Backscatter Measurements and Models for RF Sensing Applications in Cluttered Environments

A statistical backscatter channel model for indoor clutter is developed for indoor RF sensing applications based on measurements. A narrowband 28 GHz sounder used a quazi-monostatic radar arrangement with an omnidirectional transmit antenna illuminating an indoor scene and a spinning horn receive antenna less than 1 m away collecting backscattered power as a function of azimuth. Median average backscatter power was found to vary over a 12 dB range, with average power generally decreasing with increasing room size. A deterministic model of average backscattered power dependent on distance to nearest wall and wall reflection coefficient reproduces observations with 4.0 dB RMS error. Distribution of power variation in azimuth around this average is reproduced within 1 dB by a random azimuth spectrum with a lognormal amplitude distribution and uniformly random phase. The model is extended to provide power distribution over both azimuth and delay (conveying range to scatterer) by combining azimuthal distribution with published results on power delay profiles in reverberant environments. The statistical model does not require a detailed room layout description, aiming to reproduce backscatter clutter statistics, as opposed to a deterministic response

Ray-Optics Simulations of Outdoor-to-Indoor Multipath Channels at 4 and 14 GHz

Radio wave propagation simulations based on the ray-optical approximation have been widely adopted in coverage analysis for a range of situations, including the outdoor-to-indoor (O2I) scenario. In this work we present O2I ray-tracer simulations utilizing a complete building floor plan in the form of a point cloud. The ray-tracing simulation results are compared to measured channels at 4 and 14 GHz in terms of large scale parameters, namely path loss, delay spread and angular spread. In this work we address the importance of 1) interior walls and propagation paths originating therein, and 2) site-specific knowledge of window structure in accurately reproducing the O2I channel, particularly the presence of a thin insulating metal film on the windows. The best agreement between measurements and simulations was observed for the most detailed simulation. For both frequencies a mean error of less than 1.5 dB is reached for path loss, and a relative error of less than 10% for delay and angular spreads. Not including the metal film in simulations increases error of estimated building entry loss considerably, whereas absence of interior walls is detrimental to reproduction of large scale parameters

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

Interaction of Antenna, Human and Channel at 28 GHz

This master's thesis studies millimetre-wave antenna arrays at 28 GHz under realistic operational conditions, taking into account the interaction of the Antenna, the Body of the human user and the propagation Channel (A-B-C). The main goal of the thesis is to develop a framework in MATLAB that uses a numerical approach to evaluate the total array gain and the spherical coverage of two modular sub-array designs on a mobile phone chassis. State-of-the-art numerical methods, such as simulations of scattered fields from antenna elements near a full-size human body and polarimetric ray-optical multipath radio channel simulations from an in-house ray-tracer, are used to generate the channel data for an outdoor and an indoor small-cellular site. The method was applied, showing that sub-arrays that point in opposite directions have 3 dB better median (50 per cent) link performance and 8-12 dB better outage performance (1 per cent or 10 per cent respectively), and similar peak performance, compared to sub-arrays that point into the same direction. Further, results showed that beam steering in co-located sub-arrays offered the best peak performance and that the median performance is about 6 dB better than the distributed array. The outage performance (10 per cent) of the co-located array and the distributed array modules was similar, while the distributed array had a 2-3 dB advantage. This insight differs from those obtained in spherical coverage, where the distributed array is inferior to the co-located array at outage levels. Results showed that median and outage total array gain reveals additional insights compared to spherical coverage, where the former shows equally capable gains of the co-located array and the distributed array, while the latter justifies only the co-located array and does not support the distributed array. It was shown that the performance of phased-antenna configurations should be evaluated based on empirical statistics of two types of antenna gains, i.e., spherical coverage and total array gain, as antenna and link gain metrics, respectively. It is thereby demonstrated that the inter-play of antenna beams and multipath channels needs to be quantified through the link gain metric, i.e., total array gain, and the antenna gain metric, i.e., spherical coverage, when evaluating, comparing and ranking different phased antenna array designs

Experimental evaluation of modular antenna arrays at 28 GHz under the presence of human body

The goal of this thesis is to develop and test an experimental method for characterising antenna arrays for mobile phones at 28 GHz under the presence of the user. Previous studies were based merely on computer simulations, or on measurements with actual humans, where repeatability is an unsolved issue. Antenna measurements with a human phantom have now been carried out and analysed for the first time. For their validation, simulation methods for characterising mm-wave mobile phone antennas under the presence of a human body, and the detailed evaluation process are presented here, including spherical coverage and total array gain. Utilising the presented simulation methods, a simplified human phantom is designed, validated, and manufactured. The electrical properties of human tissues are well known, and different material recipes to mimic human skin were reported in previous studies. Based on these, we created a polyethylene-based skin-like material with electrical properties similar as in human skin. This material was used as a surface for the final human phantom. This phantom was then used in radiation-pattern measurements at 28 GHz. Two planar 2x2 dual-polarised antenna arrays were designed and manufactured. As expected, the design of the microstrip-feed line network was crucial in the design of the antenna arrays, especially the mutual coupling needs to be low to ensure the designed operation of the arrays. Antenna radiation pattern measurements, both in free space and with the human phantom, were carried out in an anechoic chamber. The losses of feed cables and connectors were de-embedded by calculating suitable amplitude correction terms that normalize differences between measured and simulated free-space element patterns. The phantom measurements were performed with both antenna arrays, and after mathematical beam-forming with a suitable amount of element-phasing cases, the spherical coverage of each array was calculated. Element radiation patterns and spherical coverage of both antenna arrays under the presence of the human phantom were compared to the simulations. In the spherical coverage CDFs of both arrays, the difference between measured and simulated peak gain is 1 - 2 dB, and the difference between measured and simulated median gain level is 0.6 - 2 dB. This comparison shows that the proposed experimental method for characterising mm-wave mobile antenna arrays in the presence of the user is feasible. One test array also was measured twice with the phantom and the maximum difference between spherical coverage CDFs was 1 dB proving good repeatability of the proposed experimental method

Reports to the President

A compilation of annual reports for the 1988-1989 academic year, including a report from the President of the Massachusetts Institute of Technology, as well as reports from the academic and administrative units of the Institute. The reports outline the year's goals, accomplishments, honors and awards, and future plans

ESARDA 39th Annual Meeting: 2017 Symposium

The 39th ESARDA symposium on Safeguards and Nuclear Non-Proliferation was held in Düsseldorf, Germany from 16-18 May, 2017. The Symposium has been preceded by meetings of the ESARDA Working Groups on 15 May 2017. The event has once again been an opportunity for research organisations, safeguards authorities and nuclear plant operators to exchange information on new aspects of international safeguards and non-proliferation, as well as recent developments in nuclear safeguards and non-proliferation related research activities and their implications for the safeguards community.JRC.G.II.7-Nuclear securit

Social work with airports passengers

Social work at the airport is in to offer to passengers social services. The main methodological position is that people are under stress, which characterized by a particular set of characteristics in appearance and behavior. In such circumstances passenger attracts in his actions some attention. Only person whom he trusts can help him with the documents or psychologically