Adaptive Cellular Layout in Self-Organizing Networks using Active Antenna Systems

The rapidly growing demand of capacity by wireless services is challenging the mobile industry with a need of new deployment strategies. Besides, the nature of the spatial and temporal distribution of user traffic has become heterogeneous and fluctuating intermittently. Those challenges are currently tackled by network densification and tighter spatial reuse of radio resources by introducing a heterogeneous deployment of small cells embedded in a macro cell layout. Since user traffic is varying both spatially and temporally, a so called busy hour planning is typically applied where enough small cells are deployed at the corresponding locations to meet the expected capacity demand. This deployment strategy, however, is inefficient as it may leave plenty of network resources under-utilized during non-busy hour, i.e., most of the operation time. Such over-provisioning strategy incurs high capital investment on infrastructure (CAPEX) as well as operating cost (OPEX) for operators. Therefore, optimal would be a network with flexible capacity accommodation by following the dynamics of the traffic situation and evading the inefficiencies and the high cost of the fixed deployment approach. The advent of a revolutionizing base station antenna technology called Active Antenna Systems (AAS) is promising to deliver the required flexibility and dynamic deployment solution desired for adaptive capacity provisioning. Having the active radio frequency (RF) components integrated with the radiating elements, AAS supports advanced beamforming features. With AAS-equipped base station, multiple cell-specific beams can be simultaneously created to densify the cell layout by means of an enhanced form of sectorization. The radiation pattern of each cell-beam can be dynamically adjusted so that a conventional cell, for instance, can be split into two distinct cells, if a high traffic concentration is detected. The traffic in such an area is shared among the new cells and by spatially reusing the frequency spectrum, the cell-splitting (sectorization) doubles the total available radio resources at the cost of an increased co-channel interference between the cells. Despite the AAS capability, the realization of flexible sectorization for dynamic cell layout adaptation poses several challenges. One of the challenges is that the expected performance gain from cell densification can be offset by the ensuing co-channel interference in the system. It is also obvious that a self-organized autonomous management and configuration is needed, if cell deployment must follow the variation of the user traffic over time and space by means of a sectorization procedure. The automated mechanism is desired to enhance the system performance and optimize the user experience by automatically controlling the sectorization process. With such a dynamic adaptation scheme, the self-organizing network (SON) facilities are getting a new dimension in terms of controlling the flexible cell layout changes as the environment including the radio propagation characteristics cannot be assumed stationary any longer. To fully exploit the flexible sectorization feature in three-dimensional space, reliable and realistic propagation models are required which are able to incorporate the dependency of the radio channel characteristics in the elevation domain. Analysis of the complex relationship among various system parameters entails a comprehensive model that properly describes the AAS-sectorization for conducting detailed investigation and carrying out precise evaluation of the ensuing system performance. A novel SON algorithm that automates the AAS-sectorization procedure is developed. The algorithm controls the activation/deactivation of cell-beams enabling the sectorization based cell layout adjustment adaptively. In order to effectively meet the dynamically varying network capacity demand that varies according to the spatial user distribution, the developed SON algorithm monitors the load of the cell, the spatial traffic concentrations and adapts the underlying cell coverage layout by autonomously executing the sectorization either in the horizontal or vertical plane. The SON algorithm specifies various procedures which rely on real time network information collected using actual signal measurement reports from users. The particular capability of the algorithm is evading unforeseen system performance degradation by properly executing the sectorization not only where in the network and when it is needed, but also only if the ensuing co-channel interference does not have adverse impact on the user experience. To guarantee the optimality of the network performance after sectorization, a performance metric that takes both the expectable gain from radio resource and impact of the co-channel interference into account is developed. In order to combat the severity of the inter-cell interference problem that arises with AAS-sectorization between the co-channel operated cells, an interference mitigation scheme is developed in this thesis. The proposed scheme coordinates the data transmission between the co-sited cells by the transmission muting principle. To ensure that the transmission muting is not degrading the overall system performance by blanking more data transmission, a new SON algorithm that controls the optimal usage the proposed scheme is developed. To appropriately characterize the spatial separation of the cell beams being activated with sectorization, a novel propagation shadowing model that incorporates elevation tilt parameter is developed. The new model addresses the deficiencies of the existing tilt-independent shadowing model which inherently assumes a stationary propagation characteristics in the elevation domain. The tilt-dependent shadowing model is able to statistically characterize the elevation channel variability with respect to the tilt configuration settings. Simplified 3D beamforming models and beam pattern synthesis approaches required for fast cell layout adaptation and dynamic configuration of the AAS parameters are developed for the realization of various forms of AAS-based sectorization. Horizontal and vertical sectorization are the two forms of AAS-based sectorization considered in this thesis where two beams are simultaneously created from a single AAS to split the underlying coverage layout in horizontal or vertical domain, respectively. The performance of the developed theoretical AAS-sectorization concepts and models are examined by means of system level simulations considering the Long Term Evolution-Advanced (LTE-A) macro-site deployment within exemplifying scenarios. Simulation results have demonstrated that the SON mechanism is able to follow the different conditions when and where the sectorization delivers superior performance or adversely affects the user experience. Impacts on the performance of existing SON operations, like Mobility Robustness Optimization (MRO), which are relying on stationary cell layout conditions have been studied. Further investigations are carried out in combination with the cell layout changes triggered by the dynamic AAS-based sectorization. The observed results have confirmed that proper coordination is needed between the SON scheme developed for AAS sectorization and the MRO operation to evade unforeseen performance degradation and to ensure a seamless user experience. The technical concepts developed in this thesis further have impacted the $3^\textrm{rd}$ Generation Partnership Project (3GPP) SON for AAS Work Item (WI) discussed in the Radio Access Network (RAN)-3 Work Group (WG). In particular, the observed study results dealing with the interworking of the existing SON features and AAS sectorization have been noted in the standardization work

A systematic review of perception system and simulators for autonomous vehicles research

This paper presents a systematic review of the perception systems and simulators for autonomous vehicles (AV). This work has been divided into three parts. In the first part, perception systems are categorized as environment perception systems and positioning estimation systems. The paper presents the physical fundamentals, principle functioning, and electromagnetic spectrum used to operate the most common sensors used in perception systems (ultrasonic, RADAR, LiDAR, cameras, IMU, GNSS, RTK, etc.). Furthermore, their strengths and weaknesses are shown, and the quantification of their features using spider charts will allow proper selection of different sensors depending on 11 features. In the second part, the main elements to be taken into account in the simulation of a perception system of an AV are presented. For this purpose, the paper describes simulators for model-based development, the main game engines that can be used for simulation, simulators from the robotics field, and lastly simulators used specifically for AV. Finally, the current state of regulations that are being applied in different countries around the world on issues concerning the implementation of autonomous vehicles is presented.This work was partially supported by DGT (ref. SPIP2017-02286) and GenoVision (ref. BFU2017-88300-C2-2-R) Spanish Government projects, and the “Research Programme for Groups of Scientific Excellence in the Region of Murcia" of the Seneca Foundation (Agency for Science and Technology in the Region of Murcia – 19895/GERM/15)

Adaptive Interference Mitigation in GPS Receivers

Satellite navigation systems (GNSS) are among the most complex radio-navigation systems, providing positioning, navigation, and timing (PNT) information. A growing number of public sector and commercial applications rely on the GNSS PNT service to support business growth, technical development, and the day-to-day operation of technology and socioeconomic systems. As GNSS signals have inherent limitations, they are highly vulnerable to intentional and unintentional interference. GNSS signals have spectral power densities far below ambient thermal noise. Consequently, GNSS receivers must meet high standards of reliability and integrity to be used within a broad spectrum of applications. GNSS receivers must employ effective interference mitigation techniques to ensure robust, accurate, and reliable PNT service. This research aims to evaluate the effectiveness of the Adaptive Notch Filter (ANF), a precorrelation mitigation technique that can be used to excise Continuous Wave Interference (CWI), hop-frequency and chirp-type interferences from GPS L1 signals. To mitigate unwanted interference, state-of-the-art ANFs typically adjust a single parameter, the notch centre frequency, and zeros are constrained extremely close to unity. Because of this, the notch centre frequency converges slowly to the target frequency. During this slow converge period, interference leaks into the acquisition block, thus sabotaging the operation of the acquisition block. Furthermore, if the CWI continuously hops within the GPS L1 in-band region, the subsequent interference frequency is locked onto after a delay, which means constant interference occurs in the receiver throughout the delay period. This research contributes to the field of interference mitigation at GNSS's receiver end using adaptive signal processing, predominately for GPS. This research can be divided into three stages. I first designed, modelled and developed a Simulink-based GPS L1 signal simulator, providing a homogenous test signal for existing and proposed interference mitigation algorithms. Simulink-based GPS L1 signal simulator provided great flexibility to change various parameters to generate GPS L1 signal under different conditions, e.g. Doppler Shift, code phase delay and amount of propagation degradation. Furthermore, I modelled three acquisition schemes for GPS signals and tested GPS L1 signals acquisition via coherent and non-coherent integration methods. As a next step, I modelled different types of interference signals precisely and implemented and evaluated existing adaptive notch filters in MATLAB in terms of Carrier to Noise Density (\u1d436/\u1d4410), Signal to Noise Ratio (SNR), Peak Degradation Metric, and Mean Square Error (MSE) at the output of the acquisition module in order to create benchmarks. Finally, I designed, developed and implemented a novel algorithm that simultaneously adapts both coefficients in lattice-based ANF. Mathematically, I derived the full-gradient term for the notch's bandwidth parameter adaptation and developed a framework for simultaneously adapting both coefficients of a lattice-based adaptive notch filter. I evaluated the performance of existing and proposed interference mitigation techniques under different types of interference signals. Moreover, I critically analysed different internal signals within the ANF structure in order to develop a new threshold parameter that resets the notch bandwidth at the start of each subsequent interference frequency. As a result, I further reduce the complexity of the structural implementation of lattice-based ANF, allowing for efficient hardware realisation and lower computational costs. It is concluded from extensive simulation results that the proposed fully adaptive lattice-based provides better interference mitigation performance and superior convergence properties to target frequency compared to traditional ANF algorithms. It is demonstrated that by employing the proposed algorithm, a receiver is able to operate with a higher dynamic range of JNR than is possible with existing methods. This research also presents the design and MATLAB implementation of a parameterisable Complex Adaptive Notch Filer (CANF). Present analysis on higher order CANF for detecting and mitigating various types of interference for complex baseband GPS L1 signals. In the end, further research was conducted to suppress interference in the GPS L1 signal by exploiting autocorrelation properties and discarding some portion of the main lobe of the GPS L1 signal. It is shown that by removing 30% spectrum of the main lobe, either from left, right, or centre, the GPS L1 signal is still acquirable

Active Plasmonic and Dielectric Nanoantennas

This thesis presents results on the fabrication, investigation and characterization of active optical nanoantennas. The three partial results in order of their occurrence are: (i) The demonstration of the operational capability and versatility of a quantum dot deposition technique by fabricating active plasmonic and dielectric nanoantennas. (ii) The optical detection of dark modes of plasmonic nanoantennas. (iii) The optical characterization of the novel dielectric nanoantennas. A versatile method to deposit quantum dots on nanostructured samples to produce an active optical nanoantennas was developed during the course of this thesis. The deposition technique is based on electron-beam lithography, where a template is written in a resist. The developed holes in the polymer define sites to deposit the quantum dots. To ensure an enduring attachment, a zero-length linking is used. The versatility of the method was shown in this thesis by producing structured quantum dot films of various sizes and placing quantum dots on top of nanostructures of divers materials. Precise placed quantum dots were used to built active gold and hafnium dioxide nanoantennas. The experiments on the well known gold rod nanoantennas focused on the investigation of dark modes. Modes are called dark, when they are non-dipolar and thus do not or only weakly interact with far fields under normal incident. Using the quantum dots as feed elements in the hot spot of the antennas, resonances in the nanoantennas were excited with a near-field method, i.e., the quantum dot emitted fluorescence moderated by the antenna into the far field. As expected, the first-order resonance, as measured with the dark-field spectroscope, produced an enhanced, polarized fluorescence signal. Additionally, a fluorescence enhancement for longer antennas was measured. Since it does not coincidence in strength or spectrally with the third-order mode, it can be attributed to the second-order, non-dipolar mode. Thus, this measurement is a proof of principle of a direct detection of dark modes in nanostructures. This additional insight in the operating principles of nanostructures could benefit the design of more complex plasmonic applications. The second nanostructure investigated is a novel type of optical antenna. The nanoantenna design based on the operating principle of leaky-wave antennas was fabricated and equipped with quantum dots. It consists of only two simple dielectric building blocks and has a total length of approximately three times the free-space operation wavelength. The fluorescence of the quantum dots excites a leaky mode in the director by end-fire coupling. Light propagating along the director is continuously coupled to radiating modes in the substrate and emitted into the glass. With Fourier imaging, the far-field pattern of individual antennas was measured and shown to be highly directional. The directivity of the antenna was measured to be D=12.5 dB.Together with numerical calculations, polarization dependent measurements gave insight in the different coupling strength in regards of the quantum dots' dipole orientation relative to the antenna. Experiments with different antenna sizes indicate the broadband operation of the nanoantenna design. It can be easily adapted to various low-loss dielectric materials. Moreover, its non-resonant nature makes the antenna design inherently robust against fabrication imperfections and guarantees broad-band operation

Interference Mitigation and Localization Based on Time-Frequency Analysis for Navigation Satellite Systems

Interference Mitigation and Localization Based on Time-Frequency Analysis for Navigation Satellite SystemsNowadays, the operation of global navigation satellite systems (GNSS) is imperative across a multitude of applications worldwide. The increasing reliance on accurate positioning and timing information has made more serious than ever the consequences of possible service outages in the satellite navigation systems. Among others, interference is regarded as the primary threat to their operation. Due the recent proliferation of portable interferers, notably jammers, it has now become common for GNSS receivers to endure simultaneous attacks from multiple sources of interference, which are likely spatially distributed and transmit different modulations. To the best knowledge of the author, the present dissertation is the first publication to investigate the use of the S-transform (ST) to devise countermeasures to interference. The original contributions in this context are mainly: • the formulation of a complexity-scalable ST implementable in real time as a bank of filters; • a method for characterizing and localizing multiple in-car jammers through interference snapshots that are collected by separate receivers and analysed with a clever use of the ST; • a preliminary assessment of novel methods for mitigating generic interference at the receiver end by means the ST and more computationally efficient variants of the transform. Besides GNSSs, the countermeasures to interference proposed are equivalently applicable to protect any direct-sequence spread spectrum (DS-SS) communication

Television broadcast from space systems: Technology, costs

Broadcast satellite systems are described. The technologies which are unique to both high power broadcast satellites and small TV receive-only earth terminals are also described. A cost assessment of both space and earth segments is included and appendices present both a computer model for satellite cost and the pertinent reported experience with the Japanese BSE

Développement et caractérisation de techniques de réduction d’interférences pulsées pour récepteurs GNSS embarqués

Les organismes de standardisation de l’aviation civile (OACI, RTCA, EUROCAE) mènent actuellement des études sur l'utilisation des systèmes de navigation par satellite fournissant une couverture globale, tels GPS ou Galileo, en tant que moyen de navigation embarque unique. L’OACI regroupe l’ensemble de ces systèmes de navigation satellitaires et de leurs systèmes d’augmentation sous la dénomination GNSS. Pour des raisons de sécurité évidentes, les performances des récepteurs GNSS embarques doivent garantir des minima propres à chaque phase de vol et chaque procédure d’approche. Ces exigences de performances sont spécifiées dans les spécifications des performances opérationnelles minimales, documents publiés (ou en cours de publication) par les autorités sus-citées. Le GNSS est en passe d’être amélioré par la diffusion de nouveaux signaux. Parmi eux, les signaux Galileo E5 et GPS L5 devraient permettre l’amélioration du service de navigation par satellite. Cependant, ces signaux seront émis dans une bande déjà utilisée par des systèmes radiofréquences. Il est donc primordial de s’assurer de la possibilité de la coexistence de ces systèmes. Plus particulièrement, il est nécessaire de s’assurer que les récepteurs GNSS embarqués utilisant les signaux sus-cités respectent les exigences de performance. La menace principale au bon fonctionnement des récepteurs GNSS utilisant les signaux E5/L5 a été identifiée comme étant les émissions pulsées des systèmes DME, TACAN, JTIDS et MIDS. Sans moyen de lutte contre ces interférences, les performances des récepteurs GNSS embarqués peuvent être dégradées de manières significatives, empêchant les récepteurs de se conformer aux exigences de sécurité sur l’ensemble du monde, et plus particulièrement sur des ≪ points chauds ≫ ayant été identifies comme les lieux ou l’impact de ces interférences sur lesdits récepteurs est la plus importante. Deux techniques de réduction d’interférences ont été proposées pour lutter contre cette menace, le Blanker temporel et le Frequency Domain Interference Suppressor (FDIS). Le Blanker temporel est une technique de traitement du signal consistant en un test de puissance, relativement simple a mettre en oeuvre et dont la capacité de rejection des interférences a été démontrée suffisante pour assurer les exigences de l’aviation civile dans toutes les phases de vols sur l’ensemble du monde pour les récepteurs GPS et Galileo utilisant respectivement les signaux L5 et E5, dans [Bastide, 2004]. Toutefois, cette technique permet de respecter les exigences avec une marge faible, dans les environnements les plus riches en interférences, autrement dit les « points chauds ». En revanche, le FDIS est une technique de lutte contre les interférences pulsées beaucoup plus exigeante en termes de ressources, puisque basée sur l’excision des interférences dans le domaine fréquentiel. Cependant, elle permet une amélioration sensible des performances du récepteur, et donc une augmentation des marges vis-à-vis des exigences fixées par l’Aviation Civile. Le FDIS a été propose comme une alternative au blanker temporel, mais ses problèmes d’implantation et ses performances n’ont été que peu étudies. La dissertation a pour but de participer a cette étude de performance afin de valider son intérêt. Le plan de la thèse est le suivant : tout d'abord, les signaux de navigation, Galileo E5a/E5b et GPS L5, les interférences pulsées, ainsi que leur impact sur les performances des récepteurs GNSS sont présentes. Ensuite, une description des techniques de suppression d’interférences (blanker temporel, FDIS), leurs caractéristiques théoriques et les dégradations de performances subies par un récepteur GNSS utilisant ces techniques en présence d'interférences pulsées sont présentées. Les conditions dans lesquelles ont été obtenues ces performances, c’est à dire le choix des scenarios joues ainsi que des paramètres observés, ou encore les outils de simulation sont décrits. La conclusion résume l’analyse des performances, les compare aux exigences de l’Aviation Civile, et propose des recommandations pour la conception de récepteurs GNSS embarqués. ---------------------------------------------------------------------------------------------------------------------------------------------- Civil Aviation standardisation bodies (ICAO, RTCA, EUROCAE) are currently investigating the use of the Global Navigation Satellite System (GNSS) as a stand-alone navigation solution for civil aircraft. For obvious safety reasons, on-board GNSS receivers must guarantee minimum performance requirements in given phases of flights. These requirements, dependent upon the system and signals used, are stated in the Minimum Operational Performance Specification (MOPS), published (or being published) by the corresponding authorities. With that respect, the future use of Galileo E5 and GPS L5 bands has raised, among others, interference issues. Indeed, pre-existent RF systems emit in this band, thus interfering with the E5/L5 signals. The main threat was identified as being DME/TACAN ground beacons pulsed emissions. Without any mitigation capability, these systems can disturb the proper operation of on-board GNSS receivers, preventing them from complying with safety requirements. Two Interference Mitigation Techniques (IMT) have been proposed to fight this threat, the Temporal Blanker and the Frequency Domain Interference Suppressor (FDIS). The Temporal Blanker technique offers a fairly simple implementation and was shown to provide enough benefits to ensure that the specified requirements were met in all phases of flight for a GPS L5 or Galileo E5 receiver. However, it was also demonstrated that the resulting performances were meeting the requirements by only a small margin on the worst DME/TACAN interference environment that can be found in Europe and USA, so called the European and USA “hot spots”. In contrast, the FDIS is a more demanding mitigation technique against pulsed interference in terms of required resources but improves the performances of the receiver, thus allowing larger margins with respect to the civil aviation requirements. The core of the study is the analysis of the performances of GNSS receivers using FDIS as IMT. The dissertation architecture is the following: first, the navigation signals, Galileo E5a/E5b and GPS L5, as long as the interferences that constitute a threat for GNSS navigation and their impact on GNSS receivers operations are presented. Then, a description of the studied IMTs (Temporal Blanker, FDIS), their theoretical characteristics and the theoretical derivations of the post-correlation C/N0 degradation suffered by a receiver using these techniques in presence of pulsed interference are depicted. Afterwards, all the results obtained concerning the IMTs performance assessments are presented. Firstly, the Figures Of Merit chosen to analyze the performance of both techniques are presented and their choice is motivated. Then, the chosen interference and signal scenarios, along with the simulation tools and means are finely detailed. Finally, a confrontation of Temporal Blanker and FDIS performances is given using the previously described FOMs. The conclusion summarizes the performances analysis, compares them to - 6 - civil aviation performances requirements, and proposes recommendations for on-board GNSS receivers desig

State of the art survey of technologies applicable to NASA's aeronautics, avionics and controls program

The state of the art survey (SOAS) covers six technology areas including flightpath management, aircraft control system, crew station technology, interface & integration technology, military technology, and fundamental technology. The SOAS included contributions from over 70 individuals in industry, government, and the universities