1,721,077 research outputs found
Autonomy for Sustainability: An AESS Vision and Perspectives
No full textSustainability is a key challenge for the future of humanity. In this frame, the AESS Working Group on Vision and Perspectives has identified "autonomy for sustainability"as a super topic where the broad field of interest of AESS and the related focus on complex systems in multiple domains can play the difference for an effective and timely implementation of the sustainability goal. This article presents ideas and possible developments of the super topic in some of the technical domains of the AESS panels. The aim is to share this vision with AESS members and readers and to start the interaction that is needed to transform an idea into a live matter, where AESS panels and members work together for a promising perspective
A Run-time method based on observable data for the quality assessment of gnss positioning solutions
Full text linkSeveral location-aware applications rely on the position estimated by means of Global Navigation Satellite Systems (GNSS), which are known to estimate an accurate position in an open environment. However, the quality of the estimated position is degraded in harsh environments in terms of accuracy and reliability. Liability-critical services, such as location-based charging, transportation, and road tolling, are threatened by the use of an unreliable position of the user, and the level of trust in the estimated position has to be considered to avoid a failure of the full service chain. Such an issue is faced by means of integrity monitoring methods in the field of GNSS. However, when dealing with harsh environments, integrity monitoring techniques designed for aeronautical applications would lead to very conservative results and to the rejection of all the positions obtained. Such conservative approach is based on the theoretical error models for the estimation of the pseudorange standard deviation in open sky. The purpose of this work is to propose an innovative method for estimating the pseudorange standard deviation extrapolating it from measurements of observable data, to assess the confidence level in the obtained positions in relation to the real environment surrounding the user. While measuring the pseudorange standard deviation taking into account environment conditions and receiver accuracy, the user is able to achieve better estimation of the user equivalent range error (UERE). Estimating the UERE from raw pseudorange measurements with the proposed run-time method and its subsequent use in the computation of protection levels using the receiver autonomous integrity monitoring (RAIM) algorithm shows significant improvement in navigation system availability by deriving tight protection level
GNSS integrity for aviation and road user applications
No full textThe evolution of Global Navigation Satellite System (GNSS) is paving the way for new satellite constellations and civil signals. Currently, the European Galileo and Chinese BeiDou are in deployment phases, while the American GPS and Russian GLONASS are going through modernization. On completion, satellite navigation users are expected to receive a large number of ranging signals on two civil frequencies instead of one. These significant improvements open up new possibilities to extend the use of satellite navigation for worldwide vertical guidance of aircraft down to 200 ft. above ground level. GNSS Evolutionary Architecture Study (GEAS) panel proposed several candidate integrity architectures for worldwide vertical guidance of aircraft.
Among the candidate integrity architectures, Advanced Receiver Autonomous Integrity Monitoring (ARAIM), which is an extension of single frequency and lateral guidance-only RAIM, is expected to
utilize minimal infrastructure in the provision of vertically guided approach down to Localizer Performance with Vertical guidance at a decision altitude of 200 ft. above ground level or LPV-200.
The first contribution of this thesis is to analyze worldwide availability of Advanced RAIM for the provision of LPV-200 approach procedure. In this regard, ARAIM availability is evaluated using MATLAB Algorithm Availability Simulation Tool (MAAST) considering single and multiple GNSS constellations including GPS, Galileo, GLONASS and BeiDou. Furthermore, several Signal In Space (SIS) error characterizations and multiple satellite and constellation failures are taken into account during the analysis of ARAIM availability. Advanced RAIM user algorithm relies on external information in providing real-time integrity monitoring on board aircraft. This external information would be disseminated by ground station in the form of Integrity Support Message (ISM). Unlike Satellite Based Augmentation System (SBAS), Advanced RAIM does not require a realtime
communication channel for the dissemination of ISM, thanks to the distribution of integrity burden between the airborne receiver, ground monitoring network, and core constellation service providers.
This distribution of integrity burden using ARAIM concept opens up new possibilities to investigate various channels for dissemination of ISM to the aircraft. In this framework, this thesis analyzes Terrestrial Trunked Radio (TETRA) for the dissemination of ISM to the State Aircraft. A State Aircraft is defined as an aircraft used for the customs, military, and police services. TETRA Air-Ground-Air operation supported by aeronautical base station presents an attractive solution for the dissemination of ISM to the State Aircraft. The analysis of TETRA for the dissemination of ISM to the State Aircraft is based on average and maximum end-to-end ISM dissemination latency considering
a variety of parameters that directly impacts the end-to-end ISM dissemination latency, which include different ISM contents, ISM formats, ISM update intervals, channel Bit Error Rate (BER), and different number of users.
Research on ARAIM is still evolving while the current research is focused on Advanced RAIM system architecture. This thesis contributes to on going discussion on Advanced RAIM architecture by
outlining the system architecture. Furthermore, this thesis proposes three-tiers integrity monitoring strategy, which is the extension of multiple ISM Advanced RAIM architecture for the worldwide vertical guidance of aircraft. The three-tiers integrity monitoring strategy uses distinct SIS error bounding methodology within each tier and provides ground validated extended ephemerides within tier-1 and ephemerides with improved accuracy within tier-2 using TETRA network. The three-tiers strategy, on one hand, protects the airborne receiver against the threat of constellation wide faults, while on the other, it makes use of the TETRA Air-Ground-Air technological solution that allows the dissemination of ISM to the State Aircraft over a wide coverage area and at higher altitude. GNSS integrity monitoring is the key enabler of Safety of Life (SoL) applications relying on the use of satellite navigation such as aviation. However, integrity monitoring of GNSS is not limited to applications that involve life safety but also plays a key role in enabling applications in which positioning errors may have legal or economic consequences. Such applications are known as liability-critical applications to distinguish it from safety-critical applications. The existing integrity paradigms are mainly developed for aviation considering the International Civil Aviation Organization (ICAO) performance requirements and are meeting the Required Navigation Performance (RNP). The "as is" application of existing integrity concept in the urban and road user environment does not satisfies the integrity and more importantly the navigation system availability requirements. One of the reasons is the mismatch of the pseudorange error estimation model and the urban environment. This thesis contributes in evaluating the performance of a novel method of pseudorange error estimation that does not rely on the theoretical and/or empirical models
but considers the environment surrounding the user. Another issue that is considered in this thesis is the impact of solar radio burst on the performance of GNSS receivers. Solar radio burst is the sudden outburst of radio noise from the Sun, which decreases C/N0 of every tracked satellite signal by increasing the noise floor of GNSS receiver. The degradation in C/N0 due to the solar radio
frequency interference can result in degraded navigation accuracy or complete loss of receiver tracking. This could be an issue for wide range of applications that demand uninterrupted satellite navigation service with certain level of accuracy, particularly for the Safety of Life (SoL) applications relying on the use of GNSS, for instance, aircraft landing procedures in civil aviation. Finally, this thesis analyses the performance of large subset of GPS receiver including aviation and survey grade receivers located worldwide. The performance assessment includes estimation of GPS L1/L2 C/N0 degradation and rise in horizontal and vertical positioning error during the September 24, 2011 solar radio burst event
Uwb microwave radar for early detection of head stroke
No full textHead stroke compromises cerebral blood flowing, leading to brain injuries. It is one of the main causes of disability and death worldwide and it requires an immediate diagnostic investigation and therapeutic solution. It would be extremely important to detect as soon as possible any abnormality, by using a device that can be carried on site by first response paramedical teams or in the ambulance. This is not possible with traditional diagnostics tools, such as CT (Computed Tomography) or MRI (Magnetic Resonance Imaging), which can be used only in hospital, under specific conditions. Furthermore, the response time might be long (the CT exam takes about 10 minutes, while the MRI takes about 30 minutes).
The objective of this work is the design of a diagnostic device for early detection of cerebral vascular diseases in adults, which is accurate and reliable, low cost, low complex, non-invasive for patients, able to provide a fast response (about few minutes) and transportable. Such a device could be used by first responders or on the ambulance. In such a way, upon arrival at the hospital, physicians already know critical patients that need further diagnostic exams. In this way, unnecessary costly diagnostic exams (and in some cases, invasive) can be avoided and the management of the emergency situations (where there are more injured patients) could be greatly improved.
Moreover, the device could be also used in hospital for daily monitoring of patients at risk.
For the purpose of this work, Microwave Imaging (MWI) is emerging as an interesting solution. MWI is not invasive and allows to design low cost and low complexity devices. In this work, we focused on one of the possible MWI approaches, the microwave UWB radar.
The backscattered signals acquired are first pre-processed by artifacts removal algorithms. Then, those cleaned signals are processed by beamforming algorithms.
This work reveals that not all of the state-of-the-art artifacts removal algorithms, mainly proposed for breast cancer detection, are able to achieve good performance. Some algorithms which show good performance with noiseless signals conversely provide poor results in noisy conditions. Therefore, novel algorithms for both artifacts removal and beamforming phase have been proposed, showing very reliable and good
2
performance, in terms of accuracy of stroke localization, amount of artifacts not completely removed and computational complexity, even in noisy conditions.
The thesis is organized as follows.
In Chapter 1 the background of the proposed system is presented. The traumatic brain injury is defined. Microwave imaging approaches, namely microwave tomography and UWB radar, are presented. We then focus on UWB radar imaging devices for stroke detection. Finally, the analysis of the state-of-the-art supports motivation and objectives of the thesis.
In Chapter 2 the main assumptions of the system model are presented, with the description of the antennas system and the head model.
Chapter 3 presents the main algorithms proposed in literature both for artifacts removal and beamforming, outlining advantages and drawbacks and identifying the directions in which improvements are needed.
Chapter 4 presents novel solutions both for the artifacts removal and the beamforming, showing, with extensive comparison results, the effectiveness of the proposed solutions with respect to the state-of-the art algorithms.
Finally, the conclusions and future perspectives are discussed in Chapter 5
Graphene Devices for Aerial Wireless Communications at THz
Full text linkThis paper investigates the state-of-the-art of graphene-based technologies for the prospective use cases of end-to-end terahertz (THz) communication systems, such as industrial Internet of Things (IoT) applications and unmanned aerial vehicles (UAVs). THz communications offer ultra-high throughput and enhanced sensing capabilities, enabling advanced applications like UAV swarms and integrated sensing, localization, and mapping. The potential of wireless THz communication can be unlocked by graphene technology. Graphene, owing to its remarkable electrical, thermal, and mechanical properties, emerges as a promising candidate for a multitude of applications in aerial wireless communications in the THz band, including high-speed electronic devices, tunable metamaterials, and innovative antennas. However, reliable tools for the simulation-based design of graphene components, able to account for the fabrication-related uncertainties, are still missing. This paper presents the envisaged possibilities of wireless communications in THz bands, overviews graphene devices for RF applications at THz, and discusses the open issues of modelling THz devices and THz channel
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Terrestrial/Non-terrestrial Integrated Networks for Beyond 5G Communications
No full textThis chapter aims at providing an overview of the activities and goals
of the Italian National project ITA NTN (Integrated Terrestrial and Non-Terrestrial
Networks) that has been proposed and funded in the framework of the EU initiative defined as the Italian National Resilience and Restart Program. Therefore it presents an overview of the upcoming 6G-oriented scenario, where space network entities such as low-Earth orbit mega-constellations of nano-satellites, High-Altitude Platforms (HAP), and unmanned aerial vehicles (UAVS) cooperate with terrestrial networks to provide a 3-dimensional (3D) wireless connectivity. Moreover, the evolution from interoperable to fully integrated scenarios is summarized and discussed together with the description of the future architectures and a brief overview of the 3GPP technical specifications about terrestrial and non-terrestrial systems and subnetworks. Finally, the project vision and the envisaged road map are presented
Codifica e modulazione per una maggiore robustezza al jamming del collegamento satellitare TTC
No full textThe main contributions of this thesis can be summarized in:
1) Proper modeling of the cycle slip phenomenon and evaluation of its impact in the performance of TT&C.
2) Better understanding of the behavior of several channel codes, combined with interleavers, in terms of performance and latency, in presence of pulsed jammer and occurrence of cycle slips.
3) Prove of the effectiveness of combining differential modulation and advanced channel codes to get higher jammer robustness and still good performance in absence of jamming
- …
