Cognitive radio networks have recently been proposed as a promising approach to overcome the serious problem of spectrum scarcity. Other emerging concept for innovative spectrum utilization is femtocells. Femtocells are low-power and short-range wireless access points installed by the end-user in residential or enterprise environments. A common feature of cognitive radio and femtocells is their two-tier nature involving primary and secondary users (PUs, SUs). While this new paradigm enables innovative alternatives to conventional spectrum management and utilization, it also brings its own technical challenges. A main challenge in cognitive radio is the design of efficient resource (spectrum) trading methods. Game and microeconomics theories provide tools for studying the strategic interactions through rationality and economic benefits between PUs and SUs for effective resource allocation. In this thesis, we investigate some efficient game theoretic and microeconomic approaches to address spectrum trading in cognitive networks. We propose two auction frameworks for shared and exclusive use models. In the first auction mechanism, we consider the shared used model in cognitive radio networks and design a spectrum trading method to maximize the total satisfaction of the SUs and revenue of the Wireless Service Provider (WSP). In the second auction mechanism, we investigate spectrum trading via auction approach for exclusive usage spectrum access model in cognitive radio networks. We consider a realistic valuation function and propose an efficient concurrent Vickrey-Clarke-Grove (VCG) mechanism for non-identical channel allocation among r-minded bidders in two different cases. The realization of cognitive radio networks in practice requires the development of effective spectrum sensing methods. A fundamental question is how much time to allocate for sensing purposes. In the literature on cognitive radio, it is commonly assumed that fixed time durations are assigned for spectrum sensing and data transmission. It is however possible to improve the network performance by finding the best tradeoff between sensing time and throughput. In this thesis, we derive an expression for the total average throughput of the SUs over time-varying fading channels. Then we maximize the total average throughput in terms of sensing time and the number of SUs assigned to cooperatively sense each channel. For practical implementation, we propose a dynamical programming algorithm for joint optimization of sensing time and the number of cooperating SUs for sensing purpose. Simulation results demonstrate that significant improvement in the throughput of SUs is achieved in the case of joint optimization. In the last part of the thesis, we further address the challenge of pricing in oligopoly market for open access femtocell networks. We propose dynamic pricing schemes based on microeconomic and game theoretic approaches such as market equilibrium, Bertrand game, multiple-leader-multiple-follower Stackelberg game. Based on our approaches, the per unit price of spectrum can be determined dynamically and mobile service providers can gain more revenue than fixed pricing scheme. Our proposed methods also provide residential customers more incentives and satisfaction to participate in open access model.

The current cellular industry is undergoing a huge paradigm shift from an old homogeneous one-tier network structure to a new heterogeneous two-tier structure with joint deployment of traditional macrocell base stations along with a relatively new small cell base stations, widely known as femtocells. Femtocells are low-powered, low-cost, user-deployed base stations meant to improve poor network coverage and, thereby, increase overall system capacity. As more and more femtocells are deployed, their spectrum usage and resulting interference become non-negligible. While using different operating frequency for femtocells is indeed possible, a co-channel deploy- ment of these will increase spectral efficiency, a much sought design by cellular opera- tors. In this thesis, a femtocell-based scheme is considered as a prospective means to enhance the performance of the current cellular infrastructure. In the adopted frame- work, the femtocell access point is tasked with connecting local femtocell users to the network operator without creating undue interference to cellular users. As such, the femtocell is required to cease communication when a nearby cellular user is present to prevent interference. In the envisioned paradigm, an access point possesses little information about the parent cellular base station. For instance, it may not know the individual channel gains, user locations or frequency allocations. To achieve this goal, femtocell users collectively act as sensing devices and are used to acquire data about local signal strength. This work shows that, despite having little knowledge of the operation of the macro environment, a femtocell can take advantage of the data provided by the acquisition devices and agility of the re-configurable antenna to gain insight about proximate cellular devices. The proposed inference scheme leads to a significant performance gain over oblivious femtocells. Experimental results are provided to support this study and its conclusions.

Since 2004, when the Long Term Evolution (LTE) was first proposed to be publicly available in the year 2009, a plethora of new characteristics, techniques and applications have been constantly enhancing it since its first release, over the past decade. As a result, the research aims for LTE-Advanced (LTE-A) have been released to create a ubiquitous and supportive network for mobile users. The incorporation of heterogeneous networks (HetNets) has been proposed as one of the main enhancements of LTE-A systems over the existing LTE releases, by proposing the deployment of small-cell applications, such as femtocells, to provide more coverage and quality of service (QoS) within the network, whilst also reducing capital expenditure. These principal advantages can be obtained at the cost of new challenges such as inter-cell interference, which occurs when different network applications share the same frequency channel in the network. In this thesis, the main challenges of HetNets in LTE-A platform have been addressed and novel solutions are proposed by using self-organising network (SON) management approaches, which allows the cooperative cellular systems to observe, decide and amend their ongoing operation based on network conditions. The novel SON algorithms are modelled and simulated in OPNET modeler simulation software for the three processes of resource allocation, mobility management and interference coordination in multi-tier macro-femto networks. Different channel allocation methods based on cooperative transmission, frequency reuse and dynamic spectrum access are investigated and a novel SON sub-channel allocation method is proposed based on hybrid fractional frequency reuse (HFFR) scheme to provide dynamic resource allocation between macrocells and femtocells, while avoiding co-tier and cross-tier interference. Mobility management is also addressed as another important issue in HetNets, especially in hand-ins from macrocell to femtocell base stations. The existing research considers a limited number of methods for handover optimisation, such as signal strength and call admission control (CAC) to avoid unnecessary handovers, while our novel SON handover management method implements a comprehensive algorithm that performs sensing process, as well as resource availability and user residence checks to initiate the handover process at the optimal time. In addition to this, the novel femto over macro priority (FoMP) check in this process also gives the femtocell target nodes priority over the congested macrocells in order to improve the QoS at both the network tiers. Inter-cell interference, as the key challenge of HetNets, is also investigated by research on the existing time-domain, frequency-domain and power control methods. A novel SON interference mitigation algorithm is proposed, which is based on enhanced inter-cell interference coordination (eICIC) with power control process. The 3-phase power control algorithm contains signal to interference plus noise ratio (SINR) measurements, channel quality indicator (CQI) mapping and transmission power amendments to avoid the occurrence of interference due to the effects of high transmission power. The results of this research confirm that if heterogeneous systems are backed-up with SON management strategies, not only can improve the network capacity and QoS, but also the new network challenges such as inter-cell interference can also be mitigated in new releases of LTE-A network.

The overarching goal of this thesis is to investigate network architectures, and find the trade-off between low overall energy use and maintaining the level of quality of service (QoS), or even improve it. The ubiquitous wireless communications environment supports the exploration of different network architectures and techniques, the so-called heterogeneous network. Two kinds of heterogeneous architectures are considered: a combined cellular and femtocell network and a combined cellular, femtocell and Wireless Local Area Network(WLAN) network. This thesis concludes that the investigated heterogeneous networks can significantly reduce the overall power consumption, depending on the uptake of femtocells and WLANs. Also, QoS remains high when the power consumption drops. The main energy saving is from reducing the macrocell base station embodied and operational energy. When QoS is evaluated based on the combined cellular and femtocell architecture, it is suggested that use of resource scheduling for femtocells within the macrocell is crucial since femtocell performance is affected significantly by interference when installed in a co-channel system. Additionally, the femtocell transmission power mode is investigated using either variable power level or a fixed power level. To achieve both energy efficiency and QoS, the choice of system configurations should change according to the density of the femtocell deployment. When combining deployment of femtocells with WLANs, more users are able to experience a higher QoS. Due to increasing of data traffic and smartphone usage in the future, WLANs are more important for offloading data from the macrocell, reducing power consumption and also increasing the bandwidth. The localised heterogeneous network is a promising technique for achieving power efficiency and a high QoS system.

Strong demand for wireless communications encourages academic research centres and industrial electronics and communication companies to keep improving the performance, increase the speed, extend the coverage area and enlarge the baud rate and capacity. LTE (Long Term Evolution) and WiMAX (the Worldwide Interoperability Microwave Access) are recent solutions for most wireless technologies. LTE and WiMAX coverage range are one of the important factors that affect the quality of broadband access services and mobile cellular systems in wireless communication. Predicting and evaluating the path loss is essential in planning and designing cellular mobile systems. This thesis presents a comprehensive study of path loss on LTE and mobile WiMAX to achieve large throughputs and wide coverage at the Cell-edge. The thesis introduces, analyzes and compares the path loss values, based on LTE and WiMAX standard at one carrier frequency, namely 3.5GHz and a variation of distances in the range of 1 to 50 km, in flat rural, suburban and urban environments. The thesis discusses and implements the Okumura, Hata, Cost-231, Ericsson, Erceg, Walfish, Ecc-33, Lee and the simplified free space path loss models. The objectives of path loss evaluation results are to calculate the link budget, the power outage and the base station cell coverage area for mobile cellular systems. A femtocell (FMC) is a low cost low power cellular home base station, operating in licensed spectrum. Because of the requirement for high data rates and improved coverage indoors, FMC provides a solution to these requirements. FMC is deployed mainly indoors and sometimes outdoors at the cell-edge to increase the area of coverage, capacity and in order to enhance the received signal in the user’s premises. The thesis presents the interference, SINR and the probability of connection for the downlink with different numbers of FMCs based on LTE and WiMAX OFDMA. Moreover, comparisons of interference, SINR and probability of connection for three different numbers of FMCs and for three different indoor areas are presented. In addition, a comparison for the probability of connection with various threshold values and numbers of FMCs is simulated and presented in 3-D. The probability of connection for a varied number of FMCs is a guide study to find the appropriate number of FMCs that could serve a specific indoor area and the proper number of UEs in the specified area. The thesis also presents the interference, SINR and the probability of connection at the uplink for a user equipment device (UE) to an FMC with varied number of UEs based on LTE and WiMAX OFDMA. Moreover, comparisons of the interference, SINR and probability of connection for three different areas at the uplink are presented. Therefore, analyzing probability of connection with varied number of UEs is a worthy study in order to identify the appropriate number of UEs that could be served by a specific number of FMCs at a specific indoor location. The thesis presents and investigates the capacity of MIMO with the presence of FMCs to perform cancellation of co-channel interference. The research introduces algorithms to calculate the capacity of MIMO with the presence of FMCs by two models. The simulation results show that the capacity equations of model-2 give better results than the capacity equations of model-1. Therefore, model-2 is used for the interference cancellation of MIMO in the presence of MIMO. Interference cancellation is performed at the downlink when the signal is transmitted from FMC to UE by mitigating and cancelling the interference which comes from the neighbouring FMCs to the target UE. The thesis introduces, explains and applies a novel algorithm to calculate the capacity of MIMO at the presence of FMCs with interference cancellation by these channel equalizers ZF, MMSE, VBLAST ZF, VBLAST MMSE and VBLAST OFDM MMSE.

Femtocells have been introduced as a solution to poor indoor coverage in cellular communication which has hugely attracted network operators and stakeholders. However, femtocells are designed to co-exist alongside macrocells providing improved spatial frequency reuse and higher spectrum efficiency to name a few. Therefore, when deployed in the two-tier architecture with macrocells, it is necessary to mitigate the inherent co-tier and cross-tier interference. The integration of cognitive radio (CR) in femtocells introduces the ability of femtocells to dynamically adapt to varying network conditions through learning and reasoning. This research work focuses on the exploitation of cognitive radio in femtocells to mitigate the mutual interference caused in the two-tier architecture. The research work presents original contributions in mitigating interference in femtocells by introducing practical approaches which comprises a power control scheme where femtocells adaptively controls its transmit power levels to reduce the interference it causes in a network. This is especially useful since femtocells are user deployed as this seeks to mitigate interference based on their blind placement in an indoor environment. Hybrid interference mitigation schemes which combine power control and resource/scheduling are also implemented. In a joint threshold power based admittance and contention free resource allocation scheme, the mutual interference between a Femtocell Access Point (FAP) and close-by User Equipments (UE) is mitigated based on admittance. Also, a hybrid scheme where FAPs opportunistically use Resource Blocks (RB) of Macrocell User Equipments (MUE) based on its traffic load use is also employed. Simulation analysis present improvements when these schemes are applied with emphasis in Long Term Evolution (LTE) networks especially in terms of Signal to Interference plus Noise Ratio (SINR).

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Dans ce travail, notre contribution est double. Nous développons un cadre d’apprentissage stochastique distribué pour la recherche des équilibres de Nash dans le cas de fonctions de paiement dépendantes d’un état. La plupart des travaux existants supposent qu’une expression analytique de la récompense est disponible au niveau des noeuds. Nous considérons ici une hypothèse réaliste où les noeuds ont seulement une réalisation quantifiée de la récompense à chaque instant et développons un modèle stochastique d’apprentissage à temps discret utilisant une perturbation en sinus. Nous examinons la convergence de notre algorithme en temps discret pour une trajectoire limite définie par une équation différentielle ordinaire (ODE). Ensuite, nous effectuons une analyse de la stabilité et appliquons le schéma proposé dans un problème de commande de puissance générique dans les réseaux sans fil. Nous avons également élaboré un cadre de partage de ressources distribuées pour les réseaux –cloud– en nuage. Nous étudions la stabilité de l’évolution de l’équilibre de Nash en fonction du nombre d’utilisateurs. Dans ce scénario, nous considérons également le comportement des utilisateurs sociaux. Enfin nous avons également examiné un problème de satisfaction de la demande où chaque utilisateur a une demande propre à lui qui doit être satisfaite / As systems are becoming larger, it is becoming difficult to optimize them in a centralized manner due to insufficient backhaul connectivity and dynamical systems behavior. In this thesis, we tackle the above problem by developing a distributed strategic learning framework for seeking Nash equilibria under state dependent payoff functions. We develop a discrete time stochastic learning using sinus perturbation with the realistic assumption, that each node only has a numerical realization of the payoff at each time. We examine the convergence of our discrete time algorithm to a limiting trajectory defined by an ordinary differential equation (ODE). Finally, we conduct a stability analysis and apply the proposed scheme in a generic wireless networks. We also provide the application of these algorithms to real world resource utilization problems in wireless. Our proposed algorithm is applied to the following distributed optimization problems in wireless domain. Power control, beamforming and Bayesian density tracking in the interference channel. We also consider resource sharing problems in large scale networks (e.g. cloud networks) with a generalized fair payoff function. We formulate the problem as a strategic decision-making problem (i.e. a game). We examine the resource sharing game with finite and infinite number of players. Exploiting the aggregate structure of the payoff functions, we show that, the Nash equilibrium is not an evolutionarily stable strategy in the finite regime. Then, we introduce a myopic mean-field response where each player implements a mean-field-taking strategy. We show that such a mean-field-taking strategy is evolutionarily stable in both finite and infinite regime. We provide closed form expression of the optimal pricing that gives an efficient resource sharing policy. As the number of active players grows without bound, we show that the equilibrium strategy converges to a mean-field equilibrium and the optimal prices for resources converge to the optimal price of the mean-field game. Then, we address the demand satisfaction problem for which a necessary and sufficiency condition for satisfactory solutions is provided

The surest way to increase the capacity of a wireless system is by getting the transmitters and receivers closer to each other, which creates the dual bene¯ts of higher quality links and more spatial reuse. In a network with nomadic users, this inevitably involves deploying more infrastructure, typically in the form of microcells, hotspots, distributed antennas, or relays. Compared to these deployments, a less expensive alternative for cellular operators is the recent concept of femtocells { also called home base-stations { which are end consumer installed data access points in the desire to get better indoor voice and data coverage. A two-tier network consisting of a conventional macrocell overlaid with shorter range wireless hotspots o®ers poten- tial capacity bene¯ts with low upfront costs to cellular operators. This dissertation addresses the key technical challenges inherent to a femtocell-aided cellular network, speci¯cally managing radio interference and providing reliable coverage at either tier, for di®erent physical layer technologies. Speci¯c contributions include 1) an uplink capacity analysis and interference avoidance in two-tier networks employing Code Di- vision Multiple Access (CDMA), 2) a decentralized power control scheme in two-tier networks with universal frequency reuse, 3) a coverage analysis of multi-antenna two- tier networks, and 4) spectrum allocation in two-tier networks employing Orthogonal Frequency Division Multiple Access (OFDMA). The goal of this research is to inspire and motivate the use of decentralized interference management techniques requir- ing minimal network overhead in ongoing and future deployments of tiered cellular architectures. / text

a course vers des débits plus élevés pour les utilisateurs de réseaux cellulaires devient plus difficile chaque jour. La nouvelle technologie surnommée "Femtocell" est considérée comme le potentiel sauveur des opérateurs menacés par la concurrence du Wifi. Ce point d'accès résidentiel au réseau cellulaire offre une meilleure couverture et un plus haut débit aux utilisateurs situés en intérieur. Dans cette thèse, nous évaluons séparément, la capacité utile offerte par un point d'accès Wifi et par un point d'accès "Femtocell". Dans la première partie nous proposons un modèle réaliste du mécanisme d'accès à la ressource du Wifi appelé EDCA. Notre modèle est basé sur les chaînes de Markov. Nous évitons les principales approximations faites dans les modèles antérieurs en prenant en compte, un régime non saturé et un canal non idéal. Ainsi nous pouvons obtenir les performances attendues avec plus de précision pour différentes charges de trafic et divers taux d'erreur binaire (BER). Dans un second temps nous évaluons les performances des Femtocells en proposant une nouvelle planification de la ressource radio, ce qui est considérée comme un des principaux défis étant donné le déploiement imprévisible des Femtocells par leurs propres utilisateurs. Nous proposons dans cette thèse différents schéma de "double" réutilisation des fréquences consistant à allouer au femtocell les fréquences déjà utilisées par les macrocells avoisinantes. Nous évaluons les performances en termes de puissance de signal reçue et rapport signal à interférence plus bruit. Nous montrons que femtocells contribue à une amélioration significative par rapport à une couverture macrocell classique.