A statistical ultra wideband indoor channel model and the effects of antenna directivity on multipath delay spread and path loss in ultra wideband indoor channels

Ultra-wideband (UWB) indoor frequency domain channel measurements have been performed in the 2 GHz to 6 GHz frequency band using three different transmitter/receiver (Tx/Rx) antenna combination pairs. The effects of antenna directivity on path loss and multipath propagation in the channel were analyzed extensively for various omni-directional and directional antenna combinations. A statistical model of the path loss in the channel is presented, where the parameters in the model (i.e., path loss exponent and shadow fading statistics) are dependent on the particular Tx/Rx antenna combination. Time domain statistics of the channel (i.e., mean delay spread and RMS delay spread) are analyzed thoroughly for each antenna combination. Results show that RMS delay spread increases over distance for all three antenna combinations, but at a greater rate when directional antennas are used in the channel. There is a significant reduction in RMS delay spread when directional antennas are used at the transmitter and receiver or solely at the receiver with respect to an omni-directional/omni-directional antenna pair. Results show that directional antennas can be used as an effective way of mitigating the effects of multipath propagation in UWB indoor channels. A distance dependent statistical impulse response model of the channel is also presented, which statistically reproduces the impulse response of the channel with high fidelity

THZ RF measurement techniques

Abstract. In this thesis, literature review on available methods, techniques and procedures for terahertz antenna measurement system and terahertz propagation measurement system are reported. The paper presented the terahertz frequency spectrum allocation by FCC, ITU, ETSI and its application in wireless communication system with advantage in obtaining terabits per second data rates. Terahertz antenna parameters are reported and measurement systems for measurement of these chapters are reviewed. Literature of three papers on terahertz antenna measurement system with their respective measurement setup, calibration techniques and measurement procedures are reviewed. An automated antenna measurement system is reviewed with stochastic and systematic measurements and has achieved terahertz antenna s-parameter measurements in far field region at frequency range of 220 GHz to 330 GHz. Another measurement system with single port short-open-load (SOL) calibration technique is reviewed. In this measurement of s-parameter of terahertz antenna is carried out, using receiver horn placed on 3 D positioner, which records the AUT 3D radiation pattern. The third paper reviewed, is a reconfigurable terahertz antenna measurement system, with capabilities of working on large bandwidths, with small change in work bench instrumentation. This setup contains the multiplexing stages for terahertz frequency generation. Beam pattern measurements are conducted at 1.37 THz supporting the simulations and the system stability for reconfigurations. In the later study, terahertz propagation parameters are studied and presented for review of available terahertz propagation measurement systems. Literature review of three papers describing different setup and procedures for terahertz propagation measurement system are reported. The first system with the setup to record path loss in LOS and NLOS links at 260 GHz to 400 GHz is presented. Propagation parameters containing reflections, shadowing is measured. LOS and NLOS channel capacity models are obtained based on data rates in terabits per second for using above 5G wireless communication systems. Another system with office architecture, indoor LOS link, viable for indoor wireless communication applications is reported. Propagation parameters containing power density profile (PDP) are measured and validated for 140 GHz to 220 GHz. A measurement system which reports effect of atmospheric pressure, temperature and humidity is reported in the last. The setup used short, offset-short, load and thru (SOLT) technique for calibration and PDP propagation parameter is measured for 0.5 THz to 0.75 THz. Terahertz antenna and wave propagation measurement system reviewed in the papers are vital for development of terahertz systems in wireless and mobile communication. Further the study can be extended for measurement of terahertz antennas and wave propagation parameters with models of use in wireless hand-held devices, connected devices, mobile backhaul system and more

Empirical multi-band characterization of propagation with modelling aspects for communictions

Diese Arbeit präsentiert eine empirische Untersuchung der Wellenausbreitung für drahtlose Kommunikation im Millimeterwellen- und sub-THz-Band, wobei als Referenz das bereits bekannte und untersuchte sub-6-GHz-Band verwendet wird. Die großen verfügbaren Bandbreiten in diesen hohen Frequenzbändern erlauben die Verwendung hoher instantaner Bandbreiten zur Erfüllung der wesentlichen Anforderungen zukünftiger Mobilfunktechnologien (5G, “5G and beyond” und 6G). Aufgrund zunehmender Pfad- und Eindringverluste bei zunehmender Trägerfrequenz 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 räumlichen Kenntnis der Systeme mit sich bringt: Woher kommt das Signal? Darüber hinaus erhöhen größere Anwendungsbandbreiten die Auflösung im Zeitbereich, reduzieren das small-scale Fading und ermöglichen die Untersuchung innerhalb von Clustern von Mehrwegekomponenten. Daraus ergibt sich für Kommunikationssysteme ein vorhersagbareres Bild im Winkel-, Zeit- und Polarisationsbereich, welches Eigenschaften sind, die in Kanalmodellen für diese Frequenzen widergespiegelt werden müssen. 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-Bändern vorgestellt. Zu Beginn wurde die Eignung des simultanen Multiband-Messverfahrens zur Charakterisierung der Ausbreitung von Grenzwert-Leistungsprofilen und large-scale Parametern bewertet. Anschließend wurden wichtige Wellenausbreitungsaspekte für die Ein- und Multibandkanalmodellierung innerhalb mehrerer Säulen der 5G-Technologie identifiziert und Erweiterungen zu verbreiteten räumlichen Kanalmodellen eingeführt 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 “where does the signal come from?” 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

Millimeter wave radio channels: properties, multipath modeling and simulations

Based on the characterization of realistic radio channels, results presented in this dissertation lead towards an understanding that when moving up to the higher frequencies, frequency itself does not play a significant role in defining the channel modeling methodology. In fact, how a propagation channel is illuminated is of fundamental importance. Therefore, millimeter wave (mmWave) system properties such as a high antenna directivity and system bandwidth are shown to have a great influence on the channel model definition. In this thesis, a fundamental assumption made in the state-of-the-art millimeter wave wireless channel models is challenged. It has been shown that Rayleigh-Rice fading assumption made in the state-of-the-art channel models for resolvable channel taps does not remain valid. This is mainly due to the sparse multipath illumination caused by high antenna directivity and high bandwidth of a mmWave system.Studies presented in this thesis are based on the characterization of realistic radio channels obtained from exhaustive channel sounding campaigns. Mainly, three fundamental problems of wireless channel modelling have been investigated for millimetre wave (mmWave) radio channel modelling application, namely (i) Frequency dependence of propagation, (ii) Impact of antenna directivity on the channel model definition, and (iii) Impact of system bandwidth on the radio channel modelling. A detailed description of these problems is as follows: (i) Frequency Dependence of Propagation. Multi-band measurement campaigns arecarried out using directional antennas which do an omni-directional scan of the propagation environment. During the measurements, Tx-Rx systems are placed at fixed positions and the propagation environment remained as static as possible. Using synthesized omni-directional power delay profiles (PDPs), we aim to investigate if there exists a frequency dependency in the multipath dispersion statistics, e.g. delay and angular spreads. (ii) Impact of Antenna Directivity on the Channel Model Definition. Small-scale fading measurements are carried out which emulate a scenario, where a radio communication link is established through a single multipath cluster which is illuminated using antennas with different Half Power Beam Widths (HPBW). The major goal here is to investigate the impact of spatial multipath filtering on the small-scale fading due to high antenna directivity. In particular, the impact on variations in the receive signal strength and the validity of narrowband wide-sense stationary assumption (both in time and frequency domains) is investigated. (iii) Impact of System Bandwidth on the Radio Channel Modelling. Small-scale fading measurements are used to illuminate multipath clusters in a lecture room scenario. The primary objective is to investigate the impact of high system bandwidth on variations in the receive signal strength, randomness in the cross-polarization power ratio (XPR) and richness of the multipath scattering. Based on the characterization of realistic radio channels, results presented in this dissertation lead towards an understanding that when moving up to the higher frequencies, frequency itself does not play a significant role in defining the channel modelling methodology. In fact, how a propagation channel is illuminated is of fundamental importance. Therefore, mmWave system properties such as a high antenna directivity and system bandwidth are shown to have a high influence on the channel model definition. In general, fade depth scaling as a function of system bandwidth is quite well understood. We demonstrate that, the high antenna directivity of mmWave systems result in a further reduction in the fading depth. In addition, we explore some new directions to this line of research which are based on the second-order statistical analysis of the channel impulse response (CIR) vector. Our results emphasize that, fading statistics of resolvable channel taps in a mmWave radio channel cannot be modelled as Rayleigh-Rice distributed random variables. This is primarily due to the fact that channels with sparse scattering conditions are illuminated due to high antenna directivity and bandwidth of mmWave systems. Consequently, the complex Gaussian random variable assumption associated with Rayleigh-Rice fading distributions does not remain valid. Further, it has been demonstrated that, high antenna directivity and bandwidth of mmWave systems also raise a question mark on the validity of wide-sense stationary (WSS) assumption in the slow-time domain of mmWave radio channels. Results presented in this contribution are novel and they provide theoretically consistent insights into the measured radio channel.In dieser Arbeit werden drei grundlegende Probleme der Modellierung von Drahtloskanalen fur die Anwendung bei der Funkkanalmodellierung im Millimeterwellenbereich (mmWave) untersucht, namlich (i) die Frequenzabhangigkeit der Ausbreitung, (ii) der Einfluss der Antennenrichtwirkung auf die Definition des Kanalmodells und (iii) der Einfluss der Systembandbreite auf die Funkkanalmodellierung. Die detaillierte Beschreibung dieser Probleme lautet wie folgt: (i) Frequenzabhangigkeit der Ausbreitung. Mehrband-Messkampagnen werden mitRichtantennen durchgefuhrt, die eine omnidirektionale Abtastung der Ausbreitungsumgebung vornehmen. Wahrend der Messungen werden die Tx-Rx-Systeme an festen Positionen platziert und die Ausbreitungsumgebung bleibt so statisch wie moglich. Mit Hilfe von synthetisierten omnidirektionalen Verzogerungs-Leistungsprofilen soll untersucht werden, ob es eine Frequenzabhangigkeit in der Mehrwegeausbreitungsstatistik gibt, z.B. in der Verzogerung und der Winkelspreizung. (ii) Einfluss der Antennenrichtwirkung auf die Definition des Kanalmodells. Es werden Messungen des schnellen Schwunds durchgefuhrt, die ein Szenario emulieren, bei dem eine Funkverbindung uber ein einzelnes Mehrwege-Cluster aufgebaut wird, das mit Antennen mit unterschiedlichen Strahlbreiten ausgeleuchtet wird. Das Hauptzielist hier die Untersuchung des Einflusses der raumlichen Filterung auf den schnellen Schwund aufgrund der hohen Antennenrichtwirkung. Insbesondere wird die Auswirkung auf Variationen der Empfangssignalstarke und die Gultigkeit der Annahme der schmalbandigen Stationaritat im weiteren Sinne (sowohl im Zeit- als auch im Frequenzbereich) untersucht. (iii) Einfluss der Systembandbreite auf die Funkkanalmodellierung. Messungen desschnellen Schwunds werden verwendet, um Mehrwege-Cluster in einem Horsaal-Szenario auszuleuchten. Das primare Ziel ist es, den Einfluss einer hohen Systembandbreite auf die Variationen der Empfangssignalstarke, die Zufalligkeit des Kreuzpolarisationsverhaltnisses und die Reichhaltigkeit der Mehrwegstreuung zu untersuchen. Basierend auf der Charakterisierung realistischer Funkkanäle führen die in dieser Dissertation vorgestellten Ergebnisse zu dem Verständnis, dass beim Ubergang zu höheren Frequenzen die Frequenz x selbst keine signifikante Rolle bei der Definition der Kanalmodellierungsmethodik spielt. Vielmehr ist es von grundlegender Bedeutung, wie ein Ausbreitungskanal ausgeleuchtet wird. Daher zeigt sich, dass mmWave-Systemeigenschaften wie eine hohe Antennenrichtcharakteristik und Systembandbreite einen hohen Einfluss auf die Definition des Kanalmodells haben. Im Allgemeinen ist die Skalierung der Schwundtiefe als Funktion der Systembandbreite ziemlich gut verstanden. Wir zeigen, dass die hohe Antennenrichtwirkung von mmWave-Systemen zu einer weiteren Reduzierung der Schwundtiefe führt. Zusätzlich erforschen wir einige neue Richtungen in diesem Forschungsbereich, die auf der Analyse der Statistik zweiter Ordnung des Kanalimpulsantwort-Vektors basieren. Unsere Ergebnisse unterstreichen, dass die Schwund-Statistiken der auflösbaren Kanalabgriffe in einem mmWave-Funkkanal nicht als Rayleigh-Rice-verteilte Zufallsvariablen modelliert werden können. Dies liegt vor allem daran, dass durch die hohe Antennenrichtwirkung und Bandbreite von mmWave-Systemen Kanale mit spärlichen Streubedingungen ausgeleuchtet werden. Folglich ist die Annahme komplexer Gaus’scher Zufallsvariablen, die mit Rayleigh-Rice Schwundverteilungen verbunden ist, nicht mehr gültig. Des Weiteren wird gezeigt, dass die hohe Antennenrichtwirkung und Bandbreite von mmWave-Systemen auch die Gültigkeit der Annahme von Stationarität im weiteren Sinne im Slow-Time-Bereich von mmWave-Funkkanälen in Frage stellt. Die in diesem Beitrag vorgestellten Ergebnisse sind neuartig und bieten theoretisch konsistente Einblicke in den gemessenen Funkkanal

Antenna and radio channel characterisation for low‐power personal and body area networks

PhDThe continuous miniaturisation of sensors, as well as the progression in wearable electronics, embedded software, digital signal processing and biomedical technologies, have led to new usercentric networks, where devices can be carried in the user’s pockets, attached to the user’s body. Body-centric wireless communications (BCWCs) is a central point in the development of fourth generation mobile communications. Body-centric wireless networks take their place within the personal area networks, body area networks and sensor networks which are all emerging technologies that have a wide range of applications (such as, healthcare, entertainment, surveillance, emergency, sports and military). The major difference between BCWC and conventional wireless systems is the radio channels over which the communication takes place. The human body is a hostile environment from a radio propagation perspective and it is therefore important to understand and characterise the effects of the human body on the antenna elements, the radio channel parameters and, hence, system performance. This thesis focuses on the study of body-worn antennas and on-body radio propagation channels. The performance parameters of five different narrowband (2.45 GHz) and four UWB (3.1- 10.6 GHz) body-worn antennas in the presence of human body are investigated and compared. This was performed through a combination of numerical simulations and measurement campaigns. Parametric studies and statistical analysis, addressing the human body effects on the performance parameters of different types of narrowband and UWB antennas have been presented. The aim of this study is to understand the human body effects on the antenna parameters and specify the suitable antenna in BCWCs at both 2.45 GHz and UWB frequencies. Extensive experimental investigations are carried out to study the effects of various antenna types on the on-body radio propagation channels as well. Results and analysis emphasize the best body-worn antenna for reliable and power-efficient on-body communications. Based on the results and analysis, a novel dual-band and dual-mode antenna is proposed for power-efficient and reliable on-body and off-body communications. The on-body performance of the DBDM antenna at 2.45 GHz is compared with other five narrowband antennas. Based on the results and analysis of six narrowband and four UWB antennas, antenna specifications and design guidelines are provided that will help in selecting the best body-worn antenna for both narrowband and UWB systems to be applied in body-centric wireless networks (BCWNs). A comparison between IV the narrowband and UWB antenna parameters are also provided. At the end of the thesis, the subject-specificity of the on-body radio propagation channel at 2.45 GHz and 3-10 GHz was experimentally investigated by considering eight real human test subjects of different shapes, heights and sizes. The subject-specificity of the on-body radio propagation channels was compared between the narrowband and UWB systems as well