In recent years, cellular systems based on orthogonal frequency division multiple access – time division duplex (OFDMA-TDD) have gained considerable popularity. Two of the major reasons for this are, on the one hand, that OFDMA enables the receiver to effectively cope with multipath propagation while keeping the complexity low. On the other hand, TDD offers efficient support for cell-specific uplink (UL)/downlink (DL) asymmetry demands by allowing each cell to independently set its UL/DL switching point (SP). However, cell-independent SP gives rise to crossed slots. In particular, crossed slots arise when neighbouring cells use the same slot in opposing link directions, resulting in base station (BS)-to-BS interference and mobile station (MS)-to-MS interference. BS-to-BS interference, in particular, can be quite detrimental due to the exposed location of BSs, which leads to high probability of line-of-sight (LOS) conditions. The aim of this thesis is to address the BS-to-BS interference problem in OFDMA-TDDcellular networks. A simulation-based approach is used to demonstrate the severity of BS-to-BS interference and a signal-to-interference-plus-noise ratio (SINR) equation for OFDMA is formulated to aid system performance analysis. The detrimental effects of crossed slot interference in OFDMA-TDD cellular networks are highlighted by comparing methods specifically targeting the crossed slots interference problem. In particular, the interference avoidance method fixed slot allocation (FSA) is compared against state of the art interference mitigation approaches, viz: random time slot opposing (RTSO) and zone division (ZD). The comparison is done based on Monte Carlo simulations and the main comparison metric is spectral efficiency calculated using the SINR equation formulated in this thesis. The simulation results demonstrate that when LOS conditions among BSs are present, both RTSO and ZD perform worse than FSA for all considered performance metrics. It is concluded from the results that current interference mitigation techniques do not offer an effective solution to the BS-to-BS interference problem. Hence, new interference avoidance methods, which unlike FSA, do not sacrifice the advantages of TDD are open research issues addressed in this thesis. The major contribution of this thesis is a novel cooperative resource balancing technique that offers a solution to the crossed slot problem. The novel concept, termed asymmetry balancing, is targeted towards next-generation cellular systems, envisaged to have ad hoc and multi-hop capabilities. Asymmetry balancing completely avoids crossed slots by keeping the TDD SPs synchronised among BSs. At the same time, the advantages of TDD are retained, which is enabled by introducing cooperation among the entities in the network. If a cell faces resource shortage in one link direction, while having free resources in the opposite link direction, the free resources can be used to support the overloaded link direction. In particular, traffic can be offloaded to near-by mobile stations at neighbouring cells that have available resources. To model the gains attained with asymmetry balancing, a mathematical framework is developed which is verified by Monte Carlo simulations. In addition, asymmetry balancing is compared against both ZD and FSA based on simulations and the results demonstrate the superior performance of asymmetry balancing. It can be concluded that the novel interference avoidance approach is a very promising candidate to.

We are at that moment of network evolution when we have realised that our telecommunication systems should mimic features of human kind, e.g., the ability to understand the medium and take advantage of its changes. Looking towards the future, the mobile industry envisions the use of fully automatised cells able to self-organise all their parameters and procedures. A fully self-organised network is the one that is able to avoid human involvement and react to the fluctuations of network, traffic and channel through the automatic/autonomous nature of its functioning. Nowadays, the mobile community is far from this fully self-organised kind of network, but they are taken the first steps to achieve this target in the near future. This thesis hopes to contribute to the automatisation of cellular networks, providing models and tools to understand the behaviour of these networks, and algorithms and optimisation approaches to enhance their performance. This work focuses on the next generation of cellular networks, in more detail, in the DownLink (DL) of Orthogonal Frequency Division Multiple Access (OFDMA) based networks. Within this type of cellular system, attention is paid to interference mitigation in self-organising macrocell scenarios and femtocell deployments. Moreover, this thesis investigates the interference issues that arise when these two cell types are jointly deployed, complementing each other in what is currently known as a two-tier network. This thesis also provides new practical approaches to the inter-cell interference problem in both macro cell and femtocell OFDMA systems as well as in two-tier networks by means of the design of a novel framework and the use of mathematical optimisation. Special attention is paid to the formulation of optimisation problems and the development of well-performing solving methods (accurate and fast).

This thesis proposes four novel techniques to solve the problem of growing energy consumption requirements in cellular communication networks. The first and second part of this work propose a novel energy efficient scheduling mechanism and two new bandwidth management techniques, while the third part provides an algorithm to actively manage the power state of base stations (BSs) so that energy consumption is minimized throughout the day while users suffer a minimal loss in achieved data rate performance within the system. The proposed energy efficient score based scheduler (EESBS) is based on the already existing principle of score based resource allocation. Resource blocks (RBs) are given scores based on their energy efficiency for every user and then their allocation is decided based on a comparison between the scores of the different users on each RB. Two additional techniques are introduced that allow the scheduler to manage the user’s bandwidth footprint or in other words the number of RBs allocated. The first one, bandwidth expansion mode (BEM), allows users to expand their bandwidth footprint while retaining their overall transmission data rate. This allows the system to save energy due to the fact that data rate scales linearly with bandwidth and only logarithmically with transmission power. The second technique, time compression mode (TCoM), is targeted at users whose energy consumption is dominated by signalling overhead transmissions. If the assumption is made that the overhead is proportional to the number of RBs allocated, then users who find themselves having low data rate demands can release some of their allocated RBs by using a higher order modulation on the remaining ones and thus reduce their overall energy expenditure. Moreover, a system that combines all of the aforementioned scheduling techniques is also discussed. Both theoretical and simulation results on the performance of the described systems are provided. The energy efficient hardware state control (EESC) algorithm works by first collecting statistical information about the loading of each BS during the day that is due to the particular mobility patterns of users. It then uses that information to allow the BSs to turn off for parts of the day when the expected load is low and they can offload their current users to nearby cell sites. Simplified theoretical, along with complete system computer simulation, results are included. All the algorithms presented are very straightforward to implement and are not computationally intensive. They provide significant energy consumption reductions at none to minimal cost in terms of experienced user data rate.

In wireless networks, there is an ever-increasing demand for higher system throughputs, along with growing expectation for all users to be available to multimedia and Internet services. This is especially difficult to maintain at the cell-edge. Therefore, a key challenge for future orthogonal frequency division multiple access (OFDMA)-based networks is inter-cell interference coordination (ICIC). With full frequency reuse, small inter-site distances (ISDs), and heterogeneous architectures, coping with co-channel interference (CCI) in such networks has become paramount. Further, the needs for more energy efficient, or “green,” technologies is growing. In this light, Uplink Interference Protection (ULIP), a technique to combat CCI via power reduction, is investigated. By reducing the transmit power on a subset of resource blocks (RBs), the uplink interference to neighbouring cells can be controlled. Utilisation of existing reference signals limits additional signalling. Furthermore, cell-edge performance can be significantly improved through a priority class scheduler, enhancing the throughput fairness of the system. Finally, analytic derivations reveal ULIP guarantees enhanced energy efficiency for all mobile stations (MSs), with the added benefit that overall system throughput gains are also achievable. Following this, a novel scheduler that enhances both network spectral and energy efficiency is proposed. In order to facilitate the application of Pareto optimal power control (POPC) in cellular networks, a simple feasibility condition based on path gains and signal-to-noise-plus- interference ratio (SINR) targets is derived. Power Control Scheduling (PCS) maximises the number of concurrently transmitting MSs and minimises their transmit powers. In addition, cell/link removal is extended to OFDMA operation. Subsequently, an SINR variation technique, Power SINR Scheduling (PSS), is employed in femto-cell networks where full bandwidth users prohibit orthogonal resource allocation. Extensive simulation results show substantial gains in system throughput and energy efficiency over conventional power control schemes. Finally, the evolution of future systems to heterogeneous networks (HetNets), and the consequently enhanced network management difficulties necessitate the need for a distributed and autonomous ICIC approach. Using a fuzzy logic system, locally available information is utilised to allocate time-frequency resources and transmit powers such that requested rates are satisfied. An empirical investigation indicates close-to-optimal system performance at significantly reduced complexity (and signalling). Additionally, base station (BS) reference signals are appropriated to provide autonomous cell association amongst multiple co-located BSs. Detailed analytical signal modelling of the femto-cell and macro/pico-cell layouts reveal high correlation to experimentally gathered statistics. Further, superior performance to benchmarks in terms of system throughput, energy efficiency, availability and fairness indicate enormous potential for future wireless networks.

O padrão IEEE 802.16e é uma tecnologia emergente para redes de próxima geração com suporte à qualidade de serviço para usuários fixos e móveis. No contexto de aplicações móveis, a técnica OFDMA (Orthogonal Frequency Division Multiple Access) deve ser empregada para multiplexação de canais de rádio frequência, suportando a alocação simultânea do canal para múltiplos usuários. Porém, essa alocação, considerando a estrutura do quadro OFDMA, não é definida pelo padrão IEEE 802.16e. A maioria das pesquisas atuais sobre arquiteturas de escalonamento baseadas nessa técnica de multiplexação estão focadas na transmissão downlink ou consideram apenas parcialmente os aspectos decorrentes do emprego da técnica OFDMA. Sendo assim, neste trabalho é apresentada uma arquitetura de escalonamento hierárquica, com dois níveis, para transmissões uplink em redes IEEE 802.16e, baseadas em OFDMA. A arquitetura proposta aborda a divisão do subquadro uplink entre oportunidades de requisição de banda e oportunidades de transmissão de dados, no Nível 1, e a seleção das requisições de banda para atendimento, no Nível 2. A proposta considera, além da técnica de multiplexação do canal, as cinco classes de serviço previstas pelo padrão IEEE 802.16e e o mecanismo de alocação de banda definido para a tecnologia. Uma ferramenta de simulação foi desenvolvida para avaliar o desempenho da proposta, considerando os diferentes aspectos da arquitetura e comparando com trabalhos relacionados. A avaliação é realizada considerando métricas como atraso médio no atendimento de requisições, percentual de requisições descartadas e a utilização do quadro. / The IEEE 802.16e standard is an emerging next generation network technology, designed to provide guaranteed QoS to both fixed and mobile users. In the context of mobile users, OFDMA technique must be used to multiplex the radio frequency channel. This technique allows to allocate the channel to multiple users at the same time. However, details about this allocation, considering the OFDMA frame structure, are not defined by the IEEE 802.16e standard. In this context, most of the current researches found on literature focus on proposing scheduling architectures for downlink transmissions only. Furthermore, researches that consider uplink transmissions, typically consider OFDMA aspects only partially. Therefore, this work presents an hierarchical scheduling architecture designed for uplink transmissions. The proposed architecture is composed of two levels. In the Level 1 the architecture addresses the division of the uplink subframe in bandwidth request opportunities, and data transmission opportunities. Level 2 is used to select among the bandwidth request, those that will be served on the next uplink subframe. The proposal considers OFDMA multiplexing technique, the five classes of service defined for QoS provisioning, and the bandwidth allocation mechanism defined in IEEE 802.16e standard. In order to evaluate the behavior of the proposed architecture, a simulation tool was developed. The approach used for evaluation was to compare the performance of the proposed architecture with related works found in the literature. The performance evaluation considers metrics such as average delay for serving requests, requests discarded, and the overall frame utilization.

<p>The new mobile standard Long Term Evolution delivers high data rates, small delay and a more efficiently utilized RF spectrum. A solution to maintain this performance in user dense areas or areas with bad reception is the deployment of so-called femtocells. Femtocells are small base stations that are deployed indoors and share the RF spectrum with the whole mobile network. The idea is that femtocells will increase mobile operators network coverage and capacity while it at the same time increase users data throughput. There are several challenges with femtocells, both technical and economical ones. The most debated issues is how femtocells should schedule users while operating in an environment where other femtocells and base stations are interfering. In this work we developed a simulation tool to simulate the scheduling interaction between femtocells and base stationsin order to show the performance of radio resource schedulers. This rapport also aims to evaluate an approach to a femtocell scheduler to solve this issue in a satisfying way. The report gives a description of the structure of the implemented simulation tool together with some reflections on how future designs of similar or more complex simulation environments could be done.</p>

<p>We are very thirsty in terms of everything to fulfil our needs in a sophisticated way, and this leads me choose the so called master thesis titled “Multihop Concept in Cellular Systems”.</p><p>This thesis introduces an approach towards the integration of relaying or multihop scheme in the next generation of cellular networks. In a multihop cellular architecture, the users send their data to the base station via relay station or with direct communication to the base station. These relay stations can either be the nomadic, fixed at specific location or users’ mobile station (i.e. mobile relay station). The main objective of this paper is to compare the difference between the relaying network architecture with different channel bandwidth as well as their performance gain. For this we integrate the relay station into conventional cellular networks using IEEE 802.16j (One of the standard introduced relay station concept in WiMAX) OFDMA (Orthogonal Frequency Division Multiple Access is a transmission technique that is based on many orthogonal subchannels (set of carriers) that transmits simultaneously). The results show that under certain conditions the throughput and coverage of the system has been increased with the introduction of the relay station in to cellular base station zone.</p>

Joint channel and rate allocation with power minimization in orthogonal frequency-division multiple access (OFDMA) has attracted extensive attention. Most of the research has dealt with the development of suboptimal but low-complexity algorithms. In this paper, the contributions comprise new insights from revisiting tractability aspects of computing the optimum solution. Previous complexity analyses have been limited by assumptions of fixed power on each subcarrier or power-rate functions that locally grow arbitrarily fast. The analysis under the former assumption does not generalize to problem tractability with variable power, whereas the latter assumption prohibits the result from being applicable to well-behaved power-rate functions. As the first contribution, we overcome the previous limitations by rigorously proving the problem's NP-hardness for the representative logarithmic rate function. Next, we extend the proof to reach a much stronger result, namely, that the problem remains NP-hard, even if the channels allocated to each user are restricted to be a consecutive block with given size. We also prove that, under these restrictions, there is a special case with polynomial-time tractability. Then, we treat the problem class where the channels can be partitioned into an arbitrarily large but constant number of groups, each having uniform gain for every individual user. For this problem class, we present a polynomial-time algorithm and provide its optimality guarantee. In addition, we prove that the recognition of this class is polynomial-time solvable. / <p>Funding Agencies|Swedish Research Council||Linkoping-Lund Excellence Center in Information Technology||Center for Industrial Information Technology of Linkoping University||</p>

La próxima cuarta generación (4G) de redes de comunicaciones móviles celulares considera una interfaz radio basada en OFDMA (Orthogonal Frequency Division Multiple Access). Esta tecnología ofrece robustez a la propagación multicamino y diversidad en frecuencia gracias a la división del ancho de banda de operación en un conjunto de pequeños subcanales en frecuencia para así alcanzar un uso eficiente del espectro. Sin embargo, un importante desafío en una interfaz radio OFDMA es la manera en la que los subcanales en frecuencia se asignan a las distintas celdas. En primer lugar, la carga de tráfico podría variar a lo largo del tiempo y del espacio, de modo que los clásicos patrones fijos de asignación de espectro (es decir, los esquemas de planificación de frecuencias) pueden conducir a una carencia de recursos en ciertas celdas o a una falta de aprovechamiento de los mismos en otras. En segundo lugar, los futuros marcos reguladores del espectro cambiarán la mentalidad sobre su uso, planteando la coexistencia de usuarios primarios y secundarios del espectro en una misma área geográfica. Por lo tanto, una adecuada gestión del espectro primario podría facilitar la aparición de oportunidades del uso del espectro para usuarios secundarios a la vez que el operador podría obtener una nueva entrada de ingresos por ese uso. Finalmente, los futuros escenarios celulares tenderán a ser descentralizados, especialmente con la aparición de nuevos despliegues basados en femtoceldas (puntos de acceso de limitada cobertura desplegados por el propio usuario en la banda espectral en la que el operador tiene licencia), donde se requerirá un alto grado de independencia a la hora de decidir los canales que usa cada femtocelda, ya que, obviamente, las tareas centralizadas planificación de frecuencias tienen poco sentido práctico en estos escenarios.Esta tesis contribuye a la investigación sobre la asignación de espectro en redes móviles celulares 4G basadas en OFDMA proponiendo una solución para manejar dinámicamente la asignación de espectro por celda. Con este fin, se proponen estrategias dinámicas asignación de espectro (en inglés Dynamic Spectrum Assigment: DSA) y un marco práctico para ejecutarlas. Para reducir costes operacionales y la intervención humana en el proceso, el marco DSA propuesto se ha diseñado basándose en conceptos de autoorganización de modo que la red puede de forma autónoma (i) observar el funcionamiento de la asignación actual de espectro, (ii) analizar si una nueva asignación de espectro es necesaria, y (iii) decidir una nueva asignación de espectro que se adapte mejor a las condiciones de la red. Además, se propone una arquitectura funcional centralizada y descentralizada que permite que el marco DSA pueda aplicarse a varios escenarios, desde escenarios macrocelulares donde típicamente se emplea un control centralizado, a futuros escenarios con femtoceldas donde los nodos son prácticamente independientes y requieren de decisiones autónomas a nivel de celda para la asignación de espectro. La tarea de decisión del marco DSA reside en las estrategias DSA propuestas, donde una de ellas se basa en el aprendizaje máquina para explotar el conocimiento adquirido previamente en el pasado. Además, esta estrategia tiende a seleccionar una asignación de espectro óptima en el sentido de que maximiza una señal de recompensa definida apropiadamente en términos de métricas del funcionamiento de la red (e.g., eficiencia espectral, SINR, entre otras). Ciertamente, la autoorganización y el aprendizaje máquina en el contexto de la asignación de espectro en interfaces radio basadas en OFDMA se han explotado poco y constituyen así una novedad importante derivada del trabajo de esta tesis.Los resultados revelan importantes mejoras sobre estrategias del estado del arte en términos de eficiencia espectral (en bits/s/Hz), satisfacción de la calidad de servicio de los usuarios, fairness entre el throughput obtenido por los usuarios, y la capacidad para generar oportunidades para el uso secundario del espectro en grandes áreas geográficas. También, el marco DSA propuesto basado en autoorganización muestra atractivas capacidades desde la perspectiva del despliegue inicial, donde los nodos son capaces de autoconfigurarse después de su encendido introduciendo un impacto mínimo en sistema ya desplegado. Así el marco propuesto constituye una contribución práctica para solucionar el despliegue de millares de femtoceldas en un escenario macrocelular. / Next fourth generation (4G) of cellular mobile networks envisage a radio interface based on OFDMA (Orthogonal Frequency Division Multiple Access). OFDMA offers frequency diversity and robustness against multipath channel propagation thanks to the division of a wide bandwidth into small OFDMA frequency resources, so that an efficient spectrum usage is attained. However, one important challenge in a 4G OFDMA-based radio interface of a cellular network is the way in which OFDMA frequency resources are assigned to cells. First, intercell interference must be mitigated to achieve the highest spectral efficiency. Second, traffic loads could vary along time and space, so typical fixed spectrum assignment patterns (i.e., frequency planning) could lead to lack of spectrum resources in some cells or underutilization of them in others. Third, future regulatory spectrum frameworks will change the mindset about the usage of the spectrum by planning the co-existence of primary (licensees) and secondary users of the spectrum in the same geographical area. Hence, an adequate primary management of the spectrum could ease the appearance of spectrum usage opportunities for secondary users at the same time that the primary operator could obtain a new revenue income for that usage. Finally, future cellular scenarios will tend to be decentralized, especially with the appearance of new femtocell deployments (short-range user-deployed access points in the operator's licensed spectrum band), where a high degree of independency when deciding the usage of OFDMA frequency resources will be needed, since, obviously, centralized frequency planning tasks has little practical sense in those scenarios.This thesis contributes to the research on the spectrum assignment in 4G OFDMA-based mobile cellular networks by proposing a solution to dynamically manage the cell-by-cell spectrum assignment. To this end, adequate Dynamic Spectrum Assignment (DSA) strategies and a practical framework to execute them are proposed. In order to reduce operational costs and to reduce human intervention, the DSA framework has been designed based on self-organization so that the network is able to autonomously (i) observe the performance of current spectrum assignment, (ii) analyze if a new spectrum assignment is needed, and (iii) decide a new spectrum assignment to better adapt to networks conditions. Furthermore, a centralized and decentralized functional architecture is proposed so that the framework can be applied to a vast number of scenarios, ranging from typical macrocell scenarios where centralized control is employed, to future femtocell scenarios where nodes are almost independent and require autonomous spectrum assignment decisions at the cell level. The decision task of the framework resides on proposed DSA strategies, where one of them is based on machine learning to exploit knowledge previously acquired in the past. Moreover, this machine learning strategy tends to select a spectrum assignment that is optimal in the sense that maximizes a given reward signal appropriately defined in terms of network performance metrics (e.g., spectral efficiency, SINR, among others). Certainly, self-organization and machine learning on the context of spectrum assignment in OFDMA based radio interfaces have been little exploited and thus constitutes a major novelty of the work of this thesis.Performance results reveal important improvements over state-of-the-art strategies in terms of spectral efficiency (i.e. in bits/s/Hz), users' QoS satisfaction, fairness between the throughput obtained by users, and capacity for generating opportunities for secondary spectrum usage in large geographical areas. Also, the proposed DSA framework, based on self-organization, demonstrates appealing capabilities from the perspective of initial deployment, where nodes are able to self-configure after switch-on introducing a minimal impact on the already deployed system, being then a practical contribution to solve the deployment of thousands of femtocells in macrocell environments.

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.