Dissertations / Theses on the topic 'Radio resource management'

Mestrado em Engenharia Electrónica e Telecomunicações
Passive optical networks have been subject of research in recent years, standing out from the other distribution networks not only by the speed and distribution of multiple services, including video, data and voice, but also by the absence of active equipment between the central and terminal devices, not requiring the use of electricity. Also the progress made in mobile and "smart" equipment led to the increase of its popularity and personal use. The increase of mobile devices, as well as their features, were boosted by the evolution of WiFi technologies, mostly fueled by passive optical networks, favoring the connection of several devices through radio waves. There has been several improvements in wireless communications, especially in WiFi technology, in order to keep up with the speed increase in optical distribution networks. However the limitations in the frequency spectrum and the vast implementation of the technology itself became an obstacle to the development of WiFi networks. The main goal of this dissertation is the development of processes dedicated to the frequency spectrum management in WiFi networks within environments congestedbymultipleradiosignaltransmitters. Thisworkisdevelopedaround a gateway under development by Altice Labs combining optical network terminal and access point features, and presents a solution to the equipment transmission power management and the frequency channel selection.
As redes ópticas passivas têm sido alvo de grande investigação nos últimos anosdestacando-sedasoutrasredesdedistribuiçãonãosópelavelocidadee distribuição de multiplos serviços, incluindo video, dados e voz, mas também pela ausência de equipamentos activos entre a central local e o equipamento terminal, não sendo necessário o uso de energia eléctrica. Também o avanço que se tem verificado no desenvolvimento de equipamentos móveis e "inteligentes" tem levado a sua popularidade e utilização a crescer de forma constante. Por sua vez, este aumento do número de dispositivos móveis, bem como das respectivas características, foi impulsionado pela evolução da tecnologia WiFi, em grande parte alimentada pelas redes ópticas passivas, facilitando a conexão de múltiplos dispositivos através de ondas de rádio. Têm sido várias as melhorias nas comunicações sem fios, especialmente na tecnologia WiFi, no sentido de acompanhar o aumento da velocidade das redes de distribuição ópticas. No entanto as limitações ao nível do espectro de frequência e a vasta implementação da própria tecnologia têm-se revelado obstáculos ao desenvolvimento das redes WiFi. Esta dissertação tem como objectivo o desenvolvimento de soluções para a gestão do espectro de frequência das rede WiFi em ambientes congestionados pela presença de múltiplos transmissores de sinal rádio. Este trabalho é desenvolvido sob um gateway em desenvolvimento pela Altice Labs que combina as funcionalidades de um terminal de redes ópticas e de um access point, e apresenta uma solução para a gestão da potência de transmissão do equipamento e para a escolha do canal de frequência a utilizar.

Cognitive radio concept is a promising technology to cope with the spectrum scarcity issue in the emerging wireless technology. Practical cognitive radio as an intelligent radio is on the horizon, in which the system is able to observe radio environment, understanding its situation, and adapt its transceiver parameters without disruption to the licensed service. The main given functionality of the cognitive radio is dynamic spectrum management using underlay or overlay spectrum-sharing mechanisms. This thesis studies several objectives in cognitive radio networks namely; cumulative interference in multi-user overlay networks, effective capacity optimisation in time varying imperfect fading channels, and diverse spectrum decision schemes (i.e. Maximum Entropy Channel Access, MECA, and Adaptive Spectrum Opportunity Access, ASOA, schemes) in overlay networks. Also Green Cognitive Radio concept is introduced for enhancing energy efficiency in overlay networks. The cumulative interference at a cell-edge active primary receiver is estimated based on the two scenarios, the broadcast of receiver beacon signal and the broadcast of licensed transmitter beacon signal. In the proposed system topology, the cognitive users are distributed within and outside of the licensed coverage area with constant density. The results indicate that cumulative interference significantly gets low level through the broadcast of receiver beacon signal scenario in comparison with the licensed transmitter scenario. Additionally, optimising effective capacity of a secondary user subject to the interference constraint and transmission power constraint factors, in imperfect fading channels is studied. In this case, cross channel state information is a key factor in adapting transmission power and channel capacity accordingly. The numerical results show that effective capacity is influenced upon increasing cross channel error (secondary transmitter-primary receiver link), and QoS delay items. Moreover, the study is completed by proposing power control policy upon minimising interference level at the licensed receiver subject to the desired effective capacity level and transmission power constraint. Hence, performance of the proposed spectrum decision schemes (MECA, ASOA) is examined and explained by comparison with Random Channel Access (RCA), Minimum Channel Rate (MCR), and First Opportunity Channel Access (FOCA) schemes in the period of simulation time. MECA scheme uses weighted entropy function to assess usefulness of the remaining available idle channels, and so selects appropriate spectrum opportunity for secondary data delivery. The performance reveals that MECA and ASOA can potentially be considered as viable approaches in spectrum selection schemes. Additionally, in the case of GCR aspect an opportunistic power control policy using the remaining idle channel lifetime is proposed to mitigate interference power at the primary receiver. Overall, we develop and propose a unique technique in decreasing total interference in overlay networks; effective capacity optimisation in underlay networks, feasible spectrum selection schemes, and also green cognitive radio concept in the field of dynamic spectrum access networks.

Today, different types of cellular networks are actively working on the radio links. For instance, the Global System for Mobile Communication (GSM) is being used in nearly two hundred countries and currently it has around two and half billion users all over the world. Universal Mobile Telecommunication System (UMTS) is currently deployed in many countries and it is providing increased data rates, coverage and mobility as compared to GSM. Wireless Local Area Networks (WLAN) are very famous when we have a small area and none real time services. Worldwide Interoperability for Microwave Access (WiMAX) is a new technology and it is in deployment phase. In all these cellular technologies, we have very limited recourses and we have to make best use of them by proper management. Radio Resource Management (RRM) is a control mechanism for the overall system which is being used to manage radio resources in the air interface inside a cellular network. The main objective is to utilize the available spectral resources as efficiently as possible. Our aim is to use them in the best possible way to maximize the performance and spectral efficiency in such a way that we have maximum number of users in our network and Quality of Service (QoS) is up to the mark. In a cellular communication system, a service area or a geographical region is divided into a number of cells and each cell is served by an infrastructure element called the base station which works through a radio interface. The frequency license fees, real estate, distribution network and maintenance are the issues which dominates the cost for deploying a cellular network. Management of radio related resources is a critical design component in cellular communications. In RRM, we control parameters like Radio Frequency (RF) planning, link budgeting, modulation schemes, channel access schemes etc. RF planning includes cell planning, coverage of the network and capacity of the network. Our main focus in this thesis will be on cell planning and link budgeting and we will discuss them in context of a WiMAX network.

A current trend in the information society is that traditionally fixed computing resources are made available to mobile users. Most of the existing techniques for communication have been developed for stationary computing, and they must be adapted to the different connection properties of the mobile environment. One of the emerging mobile computing environments is the Universal Mobile Telecommunication System, UMTS. This system places demands on the quality of service that is provided to data flows, which requires resource management in the connection network. The most scarce resources in this system is the radio resources. The easiest way to conduct research in new and adapted techniques for communication is to perform simulations. Management of resources places restrictions on connections, and to get reliable results during simulations it must be included in the simulated environment. The thesis discusses and builds a basis for development of UMTS radio resource management in the network simulator ns-2. A limited version of UMTS radio resource management is added to ns-2 and evaluated.

In this thesis the performance of different cognitive systems are analyzed in different environments and scenarios. The main scenarios are: one cognitive and one primary user, multiple cognitive users and channels and multiple cognitive and primary users. With primary users in the vicinity, cognitive systems are evaluated both when no degradation to primary user QoS is allowed and when some degradation is allowed, measured by an outage probability. In all scenarios involving one or more primary users, the performance is evaluated over two phases. In Phase 1 the channel is idle, i.e. the primary users are silent, and in Phase 2 the primary users are active on the channel. One of the questions in this thesis is how can cognitive users transmit simultaneously with the primary user in Phase 2. Schemes that show that this is possible is presented and evaluated and performance is compared to a standard cognitive system only transmitting when the channel is idle.In scenarios with multiple cognitive users and channels, power allocation schemes are reviewed. A novel power allocation algorithm presented in cite{burr}, called modified water filling in this thesis, is implemented and referenced against other well-known power allocation schemes.All implementation and simulations were done in MATLAB. It was assumed infinite processing power at all cognitive users, i.e. no processing delay, and perfect spectral sensing at all cognitive users. The results showed that the performance gain of cognitive system utilizing simultaneous transmission achieves only a slight performance gain over a standard cognitive system, when no degradation to primary user QoS is allowed. However, by allowing only a slight degradation in primary user QoS, the gain is significant and should be included in future work on cognitive radio as it shows a promising way to exploit spectra.

As wireless technologies evolve, novel innovations and concepts are required to dynamically and automatically alter various radio parameters in accordance with the radio environment. These innovations open the door for cognitive radio (CR), a new concept in telecommunications. CR makes its decisions using an inference engine, which can learn and adapt to changes in radio conditions. Fuzzy logic (FL) is the proposed decision-making algorithm for controlling the CRâ s inference engine. Fuzzy logic is well-suited for vague environments in which incomplete and heterogeneous information is present. In our proposed approach, FL is used to alter various radio parameters according to experience gained from different environmental conditions. FL requires a set of decision-making rules, which can vary according to radio conditions, but anomalies rise among these rules, causing degradation in the CRâ s performance. In such cases, the CR requires a method for eliminating such anomalies. In our model, we used a method based on the Dempster-Shafer (DS) theory of belief to accomplish this task. Through extensive simulation results and vast case studies, the use of the DS theory indeed improved the CRâ s decision-making capability. Using FL and the DS theory of belief is considered a vital module in the automation of various radio parameters for coping with the dynamic wireless environment. To demonstrate the FL inference engine, we propose a CR version of WiMAX, which we call CogMAX, to control different radio resources. Some of the physical parameters that can be altered for better results and performance are the physical layer parameters such as channel estimation technique, the number of subcarriers used for channel estimation, the modulation technique, and the code rate.
Ph. D.

The aim of this thesis is defining and developing the concept of an efficient management of radio and computing resources in an SDR cloud. The SDR cloud breaks with today's cellular architecture. A set of distributed antennas are connected by optical fibre to data processing centres. The radio and computing infrastructure can be shared between different operators (virtualization), reducing costs and risks, while increasing the capacity and creating new business models and opportunities. The data centre centralizes the management of all system resources: antennas, spectrum, computing, routing, etc. Specially relevant is the computing resource management (CRM), whose objective is dynamically providing sufficient computing resources for a real-time execution of signal processing algorithms. Current CRM techniques are not designed for wireless applications. We demonstrate that this imposes a limit on the wireless traffic a CRM entity is capable to support. Based on this, a distributed management is proposed, where multiple CRM entities manage a cluster of processors, whose optimal size is derived from the traffic density. Radio resource management techniques (RRM) also need to be adapted to the characteristics of the new SDR cloud architecture. We introduce a linear cost model to measure the cost associated to the infrastructure resources consumed according to the pay-per-use model. Based on this model, we formulate the efficiency maximization power allocation problem (EMPA). The operational costs per transmitted bit achieved by EMPA are 6 times lower than with traditional power allocation methods. Analytical solutions are obtained for the single channel case, with and without channel state information at the transmitter. It is shown that the optimal transmission rate is an increasing function of the product of the channel gain with the operational costs divided by the power costs. The EMPA solution for multiple channels has the form of water-filling, present in many power allocation problems. In order to be able to obtain insights about how the optimal solution behaves as a function of the problem parameters, a novel technique based on ordered statistics has been developed. This technique allows solving general water-filling problems based on the channel statistics rather than their realization. This approach has allowed designing a low complexity EMPA algorithm (2 to 4 orders of magnitude faster than state-of-the-art algorithms). Using the ordered statistics technique, we have shown that the optimal transmission rate behaviour with respect to the average channel gains and cost parameters is equivalent to the single channel case and that the efficiency increases with the number of available channels. The results can be applied to design more efficient SDR clouds. As an example, we have derived the optimal ratio of number of antennas per user that maximizes the efficiency. As new users enter and leave the network, this ratio should be kept constant, enabling and disabling antennas dynamically. This approach exploits the dynamism and elasticity provided by the SDR cloud. In summary, this dissertation aims at influencing towards a change in the communications system management model (typically RRM), considering the introduction of the new infrastructure model (SDR cloud), new business models (based on Cloud Computing) and a more conciliatory view of an efficient resource management, not only focused on the optimization of the spectrum usage.
El objetivo de esta tesis es de nir y desarrollar el concepto de gesti on e ciente de los recursos de radio y computaci on en un SDR cloud. El SDR cloud rompe con la estructura del sistema celular actual. Un conjunto de antenas distribuidas se conectan a centros de procesamiento mediante enlaces de comunicaci on de bra optica. La infraestructura de radio y procesamiento puede ser compartida entre distintos operadores (virtualizacion), disminuyendo costes y riesgos, aumentando la capacidad y abriendo nuevos modelos y oportunidades de negocio. La centralizaci on de la gesti on del sistema viene soportada por el centro de procesamiento, donde se realiza una gesti on de todos los recursos del sistema: antenas, espectro, computaci on, enrutado, etc. Resulta de especial relevancia la gesti on de los recursos de computaci on (CRM) cuyo objetivo es el de proveer, din amicamente, de su cientes recursos de computaci on para la ejecuci on en tiempo real de algoritmos de procesado del señal. Las t ecnicas actuales de CRM no han sido diseñadas para aplicaciones de comunicaciones. Demostramos que esta caracter stica impone un l ímite en el tr áfi co que un gestor CRM puede soportar. En base a ello, proponemos una gesti on distribuida donde m ultiples entidades CRM gestionan grupos de procesadores, cuyo tamaño optimo se deriva de la densidad de tr áfi co. Las t ecnicas actuales de gesti on de recursos radio (RRM) tambi en deben ser adaptadas a las caracter sticas de la nueva arquitectura SDR cloud. Introducimos un modelo de coste lineal que caracteriza los costes asociados al consumo de recursos de la infraestructura seg un el modelo de pago-por-uso. A partir de este modelo, formulamos el problema de asignaci on de potencia de m axima e ciencia (EMPA). Mediante una asignaci on EMPA, los costes de operaci on por bit transmitido son del orden de 6 veces menores que con los m etodos tradicionales. Se han obtenido soluciones anal ticas para el caso de un solo canal, con y sin informacion del canal disponible en el transmisor, y se ha demostrado que la velocidad optima de transmisi on es una funci on creciente del producto de la ganancia del canal por los costes operativos dividido entre los costes de potencia. La soluci on EMPA para varios canales satisface el modelo "water- lling", presente en muchos tipos de optimizaci on de potencia. Con el objetivo de conocer c omo esta se comporta en funci on de los par ametros del sistema, se ha desarrollado una t ecnica nueva basada en estadí sticas ordenadas. Esta t ecnica permite solucionar el problema del water- lling bas andose en la estadí stica del canal en vez de en su realizaci on. Este planteamiento, despu es de profundos an alisis matem aticos, ha permitido desarrollar un algoritmo de asignaci on de potencia de baja complejidad (2 a 4 ordenes de magnitud m as r apido que el estado del arte). Mediante esta t ecnica, se ha demostrado que la velocidad optima de transmisi on se comporta de forma equivalente al caso de un solo canal y que la e ciencia incrementa a medida que aumentan el numero de canales disponibles. Estos resultados pueden aplicarse a diseñar un SDR cloud de forma m as e ciente. A modo de ejemplo, hemos obtenido el ratio optimo de n umero de antenas por usuario que maximiza la e ciencia. A medida que los usuarios entran y salen de la red, este ratio debe mantenerse constante, a fin de mantener una efi ciencia lo m as alta posible, activando o desactivando antenas din amicamente. De esta forma se explota completamente el dinamismo ofrecido por una arquitectura el astica como el SDR cloud. En de nitiva, este trabajo pretende incidir en un cambio del modelo de gesti on de un sistema de comunicaciones (t ípicamente RRM) habida cuenta de la introducci on de una nueva infraestructura (SDR cloud), nuevos modelos de negocio (basados en Cloud Computing) y una visi on m as integradora de la gesti on e ciente de los recursos del sistema, no solo centrada en la optimizaci on del uso del espectro.

The ever-increasing growth of the wireless application and services affirms the importance of the effective usage of the limited radio spectrum. Existing spectrum management policies have led to significant spectrum under-utilization. Recent measurements showed that large range of the spectrum is sparsely used in both temporal and spatial manner. This conflict between the inefficient usage of the spectrum and the continuous evolution in the wireless communication calls upon the development of more flexible management policies. Cognitive radio (CR) with the dynamic spectrum access (DSA) is considered to be a key technology in making the best solution of this conflict by allowing a group of secondary users (SUs) to share the radio spectrum originally allocated to the primary user (PUs). The operation of CR should not negatively alter the performance of the PUs. Therefore, the interference control along with the highly dynamic nature of PUs activities open up new resource allocation problems in CR systems. The resource allocation algorithms should ensure an effective share of the temporarily available frequency bands and deliver the solutions in timely fashion to cope with quick changes in the network. In this dissertation, the resource management problem in multicarrier based CR systems is considered. The dissertation focuses on three main issues: 1) design of efficient resource allocation algorithms to allocate subcarriers and powers between SUs such that no harmful interference is introduced to PUs, 2) compare the spectral efficiency of using different multicarrier schemes in the CR physical layer, specifically, orthogonal frequency division multiplexing (OFDM) and filter bank multicarrier (FBMC) schemes, 3) investigate the impact of the different constraints values on the overall performance of the CR system. Three different scenarios are considered in this dissertation, namely downlink transmission, uplink transmission, and relayed transmission. For every scenario, the optimal solution is examined and efficient sub-optimal algorithms are proposed to reduce the computational burden of obtaining the optimal solution. The suboptimal algorithms are developed by separate the subcarrier and power allocation into two steps in downlink and uplink scenarios. In the relayed scenario, dual decomposition technique is used to obtain an asymptotically optimal solution, and a joint heuristic algorithm is proposed to find the suboptimal solution. Numerical simulations show that the proposed suboptimal algorithms achieve a near optimal performance and perform better than the existing algorithms designed for cognitive and non-cognitive systems. Eventually, the ability of FBMC to overcome the OFDM drawbacks and achieve more spectral efficiency is verified which recommends the consideration of FBMC in the future CR systems.
El crecimiento continuo de las aplicaciones y servicios en sistemas inal´ambricos, indica la importancia y necesidad de una utilizaci´on eficaz del espectro radio. Las pol´ıticas actuales de gesti´on del espectro han conducido a una infrautilizaci´on del propio espectro radioel´ectrico. Recientes mediciones en diferentes entornos han mostrado que gran parte del espectro queda poco utilizado en sus ambas vertientes, la temporal, y la espacial. El permanente conflicto entre el uso ineficiente del espectro y la evoluci´on continua de los sistemas de comunicaci´on inal´ambrica, hace que sea urgente y necesario el desarrollo de esquemas de gesti´on del espectro m´as flexibles. Se considera el acceso din´amico (DSA) al espectro en los sistemas cognitivos como una tecnolog´ıa clave para resolver este conflicto al permitir que un grupo de usuarios secundarios (SUs) puedan compartir y acceder al espectro asignado inicialmente a uno o varios usuarios primarios (PUs). Las operaciones de comunicaci´on llevadas a cabo por los sistemas radio cognitivos no deben en ning´un caso alterar (interferir) los sistemas primarios. Por tanto, el control de la interferencia junto al gran dinamismo de los sistemas primarios implica nuevos retos en el control y asignaci´on de los recursos radio en los sistemas de comunicaci´on CR. Los algoritmos de gesti´on y asignaci´on de recursos (Radio Resource Management-RRM) deben garantizar una participaci´on efectiva de las bandas con frecuencias disponibles temporalmente, y ofrecer en cada momento oportunas soluciones para hacer frente a los distintos cambios r´apidos que influyen en la misma red. En esta tesis doctoral, se analiza el problema de la gesti´on de los recursos radio en sistemas multiportadoras CR, proponiendo varias soluciones para su uso eficaz y coexistencia con los PUs. La tesis en s´ı, se centra en tres l´ıneas principales: 1) el dise˜no de algoritmos eficientes de gesti´on de recursos para la asignaci´on de sub-portadoras y distribuci´on de la potencia en sistemas segundarios, evitando asi cualquier interferencia que pueda ser perjudicial para el funcionamiento normal de los usuarios de la red primaria, 2) analizar y comparar la eficiencia espectral alcanzada a la hora de utilizar diferentes esquema de transmisi´on multiportadora en la capa f´ısica del sistema CR, espec´ıficamente en sistemas basados en OFDM y los basados en banco de filtros multiportadoras (Filter bank Multicarrier-FBMC), 3) investigar el impacto de las diferentes limitaciones en el rendimiento total del sistema de CR. Los escenarios considerados en esta tesis son tres, es decir; modo de transmisi´on descendente (downlink), modo de transmisi´on ascendente (uplink), y el modo de transmisi´on ”Relay”. En cada escenario, la soluci´on ´optima es examinada y comparada con algoritmos sub- ´optimos que tienen como objetivo principal reducir la carga computacional. Los algoritmos sub-´optimos son llevados a cabo en dos fases mediante la separaci´on del propio proceso de distribuci´on de subportadoras y la asignaci´on de la potencia en los modos de comunicaci´on descendente (downlink), y ascendente (uplink). Para los entornos de tipo ”Relay”, se ha utilizado la t´ecnica de doble descomposici´on (dual decomposition) para obtener una soluci´on asint´oticamente ´optima. Adem´as, se ha desarrollado un algoritmo heur´ıstico para poder obtener la soluci´on ´optima con un reducido coste computacional. Los resultados obtenidos mediante simulaciones num´ericas muestran que los algoritmos sub-´optimos desarrollados logran acercarse a la soluci´on ´optima en cada uno de los entornos analizados, logrando as´ı un mayor rendimiento que los ya existentes y utilizados tanto en entornos cognitivos como no-cognitivos. Se puede comprobar en varios resultados obtenidos en la tesis la superioridad del esquema multiportadora FBMC sobre los sistemas basados en OFDM para los entornos cognitivos, causando una menor interferencia que el OFDM en los sistemas primarios, y logrando una mayor eficiencia espectral. Finalmente, en base a lo analizado en esta tesis, podemos recomendar al esquema multiportadora FBMC como una id´onea y potente forma de comunicaci´on para las futuras redes cognitivas.

Esta tesis doctoral se enmarca en la temática de Gestion de Recursos Radioelectricos en los sistemas de comunicaciones móviles, 3G, B3G y 4G. Como es ampliamente conocido los recursos radios son escasos, particularmente en los sistemas de comunicaciones móviles celulares, y en consecuencia es de uso obligado una gestión eficiente de los mismos. Desde un punto de vista práctico si bien estos sistemas se basan en el uso de tecnologías de acceso radio estandarizada, no es este el caso para los algoritmos subyacentes a la gestión de los recursos radio, de manera que siempre son posibles nuevas realizaciones de los mismos que resulten más convenientes en el marco del estándar en cuestión. Es en esta dirección hacia donde apunta la realización de esta tesis doctoral, y entiendo que lo consigue con éxito al introducir nuevas estrategias de Gestion de los Recursos Radio en el marco de las estrategias de múltiple acceso CDMA en los sistemas 3G, TDMA/CDMA en los sistemas B3G y OFDMA en los sistemas 4G. Esta tesis, tras identificar los gestores más usuales de gestión de recursos radio y una breve descripción de los mismos, introduce una descripción básicamente autocontenida de los aspectos más relevantes de los sistemas de acceso múltiple WCDMA y OFDMA. En este sentido se detallan mecanismos de su funcionamiento que con posterioridad serán utilizados en la definición y especificación de los algoritmos de gestión de recursos propiamente dichos. Con posterioridad se hace un breve recorrido sobre lo que son las redes neuronales , para finalizar en una exposición más detallada de las Redes Neuronales de Hopfield que serán el hilo conductor de los trabajos de esta tesis. En particular se describen las ecuaciones que caracterizan estas redes como sistemas dinámicos y se establecen sus condiciones de convergencia a través de los teoremas de estabilidad Lyapunov y la definición de la función Energía.De la conjunción de las particularidades de los sistemas de acceso WCDMA, TDMA y OFDMA y de las redes neuronales de Hopfield se van desarrollando una serie de algoritmos que operan en escenarios unicelulares y que entiendo novedosos y que a continuación enumeran brevemente.Admisión en un sistema WCDMA , enlace ascendente, mediante una gestión optimizada de las distintas velocidades de transmisión asignadas a los usuarios que comparten el acceso y que se les permite distintos perfiles. Aspectos relativos a la robustez del algoritmo, y en particular a su convergencia son también detallados. Se suponen restricciones de carga de la red máxima, repartición del espectro justa y potencia máxima disponible en los terminales móviles. Se suponen un servicio en tiempo real con velocidades variables. La probabilidad de bloqueo se usa para exhibir las prestaciones del algoritmo.Gestión de las velocidades de los usuarios ya admitidos en un sistema WCDMA,enlace ascendente, con objeto de garantizarles una definida probabilidad de satisfacción superior a un determinado valor y que está basada en las velocidades reales de transmisión asignadas. Se supone también un servicio en tiempo real con velocidades variables y las mismas restricciones que en Admisión. Gestión de las velocidades de los usuarios ya admitidos en un sistema WCDMA, enlace descendente, con objeto de garantizarles un máximo retardo en la entrega de paquetes. Se suponen restricciones de repartición del espectro justa y potencia máxima disponible en la estación de base. Se supone un servicio interactivo basado en un modelo de tráfico para servicios www. Se introduce también un algoritmo de referencia a efectos comparativos. La probabilidad de pérdida es el parámetro usado para valorar las prestaciones del algoritmo.Gestión combinada de servicios en tiempo real e interactivos en sistemas WCDMA, enlace descendente. Incorpora parte de los algoritmos anteriormente enunciados y se mantienen los mismos modelos de tráfico y las mismas restricciones. Se han usado en esta caso las probabilidades de satisfacción y de pérdida para capturar el la velocidad de transmisión agregada y retardo respectivamente Algoritmo de Gestión común de recursos radio para un escenario B3G donde un usuario puede ser servido por más de un acceso. En este caso se han usado WCDMA y TDMA. Algoritmos de Gestión de las velocidades de los usuarios ya admitidos en un sistema OFDMA, enlace descendente, con objeto de garantizarles un máximo retardo en la entrega de paquetes.La tesis apunta también hacia prometedoras futuras líneas de investigación que pretenden explotar la base de la metodología desarrollada en esta tesis y que consisten en escenarios celulares centralizadas para pasar después a distribuidas en entornos multicelulares y en particular para los sistemas OFDMA , base de los accesos en 4G.

In the continuous evolution of mobile communication systems, there are many issues and aspects to be addressed, as well as in their effective implementation and deployment on cellular networks. In a general way, the most outstanding challenge is how to take the most advantage from the available resources, namely RF spectrum, to satisfy the communication requirements associated to a specific service or application offered to an end user. Energy efficiency has also become one important aspect associated to such requirements, since it has a significant practical impact on operators, namely regarding their networks operational expenditure, as well as on UEs, concerning their battery duration and associated autonomy. This thesis addresses and targets contributing to the growing concerns regarding energy efficiency in the ICT industry, specifically focusing on cellular wireless networks. Moreover, taking into account the current panorama and developments in this field, namely concerning the emerging 5G communication systems and networks, the heterogeneous network (HetNet) concept is also at the core of the work that has been carried out and is presented in this thesis. The work takes into consideration the two ends of the considered system of networks. The first are the nomad end users that should be able to roam freely in such system, always with continuous service provided in a seamless way, and the second is the core network managed by the respective telecommunications operator. To achieve this, the work carried out focused in addressing two key challenges in HetNets in general, specifically towards optimizing the energy efficiency associated to vertical handovers (VHO) and to radio resource management (RRM) mechanisms and approaches to allow energy efficient communication in a HetNet. The work addresses energy efficiency in two different perspectives, each using a different solution exploiting distinct available mechanisms specified for cellular wireless networks. One considers UEs integrating multiple RAT interfaces, and involve a VHO-based solution exploiting IEEE 802.21 standard, and the other targets both core and radio access networks, exploiting a RRM-based solution. The first proposed energy efficient solution exploiting features provided by IEEE 802.21 (MIH/MIIS) and VHO, targeting energy saving at modern multi-RAT mobile UEs, can eventually reduce the energy consumption at their RAT interfaces by roughly 30% on average, with a straightforward implementation, according to the attained simulation results. However, the currently proposed scheme presents a trade-off in terms of added packet loss linked to UEs velocity, which is mostly caused by delayed network re-association. In the second solution, for downlink OFDMA HetNet system, the proposed energy efficiency optimization algorithm for radio resource allocation, taking a given data rate requirement into account, associated to QoS, presented fast convergence, which is key in the design of real EE HetNet systems. The algorithm considers not only the radiated power, but also both types of the circuit power. Simulation results can eventually be exploited towards designing optimal energy consumption networks based on QoS-oriented HetNet method, while total power is fixed. As future work it would also be important to take into account the paradigm shift that arise with the emergence of new standards, namely 3GPP Release 15, placing the stepping stones for 5G systems and networks. In this perspective, at a first instance, it is key to go beyond the assumptions made in this work, by considering C-RAN architecture in the addressed challenge for achieving higher EE, which is a prime concern when redesigning existing and future mobile communication systems, namely in sustainable and environmental perspectives.
La continua y rápida evolución de los sistemas de comunicación actuales presenta diversas líneas de actuación, con aspectos muy diversos como el despliegue e implementación eficiente de redes celulares. En este ámbito, el mayor desafío se presenta en cómo aprovechar los recursos disponibles, principalmente en cuanto al espectro RF, para satisfacer los requisitos asociados a los servicios o aplicaciones específicas ofrecidas al usuario final. La eficiencia energética también se ha convertido en un aspecto importante, dentro de los mencionados requisitos, debido al impacto que tiene para los operadores con respecto al coste operacional de las redes, y para el usuario final, debido al efecto en la autonomía de los dispositivos móviles. Este trabajo aborda la eficiencia energética en dos perspectivas diferentes, cada una utilizando una solución diferente que explota los distintos mecanismos disponibles especificados de las redes inalámbricas celulares, en particular HetNets. Uno considera que los dispositivos móviles integran múltiples interfaces RAT e involucran una solución basada en VHO que explota el estándar IEEE 802.21, y el otro apunta a las redes de acceso radio y núcleo de red, explotando una solución basada en RRM. La primera solución de eficiencia energética propuesta aprovecha las características proporcionadas por IEEE 802.21 (MIH / MIIS) y VHO para obtener un ahorro de energía en los dispositivos móviles modernos multi-RAT, y puede eventualmente reducir el consumo de energía en sus interfaces RAT en aproximadamente un 30% en promedio, con una sencilla implementación, de acuerdo con los resultados de la simulación. En la segunda solución, para el sistema OFDMA HetNet de enlace descendente, el algoritmo de optimización de eficiencia energética propuesto para la asignación de recursos de radio, teniendo en cuenta un dado requisito de velocidad de datos, asociado a QoS, presentó una convergencia rápida, lo cual es clave en el diseño de sistemas EE HetNet. El algoritmo considera no solo la potencia radiada, sino también los dos tipos de potencia del circuito. Los resultados de la simulación pueden aprovecharse para diseñar redes de consumo de energía óptimas basadas en el método HetNet orientado a QoS con una potencia total fija.

The thesis focuses on the provision of cellular vehicle-to-everything (V2X) communications, which have attracted great interest for 5G due to the potential of improving traffic safety and enabling new services related to intelligent transportation systems. These types of services have strict requirements on reliability, access availability, and end-to-end (E2E) latency. V2X requires advanced network management techniques that must be developed based on the characteristics of the networks and traffic requirements. The integration of the Sidelink (SL), which enables the direct communication between vehicles (i.e., vehicle-to-vehicle (V2V)) without passing through the base station into cellular networks is a promising solution for enhancing the performance of V2X in cellular systems. In this thesis, we addressed some of the challenges arising from the integration of V2V communication in cellular systems and validated the potential of this technology by providing appropriate resource management solutions. Our main contributions have been in the context of radio access network slicing, mode selection, and radio resource allocation mechanisms. With regard to the first research direction that focuses on the RAN slicing management, a novel strategy based on offline Q-learning and softmax decision-making has been proposed as an enhanced solution to determine the adequate split of resources between a slice for eMBB communications and a slice for V2X. Then, starting from the outcome of the off-line Q-learning algorithm, a low-complexity heuristic strategy has been proposed to achieve further improvements in the use of resources. The proposed solution has been compared against proportional and fixed reference schemes. The extensive performance assessment have revealed the ability of the proposed algorithms to improve network performance compared to the reference schemes, especially in terms of resource utilization, throughput, latency and outage probability. Regarding the second research direction that focuses on the mode selection, two different mode selection solutions referred to as MSSB and MS-RBRS strategies have been proposed for V2V communication over a cellular network. The MSSB strategy decides when it is appropriate to use one or the other mode, i.e. sidelink or cellular, for the involved vehicles, taking into account the quality of the links between V2V users, the available resources, and the network traffic load situation. Moreover, the MS-RBRS strategy not only selects the appropriate mode of operation but also decides efficiently the amount of resources needed by V2V links in each mode and allows reusing RBs between different SL users while guaranteeing the minimum signal to interference requirements. The conducted simulations have revealed that the MS-RBRS and MSSB strategies are beneficial in terms of throughput, radio resource utilization, outage probability and latency under different offered loads comparing to the reference scheme. Last, we have focused on the resource allocation problem including jointly mode selection and radio resource scheduling. For the mode selection, a novel mode selection has been presented to decide when it is appropriate to select sidelink mode and use a distributed approach for radio resource allocation or cellular mode and use a centralized radio resource allocation. It takes into account three aspects: the quality of the links between V2V users, the available resources, and the latency. As for the radio resource allocation, the proposed approach includes a distributed radio resource allocation for sidelink mode and a centralized radio resource allocation for cellular mode. The proposed strategy supports dynamic assignments by allowing transmission over mini-slots. A simulation-based analysis has shown that the proposed strategies improved the network performance in terms of latency of V2V services, packet success rate and resource utilization under different network loads.
La tesis se centra en la provisión de comunicaciones para vehículos sistemas celulares (V2X: Vehicle to Everything), que han atraído un gran interés en el contexto de 5G debido a su potencial de mejorar la seguridad del tráfico y habilitar nuevos servicios relacionados con los sistemas inteligentes de transporte. Estos tipos de servicios tienen requisitos estrictos en términos fiabilidad, disponibilidad de acceso y latencia de extremo a extremo (E2E). Para ello, V2X requiere técnicas avanzadas de gestión de red que deben desarrollarse en función de las características de las redes y los requisitos de tráfico. La integración del Sidelink (SL), que permite la comunicación directa entre vehículos (es decir, vehículo a vehículo (V2V)) sin pasar por la estación base de las redes celulares, es una solución prometedora para mejorar el rendimiento de V2X en el sistema celular. En esta tesis, abordamos algunos de los desafíos derivados de la integración de la comunicación V2V en los sistemas celulares y validamos el potencial de esta tecnología al proporcionar soluciones de gestión de recursos adecuadas. Nuestras principales contribuciones han sido en el contexto del denominado "slicing" de redes de acceso radio, la selección de modo y los mecanismos de asignación de recursos radio. Respecto a la primera dirección de investigación que se centra en la gestión del RAN slicing, se ha propuesto una estrategia novedosa basada en Q-learning y toma de decisiones softmax como una solución para determinar la división adecuada de recursos entre un slice para comunicaciones eMBB y un slice para V2X. Luego, a partir del resultado del algoritmo de Q-learning, se ha propuesto una estrategia heurística de baja complejidad para lograr mejoras adicionales en el uso de los recursos. La solución propuesta se ha comparado con esquemas de referencia proporcionales y fijos. La evaluación ha revelado la capacidad de los algoritmos propuestos para mejorar el rendimiento de la red en comparación con los esquemas de referencia, especialmente en términos de utilización de recursos, rendimiento, y latencia . Con respecto a la segunda dirección de investigación que se centra en la selección de modo, se han propuesto dos soluciones de diferentes llamadas estrategias MSSB y MS-RBRS para la comunicación V2V a través de una red celular. La estrategia MSSB decide cuándo es apropiado usar el modo SL o el modo celular, para los vehículos involucrados, teniendo en cuenta la calidad de los enlaces entre los usuarios de V2V, los recursos disponibles y la situación de carga de tráfico de la red. Además, la estrategia MS-RBRS no solo selecciona el modo de operación apropiado, sino que también decide eficientemente la cantidad de recursos que los enlaces V2V necesitan en cada modo, y permite que los RB se reutilicen entre diferentes usuarios de SL al tiempo que garantiza requisitos mínimos de señal a interferencia. Se ha presentado un análisis basado en simulación para evaluar el desempeño de las estrategias propuestas. Finalmente, nos hemos centrado en el problema conjunto de la selección de modo y la asignación de recursos de radio. Para la selección de modo, se ha presentado una nueva estrategia para decidir cuándo es apropiado seleccionar el modo SL y usar un enfoque distribuido para la asignación de recursos de radio o el modo celular y usar la asignación de recursos de radio centralizada. Tiene en cuenta tres aspectos: la calidad de los enlaces entre los usuarios de V2V, los recursos disponibles y la latencia. En términos de asignación de recursos de radio, el enfoque propuesto incluye una asignación de recursos de radio distribuida para el modo SL y una asignación de recursos de radio centralizada para el modo celular. La estrategia propuesta admite asignaciones dinámicas al permitir la transmisión a través de mini-slots. Los resultados muestran las mejoras en términos de latencia, tasa de recepción y la utilización de recursos bajo diferentes cargas de red.

The traditional way of increasing capacity in a wirelesscommunication system has been cell splitting and fixedchannel-allocation based on prediction tools. However, theplanning complexity increases rapidly with the number of cellsand the method is not suitable for the large temporal andspatial traffic variations expected in the future. A lot ofresearch has therefore been performed regarding adaptivechannel allocation, where a channel can be used anywhere aslong as the signal-to-interference ratio (SIR) is acceptable. Acommon opinion is that these solutions must be decentralizedsince a centralized one would be overly complex.

In this thesis, we study the locally centralizedbunch conceptfor radio resource management (RRM) in aManhattan environment and show that it can give a very highcapacity both for outdoor users and for indoor users covered byoutdoor base stations. We show how measurement limitations anderrors affect the performance and wepropose methods to handlethese problems, e.g. averaging of measured values, robustchannel selection algorithms, and increased SIR margins. Wealso study the computational and signaling complexities andshow that they can be reduced by splitting large bunches, usingsparse matrix calculations, and by using a simplified admissionalgorithm. However, a reduction of the complexity often means areduction of the system capacity.

The measurements needed for RRM can also be used to find amobile terminal's geographical position. We propose and studysome simple yet accurate methods for this purpose. We alsostudy if position information can enhance RRM as is oftensuggested in the literature. In the studied scenario, thisinformation seems to be of limited use. One possible use is toestimate the mobile user's speed, to assist handover decisions.Another use is to find the location of user hotspots in anarea, which is beneficial for system planning.

Our results show that the bunch concept is a promisingcandidate for radio resource management in future wirelesssystems. We believe that the complexity is manageable and themain price we have to pay for high capacity is frequentreallocation of connections.

Keywords:bunch concept, radio resource management,network-assisted resource management, base station selection,dynamic channel allocation, DCA, channel selection,least-interfered, interference avoidance, interferenceaveraging, handover, power control, path-loss measurements,signal strength, link-gain matrix, TD-CDMA, UTRA TDD, Manhattanscenario, microcells, mobile positioning, position accuracy,trilateration, triangulation, speed estimation

A novel flexible channel allocation scheme is proposed which is applicable to medium altitude, high diversity satellite personal communication systems with an interconnected ground control segment. The scheme is built upon the establishment of several temporal master-slave network hierarchies in distinct areas of the Earth, whereby the control of radio resources in each area is granted to a single network entity, the master, located at one of the network's fixed earth station sites. The master station is entrusted with the radio resource management functionality equivalent to a base station controller in GSM, whereas the slaves, which consist of all FES sites which control satellites that have a current connectivity with the master's area, share the functionality of a GSM base transceiver station with the satellites under their control. The master maintains a table of all channel allocations within its control area in real-time, its objective is to maximise the number of channels which can be provided in its area, in response to channel requests by users, subject to known interference criteria. It can achieve this by optimising the existing and future channel allocations through the use of predictive satellite coverage, spotbeam gain models and genetic algorithms. Radio resource related signalling between master and slave stations is performed through a dedicated terrestrial fibre-optic network which interconnects the FES sites, based upon GSM interface specifications which are adapted to account for the increased propagation delays and signalling load associated with the regional network. The potential capacity gain which is available through a centralised optimisation approach over a fixed channel allocation scheme is determined through simulation. The instantaneous capacity of each scheme is highly dependent on the traffic distribution and the positions of the satellites, which causes an analytical approach to be too restrictive or simplistic. The capacity gain estimation is performed over a time period for which several samples are taken and a powerful adapted genetic algorithm is applied to the NP complete problem to determine the maximum capacity. The flexible dynamic system, entitled the hybrid-centralised DCA scheme, is shown to have a raw capacity potential in excess of the FCA scheme under the traffic distribution scenario adopted.

The purpose of this research study was to investigate solutions to degradations in QoS (Quality of Service) for Broadband Internet provision via Geostationary Satellite Systems. Analysis as well as trials using commercial equipment have shown that these can result from certain Radio Resource Management (RRM) schemes, the limited capacity per user as well as atmospheric channel impairments. The latter is being effectively addressed by Fade Mitigation Techniques, leading however in a reduction and variation of the useful capacity. In addition, internet applications and protocols have been developed for terrestrial networks and therefore their adaptation to the satellite architecture characteristics, or the opposite, is often necessary. An important challenge has also been to improve individual application performance while at the same time optimise the overall system performance and maximising the transmission capacity. The optimisation methodology adopted is cross-layer design, a concept based on the exchange of parameters between non adjacent layers of the protocol stack. Six cross-layer mechanisms are proposed as part of this research targeting VoIP (Voice over IP) as well as TCP applications (Transport Control Protocol) using connection splitting. The mechanisms employ optimisation algorithms utilising real-time information from the MAC (Medium Access Control) as well as other non adjacent layers. The performance assessment performed via software simulations demonstrated important improvements in QoS. For VoIP for example, the MOS score which can be achieved even under congestion is above or around 80 in the R factor scale, with a theoretical maximum of 93. Simulations on TCP have also indicated how a cross-layer design allows the beginning of file data transfer at the physical layer to start earlier, which is important for small files. With respect to bigger files, a "cross-layer TCP" version can reduce the transfer delay of a typical file by about 50% with respect to TCP New Reno and 30% compared to TCP Hybla. The principal conclusion from this research is that broadband satellite systems can offer comparable QoS to terrestrial networks for most popular internet applications. This is under the condition that adequate capacity is available and adaptive techniques are implemented across the network, optimising performance jointly over several layers of the protocol stack. To this purpose the cross-layer designs proposed as part of this research become an essential tool.

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Includes bibliographical references (leaves 89-99).
In this thesis, a set of unique strategies and enhanced schemes for adaptive CDMA modulation are devised. A graded resource system is proposed for better radio resource management. Subsequently, a successful adaptive CDMA algorithm is designed and a prioritised processing gain for adaptive CDMA algorithm in satellite system is introduced. The idea of the critical section in the downlink system when a user controller scheme has to be activated to improve the performance is initiated. The diversity technique and rate compatible punctured turbo-code (RCPT), which has been found to give improved throughput performance in a direct sequence (DS) CDMA, are exploited.

There is a large potential for automation and optimization in radio access networks (RANs) using a data-driven approach to efficiently handle the increase in complexity due to the steep growth in traffic and new technologies introduced with the development of 5G. Reinforcement learning (RL) has natural applications in RAN control loops such as link adaptation, interference management and power control at different timescales commonly occurring in the RAN context. Elevating the status of data-driven solutions in RAN and building a new, scalable, distributed and data-friendly RAN architecture will be needed to competitively tackle the challenges of coming 5G networks. In this work, we propose a systematic, efficient and robust methodology for applying RL on different control problems. Firstly, the proposed methodology is evaluated using a well-known control problem. Then, it is adapted to a real-world RAN scenario. Extensive simulation results are provided to show the effectiveness and potential of the proposed approach. The methodology was successfully created but results on a RAN-simulator were not mature
Det finns en stor potential automatisering och optimering inom radionätverk (RAN, radio access network) genom att använda datadrivna lösningar för att på ett effektivt sätt hantera den ökade komplexiteten på grund av trafikökningar and nya teknologier som introducerats i samband med 5G. Förstärkningsinlärning (RL, reinforcement learning) har naturliga kopplingar till reglerproblem i olika tidsskalor, såsom länkanpassning, interferenshantering och kraftkontroll, vilket är vanligt förekommande i radionätverk. Att förhöja statusen på datadrivna lösningar i radionätverk kommer att vara nödvändigt för att hantera utmaningarna som uppkommer med framtida 5G nätverk. I detta arbete föreslås vi en syetematisk metodologi för att applicera RL på ett reglerproblem. I första hand används den föreslagna metodologin på ett välkänt reglerporblem. Senare anpassas metodologin till ett äkta RAN-scenario. Arbetet inkluderar utförliga resultat från simuleringar för att visa effektiviteten och potentialen hos den föreslagna metoden. En lyckad metodologi skapades men resultaten på RAN-simulatorn saknade mognad.

Mestrado em Electrónica e Telecomunicações
A tecnologia de sinais de rádio frequência sobre fibra óptica involve o uso de links ópticos para transportar os sinais desde a unidade central de processamento até aos sites remotos (e vice-versa). A centralização do processamento dos sinais de rádio frequência permite a partilha de equipamentos, alocação dinâmica de recursos e uma manutenção mais simplificada do sistema. Embora o conceito de gestão comum dos recursos rádio tenha despertado grande interesse na comunidade científica em termos da melhor utilização desses recursos e de novos modelos de negócio, a verdade é que a sua implementação não tem sido fácil. A interligação entre diferentes componentes de rede, normalmente localizados em locais diferentes, introduz um grande atraso nas comunicações; por outro lado as implementações proprietárias e a escassez de informação global não satisfazem os requisitos de um ambiente extremamente dinâmico, como é o ambiente wireless. Uma topologia centralizada permite ultrapassar estas contrariedades, disponibilizando uma interligação eficiente entre as entidades locais e comuns de gestão de recursos rádio. Nesta dissertação é apresentada uma nova arquitectura de gestão comum de recursos rádio, baseada no conceito de interligação entre diferentes tecnologias de acesso. Esta arquitectura faz a gestão dos recursos rádio de forma centralizada, onde os sinais rádio chegam sem qualquer pré-processamento. Essa arquitectura é avaliada com a implementação de um algoritmo simples de balanceamento da carga que segue a politica de minimização da interferência e aumento da capacidade. As simulações com duas tecnologias de acesso, quando consideradas separas ou em agregado, mostraram um aumento do débito de pelo menos 51% para o mesmo valor de interferência enquanto que o erro de simbolo decresce pelo menos 20%.
Radio over fibre technology involves the use of optical fibre links to distribute radio frequency signals from a central location to remote sites (and viceversa). The centralisation of radio frequency signals processing functions enables equipment sharing, dynamic allocation of resources, and simplified system operation and maintenance. Despite the unquestionable interest concept of common radio resource management from the point of view of resource usage and novel business models, its implementation has not been easy. The interworking between the different local radio resource management entities, usually located on different places will not satisfy the requirements of the wireless dynamic behaviour due to increase of delay in communication process, less information availability and proprietary implementations. A centralised topology can overcome the drawbacks of former wireless systems architecture interconnection by providing an efficient common radio communication flow with the local radio resource management entities. In this thesis a novel common radio resource management architecture is presented based on the concept of inter-working between different technologies. This is a centralised architecture where the radio frequency signals are delivered to the central location through the optical links. The new architecture is evaluated with a common policy that minimises interference while the overall system capacity is increased. The policy is implemented through the load balancing algorithm. The simulations of two radio access technologies when separately and jointly considered show that when the load balancing algorithm is applied the available throughput increases in at least 51% while the symbol error rate decreases at least 20%.

This thesis studies intelligent spectrum and topology management through transfer learning in mobile broadband networks, to improve the capacity density and Quality of Service (QoS) as well as to reduce the cooperation overhead and energy consumption. The dense deployment of small cell base stations (BSs) is an effective approach to provide high capacity density access. In the meantime, multi-hop wireless backhaul networks enable highly flexible deployment and self-organization of small cell BSs. A heterogeneous small cell access and multi-hop backhaul network is studied in this thesis as mobile broadband system architecture. Transfer learning is applied to Radio Resource Management (RRM) as an intelligent algorithm to improve the performance of conventional reinforcement learning. In transfer learning, a BS trains its knowledge base relying on knowledge transferred from other related BSs, who are selected using an interference coordination strategy. In a network with static topology, cooperation management is developed to identify the maturity of the knowledge base and control the coordination overhead. It is demonstrated in a multi-hop backhaul network that transfer learning delivers a QoS level that is as high as achieved by a fully coordinated algorithm, but with a very low level of information exchange which is close to a fully distributed algorithm. Transfer learning is also studied in rapidly changeable network architectures to provide reliable communication. It is carried out during the changes of network topology, through mapping the learner’s knowledge base to a prioritized action space with Pareto efficiency. This process assists the BSs to quickly identify and adapt to environment changes, and makes effective decisions. Results show that transfer learning significantly reduces QoS fluctuation during traffic variation and topology changes in a highly dynamic network. Furthermore, a dynamic topology management algorithm is developed to intelligently control the working modes of BSs, based on traffic load and capacity in multiple cells. Topology management is demonstrated to reduce the number of activated BSs with adequate QoS performance provided. Dynamic capacity provision between multiple cells is achieved from transfer learning, which significantly improves QoS and reduces energy consumption.

Historically mobile Radio Access Networks (RANs) were optimised initially to maximise coverage and subsequently to improve capacity, user data rates and quality of service. However, the recent exponential growth in the volume of transmitted data coupled with the ever increasing energy costs has highlighted the need to optimise futuristic RANs from an energy efficiency perspective. This research study postulated the utilisation of radio resource management approaches to improve the energy efficiency of modern RANs, with a particular emphasis on the radio frequency energy performance. The research study yielded the following major outcomes. First, there was notable positive correlation between user channel quality improvements and the energy efficiency of RANs. Second, channel quality aware packet schedulers were more energy efficient than channel quality ignorant packet schedulers. Third, energy aware scheduling metrics coupled with power control algorithms can be utilised to optimise and refine the energy efficiency performance of the rate adaptive frequency domain packet scheduling. Fourth, the dynamic temporal and spatial traffic load characteristics, in the radio access network, present energy saving opportunities through collaborative and cooperative Inter-Cell Interference (ICI) management among neighbouring base stations. While the results presented in this thesis pertain to radio frequency and/or radio head energy consumption, the improved energy efficiency could be leveraged by increasing the inter site distance between base stations subsequently reducing the density of base stations in any given geographical area thus reducing the energy consumption of the RANs as a whole. The benefits of energy efficient RANs are twofold, i.e. reduction in the amount of CO2 emission and lower operating expenditure (OPEX).

The objective of the proposed research is to develop interference-aware resource management techniques for CR networks that opportunistically operate within the licensed primary networks spectrum and to investigate the application of such CR techniques to emerging wireless networks. In this thesis, we report on a set of laboratory experiments that we undertook to analyze the interference between the CR-based wireless regional-area network (WRAN) standard and the digital television (DTV) broadcasting system. We determined the tolerable levels of WRAN interference into DTV receivers and studied the effect of these interference levels on WRAN deployment. Based on the need for efficient utilization of the primary network spectrum, we propose efficient interference-aware radio resource allocation (RRA) techniques for orthogonal frequency-division multiple access (OFDMA) CR networks. These RRA techniques aim to maximize the CR network throughput and to keep the CR interference to the primary network at or below a predefined threshold, known as the "interference temperature" limit. Moreover, we propose a joint spectrum-sensing design and power control algorithm that lead to increased CR network throughput and efficient protection of the PUs from undue interference. Interference coordination (IC) is considered a key technique for capacity maximization in emerging heterogeneous wireless networks. We propose a CR-based IC and RRA algorithm for OFDMA femtocell deployments to achieve efficient spectrum utilization and maximum network throughput. CR is envisioned as a key enabling technology for future wireless networks; our novel CR techniques will provide other researchers useful tools to design such networks.

Cognitive radio is frequently touted as a platform for implementing dynamic distributed radio resource management algorithms. In the envisioned scenarios, radios react to measurements of the network state and change their operation according to some goal driven algorithm. Ideally this flexibility and reactivity yields tremendous gains in performance. However, when the adaptations of the radios also change the network state, an interactive decision process is spawned and once desirable algorithms can lead to catastrophic failures when deployed in a network. This document presents techniques for modeling and analyzing the interactions of cognitive radio for the purpose of improving the design of cognitive radio and distributed radio resource management algorithms with particular interest towards characterizing the algorithms' steady-state, convergence, and stability properties. This is accomplished by combining traditional engineering and nonlinear programming analysis techniques with techniques from game to create a powerful model based approach that permits rapid characterization of a cognitive radio algorithm's properties. Insights gleaned from these models are used to establish novel design guidelines for cognitive radio design and powerful low-complexity cognitive radio algorithms. This research led to the creation of a new model of cognitive radio network behavior, an extensive number of new results related to the convergence, stability, and identification of potential and supermodular games, numerous design guidelines, and several novel algorithms related to power control, dynamic frequency selection, interference avoidance, and network formation. It is believed that by applying the analysis techniques and the design guidelines presented in this document, any wireless engineer will be able to quickly develop cognitive radio and distributed radio resource management algorithms that will significantly improve spectral efficiency and network and device performance while removing the need for significant post-deployment site management.
Ph. D.

Future mobile communications systems will be designed to support a wide range of data rates with complex and conflicting quality of service requirements. It is becoming more challenging to optimize radio resource management and maximise the system capacity whilst meeting the required quality of service from users' point of view. Traditional techniques have approached this problem by mainly focusing on resources within a cell and to large extent ignoring effects of multi-cell architecture leading to non uniform and unstable capacity across the network. This thesis first investigates the potential performance improvements obtained by developing novel distributed scheduling algorithms thereby highlighting the shortcomings of conventional single-cell scheduling techniques in a multi-cell system. It was found that distributed scheduling can achieve superior performance (up to 30% increased cell throughput) compared to conventional one in low/medium system loading. However, there is little advantage in case of heavily loaded system. The main achievement in this thesis is addressing this problem by proposal of a novel technique called Load Matrix, setting a new direction for future research on resource scheduling strategies in a multi-cell system. LM facilitates joint management of interference within and between cells for efficient allocation of radio resources. Simulation results provided show significant improvement in the resource utilization and overall network performance. Using LM technique, the average cell throughput can be increased between 30% to 50%. Results also show that maintaining cell interference within a margin as opposed to a hard target, can significantly improve resource utilization over time (longevity) and over the cells (uniformity). The thesis also compares the effect of ideal LM with practical and implementable versions with channel gain errors, information delay, and reducing LM database to adjacent cells. The conclusion was interesting as the performance degradation in practical LM compared to ideal LM was found to be negligible.

In recent years, there has been tremendous growth in digital multimedia technologies, from voice to data to video, and the recent, but growing, demand of supporting diverse quality of service (QoS) guarantees. It places new demands for future wireless networks in utilising the available radio resource in a more efficient and effective way. The key to this demand is the involvement of efficient radio resource management (RRM), to provide various QoS support for multimedia service delivery. Due to the unique broadcast nature and ubiquitous coverage of satellite communication system, the synergy between satellite networks and terrestrial networks provides new opportunities for delivering point-to-multipoint (or one-to-many) multimedia content to a large audience spread over extensive geographical area. It is expected that the satellite component will play a complementary, but essential, role in delivering multimedia data to those areas where the terrestrial high-bandwidth communication infrastructures are, either economically or technically, unreachable. The emphasis throughout this research is on the potential optimization techniques pertinent to the RRM to facilitate multimedia broadcast/multicast service (MBMS) delivery over the satellite digital multimedia broadcasting (SDMB) system, which has emerged as one of the most promising approaches for this mission. We concentrate on the algorithm development and performance evaluation of RRM strategies implemented at the radio access layer in the SDMB system, aimed at the efficient delivery of multimedia applications to mobile users at satisfactory QoS. Firstly, we have developed a novel two-level channel multiplexing scheme for the radio resource allocation (RRA), which is capable of optimally performing both logical and transport channel multiplexing via two new optimization algorithms, namely optimum estimation algorithm (OEA) and power-oriented adaptation (POA) algorithm. Simulation results prove that the proposed scheme can effectively improve the performance in terms of channel utilisation, power consumption as well as transmission capacity. Secondly, we have investigated the optimization of packet scheduling algorithms via the various adaptations of a proportional differentiation model. By taking into account multiple performance measures, e.g., buffer occupancy, queuing delay and data rate, several novel algorithms, i.e. buffer-length related queue (BLRQ), delay differentiation queue (DDQ) and combined delay and rate differentiation (CDRD), are introduced for performing the packet scheduling task in SDMB. Their performance has been evaluated via simulation means and compared with existing schemes. It is demonstrated that the proposed proportional differentiation packet scheduling schemes can achieve significant performance improvements in queuing delay, jitter and channel utilisation. Finally, we further optimize the packet scheduling schemes by using cross-layer design and adaptive optimization mechanisms. Cross-layer joint priority queue (CJPQ) and adaptive multidimensional QoS-based (AMQ) packet scheduling algorithms are introduced within this context and investigated via simulations. It is shown that these proposals can significantly improve the QoS performance amongst heterogeneous competing flows in terms of both scheduling efficiency and fairness, offering better flexibility and scalability features.

Multi-hop and multi-carrier communication techniques have attracted enormous interest from both industry and academia recently, and have been envisioned very promising for the next generation mobile systems to fulfil their ambitious coverage and capacity goals. In comparison to conventional mobile networks, the radio resource management in the context of multi-hop and multi-carrier communications is generally much more complicated, due to the facts that extra components have to be introduced, and strong inter-dependency is envisioned between these components and the rest of the allocation function. The radio resource management is crucial to ensuring the benefits of multi-hop and multi-carrier transmissions, and hence warrants careful investigations. Nevertheless, it has not yet been fully explored in the literature. In our work, firstly, the radio resource allocation for single-carrier Multi-hop Cellular Networks (MCNs) is investigated. The throughput-maximization problem is formulated mathematically and proven to be NP (Non-deterministic Polynomial)-hard. Considering the prohibitive complexity of finding the optimal solution for such an NP-hard problem, we propose an efficient heuristic algorithm, named Integrated Radio Resource Allocation (IRRA), to find sub-optimal solutions. To prove the effectiveness of the proposed IRRA algorithm, a case study was carried out based on HSUPA (High Speed Uplink Packet Access) with fixed relay stations. The IRRA is evaluated through system level simulations, and compared with two other cases: 1) non-relaying, 2) relaying with a benchmark approach. The results show that the proposed algorithm can ensure significant gains in terms of cell throughput. Following the above studies, the radio resource allocation problem for OFDMA (Orthogonal Frequency Division Multiple Access)-based single-hop systems is studied. The constrained throughput-maximization radio resource allocation problem is formulated and linearized. Its NP-hardness proof is then given by reducing the problem into a classical NP-hard problem, namely Multiple Choice Knapsack Problem (MCKP). A novel mathematical analysis on the problem is then earned out based on its similarity to the MCKP, and an efficient heuristic algorithm, named Integrated Sub-carrier, Bit, and Power Allocation (ISBPA), is proposed to find sub-optimal solutions for it. The proposed algorithm is evaluated through system level simulations and compared to benchmark algorithms. The results show that the proposed ISBPA algorithm can ensure considerable gains in terms of cell throughput and user satisfaction ratio. Finally, the studies in the above two steps are merged and further developed into a complete radio resource allocation algorithm for OFDMA-based MCNs. Evaluation results show significant gains in terms of cell throughput and user satisfaction ratio compared to benchmark algorithms.

Radio Resource Management (RRM) is crucial to efficiently and correctly manage the delivery of quality-of-service (QoS) in IMT-Advanced systems. Various methods on radio resource management for LTE/LTE-Advanced traffic have been studied by researchers especially regarding QoS handling of video packet transmissions. Usually, cross-layer optimisation (CLO) involving the PHY and MAC layers, has been used to provide proper resource allocation and distribution to the entire system. Further initiatives to include the APP layer as part of CLO techniques have gained considerable attention by researchers. However, some of these methods did not adequately consider the level of compatibility with legacy systems and standards. Furthermore, the methods did not wholly address User Equipment (UE) mobility or performance metrics for a specific data type or a specified period. Consequently, in this thesis, a content-aware radio RRM model employing a cross-layer optimiser focusing on a video conferencing/streaming application for a single cell long-term evolution (LTE) system has been proposed. Based on two constructed look-up tables, the cross-layer optimiser was found to dynamically adjust the transmitted video data rates depending on the UE or eNodeB SINR performance. The proposed look-up tables were derived from the performance study of the LTE classical (baseline) simulation model for various distances at a certain UE velocity. Two performance parameters, namely the average throughput and measured SINR were matched together to find the most suitable data rates for video delivery in both the uplink and downlink transmissions. The developed content-aware RRM model was then tested against the LTE baseline simulation model, to benchmark its capability to be used as an alternative to existing RRM methods in the present LTE system. Based on the detailed simulations, the output performance demonstrated that for video packet delivery in both uplink and downlink transmissions, the content-aware RRM model vastly outperformed the legacy LTE baseline simulation model with regard to the packet loss ratio and average end-to-end delay for the same amount of throughput. The baseline simulation model and the newly developed cross-layer approach were investigated and compared with practical measurement results in which PodNode technology, besides other components and supporting simulation software, were used to emulate the LTE communication system. The first emulation experiment involving the baseline model was generally in sync with the uplink throughput simulation performance. The second test which implemented the cross-layer approach employing the look-up table derived from the previous emulated results, confirmed the viability of the proposed content-aware RRM model to be used in current LTE or LTE-Advanced systems for improving the performance in the packet loss ratio and average packet delay.

The current decade has witnessed a phenomenal growth in mobile wireless communication networks and subscribers. In 2015, mobile wireless devices and connections were reported to have grown to about 7.9 billion, exceeding human population. The explosive growth in mobile wireless communication network subscribers has created a huge demand for wireless network capacity, ubiquitous wireless network coverage, and enhanced Quality of Service (QoS). These demands have led to several challenging problems for wireless communication networks operators and designers. The Next Generation Wireless Networks (NGWNs) will support high mobility communications, such as communication in high-speed rails. Mobile users in such high mobility environment demand reliable QoS, however, such users are plagued with a poor signal-tonoise ratio, due to the high vehicular penetration loss, increased transmission outage and handover information overhead, leading to poor QoS provisioning for the networks' mobile users. Providing a reliable QoS for high mobility users remains one of the unique challenges for NGWNs. The increased wireless network capacity and coverage of NGWNs means that mobile communication users at the cell-edge should have enhanced network performance. However, due to path loss (path attenuation), interference, and radio background noise, mobile communication users at the cell-edge can experience relatively poor transmission channel qualities and subsequently forced to transmit at a low bit transmission rate, even when the wireless communication networks can support high bit transmission rate. Furthermore, the NGWNs are envisioned to be Heterogeneous Wireless Networks (HWNs). The NGWNs are going to be the integration platform of diverse homogeneous wireless communication networks for a convergent wireless communication network. The HWNs support single and multiple calls (group calls), simultaneously. Decision making is an integral core of radio resource management. One crucial decision making in HWNs is network selection. Network selection addresses the problem of how to select the best available access network for a given network user connection. For the integrated platform of HWNs to be truly seamless and efficient, a robust and stable wireless access network selection algorithm is needed. To meet these challenges for the different mobile wireless communication network users, the NGWNs will have to provide a great leap in wireless network capacity, coverage, QoS, and radio resource utilization. Moving wireless communication networks (mobile hotspots) have been proposed as a solution to providing reliable QoS to high mobility users. In this thesis, an Adaptive Thinning Mobility Aware (ATMA) Call Admission Control (CAC) algorithm for improving the QoS and radio resource utilization of the mobile hotspot networks, which are of critical importance for communicating nodes in moving wireless networks is proposed. The performance of proposed ATMA CAC scheme is investigated and compare it with the traditional CAC scheme. The ATMA scheme exploits the mobility events in the highspeed mobility communication environment and the calls (new and handoff calls) generation pattern to enhance the QoS (new call blocking and handoff call dropping probabilities) of the mobile users. The numbers of new and handoff calls in wireless communication networks are dynamic random processes that can be effectively modeled by the Continuous Furthermore, the NGWNs are envisioned to be Heterogeneous Wireless Networks (HWNs). The NGWNs are going to be the integration platform of diverse homogeneous wireless communication networks for a convergent wireless communication network. The HWNs support single and multiple calls (group calls), simultaneously. Decision making is an integral core of radio resource management. One crucial decision making in HWNs is network selection. Network selection addresses the problem of how to select the best available access network for a given network user connection. For the integrated platform of HWNs to be truly seamless and efficient, a robust and stable wireless access network selection algorithm is needed. To meet these challenges for the different mobile wireless communication network users, the NGWNs will have to provide a great leap in wireless network capacity, coverage, QoS, and radio resource utilization. Moving wireless communication networks (mobile hotspots) have been proposed as a solution to providing reliable QoS to high mobility users. In this thesis, an Adaptive Thinning Mobility Aware (ATMA) Call Admission Control (CAC) algorithm for improving the QoS and radio resource utilization of the mobile hotspot networks, which are of critical importance for communicating nodes in moving wireless networks is proposed.

Orthogonal frequency division multiple access (OFDMA) is used on the downlink of broadband wireless access (BWA) networks such as Worldwide Interoperability for Microwave Access (WiMAX) and Long Term Evolution (LTE) as it is able to offer substantial advantages such as combating channel impairments and supporting higher data rates. Also, by dynamically allocating subcarriers to users, frequency domain diversity as well as multiuser diversity can be effectively exploited so that performance can be greatly improved. The main focus of this thesis is on the development of practical resource allocation schemes for the OFDMA downlink. Imperfect Channel State Information (CSI), the limited capacity of the dedicated link used for CSI feedback, and the presence of a Connection Admission Control (CAC) unit are issues that are considered in this thesis to develop practical schemes. The design of efficient resource allocation schemes heavily depends on the CSI reported from the users to the transmitter. When the CSI is imperfect, a performance degradation is realized. It is therefore necessary to account for the imperfectness of the CSI when assigning radio resources to users. The first part of this thesis considers resource allocation strategies for OFDMA systems, where the transmitter only knows the statistical knowledge of the CSI (SCSI). The approach used shows that resources can be optimally allocated to achieve a performance that is comparable to that achieved when instantaneous CSI (ICSI) is available. The results presented show that the performance difference between the SCSI and ICSI based resource allocation schemes depends on the number of active users present in the cell, the Quality of Service (QoS) constraint, and the signal-to- noise ratio (SNR) per subcarrier. In practical systems only SCSI or CSI that is correlated to a certain extent with the true channel state can be used to perform resource allocation. An approach to quantifying the performance degradation for both cases is presented for the case where only a discrete number of modulation and coding levels are available for adaptive modulation and coding (AMC). Using the CSI estimates and the channel statistics, the approach can be used to perform resource allocation for both cases. It is shown that when a CAC unit is considered, CSI that is correlated with its present state leads to significantly higher values of the system throughput even under high user mobility. Motivated by the comparison between the correlated and statistical based resource allocation schemes, a strategy is then proposed which leads to a good tradeoff between overhead consumption and fairness as well as throughput when the presence of a CAC unit is considered. In OFDMA networks, the design of efficient CAC schemes also relies on the user CSI. The presence of a CAC unit needs to be considered when designing practical resource allocation schemes for BWA networks that support multiple service classes as it can guarantee fairness amongst them. In this thesis, a novel mechanism for CAC is developed which is based on the user channel gains and the cost of each service. This scheme divides the available bandwidth in accordance with a complete partitioning structure which allocates each service class an amount of non-overlapping bandwidth resource. In summary, the research results presented in this thesis contribute to the development of practical radio resource management schemes for BWA networks.

La bonne gestion des ressources radio est un élément clé pour offrir une bonne Qualité de Service (QdS) pour les utilisateurs tout en assurant la meilleure gestion des ressources du réseau. Nous évaluons la performance de certaines fonctionnalités de gestion de ressources, à savoir l’ordonnancement et l'accès MAC et dans une deuxième étape nous proposons des méthodes de coordination de la puissance dans les liens ascendants et descendants des systèmes LTE. Nous proposons des mécanismes de coordination des interférences dans les systèmes LTE dans le cadre de l’auto-optimisation des réseaux (Self-Optimizing Networks). Le problème est modélisé par un système multi-agent effectuant un apprentissage par renforcement. La théorie de l’apprentissage de système d’inférence floue permet d’apprendre, à partir de l’expérience les décisions optimales correspondant à chaque état du système. La logique floue permet de gérer l’état continu du système. Chaque station de base est alors un agent responsable de modéliser son propre état et l’état des stations voisines et de calculer des récompenses tout au long du processus d’apprentissage afin d’apprendre la politique optimale de façon distribuée mais coopérative. Dans le sens descendant, le but est de décider la quantité de puissance allouée par spectre, dans un contexte de réutilisation totale du spectre. Dans le sens montant, nous proposons une optimisation dynamique du mécanisme de compensation partielle de puissance, Fractional Power Control, standardisé par le 3GPP. L’algorithme de gestion de puissance est adapté pour l’optimisation des performances dans ce contexte sujet à des variations très rapides et chaotiques.

Interference is one of the most common causes of performance issues and reliability issues in wireless networks. Interference and background noise can be localized by performing spectrum analysis to measure amplitude and frequency characteristics of electromagnetic signals. Initially a theoretical description of spectrum analysis and site survey was performed. Manual spectrum analysis was also examined by performing practical measurements and creating graphs with Metageek Wi-Spy and Chanalyzer. Signals from 802.11 units were observed with spectrum analysis, and were analyzed according to their visual interference levels. This was compared to the actual interference impact of the units. This analysis showed that manual spectrum analysis could be hard to interpret when it comes to interference, as signals from units that looked harmful were in fact not. The channel access method of the units, in this case CSMA/CA, contributed to a low impact of interference, since the units waited for the medium to be free before sending, which reduced the probability of collisions. Cisco CleanAir technology has built-in spectrum analysis functionality, to detect, classify and avoid radio frequency interference. Dynamic interference detection and avoidance reduces costs in operating and network outages. This is made possible by Cisco Radio Resource Management (RRM) - a system consisting of multiple protocols that can dynamically change frequency channel and power. The protocols of RRM were examined and discussed relative to the lab measurement. The measurements showed that the Cisco Aironet 2700 access point was more robust against interference compared to a D-Link router for small offices and home use. The robustness of an access point depends on its wireless standard, modulation and dynamic management protocols. Wireless communication is a complex subject, where multiple factors has an impact on network performance. Therefore, it might not be appropriate to draw any hard conclusions from the laboratory measurements that were performed. For future studies, similar lab measurements should be carried out by creating interference from non-802.11 units to compare the interference impact from CSMA and non-CSMA communication.
Störningar är en av de vanligaste orsakerna till försämrad prestanda och tillförlitlighet i trådlösa nätverk. Frekvensstörningar och brus kan lokaliseras genom att utföra spektrumanalys för att mäta amplitud- och frekvensegenskaper hos elektromagnetiska signaler. Inledningsvis gjordes en teoretisk beskrivning av spektrumanalys och site survey. Manuell spektrumanalys undersöktes dessutom praktiskt genom laborationsmätningar och grafritning med Metageek Wi-Spy och dess mjukvara Chanalyzer. Signaler från 802.11-enheter betraktades med spektrumanalys, och analyserades utifrån hur störande dess signaler såg ut att vara. Detta jämfördes sedan mot den faktiska störningsinverkan enheterna hade. Analysen visade att manuellt genomförd spektrumanalys kan vara svårtolkad när det kommer till att identifiera störande moment, då signaler från enheter som såg ut att störa mycket i själva verket inte gjorde det. Enheternas kanalaccessmetod, i det här fallet CSMA/CA, bidrog till en låg störningsinverkan då enheterna väntade med att sända tills mediet var ledigt, vilket minskade risken för kollisioner. Ciscos nya CleanAir-teknologi har inbyggd spektrumanalysfunktionalitet, för att kunna upptäcka, klassificera och undvika radiofrekvensstörningar. Att störningar automatiskt kan upptäckas och åtgärdas sparar både driftskostnader och minimerar nätverksavbrott. Denna automatisering är möjlig tack vare Cisco Radio Resource Management (RRM) som är ett system bestående av flera protokoll, och innefattar bland annat funktioner för att byta kanal och ändra utsänd effekt automatiskt. De protokoll som ingår i RRM undersöktes och diskuterades sedan i förhållande till genomförda laborationsmätningar. Laborationsmätningar visade att Ciscos Aironet 2700-accesspunkt var mer robust mot störningar än en D-Link-router avsedd för hemmabruk och mindre kontorsmiljöer. En accesspunkts robusthet avgörs av dess trådlösa standard, modulationsteknik och dynamiska managementprotokoll. Trådlös kommunikation är ett komplext ämne, där många faktorer har betydelse för ett nätverks prestanda. Det är därför inte lämpligt att dra några konkreta slutsatser från de laborationsmätningar som genomfördes. För framtida arbeten bör liknande laborationer med störningar från icke-802.11-enheter genomföras för att jämföra störningsinverkan från CSMA- och icke-CSMA-kommunikation.

Our research aims at contributing to the evolution of modern wireless communications and to the development of software-defined radio (SDR) and cognitive radio, in particular. It promotes a general resource management framework that facilitates the integration of computing and radio resource management. This dissertation discusses the need for computing resource management in software-defined and cognitive radios and introduces an SDR computing resource management framework with cognitive capabilities. The hard real-time computing requirements of software-defined digital signal processing chains (SDR applications), the associated radio propagation and quality of service (QoS) implications, and heterogeneous multiprocessor platforms with limited computing resources (SDR platforms) define the context of these studies. We examine heterogeneous computing techniques, multiprocessor mapping and scheduling in particular, and elaborate a flexible framework for the dynamic allocation and reallocation of computing resources for wireless communications. The framework should facilitate partial reconfigurations of SDR platforms, dynamic switches between radio access technologies (RATs), and service and QoS level adjustments as a function of the environmental conditions. It, therefore, assumes the facilities of the platform and hardware abstraction layer operating environment (P-HAL-OE). We suggest a modular framework, distinguishing between the computing system modeling and the computing resource management. Our modeling proposal is based on two computing resource management techniques, which facilitate managing the strict timing constraints of real-time systems. It is scalable and can account for many different hardware architectures and computing resource types. This work focuses on processing and interprocessor bandwidth resources and processing and data flow requirements. Our computing resource management approach consists of a general-purpose mapping algorithm and a cost function. The independence between the algorithm and the cost function facilitates implementing many different computing resource management policies. We introduce a dynamic programming based algorithm, the tw-mapping, where w controls the decision window. We present a general and parametric cost function, which guides the mapping process under the given resource constraints. An instance of it facilitates finding a mapping that meets all processing and data flow requirements of SDR applications with the available processing and bandwidth resources of SDR platforms. Several SDR reconfiguration scenarios and analyses based on simulations demonstrate the suitability and potentials of our framework for a flexible computing resource management. We extend our SDR computing resource management concepts to the cognitive radio context. The two primary objectives of cognitive radio are highly reliable communications whenever and wherever needed and the efficient use of the radio spectrum. We formulate a third objective as the efficient use of computing resources. We analyze the cognitive capabilities of our framework─the cognitive radio’s interface to SDR platforms─and indicate the potentials of our cognitive computing resource management proposal. The cognitive computing resource management needs to be coordinated with the radio resource management. We, therefore, introduce the joint resource management concept for cognitive radios. We present three cognitive cycles and discuss several interrelations between the radio, computing, and application resources, where application resources refer to the available SDR and user applications. Our approach potentiates flexibility and facilitates radio against computing resource tradeoffs. It promotes cognition at all layers of the wireless system for a cooperative or integrated resource management that may increase the performance and efficiency of wireless communications.
El objetivo de las investigaciones que se están llevando a cabo dentro del grupo de investigación es contribuir a la evolución de las radiocomunicaciones modernas y, en particular, al desarrollo de los conceptos software radio (SDR) y cognitive radio. El planteamiento general es el de extender la flexibilidad global del sistema de comunicaciones planteando la definición y desarrollo de un entorno en el que pudiesen explorarse las relaciones entre la computación y las prestaciones del sistema de comunicaciones móviles facilitando la integración de los recursos de computación con los recursos radio. Dentro de este marco, la presente tesis plantea la discusión de la necesidad de la gestión de los recursos de computación en entornos SDR y cognitive radio y define un entorno de operación que asume las características especificas del concepto SDR a la vez que incorpora capacidades cognitivas en la gestión de los recursos de computación de las plataformas que den soporte a las nuevas generaciones de sistemas móviles. Los estrictos requerimientos de procesado en tiempo real de las cadenas de procesado digital de la señal definidas por software (aplicaciones SDR), las implicaciones asociadas con la propagación radio y el concepto de calidad de servicio (QoS) y plataformas heterogéneas de múltiples procesadores con recursos de computo limitados (plataformas SDR) definen el contexto de estos estudios. Se examinan técnicas de cómputo de propósito general para definir un entorno de operación que fuese capaz de asignar de forma flexible y dinámica los recursos de cómputo necesarios para facilitar las radiocomunicaciones a los niveles de QoS deseados. Ello debería facilitar los cambios dinámicos de una tecnología de acceso radio a otra, permitiendo el ajuste del tipo de servicio o calidad de servicio en función de las preferencias de los usuarios y las condiciones del entorno. Dicho entorno de operación asume las potencialidades del platform and hardware abstraction layer operating environment (P-HAL-OE). La estructura del entorno de operación se define de forma modular y consiste en un modelado genérico y flexible de las plataformas de computación SDR y en una gestión de recursos de computación abierta y capaz de ajustarse a diferentes objetivos y políticas. En el trabajo se exponen dos técnicas de gestión que pretenden asegurar la consecución estricta de los límites temporales típicos de los sistemas en tiempo real. En cuanto al modelado, este es escalable y capaz de capturar un amplio abanico de arquitecturas hardware y recursos de computación. En el presente trabajo nos centramos en los recursos y requerimientos del procesado y transferencia de datos. Se introduce un algoritmo de mapeo genérico e independiente de la función de coste. La independencia entre el algoritmo y la función de coste facilita la implementación de diferentes políticas de gestión de recursos computacionales. El tw-mapping es un algoritmo basado en dynamic programming, donde w controla la ventana de decisión. Se presenta una función de coste genérica y parametrizable que permite guiar el proceso de gestión de los recursos. Una instancia de ella facilita encontrar una solución al proceso de asignación de recursos que cumpla todos los requerimientos de procesado y trasferencia de datos de las aplicaciones SDR con los recursos disponibles de las plataformas SDR. Diferentes escenarios y varios análisis basados en simulaciones demuestran la adecuación del entorno de trabajo definido y desarrollado, así como sus potencialidades para una gestión flexible de los recursos de cómputo. Se extienden los conceptos mencionados previamente para entornos cognitive radio. Los principales objetivos del concepto cognitive radio son la disponibilidad de comunicaciones altamente robustas en cualquier lugar y momento en que sean necesarias y el uso eficiente del espectro. Como tercer objetivo formulamos el uso eficiente de los recursos de cómputo. Analizamos las capacidades cognitivas de nuestro entorno de operación─la interfaz del sistema cognitive radio a las plataformas SDR─y resaltamos las potencialidades de nuestra propuesta de gestión cognitiva de los recursos computacionales. Dicha gestión cognitiva de los recursos computacionales plantea una integración con la gestión de los recursos radio. Para ello introducimos el concepto de gestión de recursos conjunta para entornos cognitive radio. Se presentan tres ciclos cognitivos y se discuten algunas interrelaciones entre los recursos radio, de cómputo y de aplicación, donde los recursos de aplicación se refieren a las aplicaciones SDR y de usuario disponibles. Nuestra propuesta de gestión de recursos conjunta potencia la flexibilidad y facilita los intercambios entre recursos radio y de computación

Thesis (Ph.D.) - University of Waterloo, 2002.
"A thesis presented to the University of Waterloo in fulfilment of the thesis requirement for the degree of Doctor of Philosophy in Electrical and Computer Engineering". Includes bibliographical references. Also available in microfiche format.

La transmisión asistida por relay o transmisión cooperativa es una nueva técnica de diversidad espacial donde aparece un elemento nuevo (un relay o un usuario cooperativo) en la tradicional transmisión punto a punto (fuente a destino). Ahora en la comunicación intervienen tres enlaces: fuente-relay, relay-destino y fuente-destino. El relay, además de asistir a la fuente en la transmisión de un mensaje, permite combatir las degradaciones que puede sufrir el canal como el shadowing y el pathloss. Aunque esta técnica está basada en el trabajo realizado en los 70 por Van der Meulen, Cover y El Gamal, ha sido en los últimos años cuando se han vuelto a considerar el uso de relays. En realidad, la transmisión asistida por un relay puede verse como un sistema virtual multi-antena (virtual MIMO) donde las antenas están distribuidas en diferentes terminales. Sin embargo, al contrario de los sistemas multi-antena y debido a la limitación de la actual tecnología radio, el relay debe trabajar en modo half-duplex, ya que no puede transmitir y recibir simultáneamente en la misma banda. Este hecho, motiva que la transmisión deba realizarse en dos fases ortogonales en función del modo del relay (recibiendo datos - relay-receive phase o transmitiendo datos - relay-transmit phase). Estas fases pueden implementarse en el dominio de la frecuencia o el tiempo.
Esta tesis investiga protocolos y estrategias para la transmisión asistida por relay para mejorar la eficiencia espectral y homogeneizar el servicio para todos los usuarios en un sistema de comunicación celular. La introducción del relay en la comunicación implica la redefinición de muchas técnicas y protocolos considerados en las comunicaciones punto a punto y en los sistemas multi-antena, situados en la capa física y/o superiores.
En primer lugar se presentan los achievable rates obtenidos por la transmisión asistida por relay en función del rol del relay (amplifica y retransmite o decodifica y retransmite), el tipo de transmisión (siempre transmite, incremental o selectiva), los datos transmitidos por el relay (repite los símbolos recibidos o son independientes) y el tipo del protocolo half duplex. En función de los terminales activos en cada fase de la comunicación (fuente, destino o relay), existen hasta cuatro protocolos. Otro aspecto considerado es la asignación de recursos (resource allocation) para cada fase de la comunicación, la cual puede estar fijada de antemano o puede ser ajustada dinámicamente en función de los canales de los diferentes enlaces. En el caso de que todos los coeficientes del canal se conocieran perfectamente, los terminales podrían transmitir síncronamente, mejorando la comunicación gracias a la ganancia debida a técnicas de pre-codificación por medio de los autovectores del canal (con antenas distribuidas).
Además dos técnicas de transmisión asistida por relay son evaluadas cuando existen múltiples relays por destino. Ambas dependen del tipo de mensajes transmitidos a cada relay (mensajes independientes o uno común). La asignación de recursos para ambas técnicas puede verse como un problema convexo.
Tres escenarios resumen diferentes tipos de transmisión asistida por relay para múltiples fuentes y un solo destino: RMAC (Relay-assisted Multiple Access Channel), UC (User Cooperation) and MARC (Multiple Access Relay Channel). Su diferencia se basa en el tipo de relay half- duplex considerado. La transmisión puede hacerse síncrona o asíncronamente. Las fuentes y los relays están limitados en potencia y el acceso de ellos en cada fase de la comunicación pude hacerse por medio de TDMA (time division multiple access), FDMA (frequency division multiple access) or SC (superposition coding multiple access). La asignación de recursos puede ser formulada como un problema convexo en algunos casos y la solución óptima puede ser encontrada.
Seguidamente la transmisión asistida por relay y duplexada en tiempo es aplicada a un sistema celular centralizado basado en TDMA en el downlink. Con el objetivo de mejorar la eficiencia espectral se propone el reuso espacial de un slot temporal para las transmisiones de los relays hacia sus respectivos destinos (slot de relay), generando interferencia para todos los restantes destinos activos. Un algoritmo de control de potencia basado en la teoría de juegos es propuesto para combatir la interferencia generada. Bajo esa configuración, un algoritmo de scheduling investiga las posibles ganancias debidas al multi-user gain y mide el overhead introducido.
Otra forma de tratar con la interferencia es la de controlar el rate de nuestra transmisión (rate control management). Bajo ciertas condiciones es posible modelar la función de densidad de probabilidad de la potencia interferente. En ese caso, la fuente ajusta el rate para maximizar el throughput de la comunicación. Esta solución es extendida para el caso en el que cada destino es asistido por varios relays. Las dos soluciones propuestas son capaces de proporcionar mejores resultados que la transmisión directa, a pesar de la interferencia existente en el slot de relay.
Finalmente, se investiga el control dinámico del enlace para la transmisión asistida por relay con dos diferentes tipos de conocimiento sobre el canal: conocimiento estadístico (statistical knowledge of the channel state) o conocimiento del canal instantáneo (actual information about the current channel state).
Estos dos tipos de conocimiento derivan en diferentes estrategias a utilizar para seleccionar la modulación y el esquema de codificación (MCS). En el primer caso, los rates seleccionados no están adaptados al canal actual, por lo que el destino puede recibir erróneamente los mensajes. Los protocolos de retransmisión de mensajes (ARQ - automatic repeat request) son los encargados de asegurarse la correcta recepción y son redefinidos para la transmisión asistida por relay.. En este trabajo, se especifica los códigos espacio-tiempo distribuidos, la codificación en al fuente y el relay y la longitud de las retransmisiones. Cuando la fuente conoce algún parámetro del canal instantáneo puede adaptar el MCS para esa realización del canal. En ese caso se investiga la predicción del error en las transmisiones asistidas por relay, y con ello es posible diseñar el MCS para que maximice la cantidad de información transmitida para una probabilidad de pérdida de paquete o que maximice el throughput.
The relay-assisted or cooperative transmission is a relatively new class of spatial diversity technique where a new element comes up in the conventional source-destination or point-to point communication: an assisting relay or cooperating user. The relay assists to the source in transmitting a message to the destination and allows dealing with the channel impairments like shadowing and pathloss. Although the seminal works were issued in the 70's by van der Meulen, Cover and El Gamal, it has been during the last years when it has re-gained more attention by the researchers. In fact, the relay-assisted transmission can be seen as a virtual MIMO (Multiple Input Multiple Output) with distributed antennas. In contrast to MIMO systems, the transmission requires the use of additional channel resources because of the limitation of the current radio technology: the relay terminal is constrained to work in half-duplex mode, which motivates that the transmission must be carried out in two orthogonal phases (relay-receive and relay-transmit phase), duplexed in time or frequency domains.
This dissertation investigates protocols and strategies for the relay-assisted transmission which improve the spectral efficiency and homogenize service in the cellular communication systems. The new element present in the communication, the relay terminal, imposes a redefinition of many techniques and protocols commonly used in the point-to-point and MIMO systems, which are placed at the physical and upper layers.
First, achievable rates using the relay-assisted transmission are provided which depend on the role of the relay (amplify-and-forward or decode-and-forward), the type of the transmission (persistent transmission, incremental or selective relaying), the data transmitted by the relays (repetition or unconstrained coding) and the type of half-duplex protocol. There are up to four protocol definition depending on the activity of the terminals on each phase. An additional aspect addressed is the resource allocation for each phase, that is, either it is fixed beforehand (static) or it is adjusted dynamically (dynamic) as a function of the channel quality. For the single-user relay- assisted transmission the resources can be allocated based on the channel quality of the different links. Moreover, if there is complete channel state information about all channel coefficients, source and relay can transmit synchronously enhancing the transmission thanks to the (distributed) eigenvector precoding techniques.
Two relay-assisted transmission techniques are evaluated when a destination is assisted by multiple relays. Both depend on the messages intended to each assisting relay (independent or common messaging). The resource allocation for both techniques is shown to be convex.
Additionally, three different scenarios illustrate the multi-user relay-assisted transmission with a single destination and different types of half-duplex relays: RMAC (Relay-assisted Multiple Access Channel), UC (User Cooperation) and MARC (Multiple Access Relay Channel). The relay-assisted transmission can be done synchronously or asynchronously. The sources and relays are power limited and access in each phase of the communication by TDMA (time division multiple access), FDMA (frequency division multiple access) or SC (superposition coding multiple access). For those scenarios the allocation of transmitted power and time resources can be formulated as a convex problem under some circumstances, evaluating the optimal solution.
Afterwards, the relay-assisted transmission duplexed in time is applied to a centralized cellular system based on TDMA in the downlink. The reuse of one time slot for the transmissions done from the relays to destinations (relay slot) is proposed to improve the spectral efficiency. This solution produces interference for all the destinations active in that time slot. A power control algorithm (at the relays) based on game theory is proposed to combat the generated interference. Under that configuration a scheduler algorithm explores the multi-user gain for the relay-assisted transmission, measuring the introduced overhead.
Another way of dealing with the interference is by rate control management. Under some circumstances it is possible to model the probability density function (pdf) of the interfering power. In such a case, the source can tune the transmission rate in order to maximize the throughput. This solution is extended to the case where each destination is assisted by multiple relays. In spite of the interfering power, both proposed solutions are able to provide significant gains over the direct transmission.
Finally, the dynamic link control of the relay assisted transmission is investigated under two different assumptions on the knowledge about the channel: statistical knowledge of the channel state and actual information about the current channel state. Both types of knowledge lead to different transmission strategies, in terms of selecting the modulation and coding scheme (MCS). Under the first case, the transmission rates are not adapted to the current channel realization and the destination can decode wrongly the messages. The Automatic Repeat reQuest (ARQ) protocols are redefined for the relayassisted transmission to cope with these events. In this work we specify the (distributed) space-time codes, the coding at the source and relay and the length of the retransmissions. When there is actual information about the channel state the MCS can be adapted to the current channel realization. In such a case, the link error prediction for the relay-assisted transmission is investigated, and thus the MCS can be designed for maximizing the information rate for a given probability of packet loss or maximizing the throughput.

As numerous mobile applications and over-the-top (OTT) services emerge and mobile Internet connectivity becomes ubiquitous, the provision of high quality of service (QoS) is more challenging for mobile network operators (MNOs). Research efforts focus on the development of innovative resource management techniques and have introduced the long term evolution advanced (LTE-A) communication standard. Novel business models make the growth of network capacity sustainable by enabling MNOs to combine their resources. The fifth generation (5G) mobile networks will involve technologies and business stakeholders with different capabilities and demands that may affect the QoS provision, requiring efficient radio resource sharing. The need for higher network capacity has introduced novel technologies that improve resource allocation efficiency. Direct connectivity among user equipment terminals (UEs) circumventing the LTE-A infrastructure alleviates the network overload. Part of mobile traffic is offloaded to outband device-to-device (D2D) connections (in unlicensed spectrum) enabling data exchange between UEs directly or via UEs-relays. Still, MNOs need additional spectrum resources and infrastructure. The inter-operator network sharing concept has emerged motivating the adoption of virtualization that enables network slicing, i.e., dynamic separation of resources in virtual slices (VSs). VSs are managed in isolation by different tenants using software defined networking and encompass core and radio access network resources allocated periodically to UEs. When UEs access OTT applications, flows with different QoS demands and priorities determined by OTT service providers (OSPs) are generated. OSPs’ policies should be considered in VS allocation. The coexisting technologies, business models and stakeholders require sophisticated radio resource management (RRM) techniques. To that end, RRM is performed in a complex ecosystem. When D2D communication involves data concurrently downloaded by the mobile network, QoS may be affected by LTE-A network parameters (resource scheduling policy, downlink channel conditions). It is also affected by the relay selection, as UEs may not be willing to help unknown UE pairs and UEs’ social ties in mobile applications may influence willingness for D2D cooperation. Thus, effective medium access control (MAC) mechanisms should coordinate D2D transmissions employing advanced techniques, e.g., network coding (NC). When UEs access OTT applications, OSPs’ policies are not considered by MNOs in RRM and OSPs cannot apply flow prioritization. Network neutrality issues also arise when OSPs claim resources from MNOs aiming to minimize grade of service (GoS). OSPs’ intervention may delay flows’ accommodation due to the time required for OSP-MNO interaction and the time the flows spent waiting for resources. This thesis proposes novel solutions to the RRM issues of outband D2D communication and VS allocation for OSPs in 5G networks. We present a cooperative D2D MAC protocol that leverages the opportunities for NC in D2D communication under the influence of LTE-A network parameters and its throughput performance analysis. The protocol improves D2D throughput and energy efficiency, especially for UEs with better downlink channel conditions. We next introduce social awareness in D2D MAC design and present a social-aware cooperative D2D MAC protocol that employs UEs’ social ties to promote the use of friendly relays reducing the total energy consumption. Motivated by the lack of approaches for OSP-oriented RRM, we present a novel flow prioritization algorithm based on matching theory that applies OSPs’ policies respecting the network neutrality and the analysis of its GoS and delay performance. The algorithm maintains low overhead and delay without affecting fairness among OSPs. Our techniques highlight the QoS improvement induced by the joint consideration of different technologies and business stakeholders in RRM design.
A medida que varias aplicaciones móviles y servicios over-the-top (OTT) surgen y el Internet móvil se vuelve ubicua, la prestación de alta calidad de servicio (QoS) es desafiante para los operadores de red móvil (MNOs). Los estudios de investigación se enfocan en técnicas innovadoras para la gestión de recursos de red y han resultado en la especificación del estándar de comunicación long term evolution advanced (LTE-A). Modelos comerciales nuevos hacen que el crecimiento de la capacidad de red sea sostenible al permitir que MNOs combinen sus recursos. La quinta generación (5G) de redes móviles implicará tecnologías y partes comerciales interesadas con varias habilidades y demandas que pueden afectar la provisión de QoS y demandan la gestión eficaz de recursos de radio. La necesidad de capacidad de red más alta ha introducido tecnologías que hacen más eficiente la asignación de recursos. La conectividad directa entre terminales de equipos de usuarios (UEs) eludiendo la infraestructura LTE-A alivia la sobrecarga de red. Parte del tráfico es dirigido a conexiones de dispositivo a dispositivo (D2D) outband permitiendo la comunicación de UEs directamente o con relés. Los MNOs necesitan nuevos recursos de espectro e infraestructura. El intercambio de recursos entre MNOs ha surgido motivando la adopción de virtualización que realiza la segmentación de red i.e., la separación dinámica de recursos en trozos virtuales (VSs). Los VSs son administrados de forma aislada por inquilinos diferentes con software defined networking y abarcan recursos de red core y radio access asignadas periódicamente a UEs. Cuando UEs usan aplicaciones OTT, flujos de aplicación con demandas y prioridades definidas por proveedores de servicios OTT (OSPs) se generan. Las políticas de OSPs deben ser integradas en la asignación de VSs. La coexistencia de varias tecnologías y partes comerciales demanda técnicas sofisticadas de gestión de recursos radio (RRM). Con ese fin, la RRM se realiza en un ecosistema complejo. Si la comunicación D2D involucra datos descargados simultáneamente por la red móvil, los parámetros de red LTE-A (política de scheduling de recursos, condiciones de canal downlink) afectan el QoS. La selección de relés afecta el rendimiento porque los UEs no desean siempre ayudar a UEs desconocidos. Las relaciones sociales de los UEs en aplicaciones móviles pueden determinar la voluntad para la comunicación cooperativa D2D. Por lo tanto, mecanismos de control de acceso al medio (MAC) deben coordinar las transmisiones D2D con técnicas avanzadas ej., codificación de red. Si los UEs usan servicios OTT, las políticas de OSPs no son consideradas en RRM y los OSPs no emplean flujos prioritarios. Problemas de neutralidad de red surgen cuando los OSPs reclaman recursos de MNOs para minimizar el grado de servicio (GoS). La intervención de OSPs puede causar retraso en el servicio de flujos debido a la interacción OSP-MNO y el tiempo requerido para que los flujos reciban recursos. Esta tesis presenta soluciones nuevas para los problemas RRM de comunicación D2D outband y asignación de VSs a OSPs en redes 5G. Proponemos un protocolo D2D MAC cooperativo que explota las oportunidades de NC bajo la influencia de parámetros de red LTE-A y su análisis de rendimiento. El protocolo mejora el rendimiento y la eficiencia energética especialmente para UEs con mejores condiciones de canal downlink. Introducimos la conciencia social en el D2D MAC y proponemos un protocolo que utiliza relaciones sociales de UEs para elegir relés-amigos y reduce el consumo de energía. Dada la falta de técnicas que aborden el problema RRM de OSPs presentamos un algoritmo que aplique políticas de OSPs y respete la neutralidad usando la teoría de matching, y su análisis de GoS y retraso. El algoritmo induce bajo coste y retraso sin afectar la imparcialidad entre OSPs. Estas técnicas demuestran la mejora de QoS gracias a la consideración de tecnologas y partes comerciales diferentes en RRM.

A novel radio resource management (RRM) scheme, which jointly considers the system characteristics from the physical, link and network layers, is proposed for cellular code division multiple access (CDMA) systems. Specifically, the power distribution at the physical layer distributes only the necessary amount of power to each connection in order to achieve its required signal-to-interference-plus-noise ratio (SINR). The rate allocation guarantees the required delay/jitter for real-time traffic and the minimum transmission rate requirement for non-real-time traffic. Efficient rate allocation is achieved by making use of the randomness and burstiness of the packet generation process. At the link layer, a packet scheduling scheme is developed based on the information of power distribution and rate allocation from the physical layer to achieve guaranteed quality of service (QoS). It schedules the system resource on a time slot basis to efficiently utilize the system resource in every time slot and to improve the packet throughput for non-real-time traffic. A connection admission control (CAC) scheme based on the lower layer resource allocation information is proposed at the network layer. The CAC scheme also makes use of user mobility information to reduce handoff connection dropping probability (HCDP). Theoretical analysis of the grade of service (GOS) performance, in terms of new connection blocking probability (NCBP), HCDP, and resource utilization, is given. Numerical results show that the proposed RRM scheme can achieve both effective QoS guarantee and efficient resource utilization.

Abstract The application of optimization techniques for resource management in wireless communication networks is considered in this thesis. It is understood that a wide variety of resource management problems of recent interest, including power/rate control, link scheduling, cross-layer control, network utility maximization, beamformer design of multiple-input multiple-output networks, and many others are directly or indirectly reliant on the general weighted sum-rate maximization (WSRMax) problem. Thus, in this dissertation a greater emphasis is placed on the WSRMax problem, which is known to be NP-hard. A general method, based on the branch and bound technique, is developed, which solves globally the nonconvex WSRMax problem with an optimality certificate. Efficient analytic bounding techniques are derived as well. More broadly, the proposed method is not restricted to WSRMax. It can also be used to maximize any system performance metric, which is Lipschitz continuous and increasing on signal-to-interference-plus-noise ratio. The method can be used to find the optimum performance of any network design method, which relies on WSRMax, and therefore it is also useful for evaluating the performance loss encountered by any heuristic algorithm. The considered link-interference model is general enough to accommodate a wide range of network topologies with various node capabilities, such as singlepacket transmission, multipacket transmission, simultaneous transmission and reception, and many others. Since global methods become slow in large-scale problems, fast local optimization methods for the WSRMax problem are also developed. First, a general multicommodity, multichannel wireless multihop network where all receivers perform singleuser detection is considered. Algorithms based on homotopy methods and complementary geometric programming are developed for WSRMax. They are able to exploit efficiently the available multichannel diversity. The proposed algorithm, based on homotopy methods, handles efficiently the self interference problem that arises when a node transmits and receives simultaneously in the same frequency band. This is very important, since the use of supplementary combinatorial constraints to prevent simultaneous transmissions and receptions of any node is circumvented. In addition, the algorithm together with the considered interference model, provide a mechanism for evaluating the gains when the network nodes employ self interference cancelation techniques with different degrees of accuracy. Next, a similar multicommodity wireless multihop network is considered, but all receivers perform multiuser detection. Solutions for the WSRMax problem are obtained by imposing additional constraints, such as that only one node can transmit to others at a time or that only one node can receive from others at a time. The WSRMax problem of downlink OFDMA systems is also considered. A fast algorithm based on primal decomposition techniques is developed to jointly optimize the multiuser subcarrier assignment and power allocation to maximize the weighted sum-rate (WSR). Numerical results show that the proposed algorithm converges faster than Lagrange relaxation based methods. Finally, a distributed algorithm for WSRMax is derived in multiple-input single-output multicell downlink systems. The proposed method is based on classical primal decomposition methods and subgradient methods. It does not rely on zero forcing beamforming or high signal-to-interference-plus-noise ratio approximation like many other distributed variants. The algorithm essentially involves coordinating many local subproblems (one for each base station) to resolve the inter-cell interference such that the WSR is maximized. The numerical results show that significant gains can be achieved by only a small amount of message passing between the coordinating base stations, though the global optimality of the solution cannot be guaranteed
Tiivistelmä Tässä työssä tutkitaan optimointimenetelmien käyttöä resurssienhallintaan langattomissa tiedonsiirtoverkoissa. Monet ajankohtaiset resurssienhallintaongelmat, kuten esimerkiksi tehonsäätö, datanopeuden säätö, radiolinkkien ajastus, protokollakerrosten välinen optimointi, verkon hyötyfunktion maksimointi ja keilanmuodostus moniantenniverkoissa, liittyvät joko suoraan tai epäsuorasti painotetun summadatanopeuden maksimointiongelmaan (weighted sum-rate maximization, WSRMax). Tästä syystä tämä työ keskittyy erityisesti WSRMax-ongelmaan, joka on tunnetusti NP-kova. Työssä kehitetään yleinen branch and bound -tekniikkaan perustuva menetelmä, joka ratkaisee epäkonveksin WSRMax-ongelman globaalisti ja tuottaa todistuksen ratkaisun optimaalisuudesta. Työssä johdetaan myös tehokkaita analyyttisiä suorituskykyrajojen laskentatekniikoita. Ehdotetun menetelmän käyttö ei rajoitu vain WSRMax-ongelmaan, vaan sitä voidaan soveltaa minkä tahansa suorituskykymetriikan maksimointiin, kunhan se on Lipschitz-jatkuva ja kasvava signaali-häiriö-plus-kohinasuhteen funktiona. Menetelmää voidaan käyttää minkä tahansa WSRMax-ongelmaan perustuvan verkkosuunnittelumenetelmän optimaalisen suorituskyvyn määrittämiseen, ja siksi sitä voidaan hyödyntää myös minkä tahansa heuristisen algoritmin aiheuttaman suorituskykytappion arvioimiseen. Tutkittava linkki-häiriömalli on riittävän yleinen monien erilaisten verkkotopologioiden ja verkkosolmujen kyvykkyyksien mallintamiseen, kuten esimerkiksi yhden tai useamman datapaketin siirtoon sekä yhtäaikaiseen lähetykseen ja vastaanottoon. Koska globaalit menetelmät ovat hitaita suurien ongelmien ratkaisussa, työssä kehitetään WSRMax-ongelmalle myös nopeita paikallisia optimointimenetelmiä. Ensiksi käsitellään yleistä useaa eri yhteyspalvelua tukevaa monikanavaista langatonta monihyppyverkkoa, jossa kaikki vastaanottimet suorittavat yhden käyttäjän ilmaisun, ja kehitetään algoritmeja, joiden perustana ovat homotopiamenetelmät ja komplementaarinen geometrinen optimointi. Ne hyödyntävät tehokkaasti saatavilla olevan monikanavadiversiteetin. Esitetty homotopiamenetelmiin perustuva algoritmi käsittelee tehokkaasti itsehäiriöongelman, joka syntyy, kun laite lähettää ja vastaanottaa samanaikaisesti samalla taajuuskaistalla. Tämä on tärkeää, koska näin voidaan välttää lisäehtojen käyttö yhtäaikaisen lähetyksen ja vastaanoton estämiseksi. Lisäksi algoritmi yhdessä tutkittavan häiriömallin kanssa auttaa arvioimaan, paljonko etua saadaan, kun laitteet käyttävät itsehäiriön poistomenetelmiä erilaisilla tarkkuuksilla. Seuraavaksi tutkitaan vastaavaa langatonta monihyppyverkkoa, jossa kaikki vastaanottimet suorittavat monen käyttäjän ilmaisun. Ratkaisuja WSRMax-ongelmalle saadaan asettamalla lisäehtoja, kuten että vain yksi lähetin kerrallaan voi lähettää tai että vain yksi vastaanotin kerrallaan voi vastaanottaa. Edelleen tutkitaan WSRMax-ongelmaa laskevalla siirtotiellä OFDMA-järjestelmässä, ja johdetaan primaalihajotelmaan perustuva nopea algoritmi, joka yhteisoptimoi monen käyttäjän alikantoaalto- ja tehoallokaation maksimoiden painotetun summadatanopeuden. Numeeriset tulokset osoittavat, että esitetty algoritmi suppenee nopeammin kuin Lagrangen relaksaatioon perustuvat menetelmät. Lopuksi johdetaan hajautettu algoritmi WSRMax-ongelmalle monisoluisissa moniantennilähetystä käyttävissä järjestelmissä laskevaa siirtotietä varten. Esitetty menetelmä perustuu klassisiin primaalihajotelma- ja aligradienttimenetelmiin. Se ei turvaudu nollaanpakotus-keilanmuodostukseen tai korkean signaali-häiriö-plus-kohinasuhteen approksimaatioon, kuten monet muut hajautetut muunnelmat. Algoritmi koordinoi monta paikallista aliongelmaa (yhden kutakin tukiasemaa kohti) ratkaistakseen solujen välisen häiriön siten, että WSR maksimoituu. Numeeriset tulokset osoittavat, että merkittävää etua saadaan jo vähäisellä yhdessä toimivien tukiasemien välisellä viestinvaihdolla, vaikka globaalisti optimaalista ratkaisua ei voidakaan taata

A novel strategy for automatic satellite constellation design with satellite diversity is proposed. The automatic satellite constellation design means some parameters of satellite constellation design can be determined simultaneously. The total number of satellites, the altitude of satellite, the angle between planes, the angle shift between satellites and the inclination angle are considered for automatic satellite constellation design. Satellite constellation design is modelled using a multiobjective genetic algorithm. This method is applied to LEO, MEO and hybrid constellations. The advantage of this algorithm is automatic satellite constellation design whilst achieving dual satellite diversity statistics. Furthermore a new strategy of dynamic channel allocation is proposed using a genetic algorithm for use in MSS networks. The main idea behind this algorithm is to use minimum cost as a metric to provide optimum channel solutions for specified interference constraints. The frequency reuse condition for all spotbeams is investigated as a function of time. The update interval time and the sampling time are introduced in order to track time valiant coefficients and constraints of the algorithm. The method is demonstrated for S-UMTS based on a MEO satellite constellation. Using this algorithm, it is shown that the proposed model outperforms conventional DCA schemes in terms of capacity of the system and Quality of Service (QoS).We show in the thesis that the genetic algorithm is a robust method for calculation of dynamic variations in satellite constellation design and provides resource allocation improvements over DCA in MSS system networks.

The widespread data demand in emerging wireless cellular technologies necessitates the evolution of traditional networks' deployment to accommodate the ever increasing coverage and capacity requirements. In emerging wireless systems a hierarchical multi-level network that consists of a mixture of outdoor small cells (relays) and indoor small cells (femtocell) deployments underneath the traditional macro-cell architecture can be seen as a key deployment strategy to meet these growing capacity demands. In such networks, Femtocell technology has attracted much attention as a key "player" to address coverage and capacity issues mainly in home and enterprise environments. However, a major challenge that arises in such indoor networks originates from the inter-cell interference between the femtocells (commonly known as co-tier interference), assuming that femtocells share the same spectrum. The main objectives of this thesis are to investigate inter-cell interference in femtocell networks and to propose efficient multi-cell scheduling mechanisms that can mitigate inter-cell interference in dense femtocell environments while maintaining spectral efficiency at acceptable level across the cells. We begin with investigating the impact of co-tier interference in femtocells, highlighting the necessity of interference mitigation mechanisms for arbitrary deployment of femtocells. In this direction. a novel low-complex.ity graph-coloring based interference coordination mechanism is proposed to be applied on top of intra-cell radio resource management. We additionally propose two locally centralized multi-cell scheduling frameworks that enclose adaptive graph-panitioning and weighted capacity maximization concepts. In particular, we decompose the problem in the latter case based on the Exact Generalized Travelling Salesman Problem as a close match in graph-based solutions. Extensive evaluation is provided by simulations showing a significant improvement over the state-of-the-art multi-cell scheduling benchmarks in terms of outage probability as well as user and cell throughput and thus the proposed algorithms are promising candidates of multi-cell scheduling in next generation small cell networks.

In this thesis, performance of relay-assisted Device-to-device (D2D) communication is investigated where D2D traffic is carried through relay nodes. I develop resource management schemes to maximize end-to-end rate as well as conversing rate requirements for cellular and D2D UEs under total power constraint. I also develop a low-complexity distributed solution using the concept of message passing. Considering the uncertainties in wireless links (e.g., when interference from other relay nodes and the link gains are not exactly known), I extend the formulation using robust resource allocation techniques. In addition, a distributed solution approach using stable matching is developed to allocate radio resources in an efficient and computationally inexpensive way under the bounded channel uncertainties. Numerical results show that, there is a distance threshold beyond which relay-assisted D2D communication significantly improves network performance at the cost of small increase in end-to-end delay when compared to conventional approach.