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Under high-mobility scenarios, the traditional coherent demodulation schemes (CDS) have limited performance, because reference signals cannot effectively track the channel variations with an affordable overhead. As an alternative solution, non-coherent demodulation schemes (NCDS) based on differential modulation have been proposed. Even in the absence of reference signals, they are capable of outperforming the CDS with a reduced complexity. The literature on NCDS laid the theoretical foundations for simplified channel and signal models, often single-carrier and spatially uncorrelated flat-fading channels. This chapter explains the most recent results assuming orthogonal frequency division multiplexing (OFDM) signaling and realistic channel models.

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Ponencia presentada en: XXX Simposium Nacional de la Unión Científica Internacional de Radio, los dias 2 y 4 septiembre 2015, en Pamplona (españa). Video services are expected to become more than 70% of the mobile traffic in 2020. Broadcast and multicast service is the most efficient mechanism to deliver the same content to many users. Not only focusing on venue casting, but also distributing many other media such as software updates and breaking news, 5G broadcasting is a key driver to achieve the spectral efficiency needed for the 1,000 times traffic growth that is expected for the upcoming years. Improvements in some areas, such as resource allocation techniques for broadcast/multicast services, are needed. The utilization of the Conventional Multicast Scheme (CMS) approach for multicast resource allocation presents intrinsic inefficiencies, because of the different channel conditions of the users which demand the service. This paper presents some resource allocation strategies based on the use of multicast subgroups. We propose a multicast resource allocation algorithm including memory, which results in improvements of the service throughput at the time a high fairness among the users is guaranteed. In addition, an algorithm of joint resource allocation among multicast and unicast transmissions is developed. This strategy allows the system to take advantage of the subframes reserved for each purpose by the Long Term Evolution (LTE) standard, looking for the best joint allocation of the available resources, and results in important improvements in the service throughput This work was supported in part by the Spanish Ministry of Economy and Competitiveness, National Plan for Scientific Research, Development and Technological Innovation (IN-NPACTO subprogram), LTExtreme project (IPT-2012-0525-430000), and the projects TEC2011-29006-C03-03 (GRE3NSYST) and TEC2014-59255-C3-3-R (ELISA). Publicada

Proceeding of: 2nd International Conference on Wireless Communication Systems and Networks (MIC-Wireless 2015), Barcelona, August 7th-9th 2015 This paper investigates the use of bit loading al- gorithms in order to use ESIM OFDM in frequency selective channels. This work focuses on maximizing the bit rate minimiz- ing the loss of spectral efficiency because of the insertion of idle subcarriers. Besides, the modified ESIM OFDM is generalized to support groups of subcarriers of arbitrary size based on the number of idle subcarriers. The effect of this generalization, as well as the new bit distribution after using bit loading, on the peak to average power ratio (PAPR) and the bit error rate (BER) are analyzed. Additionally a novel way to evaluate the BER in such a system is proposed. The proposed scheme is shown to outperform the original ESIM OFDM performance in terms of PAPR, at the cost of a small degradation of the BER. This improvement in the PAPR makes the proposed scheme a good candidate for Optical Wireless Communication (OWC) systems, and This work has been partly funded by project TEC2014-59255-C3-3-R (ELISA)

This proceeding at: The 22nd European Signal Processing Conference (EUSIPCO), took place 2014, September, 01-05 in Lisbon (Portugal). An interference aware precoding scheme based on limited channel state information at the transmitter (CSIT) is consid-ered for its use in the downlink of a cellular system. The transmitter precoder used is based on an MMSE-ZF criterion in order to maximize the user rate while the interference to other users is reduced. The proposed scheme also exploits the network topology, so that each BS can categorize the users into two groups, according to the level of interference that the BS is introducing in those users. On the receiver end, each user makes use of the whole channel state information at the receiver (CSIR) by employing an MMSE filter. This approach enables a reduction in the complexity of the system, while improving the performance of the whole network. This work has been partially funded by research projects COMONSENS (CSD2008-00010), and GRE3N (TEC2011-29006-C03-03. Publicado

Interference in a cellular network is one of the main impairments that needs to be overcome. Coordination among the Base Stations may enable the use of the interference to improve the transmission rate at the cost of increased computational complexity and more stringent backhaul and feedback requirements. Practical problems of global coordination can be reduced through clustering which, in turn, will introduce Out of Cluster Interference (OCI). OCI can seriously hamper the advantages brought by precoding techniques like Block Diagonalization (BD). In this work we propose a mixed transmission strategy using BD and Single User transmission that is able to overcome the problems introduced by the OCI, in combination with a low complexity scheduling algorithm that enables an increased transmission rate in a multiuser scenario.

This proceeding at: Workshop on Small Cell Cooperative Communications, Lyon (Francia), 2-Mayo 2012.The event Web site at http://ic1004-iplan-2012.conf.citi-lab.fr/ Future cellular networks will be more dense and heterogeneous. A typical deployment will be based on micro, pico and femto cells. Under this scenario, novel interference management techniques such as network MIMO will be mandatory. However, it is usual to combine them with power allocation strategies to maximize the sum of the rates or minimize the power consumption. Those strategies are unfair at user level in heterogeneous networks and do not provide a "green" measure. In this work we propose some more equitable alternatives to the classical power allocation schemes and a strategy based on a green metric. Finally we compare the performance, in user spectral efficiency and power consumption terms, of these strategies in micro and femto cell deployments. This work has been partly funded by projects GRE3N TEC2011-29006-C03-03 and COMONSENS CSD2008-00010. Publicado

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Mención Internacional en el título de doctor, La necesidad de tasas de transmisión más elevadas y una mayor eficiencia en las redes celulares es la principal motivación para considerar el uso de UFR. La coordinación entre BSs se hace necesaria, entonces, para compensar los problemas introducidos por la interferencia. La coordinación global de la red es demasiado compleja y, además, presenta limitaciones intrínsecas, que impiden su utilización en escenarios reales. La utilización de grupos reducidos de BSs es una alternativa para reducir los requisitos impuestos por la coordinación. Como consecuencia de la agrupación, aparece OCI, la cual perjudica seriamente las comunicaciones. Este trabajo se centra en BD, una técnica de precodificación lineal que combina unas buenas prestaciones con una complejidad relativamente baja. Sin embargo, la interferencia empeora notablemente su funcionamiento. En esta tesis se estudia el canal descendente de una red celular conglomerada, donde se usa BD para coordinar las BSs que forman cada grupo. Se analiza la tasa media obtenible como función de múltiples parámetros del escenario. De especial interés es la dependencia con el tamaño de las agrupaciones, de donde se desprende que existe un tamaño óptimo para los grupos de BSs, por encima del cual no se obtienen mejoras significativas. La equidad del sistema se estudia en presencia de OCI, también como función de diversos parámetros del escenario, como puede ser la asignación de potencia. Se propone una estrategia mixta de transmisión, que combina BD con procesado SU, como mecanismo para combatir las dificultades introducidas por la interferencia que no se gestiona. La estrategia consiste en dos fases: • Los usuarios deciden localmente qué estrategia prefieren para la transmisión, y envían esta información a las BSs. • Las BSs utilizan las decisiones recibidas para planificar las transmisiones, de modo que se pueda optimizar el funcionamiento de la red. El resultado de la estrategia propuesta es una mejora de las prestaciones de BD en presencia de OCI, especialmente para los usuarios más desfavorecidos. Esto se traduce en que, adicionalmente, el sistema se vuelve más justo, al mismo tiempo que el rendimiento de la red aumenta., The need for higher data rates and higher efficiency in cellular networks motivates the use of Universal Frequency Reuse (UFR). Coordination among Base Stations (BSs) is required then to alleviate the performance penalty due to the interference. Global coordination is too complex and has inherent limitations that prevents it from being used in real world scenarios. Clusters of a reduced number of BSs can be considered in order to ease off the requirements of coordination. As a result, Other Cluster Interference (OCI) appears, affecting negatively the communications. This work focuses on Block Diagonalization (BD), a linear precoding technique that combines a good theoretical performance with a relatively low complexity. However, the unwanted interference seriously impacts the results obtained using BD. This thesis studies the downlink of a clustered cellular network, where BD is used to coordinate the BS within each cluster. The mean achievable rate is analyzed as a function of several scenario parameters. Of particular interest is the dependence on the cluster size, which yields that there is an optimum cluster size, beyond which no significant gain is obtained. Fairness considerations are analyzed in the presence of OCI, also studied as a function of scenario parameters such as the power allocation. A mixed strategy using BD and Single User (SU) processing is proposed as a means to overcome the impairment of the unhandled interference. The transmission consists of two stages: • Users locally decide which transmission strategy they prefer and send this information to the BSs. • BSs use the decisions of all users to schedule them for transmission so that the performance of the network is optimized. The result of the proposed strategy is an improvement in the performance of BD in the presence of OCI, especially for the users experiencing the worst conditions. This means that the fairness of the system is also increased, along with the overall performance of the network., Programa Oficial de Doctorado en Multimedia y Comunicaciones, Presidente: Lajos Hanzo.- Secretario: Raquel Perez Leal.- Vocal: Atilio Manuel da Silva Gameiro

Mención Internacional en el título de doctor Nowadays, it is nearly impossible to think of a service that does not rely on wireless communications. By the end of 2022, mobile internet represented a 60% of the total global online traffic. There is an increasing trend both in the number of subscribers and in the traffic handled by each subscriber. Larger data rates, smaller extreme-to-extreme (E2E) delays and greater number of devices are current interests for the development of mobile communications. Furthermore, it is foreseen that these demands should also be fulfilled in scenarios with stringent conditions, such as very fast varying wireless communications channels (either in time or frequency) or scenarios with power constraints, mainly found when the equipment is battery powered. Since most of the wireless communications techniques and standards rely on the fact that the wireless channel is somehow characterized or estimated to be pre or post-compensated in transmission (TX) or reception (RX), there is a clear problem when the channels vary rapidly or the available power is constrained. To estimate the wireless channel and obtain the so-called channel state information (CSI), some of the available resources (either in time, frequency or any other dimension), are utilized by including known signals in the TX and RX typically known as pilots, thus avoiding their use for data transmission. If the channels vary rapidly, they must be estimated many times, which results in a very low data efficiency of the communications link. Also, in case the power is limited or the wireless link distance is large, the resulting signal-tointerference- plus-noise ratio (SINR) will be low, which is a parameter that is directly related to the quality of the channel estimation and the performance of the data reception. This problem is aggravated in massive multiple-input multiple-output (massive MIMO), which is a promising technique for future wireless communications since it can increase the data rates, increase the reliability and cope with a larger number of simultaneous devices. In massive MIMO, the base station (BS) is typically equipped with a large number of antennas that are coordinated. In these scenarios, the channels must be estimated for each antenna (or at least for each user), and thus, the aforementioned problem of channel estimation aggravates. In this context, algorithms and techniques for massive MIMO without CSI are of interest. This thesis main topic is non-coherent massive multiple-input multiple-output (NC-mMIMO) which relies on the use of differential M-ary phase shift keying (DMPSK) and the spatial diversity of the antenna arrays to be able to detect the useful transmitted data without CSI knowledge. On the one hand, hybrid schemes that combine the coherent and non-coherent schemes allowing to get the best of both worlds are proposed. These schemes are based on distributing the resources between non-coherent (NC) and coherent data, utilizing the NC data to estimate the channel without using pilots and use the estimated channel for the coherent data. On the other hand, new constellations and user allocation strategies for the multi-user scenario of NC-mMIMO are proposed. The new constellations are better than the ones in the literature and obtained using artificial intelligence techniques, more concretely evolutionary computation. This work has received funding from the European Union Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie ETN TeamUp5G, grant agreement No. 813391. The PhD student was the Early Stage Researcher (ESR) number 2 of the project. This work has also received funding from the Spanish National Project IRENE-EARTH (PID2020-115323RB-C33) (MINECO/AEI/FEDER, UE), which funded the work of some coauthors. Programa de Doctorado en Multimedia y Comunicaciones por la Universidad Carlos III de Madrid y la Universidad Rey Juan Carlos Presidente: Luis Castedo Ribas.- Secretario: Matilde Pilar Sánchez Fernández.- Vocal: Eva Lagunas Targarona

In recent times, the immense growth of wireless traffic data generated from massive mobile devices, services, and applications results in an ever-increasing demand for huge bandwidth and very low latency, with the future networks going in the direction of achieving extreme system capacity and ultra reliable low latency communication (URLLC). Several consortia comprising major international mobile operators, infrastructure manufacturers, and academic institutions are working to develop and evolve the current generation of wireless communication systems, i.e., fifth generation (5G) towards a sixth generation (6G) to support improved data rates, reliability, and latency. Existing 5G networks are facing the latency challenges in a high-density and high-load scenario for an URLLC network which may coexist with enhanced mobile broadband (eMBB) services. At the same time, the evolution of mobile communications faces the important challenge of increased network power consumption. Thus, energy efficient solutions are expected to be deployed in the network in order to reduce power consumption while fulfilling user demands for various user densities. Moreover, the network architecture should be dynamic according to the new use cases and applications. Also, there are network migration challenges for the multi-architecture coexistence networks. Recently, the open radio access network (O-RAN) alliance was formed to evolve RANs with its core principles being intelligence and openness. It aims to drive the mobile industry towards an ecosystem of innovative, multi-vendor, interoperable, and autonomous RAN, with reduced cost, improved performance and greater agility. However, this is not standardized yet and still lacks interoperability. On the other hand, the cell-less radio access network (RAN) was introduced to boost the system performance required for the new services. However, the concept of cell-less RAN is still under consideration from the deployment point of view with the legacy cellular networks. The virtualization, centralization and cooperative communication which enables the cell-less RAN can further benefit from O-RAN based architecture. This thesis addresses the research challenges facing 5G and beyond networks towards 6G networks in regard to new architectures, spectral efficiency, latency, and energy efficiency. Different system models are stated according to the problem and several solution schemes are proposed and developed to overcome these challenges. This thesis contributes as follows. Firstly, the cell-less technology is proposed to be implemented through an Open RAN architecture, which could be supervised with the near real-time RAN intelligent controller (near-RT-RIC). The cooperation is enabled for intelligent and smart resource allocation for the entire RAN. Secondly, an efficient radio resource optimization mechanism is proposed for the cell-less architecture to improve the system capacity of the future 6G networks. Thirdly, an optimized and novel resource scheduling scheme is presented that reduces latency for the URLLC users in an efficient resource utilization manner to support scenarios with high user density. At the same time, this radio resource management (RRM) scheme, while minimizing the latency, also overcomes another important challenge of eMBB users, namely the throughput of those who coexist in such a highly loaded scenario with URLLC users. Fourthly, a novel energy-efficiency enhancement scheme, i.e., (3 × E) is designed to increase the transmission rate per energy unit, with stable performance within the cell-less RAN architecture. Our proposed (3 × E) scheme activates two-step sleep modes (i.e., certain phase and conditional phase) through the intelligent interference management for temporarily switching access points (APs) to sleep, optimizing the network energy efficiency (EE) in highly loaded scenarios, as well as in scenarios with lower load. Finally, a multi-architecture coexistence (MACO) network model is proposed to enable inter-connection of different architectures through coexistence and cooperation logical switches in order to enable smooth deployment of a cell-less architecture within the legacy networks. The research presented in this thesis therefore contributes new knowledge in the cellless RAN architecture domain of the future generation wireless networks and makes important contributions to this field by investigating different system models and proposing solutions to significant issues. Programa de Doctorado en Multimedia y Comunicaciones por la Universidad Carlos III de Madrid y la Universidad Rey Juan Carlos Presidenta: Matilde Pilar Sánchez Fernández.- Secretario: Alberto Álvarez Polegre.- Vocal: José Francisco Monserrat del Río

In MIMO (multiple input-multiple output) communication, the adaptation of the modulation and coding at the transmitter side according to the channel characteristics allows reducing the transmission power and/or enhancing the data rates. However, it is not always feasible to have instantaneous knowledge of the channel at the transmitter. This Thesis focuses on the case that the receiver has (perfect) instantaneous Channel State Information (CSIR) but the transmitter has only access to its distribution (CDIT). This is a practical case that applies, particularly, to situations where the channel varies rapidly. Under CDIT, the input cannot be adapted to the instantaneous state of the channel and thus SVD (singular value decomposition) cannot be used to diagonalize the channel. Achieving capacity requires a complex Gaussian input vector with a covariance that depends on the channel distribution. In practice, however, discrete constellations are used instead of Gaussian signals. Determining the optimum signalling strategy with discrete constellations is difficult in general, and thus a pragmatic approach is using the spatial signalling directions indicated by the capacityachieving covariance. Several classical practical bit and power loading algorithms are available for parallel-channel settings. To guarantee the quality of service, a certain average bit error probability (BER) is required at the receiver side. Different types of receiver correspond to differente relationships between the BER and the SINR. With the feedback of the parameters of the SINR (Signal-to-Interference-plus-Noise Ratio) distribution, two optimization problems for single user MIMO systems with correlation at the transmitter side can be solved, namely rate maximization with a total power constraint and power minimization with a target bit rate. The goal of this Thesis is to devise practical bit and power loading schemes for MIMO that can operate on the basis of CDIT only. For practical reasons, three typical receivers are considered, namely zero-forcing (ZF), minimum mean squared error (MMSE) and zero-forcing with successive interference cancellation (ZF-SIC). The following problems are addressed: • Maximization of the bit rates with discrete constellations, using the transmit directions given by the capacity achieving input covariance, at a certain average bit error probability (BER) and a constraint of total transmit power. • Minimization of the transmit power with discrete constellations, using the transmit directions given by the capacity achieving input covariance, at a certain average bit error probability (BER) and a target transmit bit rate. • Evaluation and comparison of the power gain when optimizing the transmission with the three mentioned types of receivers relative to a non-optimized transmission. In order to address these items, in this work it is essential to establish a relationship between the average BER corresponding to each of the three receivers and the powers allocated at the transmitter under the premise of CDIT. By utilizing these BER approximations, two dual optimization problems, bit maximization and power minimization, are solved for the practical case of statistical channel knowledge at the transmitter side and discrete constellations. Using a Gamma or a generalized Gamma distribution of the SINR, BER approximations can be obtained through integration. For a single user MIMO system with correlated channel, to accomplish the optimization process the mathematical methods used are a Levin-Campello algorithm for ZF, exhaustive search with additional constraints for MMSE and tree search with bit rate boundary for ZF-SIC. The accuracy of the developed expressions is verified with Monte Carlo simulations. The transmission environment is specified to be a Rayleigh flat-fading channel with correlation at the transmitter side. The Thesis is structured as follows. An introduction is presented at the first chapter, explaining the contents of this Thesis. Following a description of the basic process which takes place at the transmitter side, the second chapter presents the characteristics of the MIMO channel. Moreover, the system models of three typical receivers are described, namely ZF, MMSE and ZF-SIC. The third chapter starts with a review of capacity, and leads to the so-called waterfilling distribution. The dual optimization problems, bit rate maximization and power minimization, are defined with the objective of enhancing the performance via processing at the transmitter side. In some practical systems, Levin-Campello develops a solution for the dual optimization problems for discrete constellations that is described. Also, in order to further understand the power minimization problem for discrete constellations considering the loss of mutual information due to a given modulation, Mercury/Waterfilling is reviewed. In chapter IV, the BER of a ZF receiver is computed by using its SINR distribution, which is a Gamma distribution. For convenience, it is further accurately approximated at the high SNR regime. From the relationship between BER and power for different constellations, the two dual problems can be solved by a Levin-Campello algorithm, as the streams are independent with each other. To facilitate using the Levin-Campello algorithm, BER approximations are simplified to be established in convenient closedform equations. In chapter V, the BER of an MMSE receiver is also computed by using its SINR distribution, which can be modeled as a Gamma distribution or a generalized Gamma distribution. Some accurate closed-formed approximations are proposed and compared. In chapter VI, from these relationships between BER and power for different constellations, the two dual problems are solved by exhaustive search, as the streams are coupled with each other in the case of the MMSE receiver. In order to reduce the computational complexity, some additional constrains are added. For the two dual optimization problems, the total number of transmitted bits with an MMSE receiver cannot be less than those with a ZF receiver. Therefore, the starting point for the search is always the solution derived for ZF receivers, and the search progresses from that point towards higher loads until the constraints set in. The BER of MMSE can be approximated by the moment generating function (MGF), which includes the first three moments of SINR. Comparing two randomly selected antennas, when an increment of the number of bits is added to one of them, placing the increment in the antenna with better channel condition requires less total power to accomplish the transmission. Thus, it can be concluded that the better channel should be loaded with more bits. With this additional constraint, the computational complexity of the exhaustive search can be reduced even more reasonably. In chapter VII, taking into account the error propagation, a closed-form BER approximation can be derived for the ZF-SIC receiver by using the total probability theorem. Moreover, since the ordering of the decoding process can dramatically impact the system performance when using this receiver, a precoder is proposed to determine the decoder ordering to minimize the total power. Moreover, a boundary of possible bit rates for ZF-SIC is presented, considering the bit rate of ZF and ZF-PSIC (perfect SIC), for the two dual optimization problems. To make the search converge more efficiently, a tree search is implemented making use of this boundary. In the final chapter, the results obtained for the different receivers are compared to conclude the core of this Thesis. Then, some future work is outlined., En los sistemas de comunicaciones multiantena (MIMO: multiple inputmultiple output), la adaptación de los esquemas de modulación y codificación en el extremo transmisor según las características del canal permite reducir la potencia de transmisión y/o aumentar la velocidad de transmisión. Sin embargo, no siempre es posible tener conocimiento instantáneo del canal en el transmisor. Esta Tesis se centra en el caso en que el receptor tiene (perfecta) información instantánea del canal (CSIR: Channel State Information at the Receiver), pero el transmisor únicamente tiene acceso a su distribución (CDIT: Channel Distribution Information at the Transmitter). Este es un caso práctico que sucede, en particular, en situaciones en las que el canal varía rápidamente. Con CDIT, la señal no se puede adaptar al estado instantáneo del canal y, por tanto, no es posible usar una descomposición en valores singulares para diagonalizar el canal. Alcanzar la capacidad requiere el uso de señales Gaussianas cuya correlación depende de la distribución del canal. En la práctica, sin embargo, se utilizan constelaciones discretas y no señales Gaussianas. Determinar la estrategia óptima de transmisión con constelaciones discretas es difícil en general y, por ello, tomaremos una aproximación pragmática consistente en utilizar las direcciones espaciales correspondientes a la matriz de covarianza que permite obtener la capacidad (con señales Gaussianas). Para constelaciones discretas y canales paralelos independientes existen varios algoritmos de carga adaptativa de bits y potencia (bit and power loading) clásicos, que no son directamente aplicables al sistema bajo estudio. Si deseamos garantizar la calidad de servicio, se requiere una cierta probabilidad de error promedio (BER: bit error rate) en el extremo receptor. A diferentes tipos de receptor corresponden relaciones distintas entre la BER y la relación señal a interferencia (SINR: signal to interference plus noise ratio). Con la realimentación de los parámetros de la distribución de SINR al transmisor es posible resolver dos problemas duales de optimización en sistemas MIMO de usuario único con canal con correlación en el extremo transmisor: maximización de la tasa binaria con una restricción de potencia y minimización de la potencia transmitida con una restricción de la tasa binaria objetivo. El objetivo de esta Tesis es diseñar esquemas prácticos de carga adaptativa de bits y potencia para sistemas MIMO, que puedan operar sobre la base de conocimiento estadístico del canal en el transmisor (CDIT) únicamente. Por motivos prácticos, consideramos tres tipos de receptores típicos: receptor de forzado a cero (ZF), receptor de mínimo error cuadrático medio (MMSE), y receptor ZF con cancelación sucesiva de interferencias (ZF-SIC). Para estos tres receptores se abordan los siguientes problemas: • Maximizar la tasa binaria con constelaciones discretas, usando las direcciones espaciales de transmisión dictadas por la matriz de covarianza que alcanza la capacidad, garantizando una cierta probabilidad de error promedio y con la restricción de la potencia total a transmitir. • Minimizar la potencia de transmisión con constelaciones discretas, usando las direcciones espaciales de transmisión dictadas por la matriz de covarianza que alcanza la capacidad, garantizando una cierta probabilidad de error promedio y satisfaciendo un requisito de tasa binaria. • Obtener y comparar la ganancia de potencia de los tres tipos de receptores mencionados en relación con una transmisión sin optimizar. Para abordar estos problemas, es esencial establecer una relación entre la probabilidad de error promedio de cada uno de los receptores y la potencia asignada en el transmisor a cada flujo de datos MIMO, bajo la premisa de conocimiento CDIT. A partir de la distribución Gamma o Gamma generalizada de la SINR, se obtienen aproximaciones para la probabilidad de error promedio mediante integración. Para un sistema MIMO de usuario único con canal correlado, los métodos matemáticos empleados para resolver los problemas de optimización son: algoritmo “Levin-Campello” para ZF, búsqueda exhaustiva con restricciones adicionales para MMSE, y búsqueda en árbol con tasa binaria acotada para ZF-SIC. La precisión de las aproximaciones y las prestaciones de los algoritmos desarrollados se evalúan mediante simulación de Monte Carlo. El entorno de transmisión viene dado por un canal MIMO con desvanecimiento tipo Rayleigh, plano en frecuencia y con correlación en el extremo transmisor. La estructura de la Tesis es la siguiente. En el primer capítulo se presenta una introducción y se describe el contenido de la Tesis. A continuación, tras una descripción del procesado básico que tiene lugar en el transmisor, el capítulo II presenta las características del canal MIMO. Además, se describen el modelo del sistema y los tres receptores que se van a tratar: ZF, MMSE y ZF-SIC. El capítulo III comienza con una revisión de la capacidad, lo que conduce a la denominada distribución de “waterfilling” en sistemas MIMO. Los dos problemas de optimización duales, maximización de la tasa binaria y minimización de la potencia, se definen para mejorar las prestaciones mediante procesado en el extremo transmisor. En algunos sistemas prácticos, el algoritmo de Levin-Campello constituye una solución para estos problemas de optimización duales con constelaciones discretas, por lo que se presenta una revisión del mismo. Con el fin de comprender mejor el problema de minimización de potencia para constelaciones discretas, considerando la pérdida de información mutua debida a una modulación concreta, se revisa a continuación la distribución conocida como “mercury/waterfilling”. En el capítulo IV, se estima la probabilidad de error promedio para un receptor ZF utilizando la distribución de la SINR, que corresponde a una función de densidad de probabilidad Gama, y se encuentra una aproximación para relación señal a ruido alta que resulta muy precisa. A partir de la relación entre la BER y la potencia requerida para diferentes constelaciones, los dos problemas duales se pueden resolver mediante un algoritmo tipo “Levin-Campello”, dado que los flujos de datos son independientes. Para facilitar el uso de este algoritmo, se mejoran las aproximaciones de la BER, obteniendo cómodas ecuaciones en forma compacta. En el capítulo V, se estima la probabilidad de error promedio para un receptor MMSE, también utilizando la distribución de la SINR, que ahora corresponde a una Gama o Gama generalizada. Se proponen y comparan varias expresiones en forma cerrada. En el capítulo VI, a partir de la relación entre la BER y la potencia requerida para diversas constelaciones, se resuelven los dos problemas duales mediante búsqueda exhaustiva, dado que en este caso los flujos de datos están acoplados debido a que el receptor MMSE no cancela la interferencia. Para reducir la carga computacional se añaden algunas restricciones. Para los dos problemas duales, el número total de bits que se pueden transmitir cuando el receptor es MMSE no puede ser menor que el correspondiente a un receptor ZF. Así pues, el punto de partida de la búsqueda es la solución para el receptor ZF y la búsqueda progresa desde ese punto hacia mayores tasas mientras lo permiten las restricciones. La probabilidad de error tras el receptor MMSE se puede aproximar a trav´es de la MGF (moment generating function) que incluye los tres primeros momentos de la SINR. Comparando dos antenas cualesquiera se demuestra que si hay que añadir un cierto incremento de bits en una de ellas, la antena con mejor canal es la que requiere menor incremento de potencia total para transmitirlo. Así, se puede concluir que los mejores canales deben llevar mayor número de bits y esto permite añadir una restricción adicional a la búsqueda, que conlleva, de este modo, una carga computacional razonable. En el capítulo VII, se obtiene una aproximación cerrada para la BER de un receptor ZF-SIC considerando la propagación de errores, a partir del teorema de la probabilidad total. Dado que el orden del proceso de decodificación tiene un impacto importante en las prestaciones del sistema con este receptor, se propone un precodificador que determina el orden que minimiza la potencia total. Por otra parte, se presentan unas cotas de las tasas binarias posibles con ZF-SIC, considerando las de ZF y ZF-PSIC (perfect SIC) para los dos problemas duales de optimización. Haciendo uso de estas cotas, se emplea una búsqueda en árbol para agilizar la convergencia.

The fifth-generation (5G) of cellular communications is expected to be deployed in the next years to support a wide range of services with different demands of peak data rates, latency and quality of experience (QoE). To support higher data rates and latency requirements third-generation partnership project (3GPP) has introduced numerology and bandwidth parts (BWPs) for provisioning of 5G services through new radio (NR). The legacy 4G network has generated a lot of data which can be helpful to reveal insights about subscriber's traffic and infrastructure of the mobile network operators (MNOs), in order to identify 5G deployment area (5GDA) for planning new services. Given the mission-critical nature of 5G services, QoE is a big challenge for MNOs to guarantee peak data rates for a defined percentage of time. Apart from the access network, MNOs also face challenges of capacity and connectivity in the backhaul network. These challenges must be considered during the radio network planning (RNP) process to configure various network parameters such that the defined targets are met and the cost of network deployment is minimized. Therefore, the aim of this dissertation is to study and develop network planning methods for 5G, considering the pragmatic aspects of new radio (NR), capacity modelling, cost optimization, data acquisition and machine learning (ML). Contrasting to legacy networks, where radio planning is focused on provisioning of higher data rates, in 5G there are multiple use cases with different requirements of numerology, BWPs and QoE, which should be an integral part of the RNP. Our proposal takes these requirements into consideration by introducing two inter connected models, namely the transmission and capacity model. The transmission model incorporates 5G numerology and BWPs in service definition being offered by the MNO. It specifies each new service in an allocated BWP according to the peak data rate requirements which corresponds to the number of physical resource blocks (PRBs) and transmit power level of the next generation Node-B (gNB). Each service is configured with different numerology factor which correlates with a specific sub-carrier spacing to achieve desired latency in different frequency ranges supported by NR. As a rule of thumb, to support ultra-low latency services a larger sub-carrier spacing is configured and vice versa. Once the parameters of the transmission models are defined, the maximum transmission bandwidth per service and peak data rates per user are provided as inputs to the capacity model. The capacity model uses this input along with probabilistic modeling of the radio resource control (RRC) states of the 5G users to guarantee QoE by provisioning the peak data rates for MNO's required percentage of time. The simulation results show that our proposed model fulfils the QoE requirements for each service defined in the transmission model with the trade-off in confining the total number of subscribers per gNB. The utilization of the available capacity per gNB is the assurance for the MNO to a reduced cost per bit. The higher the network utilization the lower is the cost per bit which increases the revenue stream of the MNO. The higher network utilization can only be achieved if the planning of new deployments are assisted by real data to determine the area of the highest traffic density. To achieve this, we propose a network data acquisition procedure based on LTE identifiers to estimate traffic and to determine the 5GDA where the subscribers concentration is maximum. We propose a confidence benchmark sample (CBS) approach to take traffic information from reliable cells. We apply different combinations of the long term evolution (LTE) identifiers on network data to infer traffic and infrastructure information of the legacy network with a specified country code. We use the proposed procedure to determine the traffic patterns by visualizing the data with respect to geographical locations of the cells, though, the demarcation of the 5GDA is performed manually. Consequently, we propose a machine learning (ML) based framework to automate the demarcation of 5GDA by determining the highest traffic cluster. In contrast to Elbow method of computing the number of clusters, a cluster analysis approach is proposed to determine appropriate value of clusters based on MNO's requirement. The results are promising as higher network utilization is achieved with lower cost per bit values by identifying the highest traffic region on the cluster level. Given the highest traffic demands of the present-day networks, the cost and capacity considerations in the network planning play a vital role in establishing the connectivity of the backhaul segment with the core network. The new 5G deployments require higher capacity at the distribution or gateway nodes for transmission between radio sites with the core network. The problem of connecting the radio sites with the distribution nodes has been investigated in the context of cost and capacity. An integer liner programing (ILP) model has been formulated that minimizes the deployment cost by selecting the required number of distribution nodes given that the capacity constraint is not violated. At the same time, the model selects the distribution nodes based on centrality scores to determine near-by nodes such that the geographical distance is minimized to save the link cost. Moreover, we propose to co-site the distribution nodes with the already deployed macro-sites to minimize the backhaul deployment cost. The proposed ILP model provides the optimal topology solution at the cost of computational complexity. However, we also proposed a backhaul connectivity algorithm with much lower computational cost in the number of nodes compared to the optimal ILP model. The results show that the proposed algorithm solves the backhaul connectivity and cost minimization problem with a very small difference in the optimal topology solution obtained from ILP model with a cost loss of 11%. However, the advantage of the lower complexity algorithm is that the near optimal solution can be obtained for real-time network applications where immediate decision taking is essential. Programa de Doctorado en Multimedia y Comunicaciones por la Universidad Carlos III de Madrid y la Universidad Rey Juan Carlos Presidente: Carlos Bousoño Calzón.- Secretario: Borja Genovés Guzmán.- Vocal: Sancho Salcedo Sanz

Mención Internacional en el título de doctor Wireless communications have become a key pillar in our modern society. It can be hard to think of a service that somehow does not rely on them. Particularly, mobile networks are one of the most necessary technologies in our daily life. This produces that the demand for data rates is by no means stopping from increasing. The cellular architecture is facing a crucial challenge under limited performance by interference and spectrum saturation. This involves cell-edge users experiencing poor performance due to the close vicinity of base stations (BSs) using the same carrier frequency. Based on a combination of the coordinated multi-point (CoMP) technique and traditional massive multiple-input multiple-output (MIMO) systems, cell-free (CF) massive MIMO networks have irrupted as a solution for avoiding inter-cell interference issues and for providing uniform service in large coverage areas. This thesis focuses on the analysis and design of CF massive MIMO networks assuming a spatially correlated fading model. A general-purpose channel model is provided and the whole network functioning is given in detail. Despite the many characteristics a CF massive MIMO system shares with conventional colocated massive MIMO its distributed nature brings along new issues that need to be carefully accounted for. In particular, the so-called channel hardening effect that postulates that the variance of the compound wireless channel experienced by a given user from a large number of transmit antennas tends to vanish, effectively making the channel deterministic. This critical assumption, which permeates most theoretical results of massive MIMO, has been well investigated and validated in centralized architectures, however, it has received little attention in the context of CF massive MIMO networks. Hardening in CF architectures is potentially compromised by the different large-scale gains each access point (AP) impinges on the transmitted signal to each user, a condition that is further stressed when not all APs transmit to all users as proposed in the user-centric (UC) variations of CF massive MIMO. In this document, the presence of channel hardening in this new architecture scheme is addressed using distributed and cooperative precoders and combiners and different power control strategies. It is shown that the line-of-sight (LOS) component, spatially correlated antennas, and clustering schemes have an impact on how the channel hardens. In addition, we examine the existent gap between the estimated achievable rate and the true network performance when channel hardening is compromised. Exact closed-form expressions for both a hardening metric and achievable downlink (DL) and uplink (UL) rates are given as well. We also look into the pilot contamination problem in the UL and DL with different degrees of cooperation between the APs. The optimum minimum mean-squared error (MMSE) processing can take advantage of large-scale fading coefficients for canceling the interference of pilot-sharing users and thus achieves asymptotically unbounded capacity. However, it is computationally demanding and can only be implemented in a fully centralized network. Here, sub-optimal schemes are derived that provide unbounded capacity with much lower complexity and using only local channel estimates but global channel statistics. This makes them suited for both centralized and distributed networks. In this latter case, the best performance is achieved with a generalized maximum ratio combiner that maximizes a capacity bound based on channel statistics only. Programa de Doctorado en Multimedia y Comunicaciones por la Universidad Carlos III de Madrid y la Universidad Rey Juan Carlos Presidente: Rui Dinis.- Secretario: María Julia Fernández-Getino García.- Vocal: Carmen Botella Mascarell

The explosive usage of rich multimedia content in wireless devices has overloaded the communication networks. Moreover, the fifth generation (5G) of wireless communications involves new requirements in the radio access network (RAN) which require higher network capacities and new capabilities such as ultra-reliable and low-latency communication (URLLC), vehicular communications or augmented reality. All this has encouraged a remarkable spectrum crisis in the RF bands. A need for searching alternative techniques with more spectral efficiency to accommodate the needs of future emerging wireless communications is emerging. In this context, massive MIMO (m-MIMO) systems have been proposed as a promising solution for providing a substantial increase in the network capacity, becoming one of the key enabling technologies for 5G and beyond. m-MIMO provides high spectral- and energy-efficiency thanks to the deployment of a large number of antennas at the BS. However, we have to take into account that the current communication technologies are based on coherent transmission techniques so far, which require the transmission of a huge amount of signaling. This drawback is escalating with the excessive available number of antennas in m-MIMO. Therefore, the differential encoding and non coherent (NC) detection are an alternative solution to circumvent the drawbacks of m-MIMO in coherent systems. This Ph.D. Thesis is focused on signal processing techniques for NC detection in conjunction with m-MIMO, proposing new constellation designs and NC detection algorithms, where the information is transmitted in the signal differential phase. First, we design new constellation schemes for an uplink multiuser NC m-MIMO system in Rayleigh fading channels. These designs allow us to separate the users' signals at the receiver thanks to a one-to-one correspondence between the constellation for each user and the received joint constellation. Two approaches are considered in terms of BER: each user achieves a different performance and, on the other hand, the same performance is provided for all users. We analyze the number of antennas needed for those designs and compare to the required number by other designs in the literature. It is shown that our designs based on DPSK require a lower number of antennas than that required by their counterpart schemes based on energy. In addition, we compare the performance to their coherent counterpart systems, resulting NC-m-MIMO based on DPSK capable of outperforming the coherent systems with the suitable designs. Second, in order to reduce the number of antennas required for a target performance we propose a multi-user bit interleaved coded modulation - iterative decoding (BICM-ID) scheme as channel coding for a NC-m-MIMO system based on DPSK. We propose a novel NC approach for calculating EXIT curves based on the number of antennas. Then using the EXIT chart we find the best channel coding scheme for our NC-m-MIMO proposal. We show that the number of users served by the BS can be increased with a 70% reduction in the number of antennas with respect to the case without channel coding. In particular, we show that with 100 antennas for error protection equal design for all users and a coding rate of 1/2 we achieve the minimum probability of error. Third, we consider that current scenarios such as backhaul wireless systems, rural or suburban environments, and even new device-to-device (D2D) communications or the communications in higher frequencies (millimeter and the emerging ones in terahertz frequencies) can have a predominant line-of-sight (LOS) component, modeled by Rician fading. For all these new possible scenarios in 5G, we analyze the behavior of the NC m-MIMO systems when we have a Rician fading. We present a new constellation design to overcome the problem of the LOS channel component, as well as an associated detection algorithm to separate each user in reception taking into account the characterization of the constellation. In addition, for contemplating a more realistic scenario, we propose grouping users which experience a Rayleigh fading with those with Rician fading, analyzing the SINR and the performance of such combination in a multi-user NC m-MIMO system based on M-DPSK. The adequate user grouping allows unifying the constellation for both groups of users and the detection algorithm, reducing the complexity of the receiver. Also, the number of users that may be multiplexed may be further increased thanks to the improved performance. In the fourth part of this Thesis, we analyse the performance of multi-user NC m- MIMO based on DPSK in real environments and practical channels defined for the current standards such as LTE, the future technologies such as 5G and even for communications in the terahertz band. For this purpose, we use a metric to model the time-varying characteristics of the practical channels. We employ again the EXIT charts tool for analyzing and designing iteratively decoded systems. This analysis allows us to obtain an estimate of the degradation of the system's performance imposed by realistic channels. Hence, we show that our proposed system is robust to temporal variations, thus it is more recommendable the employment of NC-m-MIMO-DPSK in the future communication standards such as 5G. In order to reduce he number of hardware resources required in terms of RF chains, facilitating its implementation in a real system, we propose incorporating differential spatial modulation (DSM). We present and analyze a novel multiuser scheme for NC-m-MIMO combined with DSM with which we can see that the number of antennas is not a affected by the incorporation of DSM, even we have an improvement on the performance with respect to the coherent case. Finally, we study the viability of multiplexing users by constellation schemes against classical multiplexing techniques such as time division multiple access (TDMA). In order to fully characterize the system performance we analyze the block error rate (BLER) and the throughput of a NC-m-MIMO system. The results show a significant advantage regarding the number of antennas for multiplexing in the constellation against TDMA. However, in some cases, the demodulation of multiple users in constellation could require an excessively large number of antennas compared to TDMA. Therefore, it is necessary to properly manage the tradeoff between throughout and the number of antennas, to reach an optimal operational point, as shown in this Thesis. El inmenso uso de contenido multimedia en los dispositivos inalámbricos ha sobrecargado las redes de comunicaciones. Además, la quinta generación (5G) de sistemas de comunicaciones demanda nuevos requisitos para la red de acceso radio, la cual requiere ofrecer capacidades de red mayores y nuevas funcionalidades como comunicaciones ultra fiables y con muy poca letancia (URLLC), comunicaciones vehiculares o aplicaciones como la realidad aumentada. Todo esto ha propiciado una crisis notable en el espectro electromagnético, lo que ha llevado a una necesidad por buscar técnicas alternativas con más eficiencia espectral para acomodar todos los requisitos de las tecnologías de comunicaciones emergentes y futuras. En este contexto, los sistemas multi antena masivos, conocidos como massive MIMO, m-MIMO, han sido propuestos como una solución prometedora que proporciona un incremento substancial de la capacidad de red, convirtiéndose en una de las tecnologías claves para el 5G. Los sistemas m-MIMO elevan enormemente el número de antenas en la estación base, lo que les permite ofrecer alta eficiencia espectral y energética. No obstante, tenemos que tener en cuenta que las actuales tecnologías de comunicaciones emplean técnicas coherentes, las cuales requieren de información del estado del canal y por ello la transmisión de una enorme cantidad de información de señalización. Este inconveniente se ve agravado en el caso del m-MIMO debido al enorme número de antenas. Por ello, la codificación diferencial y la detección no coherente (NC) son una solución alternativa para solventar el problema de m-MIMO en los sistemas coherentes. Esta Tesis se centra en las técnicas de procesado de señal para detección NC junto con m-MIMO, proponiendo nuevos esquemas de constelación y algoritmos de detección NC, donde la información sea transmitida en la diferencia de fase de la señal. Primero, diseñamos nuevas constelaciones para un sistema multi usuario NC en m- MIMO en enlace ascendente (uplink) en canales con desvanecimiento tipo Rayleigh. Estos diseños nos permiten separar las señales de los usuarios en el receptor gracias a la correspondencia unívoca entre la constelación de cada usuario individual y la constelación conjunta recibida en la estación base. Hemos considerado dos enfoques para el diseño en términos de probabilidad de error: cada usuario consigue un rendimiento distinto, mientras que por otro lado, todos los usuarios son capaces de recibir las mismas prestaciones de probabilidad de error. Analizamos el número de antenas necesario para estos diseños y comparamos con el número requerido por otros diseños propuestos en la literatura. Nuestro diseño basado en DPSK requiere un número menor de antenas comparado con los sistemas basados en detección de energía. También comparamos con su homólogo coherente, resultando que NC-m-MIMO basado en DPSK es capaz de superar a los sistemas coherentes con los diseños adecuados. En segundo lugar, para reducir el número de antenas requerido para un rendimiento dado, proponemos incluir un esquema de codificación de canal. Hemos optado por un esquema de modulación codificado por bit entrelazado y decodificación iterativa (BICMID). Hemos empleado la herramienta EXIT chart para el diseño de la codificación de canal, proponiendo un nuevo enfoque para calcular las curvas EXIT de forma NC y basadas en el número de antenas. Los resultados muestran que el número de usuarios servidos por la estación base puede ser incrementado reduciendo un 70% el número de antenas con respecto al caso sin codificación de canal. En particular, para un array de 100 antenas y un diseño que ofrezca iguales prestaciones a todos los usuarios, con un código de tasa 1=2, podemos conseguir la mínima probabilidad de error. En tercer lugar, consideramos escenarios donde el canal tenga una componente predominante de visión directa (LOS) con la estación base modelada mediante un desvanecimiento tipo Rician. Por ejemplo, sistemas inalámbricos de backhaul, entornos rurales o sub urbanos, comunicaciones entre dispositivos (D2D), también cuando nos movemos hacia frecuencias superiores como son en la banda de milimétricas o más recientemente, la banda de terahercios para buscar mayores anchos de banda. Todos estos escenarios están contemplados en el futuro 5G. Los diseños presentados para canales Rayleigh ya no son válidos debido a la componente LOS del canal, por ello presentamos un nuevo diseño de constelación que resuelve el problema de la componente LOS, así como una guía para diseñar nuevas constelaciones. También proponemos un algoritmo asociado al diseñno de la constelación para poder separar a los usuarios en recepción. Además, para contemplar un escenario más realista donde podamos encontrar tanto desvanecimiento Rayleigh como Rice, proponemos agrupar usuarios de ambos grupos, analizando su rendimiento y relación señal a interferencia en la combinación. El adecuado agrupamiento permite unificar el diseño de la constelación para ambos desvanecimientos y por tanto reducir la complejidad en el receptor. También, el número de usuarios multiplicados en la constelación podría ser incrementado, gracias a la mejora en el rendimiento. El cuarto módulo de esta tesis es dedicado a analizar el rendimiento de los diseños propuestos en presencia de canales reales, donde disponemos de variabilidad temporal y en frecuencia. Proponemos usar una métrica que modela las características de la variabilidad temporal y, usando de nuevo la herramienta EXIT, analizamos los sistemas decodificados iterativamente considerando ahora los parámetros prácticos del canal. Este análisis nos permite obtener una estimación de la degradación que sufre el rendimiento del sistema impuesto por canales reales. Los resultados muestran que los sistemas NC-m-MIMO basados en DPSK son muy robustos a la variabilidad temporal por lo que son recomendables para los nuevos escenarios propuestos por el 5G, donde el canal cambia rápidamente. Otra consideración para introducir los sistemas NC con m-MIMO es la problemática de necesitar muchas cadenas de radio frecuencia que llevarían a tamaños de dispositivos enormes. Para reducir este número se propone la modulación espacial. En esta Tesis, estudiamos su uso con los sistemas NC, proponiendo una solución de modulación espacial diferencial para esquemas con múltiples usuarios combinado con NC-m-MIMO. Finalmente, estudiamos la viabilidad de multiplexar usuarios en la constelación frente a usar técnicas clásicas de multiplexación como TDMA. Para caracterizar completamente el rendimiento del sistema, analizamos la tasa de error de bloque (BLER) y el throughput de un sistema NC-m-MIMO. Los resultados muestran una ventaja significativa en cuanto al número de antennas para multiplexar usuarios en la constelación frente al requerido por TDMA. No obstante, en algunos casos, la demodulación de múltiples usuarios en la constelación podría requerir un número de antennas excesivamente grande comparado con la multiplexación en el tiempo. Por ello, es necesario gestionar adecuadamente un balance entre el throughput y el número de antenas para alcanzar un punto operacional óptimo, como se muestra en esta Tesis. Programa Oficial de Doctorado en Multimedia y Comunicaciones por la Universidad Carlos III de Madrid y la Universidad Rey Juan Carlos Presidente: Ana Isabel Pérez Neira.- Secretario: Máximo Morales Céspedes.- Vocal: María del Carmen Aguayo Torres

Mención Internacional en el título de doctor Video services have become highly demanded in mobile networks leading to an unprecedented traffic growth. It is expected that traffic from wireless and mobile devices will account for nearly 70 percent of total IP traffic by the year 2020, and the video services will account for nearly 75 percent of mobile data traffic by 2022. Multicast transmission is one of the key enablers towards a more spectral and energy efficient distribution of multimedia content in current and envisaged mobile networks. It is worth noting that multicast is a mechanism that efficiently delivers the same content to many users, not only focusing on video broadcasting, but also distributing many other media, such as software updates, weather forecast or breaking news. Although multicast services are available in Long Term Evolution (LTE) and LTE-Advanced (LTE-A) networks, new improvements are needed in some areas to handle the demands expected in the near future. Resource allocation techniques for multicast services are one of the main challenging issues, since it is required the development of novel schemes to meet the demands of their evolution towards the next generation. Most multicast techniques adopt rather conservative strategies that select a very robust modulation and coding scheme (MCS), whose characteristics are determined by the propagation conditions experienced by the worst user in the group in order to ensure that all users in a multicast group are able to correctly decode the received data. Obviously, this robustness comes at the prize of a low spectral efficiency. This thesis presents an exhaustive study of broadcast/multicast technology for current mobile networks, especially focusing on the scheduling and resource allocation (SRA) strategies to maximize the potential benefits that multicast transmissions imply on the spectral efficiency. Based on that issue, some contributions have been made to the state of the art in the radio resource management (RRM) for current and beyond mobile multicast services. • In the frame of LTE/LTE-A, the evolved multimedia broadcast and multicast service (eMBMS) shares the physical layer resources with the unicast transmission mode (at least up to Release 12). Consequently, the time allocation to multicast transmission is limited to a maximum of a 60 percent, and the remaining subframes (at least 40 percent) are reserved for unicast transmissions. With the aim of achieving the maximum aggregated data rate (ADR) among the multicast users, we have implemented several innovative SRA schemes that combine the allocation of multicast and unicast resources in the LTE/LTE-A frame, guaranteeing the prescribed quality of service (QoS) requirements for every user. • In the specific context of wideband communication systems, the selection of the multicast MCS has often relied on the use of wideband channel quality indicators (CQIs), providing rather imprecise information regarding the potential capacity of the multicast channel. Only recently has the per-subband CQI been used to improve the spectral efficiency of the system without compromising the link robustness. We have proposed novel subband CQI-based multicast SRA strategies that, relying on the selection of more spectrally efficient transmission modes, lead to increased data rates while still being able to fulfill prescribed QoS metrics. • Mobile broadcast/multicast video services require effective and low complexity SRA strategies. We have proposed an SRA strategy based on multicast subgrouping and the scalable video coding (SVC) technique for multicast video delivery. This scheme focuses on reducing the search space of solutions and optimizes the ADR. The results in terms of ADR, spectral efficiency, and fairness among multicast users, along with the low complexity of the algorithm, show that this new scheme is adequate for real systems. These contributions are intended to serve as a reference that motivate ongoing and future investigation in the challenging field of RRM for broadcast/ multicast services in next generation mobile networks. La demanda de servicios de vídeo en las redes móviles ha sufrido un incremento exponencial en los últimos años, lo que a su vez ha desembocado en un aumento sin precedentes del tráfico de datos. Se espera que antes del año 2020, el trafico debido a dispositivos móviles alcance cerca del 70 por ciento del tráfico IP total, mientras que se prevé que los servicios de vídeo sean prácticamente el 75 por ciento del tráfico de datos en las redes móviles hacia el 2022. Las transmisiones multicast son una de las tecnologías clave para conseguir una distribución más eficiente, tanto espectral como energéticamente, del contenido multimedia en las redes móviles actuales y futuras. Merece la pena reseñar que el multicast es un mecanismo de entrega del mismo contenido a muchos usuarios, que no se enfoca exclusivamente en la distribución de vídeo, sino que también permite la distribución de otros muchos contenidos, como actualizaciones software, información meteorológica o noticias de última hora. A pesar de que los servicios multicast ya se encuentran disponibles en las redes Long Term Evolution (LTE) y LTE-Advanced (LTE-A), la mejora en algunos ámbitos resulta necesaria para manejar las demandas que se prevén a corto plazo. Las técnicas de asignación de recursos para los servicios multicast suponen uno de los mayores desafíos, ya que es necesario el desarrollo de nuevos esquemas que nos permitan acometer las exigencias que supone su evolución hacia la próxima generación. La mayor parte de las técnicas multicast adoptan estrategias conservadoras, seleccionando esquemas de modulación y codificación (MCS) impuestos por las condiciones de propagación que experimenta el usuario del grupo con peor canal, para así asegurar que todos los usuarios pertenecientes al grupo multicast sean capaces de decodificar correctamente los datos recibidos. Como resulta obvio, la utilización de esquemas tan robustos conlleva el precio de sufrir una baja eficiencia espectral. Esta tesis presenta un exhaustivo estudio de la tecnología broadcast/ multicast para las redes móviles actuales, que se centra especialmente en las estrategias de asignación de recursos (SRA), cuyo objetivo es maximizar los beneficios que la utilización de transmisiones multicast potencialmente implica en términos de eficiencia espectral. A partir de dicho estudio, hemos realizado varias contribuciones al estado del arte en el ámbito de la gestión de recursos radio (RRM) para los servicios multicast, aplicables en las redes móviles actuales y futuras. • En el marco de LTE/LTE-A, el eMBMS comparte los recursos de la capa física con las transmisiones unicast (al menos hasta la revisión 12). Por lo tanto, la disponibilidad temporal de las transmisiones multicast está limitada a un máximo del 60 por ciento, reservándose las subtramas restantes (al menos el 40 por ciento) para las transmisiones unicast. Con el objetivo de alcanzar la máxima tasa total de datos (ADR) entre los usuarios multicast, hemos implementado varios esquemas innovadores de SRA que combinan la asignación de los recursos multicast y unicast de la trama LTE/LTE-A, garantizando los requisitos de QoS a cada usuario. • En los sistemas de comunicaciones de banda ancha, la selección del MCS para transmisiones multicast se basa habitualmente en la utilización de CQIs de banda ancha, lo que proporciona información bastante imprecisa acerca de la capacidad potencial del canal multicast. Recientemente se ha empezado a utilizar el CQI por subbanda para mejorar la eficiencia espectral del sistema sin comprometer la robustez de los enlaces. Hemos propuesto nuevas estrategias para SRA multicast basadas en el CQI por subbanda que, basándose en la selección de los modos de transmisión con mayor eficiencia espectral, conducen a mejores tasas de datos, a la vez que permiten cumplir los requisitos de QoS. • Los servicios móviles de vídeo broadcast/multicast precisan estrategias eficientes de SRA con baja complejidad. Hemos propuesto una estrategia de SRA basada en subgrupos multicast y la técnica de codificación de vídeo escalable (SVC) para la difusión de vídeo multicast, la cual se centra en reducir el espacio de búsqueda de soluciones y optimizar el ADR. Los resultados obtenidos en términos de ADR, eficiencia espectral y equidad entre los usuarios multicast, junto con la baja complejidad del algoritmo, ponen de manifiesto que el esquema propuesto es adecuado para su implantación en sistemas reales. Estas contribuciones pretenden servir de referencia que motive la investigación actual y futura en el interesante ámbito de RRM para los servicios broadcast/multicast en las redes móviles de próxima generación. Programa Oficial de Doctorado en Multimedia y Comunicaciones Presidente: Atilio Manuel Da Silva Gameiro.- Secretario: Víctor Pedro Gil Jiménez.- Vocal: María de Diego Antón

Este proyecto tiene como objetivo el diseño completo de una red de radioenlaces entre los principales aeropuertos de Yemen para mejorar la coordinación y organización de su espacio aéreo. En los capítulos en los que se divide este documento se pueden ver las distintas fases del proceso de diseño hasta llegar a una solución optimizada para implantar en campo. Se analiza en un principio el problema y el objetivo que se pretende conseguir con una red de este tipo, y se estudia uno a uno los emplazamientos que se necesitan conectar. Se presenta como resultado de estos primeros pasos, una arquitectura de red basada en un diseño preliminar que es necesario chequear para analizar las ventajas y desventajas que pueden ofrecer unas y otras opciones. Por supuesto como en todo estudio de red de radioenlaces se tiene muy en cuenta la orografía del terreno ya que influye directamente en la topología de la red y en el diseño de cada vano. Una vez se tienen localizados los emplazamientos y los puntos repetidores necesarios, se estudiará cada enlace en la banda de frecuencias disponible con los requerimientos técnicos, para verificar uno a uno la viabilidad de cada enlace, la planificación de frecuencias y la disponibilidad de la red a conseguir. Al final de este documento se presenta la solución de radioenlaces propuesta, pero es estrictamente necesario antes de empezar la instalación, realizar una verificación in-situ de cada emplazamiento (aeropuertos, repetidores, etc.) para confirmar el diseño y evitar así problemas que puedan surgir en la fase de implantación. Ingeniería Técnica en Sistemas de Telecomunicación

This report represents the last and most important document I have made during my time in the university. The main idea that surrounds all this work is the elaboration of a source code by a student for students. Because of that, the simulation is based in MATLAB and oriented to be as changeable as possible to allow people with a medium knowledge of this program to understand and modify it. The initial step of this project is the simulation of an Orthogonal Frequency-Division Multiplexing (OFDM) system and its later validation. The system applies the fundamental orthogonality principles of the signals and creates a multiple carrier waveform including a modulated symbol in each carrier. This systems are usually in a certain central frequency with established bandwidth in the frequency spectrum. In this case the situation is a low-pass equivalent simulation only to see the waveform and error results of the modulation/demodulation process. The motivation for this report comes from the implementation of the 5G network in mobile communication and the uncertainty of the new OFDM waveform. There are two systems that have real chances to become the new waveform: Zero Tail based OFDM and Filter Bank Multicarrier based OFDM. The 5G networks are the immediate future for mobile communications and their development has to be in the hands of the system performance instead of the different companies’ interest. To be impartial developing this new systems requires an academic point of view in favor of the better solution possible for the new mobile networks. The aim of this simulation is to be able to compare this new systems with a working model of the standard OFDM. In this report it was only possible to study and analyze the Zero Tail based OFDM leaving the rest for future projects. However the simulation goal is to be as adaptable as possible, the channel models implemented in the source code are Long Term Evolution (commonly known as 4G) because of the drive of this new OFDM waveforms. The ideal situation to this experiments would be working with the 5G channel models (which are not decided yet), but it would be accurate enough to start with the already established ones. Ingeniería de Sistemas Audiovisuales