69 research outputs found
Multi-Antenna Array Topologies Optimization for Future Wireless Networks by Employing Particle Swarm Optimization
The purpose of this work is to design novel antenna array topologies that maximize channel capacity. Accordingly, we employ the particle swarm optimization (PSO) algorithm as an effective technique in similar electromagnetic problems. We use a novel modelling approach to derive the spatial fading correlation function by employing a generic three-dimensional (3-D) angle of arrival (AOA) model. We then employ the PSO algorithm to find the antenna array topology that maximizes the channel capacity. The use of the PSO algorithm together with the new modelling approach for the spatial correlation is sufficiently tested and verified in terms of efficiency and correctness of addressing similar type of electromagnetic problems. Moreover, the general AOA model of this work is adaptable to different propagation environments, thus our approach is very promising in this regard
State-of-the-art assessment of 5G mmWave communications
Deliverable D2.1 del proyecto 5GWirelessMain objective of the European 5Gwireless project, which is part of the H2020 Marie Slodowska-
Curie ITN (Innovative Training Networks) program resides in the training and involvement of young
researchers in the elaboration of future mobile communication networks, focusing on innovative
wireless technologies, heterogeneous network architectures, new topologies (including ultra-dense
deployments), and appropriate tools. The present Document D2.1 is the first deliverable of Work-
Package 2 (WP2) that is specifically devoted to the modeling of the millimeter-wave (mmWave)
propagation channels, and development of appropriate mmWave beamforming and signal
processing techniques. Deliver D2.1 gives a state-of-the-art on the mmWave channel measurement,
characterization and modeling; existing antenna array technologies, channel estimation and
precoding algorithms; proposed deployment and networking techniques; some performance
studies; as well as a review on the evaluation and analysis toolsPostprint (published version
Multiple-Input Multiple-Output Communications Systems Using Reconfigurable Antennas
RĂSUMĂ Depuis les annĂ©es 1990, l'utilisation des systĂšmes de communications sans-fil Ă entrĂ©es multiples-sorties multiples (MIMO) a Ă©tĂ© introduit pour fournir des transmissions fiables Ă grande vitesse. Cette thĂšse porte sur l'application et lâĂ©tude des systĂšmes MIMO avec des antennes reconfigurables, qui sont ajustable Ă©lectroniquement pour produire diffĂ©rents diagrammes de rayonnement d'un seul Ă©lĂ©ment d'antenne et ainsi offrir une diversitĂ© de diagrammes de rayonnement. En particulier, nous Ă©tudions le comportement de la capacitĂ© de canal des systĂšmes MIMO Ă sĂ©lection de diagrammes de rayonnement (PS-MIMO), et nous proposons aussi des algorithmes de sĂ©lection du diagramme de rayonnement atteignant la capacitĂ© maximale.
Tout d'abord, nous Ă©tudions l'application des antennes reconfigurables dans l'estimation des statistiques spatiales Ă long terme de canaux spatiaux avec grappes de multi-trajets (cluster). Nous proposons un estimateur de spectre de type Capon et une technique d'adaptation de la covariance (COMET) pour estimer conjointement l'angle moyen et lâĂ©talement angulaire de la grappe spatiale avec des antennes reconfigurables. En second lieu, sur la base des statistiques Ă long terme du canal MIMO, nous proposons des algorithmes de sĂ©lection de diagramme de rayonnement MIMO (SPS-MIMO) pour atteindre la capacitĂ© maximale de canal ergodique. L'analyse de la maximisation de la capacitĂ© ergodique du systĂšme SPS-MIMO indique que le modĂšle statistique de sĂ©lection fournit des gains supplĂ©mentaires en amĂ©liorant la puissance du signal reçu et en dĂ©corrĂ©lant les signaux reçus avec diffĂ©rents diagrammes de rayonnement directionnels. TroisiĂšmement, nous nous concentrons sur le modĂšle de sĂ©lection instantanĂ©e des diagrammes de rayonnement MIMO (IPS-MIMO) basĂ© sur des informations instantanĂ©es d'Ă©tat de canal (CSI) afin de maximiser la capacitĂ© instantanĂ©e pour chaque rĂ©alisation de canal. Nous dĂ©montrons que lâordre de diversitĂ© des systĂšmes MIMO peut ĂȘtre multipliĂ©e par le nombre de diagrammes de rayonnement avec sĂ©lection de diagramme instantanĂ©e. Afin d'Ă©valuer la capacitĂ© moyenne de l'IPS-MIMO, nous proposons un nouvel algorithme qui permet dâapproximer Ă©troitement la moyenne de la valeur maximale de la capacitĂ© du canal MIMO avec des trajets arbitrairement corrĂ©lĂ©s. Nous proposons Ă©galement un algorithme pour sĂ©lectionner instantanĂ©ment les diagrammes de rayonnement pour atteindre la capacitĂ© moyenne. En outre, sur la base d'une simple expression en forme fermĂ©e de la capacitĂ© coefficient de corrĂ©lation, nous sommes en mesure de proposer un algorithme de sĂ©lection de sous-ensemble de diagrammes qui offre un compromis entre performances et la complexitĂ© de lâalgorithme de sĂ©lection. En conclusion, des gains de performance importants peuvent ĂȘtre obtenus grĂące Ă la combinaison de l'utilisation dâantennes reconfigurables et de systĂšmes MIMO avec soit des algorithmes de sĂ©lection de diagramme de rayonnement statistique ou instantanĂ©e. La capacitĂ© des systĂšmes PS-MIMO Ă amĂ©liorer les performances du systĂšme, y compris la capacitĂ© et de l'ordre de la diversitĂ©, est dĂ©montrĂ©e par l'analyse thĂ©orique et des simulations numĂ©riques.----------ABSTRACT Since the 1990s, the use of multiple-input multiple-output (MIMO) systems has been introduced to modern wireless communications to provide reliable transmission at high data rates. This thesis focuses on the application of MIMO systems with reconfigurable antennas, which are electronically tunable to produce a number of radiation patterns at a single antenna element and provide pattern diversity. In particular, we investigate the capacity performance of the pattern selection MIMO (PS-MIMO) systems, and we also present maximum capacity achieving algorithms for radiation pattern selection. First, we investigate the application of reconfigurable antennas in estimating long term spatial statistics of spatial clustered channels. We propose a Capon-like spectrum estimator and a covariance matching technique (COMET) to jointly estimate the mean angle and the angular spread of the spatial cluster with reconfigurable antennas. Second, based on the long term statistics of the MIMO channel, we propose statistical pattern selection MIMO (SPS-MIMO) algorithms to achieve maximum ergodic channel capacity. Analysis of the ergodic capacity maximization of the SPS-MIMO indicates that the statistical pattern selection provides additional gains by enhancing received signal power and decorrelating received signals with different directional radiation patterns. Third, we focus on the instantaneous pattern selection MIMO (IPS-MIMO) based on instantaneous channel state information (CSI) in order to maximize the instantaneous capacity for every channel realization. We prove that the diversity order of MIMO systems can be multiplied by the number of radiation patterns with instantaneous pattern selection. In order to evaluate the mean capacity of the IPS-MIMO, we propose a novel algorithm which closely approximates the mean of the maximum of the channel capacity of arbitrarily correlated MIMO channels. We also propose an algorithm for instantaneously selecting radiation patterns to achieve the mean capacity. In addition, based on a simple closed-form approximation to the capacity correlation coefficient, we are able to propose a subset pattern selection algorithm which enables the trade-off between performances and complexity. In conclusion, important extra gains can be obtained as a result of combining the use of reconfigurable antennas and MIMO systems with either statistical or instantaneous radiation pattern selection. The capability of the PS-MIMO to improve system performances, including capacity and diversity order, is demonstrated through theoretical analysis and numerical simulations
Development of multi-link geometry-based MIMO channel model
Projecte final de carrera realitzat en col.laboraciĂł amb A<lto University. Department of Radio Science and EngineeringForthcoming wireless communication systems need larger capacity. MIMO systems are already an answer that enables to achieve large increase to the link capacity. However, a wide and precise knowledge of the radio propagation channel is required in order to exploit the many benefits and capabilities of MIMO systems.
In this masterâs thesis a multi-link geometry-based MIMO channel model was developed. This work analyses the effect of common clusters on multi-link MIMO capacity and inter-link correlation based on simulation studies. Furthermore, the basics on radio wave propagation and MIMO systems as well as a review on existing MIMO channel models are also provided.
Finally simulation results revealed that, in general, common clusters increase the inter-link correlation, and so the ML-MIMO capacity decrease. But sometimes cluster geometry together with array geometry fully determines the MIMO system performance independently of the significance of common clusters. In addition, it was shown how often the overall system performance is degraded. Finally, it was also investigated that a common cluster which is really significant for only one link is not in fact a common cluster
Transmission strategies for broadband wireless systems with MMSE turbo equalization
This monograph details efficient transmission strategies for single-carrier wireless broadband communication systems employing iterative (turbo) equalization. In particular, the first part focuses on the design and analysis of low complexity and robust MMSE-based turbo equalizers operating in the frequency domain. Accordingly, several novel receiver schemes are presented which improve the convergence properties and error performance over the existing turbo equalizers. The second part discusses concepts and algorithms that aim to increase the power and spectral efficiency of the communication system by efficiently exploiting the available resources at the transmitter side based upon the channel conditions. The challenging issue encountered in this context is how the transmission rate and power can be optimized, while a specific convergence constraint of the turbo equalizer is guaranteed.Die vorliegende Arbeit beschÀftigt sich mit dem Entwurf und der Analyse von
effizienten Ăbertragungs-konzepten fĂŒr drahtlose, breitbandige
EintrÀger-Kommunikationssysteme mit iterativer (Turbo-) Entzerrung und
Kanaldekodierung. Dies beinhaltet einerseits die Entwicklung von
empfÀngerseitigen Frequenzbereichs-entzerrern mit geringer KomplexitÀt
basierend auf dem Prinzip der Soft Interference Cancellation Minimum-Mean
Squared-Error (SC-MMSE) Filterung und andererseits den Entwurf von
senderseitigen Algorithmen, die durch Ausnutzung von
Kanalzustandsinformationen die Bandbreiten- und Leistungseffizienz in Ein-
und Mehrnutzersystemen mit Mehrfachantennen (sog. Multiple-Input
Multiple-Output (MIMO)) verbessern.
Im ersten Teil dieser Arbeit wird ein allgemeiner Ansatz fĂŒr Verfahren zur
Turbo-Entzerrung nach dem Prinzip der linearen MMSE-SchÀtzung, der
nichtlinearen MMSE-SchÀtzung sowie der kombinierten MMSE- und
Maximum-a-Posteriori (MAP)-SchÀtzung vorgestellt. In diesem Zusammenhang
werden zwei neue EmpfÀngerkonzepte, die eine Steigerung der
LeistungsfÀhigkeit und Verbesserung der Konvergenz in Bezug auf
existierende SC-MMSE Turbo-Entzerrer in verschiedenen Kanalumgebungen
erzielen, eingefĂŒhrt. Der erste EmpfĂ€nger - PDA SC-MMSE - stellt eine
Kombination aus dem Probabilistic-Data-Association (PDA) Ansatz und dem
bekannten SC-MMSE Entzerrer dar. Im Gegensatz zum SC-MMSE nutzt der PDA
SC-MMSE eine interne EntscheidungsrĂŒckfĂŒhrung, so dass zur UnterdrĂŒckung
von Interferenzen neben den a priori Informationen der Kanaldekodierung
auch weiche Entscheidungen der vorherigen Detektions-schritte
berĂŒcksichtigt werden. Durch die zusĂ€tzlich interne
EntscheidungsrĂŒckfĂŒhrung erzielt der PDA SC-MMSE einen wesentlichen Gewinn
an Performance in rĂ€umlich unkorrelierten MIMO-KanĂ€len gegenĂŒber dem
SC-MMSE, ohne dabei die KomplexitÀt des Entzerrers wesentlich zu erhöhen.
Der zweite EmpfĂ€nger - hybrid SC-MMSE - bildet eine VerknĂŒpfung von
gruppenbasierter SC-MMSE Frequenzbereichsfilterung und MAP-Detektion.
Dieser EmpfÀnger besitzt eine skalierbare BerechnungskomplexitÀt und weist
eine hohe Robustheit gegenĂŒber rĂ€umlichen Korrelationen in MIMO-KanĂ€len
auf. Die numerischen Ergebnisse von Simulationen basierend auf Messungen
mit einem Channel-Sounder in MehrnutzerkanÀlen mit starken rÀumlichen
Korrelationen zeigen eindrucksvoll die Ăberlegenheit des hybriden
SC-MMSE-Ansatzes gegenĂŒber dem konventionellen SC-MMSE-basiertem EmpfĂ€nger.
Im zweiten Teil wird der Einfluss von System- und Kanalmodellparametern auf
die Konvergenzeigenschaften der vorgestellten iterativen EmpfÀnger mit
Hilfe sogenannter Korrelationsdiagramme untersucht. Durch semi-analytische
Berechnungen der Entzerrer- und Kanaldecoder-Korrelationsfunktionen wird
eine einfache Berechnungsvorschrift zur Vorhersage der
Bitfehlerwahrscheinlichkeit von SC-MMSE und PDA SC-MMSE Turbo Entzerrern
fĂŒr MIMO-FadingkanĂ€le entwickelt. Des Weiteren werden zwei Fehlerschranken
fĂŒr die Ausfallwahrscheinlichkeit der EmpfĂ€nger vorgestellt. Die
semi-analytische Methode und die abgeleiteten Fehlerschranken ermöglichen
eine aufwandsgeringe AbschÀtzung sowie Optimierung der LeistungsfÀhigkeit
des iterativen Systems.
Im dritten und abschlieĂenden Teil werden Strategien zur Raten- und
Leistungszuweisung in Kommunikationssystemen mit konventionellen iterativen
SC-MMSE EmpfÀngern untersucht. ZunÀchst wird das Problem der Maximierung
der instantanen Summendatenrate unter der BerĂŒcksichtigung der Konvergenz
des iterativen EmpfĂ€ngers fĂŒr einen Zweinutzerkanal mit fester
Leistungsallokation betrachtet. Mit Hilfe des FlÀchentheorems von
Extrinsic-Information-Transfer (EXIT)-Funktionen wird eine obere Schranke
fĂŒr die erreichbare Ratenregion hergeleitet. Auf Grundlage dieser Schranke
wird ein einfacher Algorithmus entwickelt, der fĂŒr jeden Nutzer aus einer
Menge von vorgegebenen Kanalcodes mit verschiedenen Codierraten denjenigen
auswÀhlt, der den instantanen Datendurchsatz des Mehrnutzersystems
verbessert. Neben der instantanen Ratenzuweisung wird auch ein
ausfallbasierter Ansatz zur Ratenzuweisung entwickelt. Hierbei erfolgt die
Auswahl der Kanalcodes fĂŒr die Nutzer unter BerĂŒcksichtigung der Einhaltung
einer bestimmten Ausfallwahrscheinlichkeit (outage probability) des
iterativen EmpfĂ€ngers. Des Weiteren wird ein neues Entwurfskriterium fĂŒr
irregulÀre Faltungscodes hergeleitet, das die Ausfallwahrscheinlichkeit von
Turbo SC-MMSE Systemen verringert und somit die ZuverlÀssigkeit der
DatenĂŒbertragung erhöht. Eine Reihe von Simulationsergebnissen von
KapazitÀts- und Durchsatzberechnungen werden vorgestellt, die die
Wirksamkeit der vorgeschlagenen Algorithmen und Optimierungsverfahren in
MehrnutzerkanĂ€len belegen. AbschlieĂend werden auĂerdem verschiedene
MaĂnahmen zur Minimierung der Sendeleistung in Einnutzersystemen mit
senderseitiger Singular-Value-Decomposition (SVD)-basierter Vorcodierung
untersucht. Es wird gezeigt, dass eine Methode, welche die Leistungspegel
des Senders hinsichtlich der Bitfehlerrate des iterativen EmpfÀngers
optimiert, den konventionellen Verfahren zur Leistungszuweisung ĂŒberlegen
ist
Link level performance evaluation and link abstraction for LTE/LTE-advanced downlink
Els objectius principals d'aquesta tesis sĂłn l'avaluaciĂł del rendiment a nivell d'enllaç i l'estudi de l'abstracciĂł de l'enllaç pel LTE/LTE-Advanced DL. Sâha desenvolupat un simulador del nivell d'enllaç E-UTRA DL basat en la tecnologia MIMO-OFDM. Es simulen els errors d'estimaciĂł de canal amb un model d'error de soroll additiu GaussiĂ anomenat CEEM. El resultat d'aquest simulador serveix per avaluar el rendiment a nivell d'enllaç del LTE/LTE-Advanced DL en diferents entorns .
La idea bĂ sica dels mĂštodes d'abstracciĂł de l'enllaç Ă©s mapejar el vector de SNRs de les subportadores a un valor escalar, l'anomenada ESNR, la qual Ă©s usada per a predir la BLER. Proposem un innovador mĂštode d'abstracciĂł de l'enllaç que pot predir la BLER amb bona precisiĂł en esvaĂŻments multicamĂ i que inclouen els efectes de les retransmissions HARQ. El mĂštode proposat es basa amb l'estimaciĂł de la informaciĂł mĂștua entre els bits transmesos i els LLRs rebuts.The main objectives of this dissertation are the evaluation of the link level performance and the study of link abstraction for LTE/LTE-Advanced DL. An E-UTRA DL link level simulator has been developed based on MIMO-OFDM technology. We simulate channel estimation errors by a Gaussian additive noise error model called CEEM. The result of this simulator serves to evaluate the MIMO-OFDM LTE/LTE-Advanced DL link level performance in different environments.
The basic idea of link abstraction methods is to map the vector of the subcarrier SNRs to a single scalar, the ESNR, which is then used to predict the BLER. We propose a novel link abstraction method that can predict the BLER with good accuracy in multipath fading and including the effects of HARQ retransmissions. The proposed method is based on estimating the mutual information between the transmitted bits and the received LLRs.Postprint (published version
MIMO Channel Modelling and Performance Evaluations
The demand on wireless networks with high throughput has grown heavily because of the increasing usage of data services. One of the key technologies to meet this requirement is the multiple-input multiple-output (MIMO) communication system, which improves the spectrum effciency without too much investment on the infrastructure and new frequency spectrum.
In this theis, a new MIMO channel model is developed that is specifc to real scenarios. This kind of channel models is more suitable for network planning tools because it takes the environment details into account. The frst step of this work is a review on the state-of-the-art MIMO channel modelling and radio propagation modelling studies. It is then followed by a comparison of two propagation models that use different algorithms, i.e. ray optical and partial ïŹow. The comparison leads to a decision that ray optical method is used for MIMO channel modelling in this thesis. After that, a spatial channel model based on a deterministic ray optical propagation model is proposed. The fnal MIMO channel model takes the polarisation and the
Doppler effect in to account so that it can be used for MIMO systems with polarised antennas and moving objects as well. The model is used in a system level simulator and then validated in an indoor offce building using measurement data.
It is concluded from this thesis that the chosen propagation model can be used for MIMO channel modelling, and the proposed MIMO channel model based on it is accurate and can be used for MIMO system design
Empirical multi-band characterization of propagation with modelling aspects for communictions
Diese Arbeit prĂ€sentiert eine empirische Untersuchung der Wellenausbreitung fĂŒr drahtlose Kommunikation im Millimeterwellen- und sub-THz-Band, wobei als Referenz das bereits bekannte und untersuchte sub-6-GHz-Band verwendet wird. Die groĂen verfĂŒgbaren Bandbreiten in diesen hohen FrequenzbĂ€ndern erlauben die Verwendung hoher instantaner Bandbreiten zur ErfĂŒllung der wesentlichen Anforderungen zukĂŒnftiger Mobilfunktechnologien (5G, â5G and beyondâ und 6G). Aufgrund zunehmender Pfad- und Eindringverluste bei zunehmender TrĂ€gerfrequenz ist die resultierende Abdeckung dabei jedoch stark reduziert. Die entstehenden Pfadverluste können durch die Verwendung hochdirektiver Funkschnittstellen kompensiert werden, wodurch die resultierende Auflösung im Winkelbereich erhöht wird und die Notwendigkeit einer rĂ€umlichen Kenntnis der Systeme mit sich bringt: Woher kommt das Signal? DarĂŒber hinaus erhöhen gröĂere Anwendungsbandbreiten die Auflösung im Zeitbereich, reduzieren das small-scale Fading und ermöglichen die Untersuchung innerhalb von Clustern von Mehrwegekomponenten. Daraus ergibt sich fĂŒr Kommunikationssysteme ein vorhersagbareres Bild im Winkel-, Zeit- und Polarisationsbereich, welches Eigenschaften sind, die in Kanalmodellen fĂŒr diese Frequenzen widergespiegelt werden mĂŒssen. Aus diesem Grund wurde in der vorliegenden Arbeit eine umfassende Charakterisierung der Wellenausbreitung durch simultane Multibandmessungen in den sub-6 GHz-, Millimeterwellen- und sub-THz-BĂ€ndern vorgestellt. Zu Beginn wurde die Eignung des simultanen Multiband-Messverfahrens zur Charakterisierung der Ausbreitung von Grenzwert-Leistungsprofilen und large-scale Parametern bewertet. AnschlieĂend wurden wichtige Wellenausbreitungsaspekte fĂŒr die Ein- und Multibandkanalmodellierung innerhalb mehrerer SĂ€ulen der 5G-Technologie identifiziert und Erweiterungen zu verbreiteten rĂ€umlichen Kanalmodellen eingefĂŒhrt und bewertet, welche die oben genannten Systemaspekte abdecken.This thesis presents an empirical characterization of propagation for wireless communications at mm-waves and sub-THz, taking as a reference the already well known and studied sub-6 GHz band. The large blocks of free spectrum available at these high frequency bands makes them particularly suitable to provide the necessary instantaneous bandwidths to meet the requirements of future wireless technologies (5G, 5G and beyond, and 6G). However, isotropic path-loss and penetration-loss are larger with increasing carrier frequency, hence, coverage is severely reduced. Path-loss can be compensated with the utilization of highly directive radio-interfaces, which increases the resolution in the angular domain. Nonetheless, this emphasizes the need of spatial awareness of systems, making more relevant the question âwhere does the signal come from?â In addition, larger application bandwidths increase the resolution in the time domain, reducing small-scale fading and allowing to observe inside of clusters of multi-path components (MPCs). Consequently, communication systems have a more deterministic picture of the environment in the angular, time, and polarization domain, characteristics that need to be reflected in channel models for these frequencies. Therefore, in the present work we introduce an extensive characterization of propagation by intensive simultaneous multi-band measurements in the sub-6 GHz, mm-waves, and sub-THz bands. Firstly, the suitability of the simultaneous multi-band measurement procedure to characterize propagation from marginal power profiles and large-scale parameters (LSPs) has been evaluated. Then, key propagation aspects for single and multi-band channel modelling in several verticals of 5G have been identified, and extensions to popular spatial channel models (SCMs) covering the aforementioned system aspects have been introduced and evaluated
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Laboratory and field trials evaluation of transmit delay Diversity applied to DVB-T/H networks
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The requirements for future DVB-T/H networks demand that broadcasters design and
deploy networks that provide ubiquitous reception in challenging indoors and other
obstructed situations. It is essential that such networks are designed cost-effectively and with minimized environmental impact. The use of transmit diversity techniques with
multiple antennas have long been proposed to improve the performance and capacity of
wireless systems. Transmit diversity exploits the scattering effect inherent in the channel by means of transmitting multiple signals in a controlled manner from spatially separated antennas, allowing independently faded signals to arrive at the receiver and improves the chances of decoding a signal of acceptable quality. Transmit diversity can complement receive diversity by adding an additional diversity gain and in situations where receiver diversity is not practical, transmit diversity alone delivers a comparable amount of diversity gain. Transmit Delay Diversity (DD) can be applied to systems employing the
DVB standard without receiver equipment modifications. Although transmit DD can
provide a gain in NLOS situations, it can introduce degradation in LOS situation. The aim of this thesis is to investigate the effectiveness in real-word applications of novel diversity techniques for broadcast transmitter networks. Tests involved laboratory experiments using a wireless MIMO channel emulator and the deployment of a field measurement campaign dedicated to driving, indoor and rooftop reception. The relationship between the diversity gain, the propagation environment and several parameters such as the transmit antenna separation, the receiver speed and the Forward Error Correction Codes (FEC) configuration are investigated. Results includes the effect of real-word parameter usually not modeled in the software simulation analysis, such as antenna radiation patterns and mutual coupling, scattering vegetation impact, non-Gaussian noise sources and receiver implementation. Moreover, a practical analysis of the effectiveness of experimental techniques to mitigate the loss due to transmit DD loss in rooftop reception is presented. The results of this thesis confirmed, completed and extended the existing predictions with real word measurement results
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