Prediction of the rapidly fading envelope of a mobile radio channel enables a number of capacity improving techniques like fast resource allocation and fast link adaptation. This thesis deals with linear prediction of the complex impulse response of a channel and unbiased quadratic prediction of the power. The design and performance of these predictors depend heavily on the correlation properties of the channel. Models for a channelwhere the multipath is caused by clusters of scatterers are studied. The correlation for the contribution from a cluster can be approximated as a damped complex sinusoid. A suitable model for the dynamics of the channel is an ARMA-process. This motivates the use of linear predictors. A limiting factor in the prediction are the estimation errors on the observed channels. This estimation error, caused by measurement noise and time variation, is analyzed for a block based least squares algorithm which operates on a Jakes channel model. Efficient noise reduction on the estimated channel impulse responses can be obtained with Wienersmoothers that are based on simple models for the dynamics of the channel combined with estimates of the variance of the estimation error. Power prediction that is based on the squared magnitude of linear prediction of the taps will be biased. Hence, a bias compensated power predictor is proposed and the optimal prediction coefficients are derived for the Rayleigh fading channel. The corresponding probability density functions for the predicted power are also derived. A performance evaluation of the prediction algorithm is carried out on measured broadband mobile radio channels. The performance is highly dependent on the variance of the estimation error and the dynamics of the individual taps.

[ES] La quinta generación de comunicaciones móviles, 5G, promete ser una revolución tecnológica que vaya más allá de multiplicar la velocidad de transmisión de datos de sus predecesoras. Pretende soportar una gran cantidad de dispositivos y alcanzar latencias muy cercanas a 1 milisegundo. Para satisfacer estos ambiciosos requisitos, se han investigado nuevas tecnologías habilitadoras. Una de ellas es el uso de las bandas de ondas milimétricas (mmW) en las cuales hay una gran cantidad de espectro disponible. Para predecir las características del canal radio y evaluar las prestaciones de la 5G de forma fiable en las bandas mmW se requieren modelos de canal complejos. Concretamente, los modelos de propagación más precisos son los basados en trazado de rayos, pero su alto costo computacional los hacen inviables para la caracterización del canal radio en escenarios complejos. Por otro lado, en los últimos años, la tecnología de videojuegos ha desarrollado potentes herramientas para modelar la propagación de la luz en escenarios superrealistas. Dada la cercanía espectral entre el espectro visible y las ondas mmW, la presente Tesis ha estudiado la aplicación de las herramientas de modelado de propagación de la luz de los motores de juego para el modelado del canal radio en mmW. Esta Tesis propone un modelo de estimación de las pérdidas de propagación en mmW llamado "Modelo de Intensidad de Luz'' (LIM). Usando este modelo, basado en los procesos de iluminación realizados por los motores de juego, los transmisores de señal se sustituyen por focos de luz y la intensidad lumínica recibida en un punto se traduce a potencia de señal en milimétricas a través de una función polinómica sencilla. Una de las ventajas de usar los motores de juego es su gran capacidad y la facilidad que tiene el usuario para crear escenarios superrealistas que representen fielmente la geometría de escenarios donde se quiera evaluar el canal radio. De esta forma se pueden obtener estimaciones precisas de las pérdidas de propagación. La estimación de las pérdidas de propagación con LIM ha sido comparada con campañas de medida en las bandas de 28 GHz y 73 GHz y con otros modelos de propagación. Como resultado, el error de estimación de LIM es menor que los modelos estocásticos actuales y es comparable con el modelo de trazado de rayos. Y, además, el coste computacional de LIM comparado con el trazado de rayos es 130 veces menor, lo que posibilita el uso de LIM en escenarios altamente complejos para la estimación del canal radio en tiempo real. Los motores de juego permiten caracterizar de forma diferente la interacción de los materiales con la luz configurando el mapa de normales de sus superficies y sus funciones de dispersión y reflexión. En esta Tesis se ha determinado la caracterización de varios materiales que mejor se ajusta a medidas de laboratorio realizadas en un escenario controlado en la banda de 28 GHz. El modelo de LIM empleando materiales con esta caracterización óptima reduce más de un 50\% su error de estimación con respecto a la aplicación de LIM con los materiales por defecto, mientras que su coste computacional sigue siendo 26 veces menor que el modelo de trazado de rayos. Finalmente, se ha desarrollado sobre un motor de juego una primera versión de plataforma para la emulación de los sistemas 5G que es el punto de partida para un emulador completo de 5G. Esta plataforma no sólo contiene el modelo de LIM sino que incluye varios casos de uso de la 5G en entornos superrealistas. La plataforma, que se basa en el concepto de "Serious Game Engineering", rompe las limitaciones de los simuladores de redes móviles en cuanto a las capacidades de visualización e interacción del usuario con los componentes de la red en tiempo real. / [CAT] La cinquena generació de comunicacions mòbils, 5G, promet ser una revolució tecnològica que vaja més enllà de multiplicar la velocitat de transmissió de dades de les seues predecessores. Pretén suportar una gran quantitat de dispositius i aconseguir latències molt pròximes a 1 mil·lisegon. Per a satisfer aquests ambiciosos requisits, s'han investigat noves tecnologies habilitadores. Una d'elles és l'ús de les bandes d'ones mil·limètriques (mmW) en les quals hi ha una gran quantitat d'espectre disponible. Per a predir les característiques del canal ràdio i avaluar les prestacions de la 5G de forma fiable en les bandes mmW es requereixen models de canal complexos. Concretament, els models de propagació més precisos són els basats en traçat de rajos, però el seu alt cost computacional els fan inviables per a la caracterització del canal ràdio en escenaris complexos. D'altra banda, en els últims anys, la tecnologia de videojocs ha desenvolupat potents eines per a modelar la propagació de la llum en escenaris superrealistes. Donada la proximitat espectral entre l'espectre visible i les ones mmW, la present Tesi ha estudiat l'aplicació de les eines de modelatge de propagació de la llum dels motors de joc per al modelatge del canal radie en mmW. Aquesta Tesi proposa un model d'estimació de les pèrdues de propagació en mmW anomenat "Model d'Intensitat de Llum'' (LIM). Usant aquest model, basat en els processos d'il·luminació realitzats pels motors de joc, els transmissors de senyal se substitueixen per focus de llum i la intensitat lumínica rebuda en un punt es tradueix a potència de senyal en mil·limètriques a través d'una funció polinòmica senzilla. Una dels avantatges d'usar els motors de joc és la seua gran capacitat i la facilitat que té l'usuari per a crear escenaris superrealistes que representen fidelment la geometria d'escenaris on es vulga avaluar el canal ràdio. D'aquesta forma es poden obtindre estimacions precises de les pèrdues de propagació. L'estimació de les pèrdues de propagació amb LIM ha sigut comparada amb campanyes de mesura en les bandes de 28~GHz i 73~GHz i amb altres models de propagació. Com a resultat, l'error d'estimació de LIM és menor que els models estocàstics actuals i és comparable amb el model de traçat de rajos. I, a més, el cost computacional de LIM comparat amb el traçat de rajos és 130 vegades menor, la qual cosa possibilita l'ús de LIM en escenaris altament complexos per a l'estimació del canal ràdio en temps real. Els motors de joc permeten caracteritzar de forma diferent la interacció dels materials amb la llum configurant el mapa de normals de les seues superfícies i les seues funcions de dispersió i reflexió. En aquesta Tesi s'ha determinat la caracterització de diversos materials que s'ajusta millor a mesures de laboratori realitzades en un escenari controlat en la banda de 28 GHz. El model de LIM emprant materials amb aquesta caracterització òptima redueix més d'un 50 % el seu error d'estimació respecte a l'aplicació de LIM amb els materials per defecte, mentre que el seu cost computacional continua sent 26 vegades menor que el model de traçat de rajos. Finalment, s'ha desenvolupat sobre un motor de joc una primera versió de plataforma per a l'emulació dels sistemes 5G que és el punt de partida per a un emulador complet de 5G. Aquesta plataforma no solament conté el model de LIM sinó que inclou diversos casos d'ús de la 5G en entorns superrealistes. La plataforma, que es basa en el concepte de "Serious Game Engineering", trenca les limitacions dels simuladors de xarxes mòbils quant a les capacitats de visualització i interacció de l'usuari amb els components de la xarxa en temps real. / [EN] The fifth generation of mobile communications, 5G, promises to be a technological revolution that goes beyond multiplying the data transmission speed of its predecessors. It aims to support a large number of devices and reach latencies very close to 1 millisecond. To meet these ambitious requirements, new enabling technologies have been researched. One of these is the use of millimetre-wave bands (mmW) in which a large amount of spectrum is available. Complex channel models are required to predict radio channel characteristics and reliably evaluate 5G performance in the mmW bands. Specifically, the most accurate propagation models are those based on ray tracing, but their high computational cost makes them unfeasible for radio channel characterization in complex scenarios. On the other hand, in recent years, video game technology has developed powerful tools to model the propagation of light in super realistic scenarios. Given the spectral closeness between the visible spectrum and the mmW waves, the present Thesis has studied the application of light propagation modeling tools from game engines for radio channel modeling in mmW. This Thesis proposes a model for estimating propagation losses in mmW called "Light Intensity Model'' (LIM). Using this model, based on the lighting processes performed by the game engines, the signal transmitters are replaced by light sources and the light intensity received at a point is translated into signal strength in mmW through a simple polynomial function. One of the advantages of using the game engines is their great capacity and the ease with which the user can create super realistic scenarios that faithfully represent the geometry of scenarios where the radio channel is to be evaluated. In this way, accurate estimates of propagation losses can be obtained. The estimation of propagation losses with LIM has been compared with measurement campaigns in the 28 GHz and 73 GHz bands and with other propagation models. As a result, the LIM estimation error is smaller than the current stochastic models and is comparable with the ray tracing model. In addition, the computational cost of LIM compared to ray tracing is 130 times lower, allowing the use of LIM in highly complex scenarios for real-time radio channel estimation. The game engines allow to characterize in a different way the interaction of the materials with the light configuring the normal map of their surfaces and their scattering and reflection functions. In this Thesis it has been determined the characterization of several materials that best fits to laboratory measurements made in a controlled scenario in the 28 GHz band. The LIM model using materials with this optimal characterization reduces by more than 50% its estimation error with respect to the application of LIM with default materials, while its computational cost remains 26 times lower than the ray tracing model. Finally, a first version of a platform for the emulation of 5G systems has been developed on a game engine, which is the starting point for a complete 5G emulator. This platform not only contains the LIM model but also includes several 5G use cases in super realistic environments. The platform, which is based on the concept of "`Serious Game Engineering", breaks the limitations of mobile network simulators in terms of visualization capabilities and user interaction with network components in real time. / Inca Sánchez, SA. (2019). Serious Game Engineering and Lighting Models for the Realistic Emulation of 5G Systems [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/132695 / TESIS

No / Narrowband path loss measurements are reported for the vehicle-to-vehicle channel between a transmitting antenna 50 cm above the ground and a car-roof-mounted receiver array. Calibration procedures and measurement results are reported for typical urban, suburban and rural-motorway environments and compared with existing mobile channel models to give insight into the large-scale fading behavior in the vehicle-to-vehicle channel.

Networks with hundreds of ad hoc nodes equipped with communication and position finding abilities are conceivable with recent advancements in technology. Methods are presented in this thesis to assess the communicative capabilities and node position estimation of mobile ad hoc networks. Specifically, we investigate techniques for providing communication and geolocation with specific characteristics in wireless ad hoc networks. The material presented in this thesis, communication and geolocation, may initially seem a collection of disconnected topics related only distantly under the banner of ad hoc networks. However, systems currently in development combining these techniques into single integrated systems. In this thesis first, we investigate the effect of multilayer interaction, including fading and path loss, on ad hoc routing protocol performance, and present a procedure for deploying an ad hoc network based on extensive simulations. Our first goal is to test the routing protocols with parameters that can be used to characterize the environment in which they might be deployed. Second, we analyze the location discovery problem in ad hoc networks and propose a fully distributed, infrastructure-free positioning algorithm that does not rely on the Global Positioning System (GPS). The algorithm uses the approximate distances between the nodes to build a relative coordinate system in which the node positions are computed in three-dimensions. However, in reconstructing three-dimensional positions from approximate distances, we need to consider error threshold, graph connectivity, and graph rigidity. We also statistically evaluate the location discovery procedure with respect to a number of parameters, such as error propagation and the relative positions of the nodes.

In this thesis a new approach for characterisation of digital mobile radio channels is investigated. The new approach is based on recognition of the fact that while the fading which is characteristic of the mobile radio channel is very rapid, the processes underlying this fading may vary much more slowly. The comparative stability of these underlying processes has not been exploited in system designs to date. Channel models are proposed which take account of the stability of the channel. Estimators for the parameters of the models are proposed, and their performance is analysed theoretically and by simulation and measurement. Bounds are derived for the extent to which the mobile channel can be predicted, and the critical factors which define these bounds are identified. Two main applications arise for these channel models. The first is the possibility of prediction of the overall system performance. This may be used to avoid channel fading (for instance by change of frequency), or compensate for it (by change of the signal rate or by power control). The second application is in channel equalisation. An equaliser based on a model which has parameters varying only very slowly can offer improved performance especially in the case of channels which appear to be varying so rapidly that the convergence rate of an equaliser based on the conventional model is not adequate. The first of these applications is explored, and a relationship is derived between the channel impulse response and the performance of a broadband system.

Recently, wireless access to Internet applications and services has attracted a lot of attention. However, there is no single wireless network that can meet all mobile users’ requirements. Con-sequently, integrated heterogeneous wireless networks are introduced to meet diverse wireless Internet applications and services requirements. On the other hand, integrated heterogeneous wireless networks pose new challenges to the design and development of reliable transport mechanisms. Wireless Application Protocol version 2 (WAP 2.0) is one of the promising trans-port mechanisms. It uses wireless profiled TCP (WP-TCP), which is fully compatible with TCP, as one of the reliable transport protocols to cope with the wireless link impairments. For WAP 2.0 to continue providing reliable and efficient transport services in the future, one of the key is-sues is to thoroughly study, understand, and improve its performance in integrated heterogeneous wireless networks. In this thesis, we develop analytical frameworks and propose a solution to respectively study and improve the performance of WP-TCP in integrated heterogeneous wireless networks. Spe-cifically, we consider WP-TCP short- and long-lived flows over integrated wireless local area network (WLAN) and wireless wide area network (WWAN), where WLAN can be static or mo-bile. In order to facilitate the analysis of WP-TCP performance in integrated WLAN and WWAN, we first construct a novel WLAN link model, which captures the impact of both uncor-related and correlated transmission errors, and derive mathematical expressions that describe packet loss probability and packet loss burst length over WWAN-WLAN link. Then, we develop analytical frameworks for studying the performance of WP-TCP short- and long-lived flows. Differently from those reported in the literature, our analytical framework for WP-TCP short-lived flows takes into account both correlated and uncorrelated packet losses. Furthermore, our analytical framework for long-lived flow can be used to study the short-term (during vertical handover) and long-term performances of WP-TCP and it captures the effects of vertical handover, such as excessive packet losses and sudden change in network characteristics, which are commonly experienced in integrated static WLAN and WWAN. By using the devel-oped analytical frameworks, we extensively analyze the performance of WP-TCP flows and in-vestigate the optimal protocol design parameters over a wide range of network conditions. Finally, based on our analytical studies, we propose a receiver-centric loosely coupled cross-layer design along with two proactive schemes, which significantly improve the vertical hand-over performance. The proposed solution is easy to implement and deploy, compatible with tra-ditional TCP, and robust in the absence of cross-layer information. Extensive simulations have been conducted to confirm the effectiveness and practicability of our schemes.

Recently, wireless access to Internet applications and services has attracted a lot of attention. However, there is no single wireless network that can meet all mobile users’ requirements. Con-sequently, integrated heterogeneous wireless networks are introduced to meet diverse wireless Internet applications and services requirements. On the other hand, integrated heterogeneous wireless networks pose new challenges to the design and development of reliable transport mechanisms. Wireless Application Protocol version 2 (WAP 2.0) is one of the promising trans-port mechanisms. It uses wireless profiled TCP (WP-TCP), which is fully compatible with TCP, as one of the reliable transport protocols to cope with the wireless link impairments. For WAP 2.0 to continue providing reliable and efficient transport services in the future, one of the key is-sues is to thoroughly study, understand, and improve its performance in integrated heterogeneous wireless networks. In this thesis, we develop analytical frameworks and propose a solution to respectively study and improve the performance of WP-TCP in integrated heterogeneous wireless networks. Spe-cifically, we consider WP-TCP short- and long-lived flows over integrated wireless local area network (WLAN) and wireless wide area network (WWAN), where WLAN can be static or mo-bile. In order to facilitate the analysis of WP-TCP performance in integrated WLAN and WWAN, we first construct a novel WLAN link model, which captures the impact of both uncor-related and correlated transmission errors, and derive mathematical expressions that describe packet loss probability and packet loss burst length over WWAN-WLAN link. Then, we develop analytical frameworks for studying the performance of WP-TCP short- and long-lived flows. Differently from those reported in the literature, our analytical framework for WP-TCP short-lived flows takes into account both correlated and uncorrelated packet losses. Furthermore, our analytical framework for long-lived flow can be used to study the short-term (during vertical handover) and long-term performances of WP-TCP and it captures the effects of vertical handover, such as excessive packet losses and sudden change in network characteristics, which are commonly experienced in integrated static WLAN and WWAN. By using the devel-oped analytical frameworks, we extensively analyze the performance of WP-TCP flows and in-vestigate the optimal protocol design parameters over a wide range of network conditions. Finally, based on our analytical studies, we propose a receiver-centric loosely coupled cross-layer design along with two proactive schemes, which significantly improve the vertical hand-over performance. The proposed solution is easy to implement and deploy, compatible with tra-ditional TCP, and robust in the absence of cross-layer information. Extensive simulations have been conducted to confirm the effectiveness and practicability of our schemes.

Nanoscale communication is appealing domain in nanotechnology. There are many existing nanoscale communication methods. In addition to these, novel techniques can be derived depending on the naturally existing phenomena such as molecular communication. It uses molecules as an information carrier such as molecular motors, pheromones and neurotransmitters for neuro-spike communication. Among them, neuro-spike communication is a vastly unexplored area. The ultimate goal of this thesis is to accurately investigate it by obtaining a realistic physical channel model. This model can be exploited in different disciplines. Furthermore, the model can help designing novel artificial nanoscale communication paradigms. The modeled channel is analyzed regarding the error probability of detecting spikes depending on channel parameters. Moreover, channel delay is characterized and information theoretical analysis of packet release mechanism in the channel is performed. The modeled channel is extended to multi-input single output terminal. In this case, input neurons can simultaneously send information through the same synapse leading to interference. However, there is an interference repressing technique in these synapses called automatic gain control. It decreases the interference level observed on weaker signal. The first aim for this case is to define the interference channel at synapse having automatic gain control. The second aim is to analyze the achievable rate region of this channel. The analysis shows that gain control mechanism prevents the decrease in achievable rate region because of the weaker signal. Moreover, power, firing rate and number of stronger inputs do not affect the achievable rate region.

The C2X Communication is of high interest to the automotive industry. Ongoing research on this topic mainly bases on the simulation of Vehicular Ad Hoc Networks. In order to estimate the necessary level of simulation details their impact on the results needs to be examined. This thesis focuses on different channel models as the freespace, shadowing, and Ricean model, along with varying parameters. For these simulations the network simulator ns-2 is extended to provide IEEE 802.11p compliance. However, the WAVE mode is not considered since it is still under development and not finally approved. Besides a more sophisticated packet error model than the existing implementation, as well as a link adaptation algorithm, is added. In this thesis several simulations examine specific details of wireless communication systems such as fairness of multiple access, interferences, throughput, and variability. Furthermore, the simulation points out some unexpected phenomena as starving nodes and saturation effects in multi hop networks. Those led to the conclusion that the IEEE 802.11 draft amendment does not solve known problems of the original IEEE 802.11 standard.

L’amélioration de la sécurité routière ainsi que le développement des systèmes de transports intelligents sont des enjeux d’avenir dans le secteur automobile avec un essor considérable du véhicule semi autonome et autonome. Les systèmes de sécurité active qui équipent de plus en plus les véhicules commercialisés utilisent des capteurs radar (longue et courte portée) fonctionnant dans les bandes 24 GHz ou 77 GHz. L’étude et la mise au point de tels capteurs peuvent être facilitées via l’utilisation d’une plate-forme de simulation générique permettant de simuler un système radar couplé à son environnement selon des scénarios types prédéfinis. Il est alors nécessaire de disposer d’une représentation fiable et réaliste de l’environnement et des objets présents.Cette thèse aborde la caractérisation et la modélisation du canal de propagation et plus largement de l’environnement radioélectrique en ondes millimétriques pour des applications radar, en termes de phénomènes de propagation (trajets multiples, réflexion, diffraction …) et de cibles électriquement larges. Une combinaison de méthodes asymptotiques a été mise en œuvre afin de permettre l'analyse de problèmes électriquement larges en bande W, tout en réduisant les exigences en temps de calcul et en capacité de mémoire. La précision du simulateur a été évaluée à l’aide d’une campagne de mesures de SER de cibles canoniques et complexes de petite taille (inférieure 6cm) dans une chambre anéchoïque. Le banc de mesure mis en œuvre a permis également de valider une procédure expérimentale de détermination de la signature radar. En effet, la procédure expérimentale a été généralisée à la mesure de la signature radar d’objets de taille réelle, dans un milieu « indoor ». Les mesures effectuées ont montré une bonne adéquation avec les résultats présentés dans la littérature. En outre, ces données expérimentales permettent d’extraire une description de la cible par des points brillants qui modélisent les phénomènes de diffusion et de réflexion spéculaire. La réponse à haute fréquence d’une cible peut être approchée par la somme de réponses de ses points brillants. On propose ainsi de simplifier les signatures mesurées pour maximiser l'efficacité de calcul. Comparé aux modèles géométriques détaillés d’une cible complexe, le modèle de points brillants conduit à une meilleure efficacité des simulations de propagation basées sur des rayons dans des scénarios routiers. Le modèle tient également compte de l’anisotropie des diffuseurs (dans le plan azimutal) en modélisant leurs amplitudes par des gaussiennes. / Improving road safety as well as the development of intelligent transport systems are issues of the future in the automotive sector with a considerable rise of the semi-autonomous and autonomous vehicle. The active safety systems that increasingly equip commercial vehicles use radar sensors (long and short range) operating in the 24 GHz or 77GHz bands. The study and development of such sensors can be facilitated through the use of a generic simulation platform to simulate a radar system coupled to its environment according to predefined standard scenarios. It is then necessary to have a reliable and realistic representation of the environment as well as targets. This thesis deals with the characterization and modelling of the propagation channel for radar applications, in terms of propagation phenomena (multipath, reflection, diffraction …) and electrically large targets. A combination of asymptotic methods was developed for the analysis of electrically large problems in W band, while reducing the requirements in CPU time and memory. The accuracy of the simulator was evaluated with radar cross section measurement of canonical and complex small targets (not exceeding 6 cm) in an anechoic chamber. The developed bench measurement also made it possible to validate an experimental procedure for determining the radar signature. Indeed, the experimental characterization was generalized to characterize various automotive related targets in an “indoor” environment. Measurement results matched well with the results presented in the literature. Moreover, the experimental data allows the extraction of a simple target description in terms of scattering points which model the diffusion and specular reflection phenomena. The high frequency response of a target can be approached by the sum of the responses of its scattering centres. It is thus proposed to simplify the measured signatures in order to increase the computation efficiency. Compared to detailed geometrical representation of a complex target, scattering centre model leads to better efficiency of ray-based propagation simulations of road scenarios. The model also takes into account the scattering centre anisotropy (in the azimuth plan) by modelling their amplitudes by Gaussian ones.