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Un radar MIMO (Multiple Input Multiple Output) est un système radar qui utilise plusieurs antennes émettrices et réceptrices, dans lequel les formes d'ondes émises peuvent être indépendantes. Par rapport aux radars utilisant des antennes en réseaux phasés, les radars MIMO offrent davantage de degrés de liberté, ce qui permet d'améliorer les performances du système en termes de détection et localisation. La technique MIMO offre également la possibilité de synthétiser un diagramme de rayonnement désiré par une définition judicieuse des formes d'ondes émises. Dans la mesure où les paramètres des cibles (positions, vitesses, directions d'arrivée (DOA), ...) sont estimés à partir des échos des signaux émis, on comprend aisément que les formes d'ondes employées jouent un rôle clé dans les performances du système. Cette thèse porte sur l'estimation de DOA et sur la conception des formes d'ondes pour un radar MIMO. Le cadre d'étude est restreint au cas où les antennes sont colocalisées et les cibles sont immobiles et supposées ponctuelles. La plupart des travaux antérieurs (au commencement de la thèse) portaient sur le radar MIMO bande étroite et faisaient l'hypothèse d'émetteurs-récepteurs idéaux et indépendants. Cette thèse contribue à élargir le cadre d'étude en s'intéressant d'une part au passage en large bande et d'autre part à la modélisation et à la prise en compte de la non-indépendance des émetteurs-récepteurs et autres imperfections. Dans la mesure où le recours à des signaux large bande est nécessaire lorsqu'une résolution importante est souhaitée, nous nous sommes attachés dans cette thèse à adapter le modèle d'un système de radar MIMO au cas large bande et à proposer de nouvelles techniques visant à améliorer les performances d'estimation de DOA dans le cas de signaux large bande. Cette thèse analyse également l'influence de conditions non idéales comme l'impact des phénomènes de couplage électromagnétique sur les diagrammes de rayonnement dans un réseau d'antennes. Cette étude est menée dans le cas bande étroite. En particulier, nous étudions l'influence du couplage direct entre les réseaux d'antennes d'émission et de réception (appelé « crosstalk ») sur les performances des techniques proposées. Nous établissons un modèle du signal permettant de prendre en compte ce phénomène et proposons une technique de réduction du « crosstalk » qui permet une estimation efficace des DOA des cibles. Nous montrons par ailleurs comment améliorer les performances d'estimation de DOA en présence de diagrammes de rayonnement incluant le couplage entre antennes. Le dernier apport principal de cette thèse est la conception et réalisation d'une plateforme expérimentale comportant une seule architecture d'émetteur-récepteur, qui permet de simuler un système MIMO utilisant des antennes colocalisées en appliquant le principe de superposition. Cette plateforme nous a permis d'évaluer les performances des techniques proposées dans des conditions plus réalistes / A Multiple-Input Multiple-Output (MIMO) radar is a system employing multiple transmitters and receivers in which the waveforms to be transmitted can be totally independent. Compared to standard phased-array radar systems, MIMO radars offer more degrees of freedom which leads to improved angular resolution and parameter identifiability, and provides more flexibility for transmit beampattern design. The main issues of interest in the context of MIMO radar are the estimation of several target parameters (which include range, Doppler, and Direction-of-Arrival (DOA), among others). Since the information on the targets is obtained from the echoes of the transmitted signals, it is straightforward that the design of the waveforms plays an important role in the system accuracy. This document addresses the investigation of DOA estimation of non-moving targets and waveform design techniques for MIMO radar with colocated antennas. Although narrowband MIMO radars have been deeply studied in the literature, the existing DOA estimation techniques have been usually proposed and analyzed from a theoretical point of view, often assuming ideal conditions. This thesis analyzes existing signal processing algorithms and proposes new ones in order to improve the DOA estimation performance in the case of narrowband and wideband signals. The proposed techniques are studied under ideal and non-ideal conditions considering punctual targets. Additionally, we study the influence of mutual coupling on the performance of the proposed techniques and we establish a more realistic signal model which takes this phenomenon into account. We then show how to improve the DOA estimation performance in the presence of distorted radiation patterns and we propose a crosstalk reduction technique, which makes possible an efficient estimation of the target DOAs. Finally, we present an experimental platform for MIMO radar with colocated antennas which has been developed in order to evaluate the performance of the proposed techniques under more realistic conditions. The proposed platform, which employs only one transmitter and one receiver architectures, relies on the superposition principle to simulate a real MIMO system

Le repérage (localisation topologique) des capteurs dans un réseau sans fil ouvre la porte à de nombreuses applications. Les techniques actuelles basées sur la puissance du signal reçu restent peu fiable compte-tenu de la stabilité des mesures dans le circuit. Des techniques plus précises inspirées des radars ont été proposées mais cela nécessite un type de radio adaptée qui s'avère trop couteuse, autant en termes d'implémentation qu'en termes de consommation électrique. Cependant, une des difficultés majeure de l'adaptation de ces techniques de localisation aux réseaux de capteurs sans fil reste leur inadéquation avec leur faible coût de réalisation et la faible consommation électrique requise pour ces dispositifs autonomes. En particulier, les étages radio et de génération d'horloge des modems ZigBee introduisent une grande incertitude sur la fiabilité des mesures. Les algorithmes digitaux très complexes demandent à être tout particulièrement étudiés et améliorés afin de ne pas dépasser un budget de consommation extrêmement réduit tout en tentant d'atteindre une complexité d'implémentation aussi faible que possible.Les travaux de cette thèse se concentrent sur 2 principaux objectifs: l'élaboration d'un circuit digital étant capable de calculer de temps d'arrivée en temps réel, et l'élaboration de prototypes permettant le positionnement d'un noeud. La principale contrainte, est l'utilisation d'un seul canal ZigBee de la norme 802.15.4. Ce travail a permi d'appréhender les problèmes liés à la mesure de distance et envisager l'adaptation de ces techniques aux contraintes spécifiques des réseaux de capteurs sans fil et du type de radio utilisée. / Tracking sensors in a wireless network leads to many applications. However, current techniques based on the received signal strength are unreliable given the stability of measurements. More accurate techniques inspired from radars have been proposed but they require an expensive radio. However, one of the most difficult aspects regarding the localization in a wireless sensor network remains their inadequacy with their low-cost and low-power characteristics. For example, clock generation of ZigBee modems introduce strong uncertainties regarding the reliability of measurements. Demanding digital algorithms must be carefully studied and improved in order not to exceed requirements defined by industrials. In other words, the purpose is to design an implementation as cheap as possible while keeping a minimum accuracy. The work of this thesis focuses on two main objectives: the development of a digital circuit capable of calculating time of arrivals, and the development of prototypes for a future positioning feature. The main constraint is the use of a single channel from the ZigBee 802.15.4 standard. This work enabled to understand issues regarding the distance measurements and adapt them given wireless sensor network constraints.

Accurate indoor positioning of narrowband Internet-of-Things (IoT) sensors has drawn more attention in recent years. The introduction of Bluetooth Low Energy (BLE) technology is one of the latest developments of IoT and especially applicable for Ultra-Low Power (ULP) applications. BLE is an attractive technology for indoor positioning systems because of its low-cost deployment and reasonable accuracy. Efficient indoor positioning can be achieved by deducing the sensor position from the estimated signal Angle-of-Arrival (AoA) at multiple anchors. An anchor is a base station of known position and equipped with a narrowband multi-antenna array. However, the design and implementation of indoor positioning systems based on AoA measurements involve multiple challenges. The first part of this thesis mainly addresses the impact of hardware impairments on the accuracy of AoA measurements. In practice, the subspace-based algorithms such as Multiple Signal Classification (MUSIC) suffer from sensitivity to array calibration errors coming from hardware imperfections. A detailed experimental implementation is performed using a Software Defined Radio (SDR) platform to precisely evaluate the accuracy of AoA measurements. For this purpose, a new Over-the-Air (OTA) calibration method is proposed and the array calibration error is investigated. The experimental results are compared with the theoretical analysis. These results show that array calibration errors can cause some degrees of uncertainty in AoA estimation. Moreover, we propose iterative positioning algorithms based on AoA measurements for low capacity IoT sensors with high accuracy and fair computational complexity. Efficient positioning accuracy is obtained by iterating between the angle and position estimation steps. We first develop a Data-Aided Maximum a Posteriori (DA- MAP) estimator based on the preamble of the transmitted signal. DA-MAP estimator relies on the knowledge of the transmitted signal which makes it impractical for narrowband communications where the preamble is short. For this reason, a Non-Data- Aided Maximum a Posteriori (NDA-MAP) estimator is developed to improve the AoA accuracy. The iterative positioning algorithms are therefore classified as Data-Aided Iterative (DA-It) and Non-Data-Aided Iterative (NDA-It) depending on the knowledge of the transmitted signal that is used for estimation. Both numerical and experimental analyses are carried out to evaluate the performance of the proposed algorithms. The results show that DA-MAP and NDA-MAP estimators are more accurate than MUSIC. The results also show that DA-It comes very close to the performance of the optimal approach that directly estimates the position based on the observation of the received signal, known as Direct Position Estimation (DPE). Furthermore, the NDA-It algorithm significantly outperforms the DA-It because it can use a much higher number of samples; however, it needs more iterations to converge. In addition, we evaluate the computational savings achieved by the iterative schemes compared to DPE through a detailed complexity analysis. Finally, we investigate the performance degradation of the proposed iterative algorithms due to the impact of multipath and NLOS propagation in indoor environments. Therefore, we develop an enhanced iterative positioning algorithm with an anchor selection method in order to identify and exclude NLOS anchors. The numerical results show that applying the anchor selection strategy significantly improves the positioning accuracy in indoor environments. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

The article examines how the German city of Leipzig governs the housing of asylum seekers. Leipzig was a frontrunner in organizing the decentralized accommodation of asylum seekers when adopting its accommodation concept in 2012. This concept aimed at integrating asylum-seeking persons in the regular housing market at an early stage of arrival. However, since then, the city of Leipzig faces more and more challenges in implementing the concept. This is particularly due to the increasingly tight situation on the housing market while the number of people seeking protection increased and partly due to discriminating and xenophobic attitudes on the side of house owners and managers. Therefore, we argue that the so-called refugee crisis of 2015–2016 has to be seen in close interaction with a growing general housing shortage in Leipzig like in many other large European cities. Furthermore, we understand the municipal governing of housing as a contested field regarding its entanglement of diverse federal levels and policy scales, the diversity of stakeholders involved, and its dynamic change over the last years. We analyze this contested field set against the current context of arrival and dynamic urban growth on a local level. Based on empirical qualitative research that was conducted by us in 2016, Leipzig’s local specifics will be investigated under the umbrella of our conceptual framework of Governance of Arrival. The issues of a strained housing market and the integration of asylum seekers in it do not apply only to Leipzig, but shed light on similar developments in other European Cities.

This master’s thesis is focused on the continuous descent approach procedure and its impact on the airspace capacity. The first part is devoted to the theoretical description of the procedure and the assessment of the current situation in implementation of continuous descent approach at the European airports. The impact on the airspace capacity is demonstrated by a detailed analysis of the procedure application at Praha – Ruzyně airport. The aim of the analysis is to define critical areas that have to be solved before permanent application of the procedure. In the following chapters there are presented possible solutions of conflict spots in the current operational environment and in the future after implementation of 4D trajectory concept as well. The last part is focused on the application of continuous descent approach at Praha – Ruzyně airport after the construction of a parallel runway.

The thesis discusses the design and experimental verification of a new method for detecting partial discharges in oil-cooled high-power transformers, emphasizing the origin of the measured signal from the outer and inner regions of the transformer tank. The detection and spatial localization of partial discharges utilizes UHF (Ultra High Frequency) electromagnetic signal measurement. The UHF partial discharge detection method, also referred as UHF PD, is one of the most advanced techniques for the accurate spatial localization of the signal source position. The focus of the thesis lies in the development of technical and software solutions for the separation of partial discharge signals originating from the internal space of the transformer and the spurious signals from the connection lines. The proposed technical and program solutions constitute a signal discriminatory method. The precise and repeatable diagnostics of the transformer state are guaranteed by observing the measurement methodology and special setting of the diagnostic system. The functionality of the signal discriminatory method was verified during real measurement of the oil-cooled power transformers at the Dukovany nuclear power plant in operation. The output of the designed methodology is to set up a calibration procedure and follow-up steps to ensure objective, repeatable, and comparable measurements for the purposes of regular predictive maintenance in transformers.

abstract: Within the near future, a vast demand for autonomous vehicular techniques can be forecast on both aviation and ground platforms, including autonomous driving, automatic landing, air traffic management. These techniques usually rely on the positioning system and the communication system independently, where it potentially causes spectrum congestion. Inspired by the spectrum sharing technique, Communications and High-Precision Positioning (CHP2) system is invented to provide a high precision position service (precision ~1cm) while performing the communication task simultaneously under the same spectrum. CHP2 system is implemented on the consumer-off-the-shelf (COTS) software-defined radio (SDR) platform with customized hardware. Taking the advantages of the SDR platform, the completed baseband processing chain, time-of-arrival estimation (ToA), time-of-flight estimation (ToF) are mathematically modeled and then implemented onto the system-on-chip (SoC) system. Due to the compact size and cost economy, the CHP2 system can be installed on different aerial or ground platforms enabling a high-mobile and reconfigurable network. In this dissertation report, the implementation procedure of the CHP2 system is discussed in detail. It mainly focuses on the system construction on the Xilinx Ultrascale+ SoC platform. The CHP2 waveform design, ToA solution, and timing exchanging algorithms are also introduced. Finally, several in-lab tests and over-the-air demonstrations are conducted. The demonstration shows the best ranging performance achieves the ~1 cm standard deviation and 10Hz refreshing rate of estimation by using a 10MHz narrow-band signal over 915MHz (US ISM) or 783MHz (EU Licensed) carrier frequency. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2020

Indoor positioning is desired in many areas for various reasons, such as positioning products in industrial environments, hospital equipment or firefighters inside a building on fire. One even tougher situation where indoor positioning can be useful is locating a specific object on a shelf in a commercial setting. This thesis aims to investigate and design different network deployment strategies in an indoor environment in order to achieve both high position estimation accuracy and availability. The investigation considers the two positioning techniques downlink time difference of arrival, DL-TDOA, and round trip time, RTT. Simulations of several deployments are performed in two standard scenarios which mimic an indoor open office and an indoor factory, respectively. Factors having an impact on the positioning accuracy and availability are found to be deployment geometry, number of base stations, line-of-sight conditions and interference, with the most important being deployment geometry. Two deployment strategies are designed with the goal of optimising the deployment geometry. In order to achieve both high positioning accuracy and availability in a simple, sparsely cluttered environment, the strategy is to deploy the base stations evenly around the edges of the deployment area. In a more problematic, densely cluttered environment the approach somewhat differs. The proposed strategy is now to identify and strategically place some base stations in the most cluttered areas but still place a majority of the base stations around the edges of the deployment area. A robust positioning algorithm is able to handle interference well and to decrease its impact on the positioning accuracy. The cost, in terms of frequency resources, of using more orthogonal signals may not be worth the small improvement in accuracy and availability.

Kvalitet är en konkurrensstärkande faktor inom processindustrin, men samtidigt ett av de mest kritiska problemen när den är bristande. Processindustrin omvandlar råvaror till produkter, ofta genom kontinuerliga och irreversibla processer. Detta kan leda till kostsamma kvalitetsproblem i form av felaktiga slutprodukter, trasiga maskiner, miljöfarliga utsläpp och i värsta fall allvarliga skador på medarbetare. Syftet med denna studie är att ta fram förslag för att effektivisera arbetssättet vid ankomst och lagring av material i processindustrin för att uppfylla de kvalitetskrav som finns. Studien har använt sig av det vetenskapliga angreppssättet abduktion för att besvara de forskningsfrågor som funnits. Syftet som studien haft är uppfyllt genom att en fallstudie har genomförts på Stora Enso Skutskärs Bruk där hanteringen av material vid ankomst och lagring har undersökts. Detta har gjorts genom intervjuer, observationer, workshops samt en litteraturstudie inom de områden som ansetts relevanta för arbetet. För att uppfylla de kvalitetskrav som finns har tre insatsvaror analyserats och legat till grund för de förbättringsförslag som framkommit. Vidare har studien bidragit med teoretiska bidrag i form av tre kritiska kvalitetsfaktorer. Dessa är analyscertifikat (bevis på utfört kvalitetstest),kontroll vid lossning samt kontroll av lagrad insatsvara. De praktiska bidrag som studien lett fram till är att ett affärssystem bör användas för informationshantering, tydliga rutiner bör skapas för de aktiviteter som görs samt att allting bör dokumenteras för att klara interna och externa revisioner. De kritiska kvalitetsfaktorerna samt förslagen för ett effektiviserat arbetssätt som ges till Stora Enso Skutskärs Bruk kan även användas av andra organisationer med liknande förutsättningar och kvalitetskrav. Dessa förslag bör implementeras stegvis och i samråd med ansvariga avdelningar i organisationen. Förbättringsåtgärderna bör även testas och utvärderas vid fortsatt forskning. Ytterligare forskning på hur förslagen har en inverkan på exempelvis miljö, arbetsmiljö och kostnadseffektivitet rekommenderas. / Quality is a competitive factor in the process industry but at the same time one of the most critical problems when it is lacking. The process industry transforms raw materials into products, often through continuous and irreversible processes. This can lead to costly quality problems in the form of faulty end products, broken machines, environmentally hazardous emissions and, in the worst case, serious injuries to employees. The purpose of this study is to develop proposals to streamline the working method of arrival and storage for materials in the process industry to meet the quality requirements that exist. The study has used the scientific approach of abduction to answer the research questions that have been defined. The purpose of the study has been fulfilled by conducting a case study at Stora Enso Skutskärs Bruk, where the handling of material on arrival and storage has been investigated. This has been done through interviews, observations, workshops and a literature study in the areas that are considered relevant to the work. In order to meet the existing quality requirements, three inputs have been analyzed and formed the basis for the improvement proposals that have emerged. Furthermore, the study has contributed to theoretical contributions in the form of three critical quality factors. These are certificate of analysis (proof of quality test performed), control during unloading and control of stored input goods. The practical contributions that the study led to are that an ERP software should be used for information management, clear routines should be created for the activities that are done and that everything should be documented to cope with internal and external audits. The critical quality factors as well as the proposals for a more efficient way of working that are given to Stora Enso Skutskärs Bruk can also be used by other organizations with similar conditions and quality requirements. These proposals should be implemented gradually and in consultation with the responsible departments in the organization. The improvement measures should also be tested and evaluated in further research. Further research on how the proposals have an impact on the environment, work environment and cost efficiency for example is recommended.