Getting better all the time - The Continued Evolution of the GNSS Software-Defined Radio

Software Defined Radio (SDR) has an infinite number of interpretations depending on the context in which it is designed and used. By way of a starting definition the authors choose to use that of ‘a reconfigurable radio system whose characteristics are partially or fully defined via software or firmware’. In various forms, SDR has permeated a wide range of user groups, from military, business, academia and to the amateur radio enthusiast

Reconfigurable Antenna Systems: Platform implementation and low-power matters

Antennas are a necessary and often critical component of all wireless systems, of which they share the ever-increasing complexity and the challenges of present and emerging trends. 5G, massive low-orbit satellite architectures (e.g. OneWeb), industry 4.0, Internet of Things (IoT), satcom on-the-move, Advanced Driver Assistance Systems (ADAS) and Autonomous Vehicles, all call for highly flexible systems, and antenna reconfigurability is an enabling part of these advances. The terminal segment is particularly crucial in this sense, encompassing both very compact antennas or low-profile antennas, all with various adaptability/reconfigurability requirements. This thesis work has dealt with hardware implementation issues of Radio Frequency (RF) antenna reconfigurability, and in particular with low-power General Purpose Platforms (GPP); the work has encompassed Software Defined Radio (SDR) implementation, as well as embedded low-power platforms (in particular on STM32 Nucleo family of micro-controller). The hardware-software platform work has been complemented with design and fabrication of reconfigurable antennas in standard technology, and the resulting systems tested. The selected antenna technology was antenna array with continuously steerable beam, controlled by voltage-driven phase shifting circuits. Applications included notably Wireless Sensor Network (WSN) deployed in the Italian scientific mission in Antarctica, in a traffic-monitoring case study (EU H2020 project), and into an innovative Global Navigation Satellite Systems (GNSS) antenna concept (patent application submitted). The SDR implementation focused on a low-cost and low-power Software-defined radio open-source platform with IEEE 802.11 a/g/p wireless communication capability. In a second embodiment, the flexibility of the SDR paradigm has been traded off to avoid the power consumption associated to the relevant operating system. Application field of reconfigurable antenna is, however, not limited to a better management of the energy consumption. The analysis has also been extended to satellites positioning application. A novel beamforming method has presented demonstrating improvements in the quality of signals received from satellites. Regarding those who deal with positioning algorithms, this advancement help improving precision on the estimated position

Design of software e hardware

The main objective of the research work described in this manuscript was to develop methods (hardware/software) for three-dimensional data acquisition in order to perform morphological analysis in sandy shore environments. This system, when concluded, intends to estimate the volumetric variations in beaches being eroded at high rates, directly contributing for studies focused on the protection of the coastline. This work is particularly focused on the development of software to estimate the 3D positions using a dedicated low-cost hardware device that was also developed in the framework of this project. Several methods have been used to study these phenomena, such as classical topography by surveying discrete points with the utilization of theodolites and/or total stations that are highly time-consuming. Other methods that start recently being used, like terrestrial or airborne LiDAR, are very costly and are not suitable to be used in many locations due to governmental requirements (like permits, environment, and security issues). Similar limitations also occur with Mobile Mapping Systems (MMS) with laser scanners that permit the survey when the vehicle is moving on the beach. In order to minimize the issues presented by the techniques described above, it was developed a simple, economic, ef cient and accurate system that can be used to study the erosion phenomena in coastal area. This system should allow one to acquire accurate GNSS positioning data on beaches, using a simple acquisition device in order to enable the creation of a three- -dimensional surface of the study area, which temporal variation can permit to quantify the erosion rates. This system is formed by an acquisition device, a GNSS receiver and antenna, and a Android Tablet/Smartphone that allows us to collect the antenna attitude from it’s internal orientation sensors. To collect information from the angles of the sensors, an Android application was developed. With the Tablet/Smartphone attitude angles, it is possible to correct the GNSS observations in order to obtain the vertical position - a dedicated C# application was developed with this objective. This corrections allows the creation of surfaces that accurately represent the terrains where the observations were conducted. In the future, using several observations at different times, it is possible to study the variations of sand volumes of the surveyed beaches and analyse the morphological variations. Some preliminary tests were performed concerning the creation of the surfaces, in order to evaluate the internal accuracy of the entire system. For this goal, we developed several scripts, using GMT (Generic Mapping Tools), that can also be used in the future to calculate the variations of the beach volume. In this respect, the results of some tests carried out to evaluate the accuracy of the developed technology are presented. In particular, by analysing the deviations with respect to a reference surface and by evaluating the sensitivity when measuring on an irregular surface.O principal objetivo do trabalho de investigação descrito neste manuscrito foi, desenvolver métodos (software/hardware) para aquisição de dados em três dimensões, de forma a realizar a análise morfológica em ambientes de costa arenosa. Este sistema, quando estiver concluído, pretende estimar as variações volumétricas em praias que estão a ser erodidas a taxas elevadas, contribuindo diretamente para estudos voltados para a proteção da zona costeira. Este trabalho está focado principalmente no desenvolvimento de software para estimar as posições em 3D utilizando um dispositivo de hardware de baixo custo dedicado que também foi desenvolvido no âmbito deste projecto. Têm sido utilizados vários métodos para estudar estes fenômenos, tais como topografia clássica através do levantamento de pontos discretos, com a utilização de teodolitos e/ou estações totais que são altamente demoradas. Outros métodos que começam recentemente a ser utilizados, é o LiDAR terrestre ou aéreo, são muito caros e não são adequados para serem utilizados em muitos locais, devido a exigências governamentais (como licenças, meio ambiente e questões de segurança). Também ocorrem limitações semelhantes com o Mapeamento de Sistemas Móveis (MMS) com scanners a laser que permitem o levantamento, quando o veículo estiver em movimento na praia. Para minimizar os problemas apresentados pelas técnicas acima descritas, desenvolveu-se um sistema simples, económico, eficiente e preciso que possa ser utilizado para estudar os fenómenos da erosão da zona costeira. Este sistema deve permitir adquirir dados de posicionamento GNSS precisos nas praias, utilizando um dispositivo simples de aquisição, para permitir a criação de uma superfície tridimensional da área de estudo, o que pode permitir a variação temporal para quantificar as taxas de erosão. Este sistema é formado por um dispositivo de aquisição, um receptor GNSS e uma antena e um Tablet/Smartphone Android que nos permita recolher a atitude da antena apartir dos sensores de orientação internos. Para a recolha da informação a partir dos ângulos dos sensores, foi desenvolvida uma aplicação Android. Com os ângulos da atitude do Tablet/Smartphone, é possível corrigir as observações GNSS, para obter uma posição vertical - foi desenvolvida uma aplicação C# com este objectivo. Esta correcção permite a criação de superfícies que representam com precisão os terrenos onde foram realizadas as observações. No futuro, utilizando várias observações em momentos diferentes, é possível estudar as variações do volume da areia das praias estudadas e analisar as variações morfológicas. Foram realizados alguns testes preliminares sobre a criação de superfícies, para avaliar a precisão interna de todo o sistema. Para este objectivo, foram desenvolvidos alguns scripts, utilizando o GMT (Generic Mapping Tools), que também podem ser utilizados no futuro, para calcular as variações de volume da praia. Assim, são apresentados os resultados de alguns testes realizados para avaliar a precisão da tecnologia desenvolvida. Em particular, através da análise dos desvios em relação a uma superfície de referência e pela avaliação da sensibilidade na medição sobre uma superfície irregular

Satellite Navigation for the Age of Autonomy

Global Navigation Satellite Systems (GNSS) brought navigation to the masses. Coupled with smartphones, the blue dot in the palm of our hands has forever changed the way we interact with the world. Looking forward, cyber-physical systems such as self-driving cars and aerial mobility are pushing the limits of what localization technologies including GNSS can provide. This autonomous revolution requires a solution that supports safety-critical operation, centimeter positioning, and cyber-security for millions of users. To meet these demands, we propose a navigation service from Low Earth Orbiting (LEO) satellites which deliver precision in-part through faster motion, higher power signals for added robustness to interference, constellation autonomous integrity monitoring for integrity, and encryption / authentication for resistance to spoofing attacks. This paradigm is enabled by the 'New Space' movement, where highly capable satellites and components are now built on assembly lines and launch costs have decreased by more than tenfold. Such a ubiquitous positioning service enables a consistent and secure standard where trustworthy information can be validated and shared, extending the electronic horizon from sensor line of sight to an entire city. This enables the situational awareness needed for true safe operation to support autonomy at scale.Comment: 11 pages, 8 figures, 2020 IEEE/ION Position, Location and Navigation Symposium (PLANS

er.autopilot 1.0: The Full Autonomous Stack for Oval Racing at High Speeds

The Indy Autonomous Challenge (IAC) brought together for the first time in history nine autonomous racing teams competing at unprecedented speed and in head-to-head scenario, using independently developed software on open-wheel racecars. This paper presents the complete software architecture used by team TII EuroRacing (TII-ER), covering all the modules needed to avoid static obstacles, perform active overtakes and reach speeds above 75 m/s (270 km/h). In addition to the most common modules related to perception, planning, and control, we discuss the approaches used for vehicle dynamics modelling, simulation, telemetry, and safety. Overall results and the performance of each module are described, as well as the lessons learned during the first two events of the competition on oval tracks, where the team placed respectively second and third.Comment: Preprint: Accepted to Field Robotics "Opportunities and Challenges with Autonomous Racing" Special Issu

GNSS-free outdoor localization techniques for resource-constrained IoT architectures : a literature review

Large-scale deployments of the Internet of Things (IoT) are adopted for performance improvement and cost reduction in several application domains. The four main IoT application domains covered throughout this article are smart cities, smart transportation, smart healthcare, and smart manufacturing. To increase IoT applicability, data generated by the IoT devices need to be time-stamped and spatially contextualized. LPWANs have become an attractive solution for outdoor localization and received significant attention from the research community due to low-power, low-cost, and long-range communication. In addition, its signals can be used for communication and localization simultaneously. There are different proposed localization methods to obtain the IoT relative location. Each category of these proposed methods has pros and cons that make them useful for specific IoT systems. Nevertheless, there are some limitations in proposed localization methods that need to be eliminated to meet the IoT ecosystem needs completely. This has motivated this work and provided the following contributions: (1) definition of the main requirements and limitations of outdoor localization techniques for the IoT ecosystem, (2) description of the most relevant GNSS-free outdoor localization methods with a focus on LPWAN technologies, (3) survey the most relevant methods used within the IoT ecosystem for improving GNSS-free localization accuracy, and (4) discussion covering the open challenges and future directions within the field. Some of the important open issues that have different requirements in different IoT systems include energy consumption, security and privacy, accuracy, and scalability. This paper provides an overview of research works that have been published between 2018 to July 2021 and made available through the Google Scholar database.5311-8814-F0ED | Sara Maria da Cruz Maia de Oliveira PaivaN/

UAV-based investigations into the hydrology and dynamics of the Greenland Ice Sheet

Variation in the rate of meltwater input into the subglacial system of the Greenland Ice Sheet can force dynamic responses on a range of scales from hourly to interannual. Observations of the ice sheet dynamic response are commonly made either through ground-based Global Navigation Satellite System (GNSS) measurements, which can provide continuous and accurate point measurements, or through satellite remote sensing, which can provide regional-scale observations but at coarse temporal resolutions. This thesis investigates the potential of Uncrewed Aerial Vehicles (UAVs) to provide intermediate-level observations of the interactions between ice sheet hydrology and dynamics at a fast-flowing, marine terminating glacier in West Greenland. I first describe the development of a low- cost UAV suitable for deriving ice sheet velocity fields from Structure-from-Motion photogrammetry. In order to geolocate products without using ground control, image locations are determined directly using an on-board L1 GNSS receiver. I validate this method, showing that accuracies are sufficient for producing velocity fields in the ice sheet interior. Next, this method is used, alongside in-situ geophysical observations, to characterise the causes and dynamic influence of a rapid supraglacial lake drainage. I show that rapid drainage can induce a significant dynamic response up to 4 km away from the lake itself, and that fracture history can exert controls on interannual lake drainage behaviour. Finally, I upscale UAV ob- servations using satellite datasets over a ~3,000 km² area, exploring dynamic controls on crevasse hydrology. I find that in compressive mean stress compressive regimes, crevasses are more likely to display ponding and rapid hydrofracture than in extensional regimes, where continuous slow drainage is typical. Continued high-resolution observations are necessary to further identify key controls on the hydrological influences of Greenland Ice Sheet dynamics.Funded by a Natural Environment Research Council studentship awarded through the Cambridge Earth System Science Doctoral Training Partnership (Grant NE/L002507/1). Research logistics funded by the European Research Council as part of the RESPONDER project under the European Union’s Horizon 2020 research and innovation program (Grant 683043)

GNSS-Free Localization for UAVs in the Wild

Considering the accelerated development of Unmanned Aerial Vehicles (UAVs) applications in both industrial and research scenarios, there is an increasing need for localizing these aerial systems in non-urban environments, using GNSS-Free, vision-based methods. This project studies three different image feature matching techniques and proposes a final implementation of a vision-based localization algorithm that uses deep features to compute geographical coordinates of a UAV flying in the wild. The method is based on matching salient features of RGB photographs captured by the drone camera and sections of a pre-built map consisting of georeferenced open-source satellite images. Experimental results prove that vision-based localization has comparable accuracy with traditional GNSS-based methods, which serve as ground truth