where N is the number of transmit antenna branches.

La dynamique sédimentaire estuarienne joue un rôle très important pour la qualité de l'eau, les écosystèmes et la navigation. Les estuaires macrotidaux comme la Gironde se caractérisent par la formation de régions très chargées en matière en suspension (MES), appelées zones de turbidité maximale (ZTM), qui influencent le transport et le dépôt des sédiments fins, l'envasement des chenaux, la consommation d'oxygène dissous et le devenir des polluants. L'objectif de ce travail est de comprendre la dynamique hydro-sédimentaire, particulièrement de la ZTM, dans la section fluviale, encore peu étudié, de l'estuaire de la Gironde en lien avec les facteurs de forçage environnementaux et les perturbations du système (changements hydrologiques et morphologiques naturels et anthropiques). La méthodologie de ce travail est basée sur l'analyse de 10 années de données continues de turbidité enregistrées par le réseau de surveillance MAGEST. L'exploitation de telles séries de données, assez novatrice dans les estuaires, a notamment impliqué le développement d'une méthode d'analyse basée sur la combinaison de plusieurs méthodes spectrales. Cette approche est complétée par l'analyse des profils de turbidité et de vitesse de courant lors de cycles de marée, l'analyse de séries temporelles historiques de marée et l'exploitation d'un modèle semi-analytique 2DV. La dynamique sédimentaire de l'estuaire fluvial est d'abord détaillée à toutes les échelles de temps représentatives. A l'échelle de temps intratidale, la distribution verticale des MES et des courants, en deux points d'une même section transversale, a permis de détailler les mécanismes de transport sédimentaire. Les flux particulaires résiduels (totaux, advection, pompage tidal) ainsi estimés pour plusieurs conditions hydrologiques, démontrent le contrôle du pompage tidal sur les flux de MES lors de l'étiage. A l'échelle de temps subtidale, la réponse de la ZTM aux fluctuations hydrologiques (crues, périodes d'augmentation ou diminution continue du débit, variabilité inter-anuelle) est analysée. Ceci a permis de définir plusieurs indicateurs hydrologiques des caractéristiques de la ZTM, qui suggèrent l'intensification de la ZTM au cours des dernières décennies en lien avec la diminution des débit. La contribution relative des facteurs de forçage à la variabilité de la turbidité a été quantifiée pour différentes régions estuariennes et échelles de temps (saisonnière et plurianuelle). L'application de la méthodologique développée à l'estuaire de la Loire, qui dispose de séries de données similaires (réseau SYVEL), a permis de généraliser ces résultats. Enfin, l'effet des changements pluri-décennaux hydrologiques et morphologiques sur la propagation de la marée et la dynamique sédimentaire est détaillé dans la Garonne tidale. Il ressort une amplification du marnage et de la asymétrie de la marée au cours des six dernières décennies, principalement liée aux changements morphologiques naturels dans la Gironde en aval, les extractions de granulat et le changement de régime hydrologique. L'implémentation d'un modèle semi-analytique a permis de vérifier ces résultats et d'analyser leurs implications sur les concentrations de MES et la limite amont de la ZTM. / Estuarine suspended sediment dynamics play an important role in water quality, ecosystems and navigation. The formation of regions of high suspended sediments (SS) concentrations, called turbidity maximum zones (TMZ), is a characteristic feature of macrotidal estuaries, such as the Gironde. The TMZ influences the transport and deposition of fine sediments, channel siltation, oxygen conditions and the particulate transport of pollutants. This work aims to understand the hydro-sedimentary dynamics of the fluvial Gironde estuary, still poorly studied, in relation with environmental forcings and system perturbations (natural and anthropic hydrological and morphological changes). The methodology of this work is based on the analysis of the 10-years continuous time series of turbidity recorded by the MAGEST monitoring network. The exploitation of such time series, quite innovative in estuaries, required the development of an analysis method based on the combination of spectral techniques. This approach is completed by the analysis of turbidity and current velocity profiles over tidal cycles, the analysis of historical tide time series, and the exploitation of a 2DV semi-analytical model. First, SS dynamics of the fluvial Gironde is detailed at all representative time scales. At the intratidal time scale, the mechanisms of SS transport were described from the vertical depth of SSC and current velocities at two points of the same section. Residual fluxes (total, advective and tidal pumping), estimated for different hydrological conditions, demonstrated the control of tidal pumping on SS fluxes during periods of low river flow. At the subtidal time scale, the TMZ response to hydrological fluctuations (floods, periods of continuous river flow increase and decrease, interannual changes) was analyzed. Hydrological indicators of the TMZ features were thus defined, which suggest the TMZ intensification over the last decades in relation to the river flow decrease. The relative contributions of environmental forcings to the turbidity variability were quantified for different estuarine regions and time scales (seasonal and multiannual). The application of the same methodology to the Loire estuary, which counts on equivalent time series (SYVEL network), allowed the generalization of these results. Finally, the impact of pluri-decades hydrological and morphological changes on tidal propagation and suspended sediments dynamics is detailed in the tidal Garonne. Both tidal range and asymmetry appear to be amplified over the last six decades, mainly due to natural changes of the down Gironde, gravel extraction in the tidal Garonne and hydrological regime shifts. The implementation of an idealized model allowed verifying such results and analyzing their implications for SS concentrations and the upper TMZ limit.