Capacidade e predição de canais sem fio em ondas milimétricas para redes celulares de quinta geração

Monografia (graduação)—Universidade de Brasília, Faculdade de Tecnologia, 2015.A utilização de ondas milimétricas para os novos sistemas sem fio tem se tornado uma proposta promissora vistas as inúmeras vantagens que a transmissão nessa faixa oferece. Dentre elas, destaca-se a enorme quantidade de espectro disponível, que permite taxas de dados elevadas e atrasos cada vez menores. Dado o comprimento de onda, as características de propagação do sinal divergem significamente em comparação a sistemas modernos de comunicação. Neste trabalho, por meio de estudos analíticos, a capacidade do canal para ondas milimétricas é comparada à capacidade das atuais tecnologias presentes no mercado brasileiro. Suas vantagens para curtas distâncias são evidenciadas nesse trabalho. Além disso, a capacidade ergódica do canal, utilizando o modelo de desvanecimento TWDP, é apresentada e comparada com o modelo de Rice, mostrando a importância do parâmetro K sobre o parâmetro _. Por último, e continuando a investigação de canais sem fio para redes celulares de quinta geração, este trabalho apresenta uma comparação entre predições de cobertura do sinal LTE em 2.5 GHz e em ondas milimétricas em 28 GHz na região de Brasília, concluindo que o sistema atual brasileiro de telecomunicações será incapaz de atender a demanda dos usuários com a infraestrutura já existente.The use of millimeter waves for new wireless systems has become a promising proposal given the many advantages that transmission in this range offers. Among them, the huge amount of available spectrum stands out, which allows higher data rates and smaller delays. Due to the small wavelength, signal propagation characteristics differ significantly in comparison to modern communication systems. In this work, through analytical studies, the channel capacity for millimeter waves is compared with current technologies available in the Brazilian telecommunication market. The advantages over short distances are evidenced in this work. Furthermore, the ergodic channel capacity over a TWDP fading model is presented and compared with a Rician model, showing the importance of parameter K over _. Finally, and continuing with the wireless channels research for fifth-generation cellular networks, this paper presents a comparison between coverage predictions of LTE signal at 2.5 GHz and millimeter waves at 28 GHz in the region of Brasilia, concluding that the current Brazilian telecommunications system will not be able to meet the demand of users with the already existing infrastructure

Six-Port Technology for Millimeter-Wave MIMO Systems

RÉSUMÉ Les taux de transmission des systèmes de communication sans-fil modernes augmentent. De nouvelles bandes de fréquences et de nouvelles technologies sont exploitées pour supporter de hauts taux de transmission. La bande d’ondes millimétriques est une bonne candidate pour supporter des taux de transmission de l’ordre des Gbps. De plus, la technologie à entrées/sorties multiples (MIMO) ouvre la porte à des systèmes de communication à bas coût à haut taux de transmission. Le récepteur hétérodyne standard est utilisé dans plusieurs systèmes de communication, puisqu’il présente une grande sélectivité et une grande sensibilité. Par contre, le récepteur à conversion directe permet un meilleur niveau d’intégration en diminuant le nombre de composants des circuits. Parmi les récepteurs à conversion directe, ceux à six ports ont un circuit passif qui sert d’interferomètre. La diversité additionnelle est produite par les sorties en quadrature, qui sont des combinaisons linéaires du signal d’entrée et du signal de référence. Les guides d’onde intégrés au substrat (SIW) peuvent être facilement intégrés à des circuits planaires. La conception est simplifiée puisqu’il existe des méthodes de conception de guides d’ondes traditionnels. Un système MIMO à six ports de type SIW est présenté dans cette dissertation. Premièrement, un diviseur de puissance et un coupleur hybride de type SIW sont présentés. L’implémentation de ces circuits, basée sur les règles de conception des structures SIW, est réalisée une bande de fréquence d’intérêt. Plusieurs paramètres critiques peuvent être manipulés pour contrôler les performances du diviseur de puissance et du coupleur hybride. Une transition de la structure SIW à la ligne micro-ruban est conçue pour permettre des mesures. Les résultats de simulation du circuit démontrent que celui-ci offre une bonne performance. Deuxièmement, à partir du diviseur de puissance et du coupleur hybride, le circuit à six ports est présenté. Trois types d’architechtures sont comparées, et l’une d’elles est choisie pour le système de démonstration. Les résultats de simulation et les résultats expérimentaux concordent, et guarantissent une bonne performance du circuit proposé et du système de communication sans-fil dans lequel le circuit est intégré. Finalement, le système de 2×2 ports est présenté. Il n’y a pas de couplage réciproque entre les deux récepteurs lorsque le critère de propagation de Rayleigh dans la ligne de visée est respecté.---------- Abstract Presently, the data rates in modern wireless communication systems are becoming higher and higher and new frequency bands and technologies are being exploited in support of high data transmissions. The millimeter-wave band is a candidate of choice to support Gbps data transmission. In addition, Multiple-Input Multiple-Output (MIMO) technology will open the way for low-cost reliable communication systems that require even higher data rates. While the conventional heterodyne receiver has been widely applied in many kinds of communication systems due to its high selectivity and sensitivity, the direct-conversion receiver allows higher-level circuit integration by reducing the number of circuit components. Among these direct-conversion receivers, six-port scheme presents a passive circuit that acts as an interferometer. The additional diversity is produced by the quadrature outputs of the six-port circuit that are linear combinations of the unknown input signal and the reference signal. Substrate integrated waveguide (SIW) can be integrated with planar circuits easily. The design procedure is obviously simplified as a result of the existing typical design methods for the rectangular waveguide. Based on the above techniques and discussions, the millimeter-wave MIMO system based on SIW six-port circuit is presented in this dissertation. First, the SIW power divider and hybrid coupler are presented. The implementation of those circuits is based on the SIW design rules, according to the working frequency band of interest. Several critical parameters can be manipulated to control performances of the SIW power divider and hybrid coupler. An SIW to microstrip line transition is designed for measurement purposes. Simulation results of the circuits show good performances. Second, based on the studied and designed SIW power divider and hybrid coupler, the six-port circuit is presented. Three types of six-port architecture are compared, with one of them chosen to work in our millimeter-wave MIMO system demonstration. Simulation and measurement results agree well and guarantee a good performance of the proposed circuit itself and wireless high-speed communication system in which the circuit is embedded. Finally, the 2×2 millimeter-wave MIMO system is presented

CHANNEL MODELING FOR FIFTH GENERATION CELLULAR NETWORKS AND WIRELESS SENSOR NETWORKS

In view of exponential growth in data traffic demand, the wireless communications industry has aimed to increase the capacity of existing networks by 1000 times over the next 20 years. A combination of extreme cell densification, more bandwidth, and higher spectral efficiency is needed to support the data traffic requirements for fifth generation (5G) cellular communications. In this research, the potential improvements achieved by using three major 5G enabling technologies (i.e., small cells, millimeter-wave spectrum, and massive MIMO) in rural and urban environments are investigated. This work develops SPM and KA-based ray models to investigate the impact of geometrical parameters on terrain-based multiuser MIMO channel characteristic. Moreover, a new directional 3D channel model is developed for urban millimeter-wave (mmW) small cells. Path-loss, spatial correlation, coverage distance, and coherence length are studied in urban areas. Exploiting physical optics (PO) and geometric optics (GO) solutions, closed form expressions are derived for spatial correlation. Achievable spatial diversity is evaluated using horizontal and vertical linear arrays as well as planar 2D arrays. In another study, a versatile near-ground field prediction model is proposed to facilitate accurate wireless sensor network (WSN) simulations. Monte Carlo simulations are used to investigate the effects of antenna height, frequency of operation, polarization, and terrain dielectric and roughness properties on WSNs performance

Χρήση του Φάσματος Συχνοτήτων 70-500GHz στις δορυφορικές επικοινωνίες

Στα πλαίσια αυτής της διπλωματικής εργασίας έγινε μία προσπάθεια να επικεντρώσουμε το ενδιαφέρον μας στις συχνότητες που αφορούν τις δορυφορικές επικοινωνίες. Στο πρώτο κεφάλαιο γίνεται μία ιστορική αναδρομή στις δορυφορικές επικοινωνίες και σε θέματα που αφορούν τη δομή τους, την αρχιτεκτονική τους, τις τροχιές, τις υπηρεσίες και τις εφαρμογές τους. Στο δεύτερο κεφάλαιο γίνεται μία παρουσίαση των δορυφορικών επικοινωνιών με τη χρήση συχνοτήτων σε TeraHertz τιμές. Παράλληλα, αναφερόμαστε στα κίνητρα για τη χρήση των TeraHertz συχνοτήτων καθώς και στην ατμοσφαιρική απορρόφηση σε αυτές τις συχνότητες. Στο τρίτο κεφάλαιο αναφερόμαστε σε μήκη κύματος της τάξης των mm και στο μοντέλο καναλιού σε μήκη κύματος mm. Ταυτόχρονα, παρουσιάζονται δύο εφαρμογές γι’ αυτά τα μήκη κύματος (mmMAGIC Project και mmWave Backhaul και Fronthaul). Τέλος, στο τέταρτο κεφάλαιο εκθέτουμε μία σειρά από συμπεράσματα που αφορούν τη χρήση υπερυψηλών συχνοτήτων στις δορυφορικές επικοινωνίες.In the context of this dissertation, an attempt was made to focus our attention on the frequencies related to satellite communications. The first chapter provides a historical overview of satellite communications and issues related to their structure, architecture, trajectories, services and applications. The second chapter presents a presentation of satellite communications using frequencies in TeraHertz values. At the same time, we refer to the incentives for the use of TeraHertz frequencies as well as to the atmospheric absorption at these frequencies. In the third chapter we refer to wavelengths of the order of mm and to the channel model in wavelengths of mm. At the same time, two applications are presented for these wavelengths (mmMAGIC Project and mmWave Backhaul and Fronthaul). Finally, in the fourth chapter we present a series of conclusions regarding the use of high frequencies in satellite communications

Wireless Friendliness Evaluation of Building Materials as Reflectors

The enormous popularity of wireless devices has prompted a rapid growth of indoor wireless traffic. To meet the high data demand and avoid inconvenient usages of a room, indoor base stations (BSs) and Wi-Fi access points (APs) with large-scale multiple-input multiple-output (MIMO) antenna arrays are likely to be deployed in the vicinity of a wall, which therefore results in non-negligible interactions between indoor electromagnetic (EM) wave propagations and building materials. The reflection characteristics of building materials, which depend on their intrinsic EM and physical properties, play a crucial role in indoor wireless communications. However, the relationship between the material properties and the indoor wireless performance has not been sufficiently studied. In this thesis, wireless friendliness is proposed as a new metric to measure the impact of a building material on indoor wireless performance as a function of its EM and physical properties. The main objectives are to develop wireless friendliness evaluation schemes for building materials as reflectors on indoor line-of-sight (LOS) MIMO communications, and to provide insights into the appropriate design and/or selection of building materials according to their wireless friendliness. To achieve these objectives, the thesis presents four major contributions. The first contribution is to propose a new two-ray channel model and a new multipath channel model that incorporate both the LOS path and the wall reflection (WR) path for indoor LOS MIMO downlink transmissions. For the first time, the relative permittivity (EM property) and thickness (physical property) of a building material are encapsulated into the channel models through the reflection coefficient of the building material, which provides theoretical prerequisites for the subsequent tractable analysis. The second contribution is to reveal the analytical relationship between the relative permittivity and thickness of building materials and the MIMO channel capacity. By exploiting the expressions of indoor wireless capacity and their asymptotic forms, four effective metrics for evaluating the wireless friendliness of building materials are proposed, i.e., the spatially averaged capacity, the spatially averaged logarithmic eigenvalue sum (LES), the spatially averaged logarithmic eigenvalue product (LEP), and the upper-bound outage probability, which are all over the room of interest. The third contribution is to develop the evaluation schemes for the wireless friendliness of building materials. The optimal values of the relative permittivity and thickness of a building material that maximise the indoor wireless capacity are obtained, shedding light on the selection and/or design of a building material accordingly, and thus paving the way for wireless friendly architectural design. The fourth contribution is to analyse the effects of the WR from building materials on the per-antenna power distribution across a precoded antenna array at a BS or an AP deployed near a wall. An uneven power distribution across antenna elements may reduce the efficiencies of their corresponding radio frequency (RF) power amplifiers. How the per-antenna power distribution changes with the building material’s relative permittivity and thickness is investigated, providing guidelines on the selection and/or design of a building material that alleviates the unevenness of per-antenna power distribution. Simulation results validate the correctness of analytical results as well as the effectiveness of the four proposed evaluation metrics, and demonstrate that the EM and physical properties of building materials have to be delicately selected or designed to avoid the risk of reducing indoor wireless capacity and RF power amplifier efficiency. More specifically, the inappropriate choices of relative permittivity and thickness of a building material may reduce the indoor wireless capacity by up to 13.5% or cause severe unevenness as large as 8 dB in the per-antenna power distribution across a precoded antenna array. The outcomes of this thesis would enable appropriate design and/or selection of building materials for building designers, e.g., civil engineers and architects, and provide wireless-friendliness information for communications engineers

Le multiplexage spatial à 60 GH en environnement interne : critères de faisabilité et analyse de performance

RESUMÉ Le sujet de ce mémoire s'intéresse aux méthodes qui permettraient de faire du MIMO sur la bande de fréquences millimétriques des 57-64 GHz qui sera utilisée dans les prochaines normes WIFI et dans les futures générations de normes 5G pour le mobile. On traite ce sujet car la technologie MIMO telle qu'on la connaît depuis les années 2000 avec la norme WIFI 802.11n ne permet pas d'être utilisée sur la bande des 57-64 GHz dans les mêmes conditions. En effet, pour bénéficier des avantages du MIMO on doit auparavant effectuer certains traitements sur les signaux. Ce traitement qui est le plus souvent une décomposition en valeurs singulières consiste à pré-traiter les signaux qui seront envoyés à travers les différentes antennes à l'émission et à faire un post-traitement des signaux reçus par les différentes antennes de réception. Les normes WIFI fonctionnent actuellement sur deux bandes de fréquences : 2.4 GHz et 5.8 GHz. Elles effectuent ce traitement numériquement via des DSP programmés pour traiter les signaux avant qu'ils soient envoyés et après avoir été reçus. Cependant, comme tous systèmes numériques programmables, les DSP comme les FPGA sont limités en vitesse de part leur fréquence de fonctionnement. Or la largeur de bande offerte à 60 GHz est près de 70 (et 45) fois supérieure à celle offerte à 2.4 GHz (et à 5.8 GHz). Ce qui nécessite autant de puissance de calcul supplémentaire. Actuellement aucun DSP ou FPGA à faible coût pouvant être embarqué dans un périphérique WIFI grand public à 60 GHz n'existe pour faire le traitement MIMO. On montre qu'en utilisant des réseaux d'antennes planaires avec certaines configurations spatiales, on est capable sans effectuer de traitement complexe du signal, d'obtenir des canaux suffisamment indépendants pour transmettre plusieurs flux de données indépendants. Lorsque les réseaux d'antennes sont suffisamment éloignés, on arrive à atteindre les mêmes performances que celles du système MIMO équivalent utilisant la décomposition en valeurs singulières. De plus, l'ajout d'une technique de traitement du signal au récepteur appelé LMMSE permet de diminuer les contraintes spatiales et d'améliorer les performances sous certaines conditions. Les mesures de la réponse fréquentielle du canal pour un système MIMO utilisant des réseaux d'antennes planaires permettent de valider les hypothèses émises et de manière indirecte certains résultats obtenues par simulation.----------ABSTRACT The topic of this report is about new methods to figure out the difficulties to use MIMO systems on the 57-64 GHz millimeter wave band which will be used in the future telecommunication standards like the next generations of WIFI and mobile standards. We interest to this subject because contrary to the MIMO system used in the current standards, with the millimeter waves the way to use the MIMO is different because of a technical and physical constraints. Indeed, to take advantage of the MIMO much signal processing is required. This processing involves most of the time a linear mathematical transformation by using a decomposition in singular values called SVD. Thank to this linear transformation we can apply a pre-processing to the signals to transmit through several antennas and a post-processing to the received signals from several antennas. Nowadays, the current WIFI standards use either the 2.4 GHz band or the 5.8 Ghz band. The signal processing at these frequencies is done digitally by the software load in the DSP which is responsible amongst other things to compute the SVD. As it is a software which handles the computation, it is necessarily limited by the speed of the DSP. However, the offered bandwidth on the 60 GHz band is about 70 (and 45) times superior to the offered bandwidth at 2.4 Ghz (and 5.8 GHz). That requires a very powerful DSP. But currently, there is no low cost DSP or FPGA that can be embedded in a commercial WIFI device at 60 GHz in order to handle the signal processing. We show that the use of the patch array antennas with certain spatial configurations allows to get pseudo orthogonal channels without using complex signal processing. When the patch array antennas are adequately spaced, we figure out to reach the same performance than the equivalent MIMO system with singular value decomposition. Moreover, the addition of a signal processing to the receiver called LMMSE allows to reduce the required spacial constraints and to improve the performance under certain conditions. The frequency response measurements of the MIMO channel using patch arrays antennas confirm the assumptions and indirectly certain results obtained by simulation