This thesis studies cooperative techniques that rely on femtocell user diversity to improve the downlink communication quality of macrocell users. We analytically analyze and evaluate the achievable performance of these techniques in the downlink of Rayleigh fading channels. We provide an approximation of both the bit-error rate (BER) and the data throughput that macrocell users receive with femtocell user cooperation. Using simulations, we show that under reasonable SNR values, cooperative schemes enhance the performances of macrocells by improving the BER, outage probability, and data throughput of macrocell users significantly when compared with the traditional, non-cooperative schemes. / Graduation date: 2012

Las demandas y expectativas de los usuarios y operadores móviles crecen sin parar y, consecuentemente, los nuevos estándares han incorporado tecnologías de acceso de radio cada vez más eficientes. Las especificaciones IMT-Advanced para la cuarta generación (4G) de redes móviles de banda ancha requieren, entre otras cosas, tasas más altas de transmisión de datos, del orden de 100 Mbps a 1 Gbps, dependiendo del nivel de movilidad. Para conseguir éstas tasas se ha escogido como tecnología de acceso el Acceso Múltiple por División de Frecuencias Ortogonal (OFDMA), y se han considerado femtoceldas para mejorar la cobertura de espacios interiores. Para explorar completamente la flexibilidad de estas tecnologías y utilizar los escasos recursos radio de la manera más eficiente posible se requieren técnicas de Gestión de Recursos Radio (RRM) adaptativas e inteligentes. En el ámbito de los sistemas celulares basados en OFDMA, uno de los problemas todavía no resuelto es el compromiso que existe entre la eficiencia en la utilización de los recursos y la equidad en su distribución entre los usuarios de la red. El compromiso entre eficiencia y equidad aparece cuando los recursos radio asignados dan lugar a diferentes indicadores de eficiencia con respecto a los distintos usuarios de red (diversidad multi-usuario). El uso de una asignación de recursos oportunista, para explorar estas diversidades y maximizar la capacidad, causa situaciones de desigualdad en la distribución de los recursos. Por otro lado, los esquemas de RRM que propician equidad absoluta consideran un escenario de peor caso, penalizando a los usuarios con mejores condiciones y reduciendo la capacidad del sistema. En esta tesis, se han propuesto varias políticas y técnicas de RRM para balancear este compromiso en el contexto de redes macrocelulares y femtocelulares. En el caso particular de sistemas macrocelulares, proponemos un nuevo paradigma de gestión de red basado en el control del índice de equidad de la celda en escenarios con servicios de tiempo no-real y de tiempo real. Se han estudiado dos enfoques para el control de la equidad: control instantáneo (a corto plazo) utilizando técnicas de RRM de adaptación de tasa y equidad, y control promediado (a mediano plazo) utilizando estructuras de RRM basadas en la Teoría de la Utilidad. En el caso de las femtoceldas, se ha formulado una nueva técnica para evitar la interferencia capaz de balancear el compromiso entre eficiencia espectral y la equidad entre los puntos de acceso de las femtoceldas. Esta estrategia de RRM se basa en una planificación a mediano/largo plazo de las frecuencias disponibles, que toma en consideración la topología de interferencia de grupos de femtoceldas vecinas. Las técnicas de RRM consideradas en esta tesis se han evaluada utilizando de forma sistemática técnicas de simulación numéricas a nivel de sistema. En el caso del escenario macrocelular, se demuestra que las técnicas adaptativas de RRM propuestas son, para los operadores móviles una, herramienta valiosa porqué, además de ser una generalización de estrategias clásicas bien conocidas, son capaces de garantizar de forma eficiente diferentes niveles de equidad en el sistema, y controlar el compromiso entre eficiencia y equidad. Además, se concluye que las estrategias basadas en la teoría de utilidad, que hacen un control promedio de la equidad, muestran resultados tan buenos ó incluso mejores que los presentados por las técnicas basadas en optimización instantánea de la adaptación de la tasa y la equidad, utilizando menores recursos computacionales. Finalmente, se demuestra que la técnica propuesta para evitar interferencia en redes de femtoceldas puede garantizar una coexistencia sin degradaciones entre punto de acceso vecinos para cualquier topología de interferencia. Esta técnica puede ser implementada mediante arquitecturas de red distribuidas ó centralizadas, presentando en ambos casos unos requisitos de señalización muy bajos. / User and cellular operator requirements and expectations have been continuously evolving, and consequently, advanced radio access technologies have emerged. The International Mobile Telecommunications - Advanced (IMT-Advanced) specifications for mobile broadband Fourth Generation (4G) networks state, among other requirements, that enhanced peak data rates of 100 Mbps and 1 Gbps for high and low mobility should be provided. In order to achieve this challenging performance, Orthogonal Frequency Division Multiple Access (OFDMA) has been chosen as the access technology, and femtocells have been considered for improving indoor coverage. In order to fully explore the flexibility of these technologies and use the scarce radio resources in the most efficient way possible, intelligent and adaptive Radio Resource Management (RRM) techniques are crucial. There are many open RRM problems in wireless networks in general and OFDMA-based cellular systems in particular. One of such problems is the fundamental trade-off that exists between efficiency in the resource usage and fairness in the resource distribution among network players. Several opportunistic RRM algorithms, which dynamically allocate the resources to the network players that present the highest efficiency indicator with regard to these resources, have been proposed to maximize the efficiency in the resource usage. The trade-off between efficiency and fairness appears when the resources have different efficiency indicators to different network players (multi-user or multi-cell diversity). The use of opportunistic resource allocation to explore these diversities causes unfair situations in the resource distribution. On the other hand, schemes that provide absolute fairness deal with the worst case scenario, penalizing players with better condition and reducing the system capacity. In this thesis, several RRM policies and techniques are proposed to balance this compromise in macrocell and femtocell networks. In the particular case of macrocell systems, we propound a new network management paradigm based on the control of a cell fairness index in scenarios with Non-Real Time (NRT) or Real Time (RT) services. Two fairness control approaches are studied: instantaneous (short-term) control by means of generalized fairness/rate adaptive RRM techniques and average (mid-term) control using utility-based frameworks. For femtocell networks, a novel interference avoidance technique able to balance the trade-off between spectral efficiency in the femtocell tier and fairness among the Femtocell Access Points (FAPs) is formulated. This RRM strategy is based on a high-level, mid/long-term frequency planning that takes into account the topology of groups of neighboring FAPs. The RRM techniques considered in this thesis are evaluated by means of extensive system-level and/or numerical simulations. Regarding the macrocell scenario, it is shown that the proposed adaptive RRM techniques are valuable tools for the mobile operators, because they are generalizations of well-known classic strategies found in the literature and they can effectively guarantee different fairness levels in the system and control the trade-off between efficiency and fairness. Furthermore, it is concluded that the utility-based strategies that perform an average fairness control can provide performance results as good as the fairness/rate adaptive techniques, which are based on instantaneous optimization, using less computational resources. Finally, it is demonstrated that the proposed interference avoidance technique for femtocell networks can guarantee a seamless coexistence between neighboring FAPs in any interference topology. Furthermore, this technique can be implemented in both centralized and distributed network architectures and generates very low signaling overhead.

The wireless networks of the future are likely to be tiered, i.e., a heterogeneous mixture of overlaid networks that have different power, spectrum, hardware, coverage, mobility, complexity, and technology requirements. The focus of this dissertation is to improve the performance and increase the throughput of tiered networks with resource/interference management methods, node densification schemes, and transceiver designs; with their applications to advanced tiered network structures such as heterogeneous networks (i.e., picocells, femtocells, relay nodes, and distributed antenna systems), device-to-device (D2D) networks, and aeronautical communication networks (ACN). Over the last few decades, there has been an incredible increase in the demand for wireless services in various applications in the entire world. This increase leads to the emergence of a number of advanced wireless systems and networks whose common goal is to provide a very high data rate to countless users and applications. With the traditional macrocellular network architectures, it will be extremely challenging to meet such demand for high data rates in the upcoming years. Therefore, a mixture of different capability networks has started being built in a tiered manner. While the number and capabilities of networks are increasing to satisfy higher requirements; Modeling, managing, and maintaining the entire structure has become more challenging. The capacity of wireless networks has increased with various different advanced technologies/methodologies between 1950-2000 which can be summarized under three main titles: spectrum increase (x25), spectrum efficiency increase (x25), and network density (spectrum reuse) increase (x1600). It is vital to note that among different schemes, the most important gain is explored with increasing the reuse and adding more nodes/cells into the system, which will be the focus of this dissertation. Increasing the reuse by adding nodes into the network in an uncoordinated (irregular in terms of power, spectrum, hardware, coverage, mobility, complexity, and technology) manner brought up heterogeneity to the traditional wireless networks: multi-tier resource management problems in uncoordinated interference environments. In this study, we present novel resource/interference management methods, node densification schemes, and transceiver designs to improve the performance of tiered networks; and apply our methodologies to heterogeneous networks, D2D networks, and ACN. The focus and the contributions of this research involve the following perspectives: 1. Resource Management in Tiered Networks: Providing a fairness metric for tiered networks and developing spectrum allocation models for heterogeneous network structures. 2. Network Densification in Tiered Networks: Providing the signal to interference plus noise ratio (SINR) and transmit power distributions of D2D networks for network density selection criteria, and developing gateway scheduling algorithms for dense tiered networks. 3. Mobility in Tiered Networks: Investigation of mobility in a two-tier ACN, and providing novel transceiver structures for high data rate, high mobility ACN to mitigate the effect of Doppler.

A variety of wide band wireless systems have been pushed towards their limits in order to meet growing interest for high data rate in wireless communications.In particular, the limit due to the spectrum scarcity forces communication systems to utilize the spectrum resource at maximum efficiency level. One of the methods that allow effective spectrum employing is to cover multiple systems over same spectrum source by allowing bearable interference to occur between them. Femtocells have been recently introduced as a remedy to spectrum scarcity and coverage problems in current cellular structures. Femtocells are personal use base stations and they share the spectrum in a way that they can coexist with the macrocell. This thesis provides a critical reviews of different access methods in femtocell networks and further introduces improvements related to these access methods. Simulation results validate capacity improvement of proposed techniques compared to the existing access methods.

No description available.

[pt] Nesta dissertação é investigada, por meio de simulações computacionais, a utilização do conceito de rádio cognitivo considerando a técnica de sensoriamento espectral aplicada às femtocélulas do sistema móvel LTE Release 10 para reduzir os problemas de interferência entre camadas (cross-tier) existentes em um cenário de coexistências das redes heterogêneas (femtocélulas e macrocélulas). Além disso, é investigada a interferência gerada por parte das femtocélulas LTE Release 10 em receptores de TV Digital operando em bandas de frequência adjacentes. Neste caso, além da simulação computacional foram realizadas medições em cenários de coexistência da femtocélula LTE e do Sistema Brasileiro de TV Digital na banda de frequência de 700 MHz. / [en] This dissertation investigates, using computer simulation, the use of spectrum sensing Cognitive Radio concept applied in femtocells of the LTE Release 10 mobile system in order to reduce the interference cross-tier problems that exists in the coexistence scenario of a heterogeneous network (femto-macrocells). Furthermore, the interference produced by LTE Release 10 femtocells in TV Digital receivers operating in adjacent frequency bands was investigated. In this case, besides the computer simulations measurements were performed in an experimental setup implementing coexistence scenarios of the LTE femtocell and the Brazilian Digital TV System at the 700 MHz frequency band.

Most of the cellular tra c (voice and data) is generated indoors. Due to attenuation from walls, quality of service (QoS) of di erent applications degrades for indoor tra c. Thus in order to provide QoS for such users the Macro base station (MBS) has to transmit at high power. This increases recurring costs to the service provider and contributes to green house emissions. Hence, Femtocells (FC) are considered as an option. Femto Access Points (FAP) are low cost, low powered, small base stations deployed indoors by customers. A substantial part of indoor tra c is diverted from the Macrocell (MC) through the FAP. Since the FCs also use the same channels as the MC, deployment of FCs causes interference to not only its neighbouring FCs but also to the users in the MC. Thus, we need better interference management techniques for this system. In this thesis, we consider a system with multiple Femtocells operating in a Macrocell. FCs and MC use same set of multiple channels and support multiple users. Each user may have a minimum rate requirement. To limit interference to the MC, there is a peak power constraint on each channel. In the rst part of the thesis, we consider sparsely deployed FCs where the interference between the FCs is negligible. For this we formulate the problem of channel allocation and power control in each FC. We develop computationally e cient, suboptimal algorithms to satisfy QoS of each user in the FC. If QoS of each user is not satis ed, we provide solutions which are fair to all the users. In the second part of the thesis, we consider the case of densely deployed FCs where we formulate the problem of channel allocation and power control in each Femtocell as a noncooperative Game. We develop e cient decentralized algorithms to obtain a Nash equilibrium (NE) at which QoS of each user is satis ed. We also obtain e cient decentralized algorithms to obtain fair NE when it may not be feasible to satisfy the QoS of all the users in the FC. Finally, we extend our algorithms to the case where there may be voice and data users in the system. In the third part of the thesis, we continue to study the problem setup in the second part, where we develop algorithms which can simultaneously consider the cases where QoS of users can be satis ed or not. We provide algorithms to compute Coarse Correlated Equilibrium (CCE), Pareto optimal points and Nash bargaining solutions. In the nal part of the thesis, we consider interference limit at the MBS and model FCs as sel sh nodes. The MBS protects itself via pricing subchannels per usage. We obtain a Stackelberg equilibrium (SE) by considering MBS as a leader and FCs as followers.

Les systèmes de communication sans fil caractérisés par des services à haute vitesse sont en évolution permanentes malgré les restrictions en termes de la capacité du système et les conflits de couverture intérieure. Récemment, les réseaux “SmallCells” basés sur le standard LTE présentent une solution prometteuse en offrant les services demandés avec une meilleure couverture à l’intérieur et augmentant la capacité du système. Cependant, de nombreux défis rencontrent les constructeurs et les opérateurs pour un déploiement efficace de ces systèmes. Dans cette thèse, afin de développer ce type de réseaux et d’apporter des améliorations considérables de Qualité de Service (QoS) et de débits, nous adoptons une stratégie se basant complémentairement sur deux différents niveaux : couche de liaison (MAC) et couche physique. En première partie, au niveau de la couche de liaison, nous proposons deux algorithmes d’ordonnancement et d’allocation conjointes de ressources se basant sur la technique d’Adaptation de Modulation et de Codage (AMC) et sur le contrôle de puissance pour les deux liaisons descendante et montante respectivement. Deux catégories distinctes d’utilisateurs qui diffèrent par la Qualité de Service demandée sont considérées. Ces algorithmes sont nommés respectivement : “Downlink AMC-QRAP” et “Uplink AMC-QRAP”. L’adaptation conjointe de puissance de transmission et de type de Modulation&Codage répond forcement aux variations de la qualité de la liaison sur chaque canal radio destiné à être alloué. Cependant, les deux liaisons, descendante et montante diffèrent par leurs spécificités. En particulier, comme mode de transmission du signal, le système 3GPP LTE utilise la technique OFDMA pour la liaison descendante et la technique SC-FDMA, plus efficace en termes d’énergie, pour la liaison montante. Une modélisation sous forme de problèmes d’optimisation linéaire est ainsi conçue. Comme compromis entre les architectures de réseaux: centralisée et distribuée, nous utilisons l’architecture de groupes ou “clusters” ainsi proposée dans la littérature. Dans la deuxième partie de notre recherche, nous avons abord´e les techniques de la “couche physique” en termes de traitement de signal comme une approche d’amélioration du système LTE. Ainsi, deux contributions basées sur la “transformée en ondelettes” (Wavelet Transform) sont proposées. Premièrement, vu que la technique de modulation multi-porteuse OFDM souffre de plusieurs limitations en termes d’efficacité spectrale et énergétique, de synchronisation et d’interférence entre porteuses, nous proposons une méthode alternative basée sur les ondelettes. Nous avons démontré que la substitution de la transformée de Fourier par la transformée en ondelettes dans la technique OFDM permet de dépasser les différentes limitations de l’OFDM. Enfin, nous avons propos´e une approche pour délimiter et détecter les différents canaux de ressources alloués. Elle est utilisée dans l’algorithme d’ordonnancement de la transmission montante pour améliorer la fiabilité de la transmission et réduire le temps de convergence du problème d’optimisation. Des simulations étendues selon différentes densités de réseau ont été réalisées, en utilisant plusieurs paramètres tels que l’efficacité spectrale, la puissance de transmission, le taux de satisfaction en termes de débits demandés et la capacité du réseau. Nous avons comparé nos méthodes à plusieurs travaux existants dans la littérature et prouvé la surperformance pour les différents paramètres pris en compte. / Responding to the huge demand for high data rates and satisfying Quality of Service (QoS) requirements are the main objectives of the wireless mobile operators. LTE-based small cell system is a promising technology offering the required services, enhanced indoor coverage and increased system capacity. However, many challenges face the constructors and the operators for an effective deployment of these systems. In this thesis, in order to evolve such systems and adduce significant enhancement in terms of QoS and throughput, we adopt a complementary strategy based on both data link layer and physical layer.First, we propose, on the link layer level, two scheduling and joint resource allocation algorithm based on the Adaptive Modulation and Coding (AMC) and the power control mechanism for OFDMA-Downlink and SC-FDMA-Uplink connections respectively. Namely, they refer to: “Downlink AMC-QRAP” and “Uplink AMC-QRAP”. The joint adaptation of the transmission power and the Modulation and Coding Scheme reliably interacts with the link quality on each allocated sub-channel. Two distinct user categories are considered to differentiate between different QoS levels required. Accordingly, a linear optimization model is performed for the problem resolution. A clustering approach proposed in the literature has been used as a tradeoff between centralized and distributed schemes. Particularly, we used the spectrum sensing technique as proposed on the physical layer to detect surrounding transmissions.After that, we tackle the physical layer “signal processing” techniques as an LTE enhancement approach. Thus, two contributions based on the “wavelet transform” (WT) are proposed.The “wavelet-based OFDM” technique is firstly proposed as an alternative transmission mode for both downlink and uplink of the LTE and beyond wireless systems. In fact, theOFDM suffers from several limitations in terms of PAPR, spectral efficiency, synchronization cost and the inter-carrier interference. We proved that with substituting the Fourier transform by the wavelet transform in the OFDM technique, the different OFDM limitations can be significantly overcame. Second, we proposed an enhanced spectrum sensing approach based on WT tool that accurately delimits the occupied resource blocks in the whole spectrum. These physical layer enhancements help improving the scheduling algorithm for the uplink proposed in our second contribution.Extensive network simulations with different network densities have been conducted, using several metrics such as spectral efficiency, throughput satisfaction rate, user outage and transmission power. We have compared our methods to several existing works in the literature and proved the outperformance for the different considered metrics.

The evolution of Mobile Internet has led to the growth of bandwidth demanding applications like video streaming and social networking. The required data rates projected for such applications cannot be sustained by current cellular networks. New network architectures like Long Term Evolution (LTE) and LTE Advanced have been carefully engineered and introduced to fulfill such large data rates. The recent introduction of femtocells enabled high data rates and better coverage indoors, without the need for site establishment or upgrading the network infrastructure. Femtocells, however, will potentially suffer from major interference problems due to their expected dense and ad hoc deployment. The main contribution in this thesis is the introduction of a new and a very promising direction in deriving capable and efficient interference mitigation schemes, and comparing this direction to current techniques in the literature. Several works have studied the effect of interference on networks employing femtocells. In this thesis, we also survey such works and provide an overview of the elements considered in mitigating interference. We introduce a new scheme known for its optimality, and use it for frequency assignment in downlink femtocell networks. The algorithm is based on optimization search rather than greedy or heuristic methods. Experimental simulations will be shown to evaluate the proposed scheme against other schemes from the literature. / Thesis (Master, Computing) -- Queen's University, 2012-03-31 02:14:28.549

Face à la croissance exponentielle des réseaux mobiles très haut débit, les opérateurs de téléphonie mobile se sont lancé dans le déploiement des réseaux dits hiérarchiques (HetNet), composés par des sous-réseaux avec des caractéristiques divergentes en termes de type des cellules déployées et des technologies d’accès radio utilisées. Avec ce caractère hétérogène des réseaux cellulaire, l’exploitation de ces derniers devienne de plus en plus compliquée et coûteuse impliquant le déploiement, la configuration et la reconfiguration de stations de base et d’équipements de différentes caractéristiques. Ainsi, l’intégration dans les réseaux HetNet de fonctionnalités d’auto-configuration automatisant et simplifiant l’exploitation des réseaux deviennent une demande forte des opérateurs. Cette thèse a pour objectif l’étude et le développement de solutions de gestion dynamique de l’équilibrage de charges entre les différentes couches composant un même HetNet, pour une expérience utilisateur (QoE) améliorée. Dans ce contexte, une classe des algorithmes d’équilibrage de charges dite ‘équilibrage de charges par adaptation dynamique des paramètres de la procédure de handover’ est étudiée. Pour commencer, nous développons un modèle théorique basé sur des solutions et des outils de la géométrie stochastique et incorporant le caractère hétérogène des réseaux cellulaires. Ensuite nous exploitons ce modèle pour introduire des algorithmes d’adaptation des paramètres de handover basés sur la maximisation de la puissance reçue et du rapport signal/brouillage plus bruit (SINR). Nous exploitons ces résultats pour implémenter et étudier, par simulation à évènements discrets, des algorithmes d’équilibrage de charges dans le contexte des réseaux LTE HetNet auto-organisés basés sur les spécifications 3GPP. Ces travaux soulignent l’importance de l’équilibrage de charges afin de booster les performances des réseaux cellulaires en termes de débit global transmis, perte de paquets de données et utilisation optimisée des ressources radio. / High demands on mobile networks provide a fresh opportunity to migrate towardsmulti-tier deployments, denoted as heterogeneous network (HetNet), involving a mix of cell types and radio access technologies working together seamlessly. In this context, network optimisation functionalities such as load balancing have to be properly engineered so that HetNet benefit are fully exploited. This dissertation aims to develop tractable frameworks to model and analyze load balancing dynamics while incorporating the heterogeneous nature of cellular networks. In this context we investigate and analyze a class of load balancingstrategies, namely adaptive handover based load balancing strategies. These latter were firstly studied under the general heading of stochastic networks using independent and homogeneous Poisson point processes based network model. We propose a baseline model to characterize rate coverage and handover signalling in K-tier HetNet with a general maximum power based cell association and adaptive handover strategies. Tiers differ in terms of deployment density and cells characteristics (i.e. transmit power, bandwidth, and path loss exponent). One of the main outcomes is demonstrating the impact of offloading traffic from macro- to small-tier. This impact was studied in terms of rate coverage and HO signalling. Results show that enhancement in rate coverage is penalized by HO signalling overhead. Then appropriate algorithms of LB based adaptive HO are designed and their performance is evaluated by means of extensive system level simulations. These latter are conducted in 3GPP defined scenarios, including representation of mobility procedures in both connectedstate. Simulation results show that the proposed LB algorithms ensure performance enhancement in terms of network throughput, packet loss ratio, fairness and HO signalling.